TY - JOUR
A1 - Joseba Ayerdi, J.
A1 - Slachciak, Nadine
A1 - Llavori, I.
A1 - Zabala, A.
A1 - Aginagalde, A.
A1 - Bonse, Jörn
A1 - Spaltmann, Dirk
T1 - On the role of a ZDDP in the tribological performance of femtosecond laser-induced periodic surface structures on titanium alloy against different counterbody materials
N2 - Laser-induced periodic surface structures (LIPSS, ripples) with ~500–700 nm period were produced on titanium alloy (Ti6Al4V) surfaces upon scan processing in air by a Ti:sapphire femtosecond laser. The tribological performance of the surfaces were qualified in linear reciprocating sliding tribological tests against balls made of different materials using different oilbased lubricants. Extending our previous work, we studied the admixture of the additive 2-ethylhexyl-zinc-dithiophosphate to a base oil containing only anti-oxidants and temperature stabilizers. The presence of this additive along with the variation of the chemical composition of the counterbodies allows us to explore the synergy of the additive with the laseroxidized nanostructures.
KW - Additives
KW - Surface structures
KW - Wear
KW - Friction
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488458
DO - https://doi.org/10.3390/lubricants7090079
SN - 2075-4442
VL - 7
SP - 79, 1
EP - 13
PB - MDPI
AN - OPUS4-48845
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gili, A.
A1 - Bischoff, B.
A1 - Simon, U.
A1 - Schmidt, Franziska
A1 - Kober, D.
A1 - Görke, O.
A1 - Bekheet, M.
A1 - Gurlo, A.
T1 - Ceria-based dual-phase membranes for high-temperature Carbon dioxide separation: Effect of iron doping and pore generation with MgO template
N2 - Dual-phase membranes for high-temperature carbon dioxide Separation have emerged as promising technology to mitigate anthropogenic greenhouse gases emissions, especially as a pre- and post-combustion separation technique in coal burning power plants. To implement These membranes industrially, the carbon dioxide permeability must be improved. In this study, Ce_(0.8) Sm_(0.2) O_(2-d) (SDC) and Ce_(0.8)Sm_(0.19)Fe_(0.01)O_(2-d) (FSDC) ceramic powders were used to form the skeleton in dual-Phase membranes. The use of MgO as an environmentally friendly pore generator allows control over the membrane porosity and microstructure in order to compare the effect of the membrane’s ceramic phase. The ceramic powders and the resulting membranes were characterized using ICP-OES, HSM, gravimetric analysis, SEM/EDX, and XRD, and the carbon dioxide flux density was quantified using a high-temperature membrane permeation setup. The carbon dioxide permeability slightly increases with the addition of iron in the FSDC membranes compared to the SDC membranes mainly due to the reported scavenging effect of iron with the siliceous impurities, with an additional potential contribution of an increased crystallite size due to viscous flow sintering. The increased permeability of the FSDC system and the proper microstructure control by MgO can be further extended to optimize carbon dioxide permeability in this membrane system.
KW - Samarium doped ceria
KW - SDC
KW - FSDC
KW - CO2 separation membranes
KW - Scavenging effect of iron
KW - Permeability
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488612
DO - https://doi.org/10.3390/membranes9090108
SN - 2077-0375
VL - 9
IS - 9
SP - 108, 1
EP - 15
PB - MDPI
AN - OPUS4-48861
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Synthesis of cyclic poly(l-lactide) catalyzed by Bismuth salicylates-A combination of two drugs
N2 - l‐lactide was polymerized in bulk at 160 or 180°C with mixtures of bismuth subsalicylate (BiSub) and salicylic (SA) as catalysts. The SA/Bi ratio and the monomer/Bi ratio were varied. The highest molecular weights (weight average, Mw) were achieved at a SA/Bi ratio of 1/1 (Mw up to 92 000 g mol−1). l‐Lactide was also polymerized with combinations of BiSub and silylated SA, and Mw values up to 120 000 g mol−1 were achieved at 180°C. MALDI‐TOF mass spectrometry and Mark‐Houwink‐Sakurada measurements proved that under optimized reaction conditions the resulting polylactides consist of cycles.
KW - Polylactide
KW - MALDI-TOF MS
KW - Cyclization
KW - Catalyst
KW - Salicylate
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488622
DO - https://doi.org/10.1002/pola.29473
SN - 0887-624X
SN - 1099-0518
SP - 29473
PB - Wiley
AN - OPUS4-48862
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Palantöken, Sinam
A1 - Bethke, K.
A1 - Zivanovic, V.
A1 - Kneipp, Janina
A1 - Rademann, Klaus
A1 - Kalinka, Gerhard
T1 - Cellulose hydrogels physically crosslinked by glycine: Synthesis, characterization, thermal and mechanical properties
N2 - Biopolymers are very efficient for significant applications ranging from tissue engineering, biological devices to water purification. There is a tremendous potential value of cellulose because of ist being the most abundant biopolymer on earth, swellability, and functional groups to be modified. A novel, highly efficient route for the fabrication of mechanically stable and natural hydrogels is described in which cellulose and glycine are dissolved in an alkaline solution of NaOH and neutralized in an acidic solution. The dissolving temperature and the glycine amount are essential parameters for the self-assembly of cellulose chains and for Tuning the morphology and the aggregate structures of the resulting hydrogels. Glycine plays the role of a physical crosslinker based on the Information obtained from FTIR and Raman spectra. Among the prepared set of hydrogels, CL5Gly30 hydrogels have the highest capacity to absorb water. The prepared CL5Gly30 gels can absorb up to seven times their dry weight due to its porous 3-D network structure. CL5Gly10 hydrogel exhibits 80% deformation under 21 N force executed. The method developed in this article can contribute to the application of heavy metal adsorption in aqueous solutions for water purification and waste management.
KW - Biopolymer
KW - Cellulose
KW - Hydrogel
KW - Natural
KW - Synthesis
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-486845
DO - https://doi.org/10.1002/APP.48380
SN - 1097-4628
SN - 0021-8995
VL - 136
SP - 48380, 1
EP - 11
PB - Wiley
CY - USA
AN - OPUS4-48684
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Provis, J. L.
A1 - Arbi, K.
A1 - Bernal, S. A.
A1 - Bondar, D.
A1 - Buchwald, A.
A1 - Castel, A.
A1 - Chithiraputhiran, S.
A1 - Cyr, M.
A1 - Dehghan, A.
A1 - Dombrowski-Daube, K.
A1 - Dubey, A.
A1 - Ducman, V.
A1 - Gluth, Gregor
A1 - Nanukuttan, S.
A1 - Peterson, K.
A1 - Puertas, F.
A1 - van Riessen, A.
A1 - Torres-Carrasco, M.
A1 - Ye, G.
A1 - Zuo, Y.
T1 - RILEM TC 247-DTA round robin test: mix design and reproducibility of compressive strength of alkali-activated concretes
N2 - The aim of RILEM TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ is to identify and validate methodologies for testing the durability of alkali-activated concretes. To underpin the durability testing work of this committee, five alkali-activated concrete mixes were developed based on blast furnace slag, fly ash, and flash-calcined metakaolin. The concretes were designed with different intended performance levels, aiming to assess the capability of test methods to discriminate between concretes on this basis. A total of fifteen laboratories worldwide participated in this round robin test programme, where all concretes were produced with the same mix designs, from single-source aluminosilicate precursors and locally available aggregates. This paper reports the mix designs tested, and the compressive strength results obtained, including critical insight into reasons for the observed variability in strength within and between laboratories.
KW - Alkali-activated materials
KW - Alkali-activated slag
KW - Compressive strength
KW - Concrete
KW - Mix-design
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-489131
DO - https://doi.org/10.1617/s11527-019-1396-z
SN - 1359-5997
SN - 1871-6873
VL - 52
IS - 5
SP - Article Number 99
PB - Springer Nature
AN - OPUS4-48913
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hussels, Maria-Teresa
A1 - Chruscicki, Sebastian
A1 - Arndt, Detlef
A1 - Scheider, Swen
A1 - Prager, Jens
A1 - Homann, Tobias
A1 - Habib, Abdel Karim
T1 - Localization of transient events threatening pipeline integrity by fiber-optic distributed acoustic sensing
N2 - Pipe integrity is a central concern regarding technical safety, availability, and environmental compliance of industrial plants and pipelines. A condition monitoring system that detects and localizes threats in pipes prior to occurrence of actual structural failure, e.g., leakages, especially needs to target transient events such as impacts on the pipe wall or pressure waves travelling through the medium. In the present work, it is shown that fiber-optic distributed acoustic sensing (DAS) in conjunction with a suitable application geometry of the optical fiber sensor allows to track propagating acoustic waves in the pipeline wall on a fast time-scale. Therefore, short impacts on the pipe may be localized with high fidelity. Moreover, different acoustic modes are identified, and their respective group velocities are in good agreement with theoretical predications. In another set of experiments modeling realistic damage scenarios, we demonstrate that pressure waves following explosions of different gas mixtures in pipes can be observed. Velocities are verified by local piezoelectric pressure transducers. Due to the fully distributed nature of the fiber-optic sensing system, it is possible to record accelerated motions in detail. Therefore, in addition to detection and localization of threatening events for infrastructure monitoring, DAS may provide a powerful tool to study the development of gas explosions in pipes, e.g., investigation of deflagration-to-detonation-transitions (DDT).
KW - Distributed acoustic sensing (DAS)
KW - Distributed vibrations sensing (DVS)
KW - Fiber-optic sensing
KW - Condition monitoring
KW - Pipeline integrity
KW - Gas explosion
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488555
DO - https://doi.org/10.3390/s19153322
SN - 1424-8220
VL - 19
IS - 15
SP - 3322, 1
EP - 20
PB - MDPI
CY - Basel, CH
AN - OPUS4-48855
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Even, Morgane
A1 - Hutzler, C.
A1 - Wilke, Olaf
A1 - Luch, A.
T1 - Emissions of volatile organic compounds from polymer-based consumer products: comparison of three emission chamber sizes
N2 - The ISO 16000 standard series provide guidelines for emission measurements of volatile organic compounds (VOCs) from building materials. However, polymer-based consumer products such as toys may also release harmful substances into indoor air. In such cases, the existing standard procedures are unsuitable for official control laboratories due to high costs for large emission testing chambers. This paper aims at developing and comparing alternative and more competitive methods for the emission testing of consumer products. The influence of the emission chamber size was investigated as smaller chambers are more suited to the common size of consumer products and may help to reduce the costs of testing. Comparison of the performance of a 203 l emission test chamber with two smaller chambers with the capacity of 24 l and 44 ml, respectively, was carried out by using a polyurethane reference material spiked with 14 VOCs during the course of 28 days. The area-specific emission rates obtained in the small chambers were always similar to those of the 203 l reference chamber after a few hours. This implies that smaller chambers can provide at least useful numbers on the extent of polymer-based consumer product emissions into indoor air, thereby supporting meaningful exposure assessments.
KW - Comparison
KW - Consumer products
KW - Emission chamber
KW - Reference material
KW - Volatile organic compounds
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-493697
DO - https://doi.org/10.1111/ina.12605
VL - 30
IS - 1
SP - 40
EP - 48
PB - Wiley VCH-Verlag
AN - OPUS4-49369
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Ahmed, R.
A1 - Vaishampayan, A.
A1 - Cuellar-Camacho, J. L.
A1 - Wight, D. J.
A1 - Donskyi, Ievgen
A1 - Unger, Wolfgang
A1 - Grohmann, E.
A1 - Haag, R.
A1 - Wagner, O.
T1 - Multivalent Bacteria Binding by Flexible Polycationic Microsheets Matching Their Surface Charge Density
N2 - Aiming at the overall negative surface charge of bacteria, a new strategy of antibacterial agents based on large polymer-modified graphene oxide (GO) sheets is assessed. The presented flexible, polycationic Sheets match the size and charge density of the Escherichia coli surface charge density (2 × 1014 cm−2). These matching parameters create an unspecific but very strong bacteria adsorber by multivalent, electrostatic attraction.
Their interaction with bacteria is visualized via atomic force and confocal microscopy and shows that they effectively bind and wrap around E. coli cells, and thereby immobilize them. The incubation of Gram-negative and -positive bacteria (E. coli and methicillin-resistant Staphylococcus aureus, MRSA) with these polycationic sheets leads to the inhibition of proliferation and a reduction of the colony forming bacteria over time.
This new type of antibacterial agent acts in a different mode of Action than classical biocides and could potentially be employed in medicinal, technical, or agriculture applications. The presented microsheets and their unspecific binding of cell interfaces could further be employed as adsorber material for bacterial filtration or immobilization for imaging, analysis, or sensor technologies.
KW - Surface charge
KW - Bacteria
KW - Graphene oxide
KW - Escherichia coli
KW - XPS
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-509651
DO - https://doi.org/10.1002/admi.201902066
VL - 7
IS - 15
SP - 1902066
PB - WILEY-VCH Verlag GmbH & Co. KGaA
CY - Weinheim
AN - OPUS4-50965
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Neukammer, J.
A1 - Hussels, M.
A1 - Kummrow, A.
A1 - Devonshire, A.
A1 - Foy, C.
A1 - Huggett, J.
A1 - Parkes, H.
A1 - Zel, J.
A1 - Milavec, M.
A1 - Schimmel, H.
A1 - Unger, Wolfgang
A1 - Akgoz, M.
A1 - McHugh, V.
A1 - Grunert, H.-P.
A1 - Zeichhardt, H.
T1 - Survey results on nucleic acid tests of infectious diseases: present status and need for rapid and patient near diagnostics
N2 - This survey will discuss current and emerging isothermal and rapid polymerase chain reaction (PCR) based nucleic acid amplification methods for patient near diagnostics. To assess the clinical need of rapid diagnostics for infectious diseases based on nucleic acid tests (NATs) we performed and analysed a questionnaire among laboratories participating in corresponding INSTAND ring trials for external quality assurance. The questions concerning new amplification technologies like isothermal nucleic acid amplification, potentially suited to significantly decrease turnaround times, were complemented by questions to evaluate the present status of NATs. Besides end-users, companies were also addressed by sending out a manufacturer specific questionnaire. Analysis of the answers from 48 laboratories in 14 European countries revealed that a much shorter turnaround time is requested for selected pathogens compared to about 2 h or longer when applying temperature cycling amplification, i.e. PCR. In this context, most frequently mentioned were MRSA, norovirus, influenza A and B viruses, cytomegalovirus (CMV) as well as hepatitis B virus (HBV) and hepatitis C virus (HCV). At present, 8% of the laboratories having participated in this survey apply isothermal amplification of nucleic acid to identify infectious pathogens.
KW - Nucleic acid tests
KW - Infectious diseases
KW - Virus detection
KW - Bacteria detection
KW - Isothermal nucleic acid amplification
KW - Status report
KW - Questionnaire
KW - NAT
KW - PCR
PY - 2014
UR - https://nbn-resolving.org/urn:nbn:de:0183-lab0000160
UR - http://www.egms.de/static/en/journals/lab/2015-6/lab000016.shtml
DO - https://doi.org/10.3205/lab000016
SN - 1869-4241
VL - 6
SP - 1
EP - 11
PB - GMS
CY - Düsseldorf
AN - OPUS4-36133
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Mozetic, M.
A1 - Ostrikov, K.
A1 - Ruzic, D.N.
A1 - Curreli, D.
A1 - Cvelbar, U.
A1 - Vesel, A.
A1 - Primc, G.
A1 - Leisch, M.
A1 - Jousten, K.
A1 - Malyshev, O.B.
A1 - Hendricks, J.H.
A1 - Kövér, L.
A1 - Tagliaferro, A.
A1 - Conde, O.
A1 - Silvestre, A.J.
A1 - Giapintzakis, J.
A1 - Buljan, M.
A1 - Radic, N.
A1 - Drazic, G.
A1 - Bernstorff, S.
A1 - Biedermann, H.
A1 - Kylián, O.
A1 - Hanus, J.
A1 - Milosevic, S.
A1 - Galtayries, A.
A1 - Dietrich, Paul
A1 - Unger, Wolfgang
A1 - Lehocky, M.
A1 - Sedlarik, V.
A1 - Stana-Kleinschek, K.
A1 - Drmota-Petric, A.
A1 - Pireaux, J.J.
A1 - Rogers, J.W.
A1 - Anderle, M.
T1 - Recent advances in vacuum sciences and applications
N2 - Recent advances in vacuum sciences and applications are reviewed. Novel optical interferometer cavity devices enable pressure measurements with ppm accuracy. The innovative dynamic vacuum standard allows for pressure measurements with temporal resolution of 2 ms. Vacuum issues in the construction of huge ultra-high vacuum devices worldwide are reviewed. Recent advances in surface science and thin films include new phenomena observed in electron transport near solid surfaces as well as novel results on the properties of carbon nanomaterials. Precise techniques for surface and thin-film characterization have been applied in the conservation technology of cultural heritage objects and recent advances in the characterization of biointerfaces are presented. The combination of various vacuum and atmospheric-pressure techniques enables an insight into the complex phenomena of protein and other biomolecule conformations on solid surfaces. Studying these phenomena at solid–liquid interfaces is regarded as the main issue in the development of alternative techniques for drug delivery, tissue engineering and thus the development of innovative techniques for curing cancer and cardiovascular diseases. A review on recent advances in plasma medicine is presented as well as novel hypotheses on cell apoptosis upon treatment with gaseous plasma. Finally, recent advances in plasma nanoscience are illustrated with several examples and a roadmap for future activities is presented.
KW - Vacuum
KW - Surface
KW - Plasma
KW - Interface
KW - Nanoscience
PY - 2014
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-304884
DO - https://doi.org/10.1088/0022-3727/47/15/153001
SN - 0022-3727
SN - 1361-6463
VL - 47
IS - 15
SP - 153001-1
EP - 153001-23
PB - IOP Publ.
CY - Bristol
AN - OPUS4-30488
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Rades, Steffi
A1 - Hodoroaba, Vasile-Dan
A1 - Salge, T.
A1 - Wirth, Thomas
A1 - Lobera, M.P.
A1 - Labrador, R.H.
A1 - Natte, Kishore
A1 - Behnke, Thomas
A1 - Gross, Thomas
A1 - Unger, Wolfgang
T1 - High-resolution imaging with SEM/T-SEM, EDX and SAM as a combined methodical approach for morphological and elemental analyses of single engineered nanoparticles
N2 - The combination of complementary characterization techniques such as SEM (Scanning Electron Microscopy), T-SEM (Scanning Electron Microscopy in Transmission Mode), EDX (Energy Dispersive X-ray Spectroscopy) and SAM (Scanning Auger Microscopy) has been proven to be a powerful and relatively quick characterization strategy for comprehensive morphological and chemical characterization of individual silica and titania nanoparticles. The selected real life test materials, silica and titania, are listed in the OECD guidance manual as representative examples because they are often used as commercial nanomaterials. Imaging by high resolution SEM and in the transmission mode by T-SEM allows almost simultaneous surface and in-depth inspection of the same particle using the same instrument. EDX and SAM enable the chemical characterization of bulk and surface of individual nanoparticles. The core–shell properties of silica based materials are addressed as well. Titania nominally coated by silane purchased from an industrial source has been found to be inhomogeneous in terms of chemical composition.
KW - surface and in-depth inspection
KW - silica nanoparticles
KW - titania nanoparticles
PY - 2014
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-316296
DO - https://doi.org/10.1039/c4ra05092d
SN - 2046-2069
VL - 4
IS - 91
SP - 49577
EP - 49587
PB - RSC Publishing
CY - London
AN - OPUS4-31629
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Guo, Y.
A1 - Lippitz, Andreas
A1 - Saftien, P.
A1 - Unger, Wolfgang
A1 - Kemnitz, E.
T1 - Tuning the surface properties of novel ternary iron(III) fluoride-based catalysts using the template effect of the matrix
N2 - Solgel prepared ternary FeF3–MgF2 materials have become promising heterogeneous catalysts due to their porosity and surface Lewis/Brønsted acidity (bi-acidity). Despite the good catalytic performance, nanoscopic characterisations of this type of material are still missing and the key factors controlling the surface properties have not yet been identified, impeding both a better understanding and further development of ternary fluoride catalysts. In this study, we characterised the interaction between the bi-acidic component (FeF3) and the matrix (MgF2) on the nano-scale. For the first time, the formation pathway of FeF3–MgF2 was profiled and the template effect of MgF2 during the synthesis process was discovered. Based on these new insights two novel materials, FeF3–CaF2 and FeF3–SrF2, were established, revealing that with decreasing the atomic numbers (from Sr to Mg), the ternary fluorides exhibited increasing surface acidity and surface area but decreasing pore size. These systematic changes gave rise to a panel of catalysts with tuneable surface and bulk properties either by changing the matrix alkaline earth metal fluoride or by adjusting their ratios to Fe or both. The template effect of the alkaline earth metal fluoride matrix was identified as the most probable key factor determining the surface properties and further influencing the catalytic performance in ternary fluoride based catalysts, and paves the way to targeted design of next-generation catalysts with tunable properties.
KW - Catalysis
KW - Surface analysis
KW - XPS
PY - 2015
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-327410
DO - https://doi.org/10.1039/c4dt03229b
SN - 1477-9226
SN - 1477-9234
SN - 1364-5447
VL - 44
IS - 11
SP - 5076
EP - 5085
PB - RSC
CY - Cambridge
AN - OPUS4-32741
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Heinrich, Thomas
A1 - Traulsen, Christoph Hans-Henning
A1 - Darlatt, Erik
A1 - Richter, S.
A1 - Poppenberg, J.
A1 - Traulsen, N.L.
A1 - Linder, I.
A1 - Lippitz, Andreas
A1 - Dietrich, Paul
A1 - Dib, B.
A1 - Unger, Wolfgang
A1 - Schalley, C.A.
T1 - The versatility of 'Click' reactions at surfaces: Molecular recognition at interfaces
N2 - In order to investigate molecular recognition on surfaces, an azide-functionalized monolayer was deposited on gold. The monolayer was characterized by X-ray photoelectron spectroscopy (XPS) and angle-resolved near-edge X-ray absorption fine structure (NEXAFS) experiments and the decomposition of the azide upon irradiation with X-ray beams was investigated. Subsequently, various alkyne-functionalized host and guest molecules were attached to the azide by 1,3-dipolar cycloaddition. These modified surfaces and their host–guest chemistry were analysed by XPS and angle-resolved NEXAFS. The reversibility of guest binding was shown for one example as a proof of principle.
KW - 'Click' reaction
KW - Azide-terminated surfaces
KW - SAMs
KW - Host guest molecules
KW - Molecular recognition at interfaces
PY - 2014
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-306463
DO - https://doi.org/10.1039/C4RA01730G
SN - 2046-2069
VL - 4
IS - 34
SP - 17694
EP - 17702
PB - RSC Publishing
CY - London
AN - OPUS4-30646
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sobol, Oded
A1 - Straub, F.
A1 - Wirth, Thomas
A1 - Holzlechner, G.
A1 - Böllinghaus, Thomas
A1 - Unger, Wolfgang
T1 - Real Time Imaging of Deuterium in a Duplex Stainless Steel Microstructure by Time-of-Flight SIMS
N2 - For more than one century, hydrogen assisted degradation of metallic microstructures has been identified as origin for severe technical component failures but the mechanisms behind have not yet been completely understood so far. Any in-situ observation of hydrogen transport phenomena in microstructures will provide more details for further elucidation of these degradation mechanisms. A novel experiment is presented which is designed to elucidate the permeation behaviour of deuterium in a microstructure of duplex stainless steel (DSS). A hydrogen permeation cell within a TOF-SIMS instrument enables electrochemical charging with deuterium through the inner surface of the cell made from DSS. The outer surface of the DSS permeation cell exposed to the vacuum has been imaged by TOF-SIMS vs. increasing time of charging with subsequent chemometric treatment of image data. This in-situ experiment showed evidently that deuterium is permeating much faster through the ferrite phase than through the austenite phase. Moreover, a direct proof for deuterium enrichment at the austenite-ferrite interface has been found.
KW - Characterization and analytical techniques
KW - Corrosion
KW - Imaging technique
KW - Mass spectrometry
PY - 2016
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-353872
UR - http://www.nature.com/articles/srep19929
DO - https://doi.org/10.1038/srep19929
SN - 2045-2322
VL - 6
IS - 19929
SP - 1
EP - 7
PB - nature publishing group
CY - London, United Kingdom
AN - OPUS4-35387
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Coelho Lima, Isabela
A1 - Robens-Radermacher, Annika
A1 - Titscher, Thomas
A1 - Kadoke, Daniel
A1 - Koutsourelakis, P.-S.
A1 - Unger, Jörg F.
T1 - Bayesian inference for random field parameters with a goal-oriented quality control of the PGD forwardmodel's accuracy
N2 - Numerical models built as virtual-twins of a real structure (digital-twins) are considered the future ofmonitoring systems. Their setup requires the estimation of unknown parameters, which are not directly measurable. Stochastic model identification is then essential, which can be computationally costly and even unfeasible when it comes to real applications. Efficient surrogate models, such as reduced-order method, can be used to overcome this limitation and provide real time model identification. Since their numerical accuracy influences the identification process, the optimal surrogate not only has to be computationally efficient, but also accurate with respect to the identified parameters. This work aims at automatically controlling the Proper Generalized Decomposition (PGD) surrogate’s numerical accuracy for parameter identification. For this purpose, a sequence of Bayesian model identification problems, in which the surrogate’s accuracy is iteratively increased, is solved with a variational Bayesian inference procedure. The effect of the numerical accuracy on the resulting posteriors probability density functions is analyzed through two metrics, the Bayes Factor (BF) and a criterion based on the Kullback-Leibler (KL) divergence. The approach is demonstrated by a simple test example and by two structural problems. The latter aims to identify spatially distributed damage, modeled with a PGD surrogate extended for log-normal random fields, in two different structures: a truss with synthetic data and a small, reinforced bridge with real measurement data. For all examples, the evolution of the KL-based and BF criteria for increased accuracy is shown and their convergence indicates when model refinement no longer affects the identification results.
KW - Variational inference
KW - Proper generalized decomposition
KW - Goal-oriented
KW - Digital twin
KW - Random field
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-555755
DO - https://doi.org/10.1007/s00466-022-02214-6
SN - 1432-0924
SP - 1
EP - 22
PB - Springer
CY - Berlin
AN - OPUS4-55575
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Oster, Simon
A1 - Fritsch, Tobias
A1 - Ulbricht, Alexander
A1 - Mohr, Gunther
A1 - Bruno, Giovanni
A1 - Maierhofer, Christiane
A1 - Altenburg, Simon
T1 - On the Registration of Thermographic In Situ Monitoring Data and Computed Tomography Reference Data in the Scope of Defect Prediction in Laser Powder Bed Fusion
N2 - The detection of internal irregularities is crucial for quality assessment in metal-based additive manufacturing (AM) technologies such as laser powder bed fusion (L-PBF). The utilization of in-process thermography as an in situ monitoring tool in combination with post-process X-ray micro computed tomography (XCT) as a reference technique has shown great potential for this aim. Due to the small irregularity dimensions, a precise registration of the datasets is necessary as a
requirement for correlation. In this study, the registration of thermography and XCT reference datasets of a cylindric specimen containing keyhole pores is carried out for the development of a porosity prediction model. The considered datasets show variations in shape, data type and dimensionality, especially due to shrinkage and material elevation effects present in the manufactured part. Since the resulting deformations are challenging for registration, a novel preprocessing methodology is introduced that involves an adaptive volume adjustment algorithm which is based on the porosity distribution in the specimen. Thus, the implementation of a simple three-dimensional image-to-image registration is enabled. The results demonstrate the influence of the part deformation on the resulting porosity location and the importance of registration in terms of irregularity prediction.
KW - Selective laser melting (SLM)
KW - Laser powder bed fusion (L-PBF)
KW - Additive manufacturing (AM)
KW - Process monitoring
KW - Infrared thermography
KW - X-ray computed tomography (XCT)
KW - Defect detection
KW - Image registration
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-549412
DO - https://doi.org/10.3390/met12060947
VL - 12
IS - 6
SP - 1
EP - 21
PB - MDPI
AN - OPUS4-54941
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Straße, Anne
A1 - Gumenyuk, Andrey
A1 - Rethmeier, Michael
T1 - Study on Duplex Stainless Steel Powder Compositions for the Coating of thick Plates of Laser Beam Welding
N2 - Duplex stainless steels combine the positive properties of its two phases, austenite and ferrite. Due to its good corrosion resistance, high tensile strength, and good ductility, it has multiple applications. But laser beam welding of duplex steels changes the balanced phase distribution in favor of ferrite. This results in a higher vulnerability to corrosion and a lower ductility. Herein, different powder combinations consisting of duplex and nickel for coating layers by laser metal deposition (LMD) are investigated. Afterward, laser tracks are welded, and the temperature cycles are measured. The ferrite content of the tracks is analyzed by feritscope, metallographic analysis, and electron backscatter diffraction. The goal is the development of a powder mixture allowing for a duplex microstructure in a two-step process, where first the edges of the weld partners are coated with the powder mixture by LMD and second those edges are laser beam welded. The powder mixture identified by the pretests is tested in the two-step process and analyzed by metallographic analysis, energy-dispersive X-ray spectroscopy, and
Vickers hardness tests. The resulting weld seams show a balanced duplex microstructure with a homogenous nickel distribution and a hardness of the weld seam similar to the base material.
KW - Duplex AISI 2205
KW - Laser metal deposition
KW - Laser beam welding
KW - Nickel
KW - Stainless steels
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-547024
DO - https://doi.org/10.1002/adem.202101327
SN - 1438-1656
SP - 1
EP - 11
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-54702
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Straße, Anne
A1 - Bakir, Nasim
A1 - Gumenyuk, Andrey
A1 - Rethmeier, Michael
ED - Schmidt, M.
ED - Vollertsen, F.
ED - Schmidt, B. M.
T1 - Preliminary study to investigate the applicability of optical strain measurement technique for the detection of hot cracks in laser metal deposited layers
N2 - Laser metal deposition (LMD) as an additive manufacturing technique became increasingly important in recent years and thus the demand for component safety. This is the reason, for the need for reliable in-situ defect detection techniques. For laser beam weld seams an optical measurement technique based on an optical flow algorithm was successfully used to define the critical straining conditions that lead to hot cracking. This algorithm was adapted for bead-on-plate weld seams on LMD deposited layers of IN718 alloy while performing external strain on the specimen in an externally loaded hot cacking test facility. The resulting transversal hot cracks along the weld seam were localized via X-Ray inspection and the type of cracking confirmed by Scanning Electron Microscopy (SEM). The strain distribution was measured in the vicinity of the solidification front and correlated to the detected hot cracks. Based on the results this technique could be adopted for LMD experiments.
T2 - 12th CIRP Conference on Photonic Technologies [LANE 2022]
CY - Fürth, Germany
DA - 04.09.2022
KW - Laser Metal Deposition (LMD)
KW - Strain measurement
KW - Optical flow
KW - Critical strain
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556445
DO - https://doi.org/10.1016/j.procir.2022.08.034
VL - 111
SP - 335
EP - 339
PB - Elsevier B.V.
CY - Amsterdam
AN - OPUS4-55644
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Bruno, Giovanni
A1 - Maierhofer, Christiane
T1 - Advanced Characterization and On-Line Process Monitoring of Additively Manufactured Materials and Components
N2 - Additive manufacturing (AM) techniques have risen to prominence in many industrial sectors. This rapid success of AM is due to the freeform design, which offers enormous possibilities to the engineer, and to the reduction of waste material, which has both environmental and economic advantages. Even safety-critical parts are now being produced using AM. This enthusiastic penetration of AM in our daily life is not yet paralleled by a thorough characterization and understanding of the microstructure of materials and of the internal stresses of parts. The same holds for the understanding of the formation of defects during manufacturing. While simulation efforts are sprouting and some experimental techniques for on-line monitoring are available, still little is known about the propagation of defects throughout the life of a component (from powder to operando/service conditions). This Issue was aimed at collecting contributions about the advanced characterization of AM materials and components (especially at large-scale experimental facilities such as Synchrotron and Neutron sources), as well as efforts to liaise on-line process monitoring to the final product, and even to the component during operation. The goal was to give an overview of advances in the understanding of the impacts of microstructure and defects on component performance and life at several length scales of both defects and parts.
KW - Non-destructive Testing
KW - Additive Manufacturing
KW - Materials Characterization
KW - Online Monitoring
KW - Residual Stress
KW - Thermography
KW - Computed Tomography
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556833
DO - https://doi.org/10.3390/met12091498
VL - 12
IS - 9
SP - 1
EP - 3
PB - MDPI
CY - Basel, Schweiz
AN - OPUS4-55683
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Priebe, Nsesheye Susan
A1 - Gluth, Gregor
A1 - Sturm, Patrick
A1 - Vogler, Nico
A1 - Kühne, Hans-Carsten
T1 - Comparison of calcined illitic clays (brick clays) and low-grade kaolinitic clays as supplementary cementitious materials
N2 - The use of calcined clays as supplementary cementitious materials (SCMs) has been identified as a viable option to decrease the CO2 emissions related to cement production. However, while extensive data is available about kaolinitic clays in this context, other clays such as illitic clays appear to be under-studied. Therefore, in the present study, two illitic clays were compared to two low-grade kaolinitic clays in terms of transformations in the calcination temperature range 650–900 °C, and performance of the calcined clays in blended cement pastes as measured by strength evolution, heat release, hydrated phase formation and portlandite consumption. The illitic clays required a higher calcination temperature for complete dehydroxylation of their illite than what is necessary for dehydroxylation of kaolinite. These higher calcination temperatures also led to particle sintering, significantly decreasing the specific surface area of the illitic clays, particularly for the clay with the higher Fe2O3 content. Nevertheless, while the kaolinitic clays generally exhibited the best performance as SCM, the illitic clay with lower Fe2O3 content performed similar to the kaolinitic clays when calcined at optimum temperature and applied at a moderate substitution rate. These findings demonstrate that several different clays have the potential to be used as SCM and indicate possible routes to identify suitable deposits for this purpose.
KW - Blended cement
KW - Calcined clay
KW - Brick clay
KW - Illite
KW - Kaolinite
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488195
DO - https://doi.org/10.1617/s11527-019-1393-2
SN - 1359-5997
SN - 1871-6873
N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S.
VL - 52
IS - 5
SP - Article Number 94
PB - Springer Nature
AN - OPUS4-48819
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Stroh, Julia
A1 - Feiler, Torvid
A1 - Ali, N. Z.
A1 - Minas da Piedade, M. E.
A1 - Emmerling, Franziska
T1 - Mechanistic Insights into a Sustainable Mechanochemical Synthesis of Ettringite
N2 - Mechanochemistry offers an environmentally benign and facile synthesis method for a variety of cement paste constituents. In addition, these methods can be used to selectively tune the properties of cement components. The mineral ettringite is an important component of cementitious materials and has additional technological potential due to its ion exchange properties.
Synthesis of ettringite via mechanochemistry is an environmentally friendly alternative to conventional wet-chemical synthesis established in industry. This contribution explores the mechanism of a two-step mechanochemical synthesis of ettringite, which was previously found to greatly improve the reaction conversion as compared with one-pot synthesis. The crystallinity of Al(OH)3 was found to decrease during the first stage of this mechanochemical synthesis. This was correlated to a significant decrease in the particle size of Al(OH)3 in this stage. No other significant changes were found for the other components, suggesting that mechanochemical activation of Al(OH)3 is responsible for the enhanced formation of ettringite by the two-step approach. The environmentally friendly approach developed for ettringite synthesis offers a versatile synthetic strategy, which can be applied to synthesise further cementitious materials.
KW - Ettringite
KW - Mechanochemistry
KW - Sustainability
KW - X-ray diffraction
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-489172
DO - https://doi.org/10.1002/open.201900215
VL - 8
IS - 7
SP - 1012
EP - 1019
PB - ChemPubSoc
AN - OPUS4-48917
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Borzekowski, Antje
A1 - Anggriawan, R.
A1 - Auliyati, M.
A1 - Kunte, Hans-Jörg
A1 - Koch, Matthias
A1 - Rohn, S.
A1 - Karlovsky, P.
A1 - Maul, Ronald
T1 - Formation of Zearalenone Metabolites in Tempeh Fermentation
N2 - Tempeh is a common food in Indonesia, produced by fungal fermentation of soybeans using Rhizopus sp., as well as Aspergillus oryzae, for inoculation. Analogously, for economic reasons, mixtures of maize and soybeans are used for the production of so-called tempeh-like products. For maize, a contamination with the mycoestrogen zearalenone (ZEN) has been frequently reported. ZEN is a mycotoxin which is known to be metabolized by Rhizopus and Aspergillus species. Consequently, this study focused on the ZEN transformation during tempeh fermentation. Five fungal strains of the genera Rhizopus and Aspergillus, isolated from fresh Indonesian tempeh and authentic Indonesian inocula, were utilized for tempeh manufacturing from a maize/soybean mixture (30:70) at laboratory-scale. Furthermore, comparable tempeh-like products obtained from Indonesian markets were analyzed. Results from the HPLC-MS/MS analyses show that ZEN is intensely transformed into its metabolites alpha-zearalenol (alpha-ZEL), ZEN-14-sulfate, alpha-ZEL-sulfate, ZEN-14-glucoside, and ZEN-16-glucoside in tempeh production. alpha-ZEL, being significantly more toxic than ZEN, was the main metabolite in most of the Rhizopus incubations, while in Aspergillus oryzae fermentations ZEN-14-sulfate was predominantly formed. Additionally, two of the 14 authentic samples were contaminated with ZEN, alpha-ZEL and ZEN-14-sulfate, and in two further samples, ZEN and alpha-ZEL, were determined. Consequently, tempeh fermentation of ZEN-contaminated maize/soybean mixture may lead to toxification of the food item by formation of the reductive ZEN metabolite, alpha-ZEL, under model as well as authentic conditions.
KW - Modified mycotoxins
KW - Zearalenone sulfate
KW - a-zearalenol
KW - Food fermentation
KW - Rhizopus and Aspergillus oryzae
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-491126
DO - https://doi.org/10.3390/molecules24152697
VL - 24
IS - 15
SP - 2697
PB - MDPI
AN - OPUS4-49112
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Nöller, Renate
A1 - Feldmann, Ines
A1 - Kasztovszky, Z.
A1 - Szőkefalvi-Nagy, Z.
A1 - Kovács, I.
T1 - Characteristic Features of Lapis Lazuli from Different Provenances, Revised by µXRF, ESEM, PGAA and PIXE
N2 - The objective of this study is to find out, to what extent the geochemical characteristics of lapis lazuli can be utilized in respect to its provenance. A wide range of variables is taken into consideration depending on the quantity of samples analysed from a specific geological region and the methods applied. In order to provide evidence, a multi-technique analytical approach using µXRF, ESEM, PGAA and PIXE is applied to samples from the most famous deposits of lapis lazuli. Special elements determined as fingerprints are compared in relation to the forming conditions obvious in textural features. The results and statistical output allow a differentiation that enables an optimized local classification of the blue stone. An absolute requirement for all geo-tracing performed on blue colored cultural objects of unknown provenance is awareness of the limits of analysis. The possible sources of lapis lazuli are tested by analysing the blue pigment used as paint on murals and ink on manuscripts from the Silk Road.
KW - Lapis lazuli
KW - Micro-XRF
KW - ESEM
KW - PGAA
KW - PIXE
KW - Pigment analyses
KW - Provenance studies
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-491181
DO - https://doi.org/10.17265/2328-2193/2019.02.003
SN - 2328-2193
VL - 7
IS - 2
SP - 57
EP - 69
PB - David
CY - New York, NY
AN - OPUS4-49118
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Herrmann, K.
A1 - Pech May, Nelson Wilbur
A1 - Retsch, M.
T1 - Photoacoustic thermal characterization of low thermal diffusivity thin films
N2 - The photoacoustic measurement technique is a powerful yet underrepresented method to characterize the thermal transport properties of thin films. For the case of isotropic low thermal diffusivity samples, such as glasses or polymers, we demonstrate a general approach to extract the thermal conductivity with a high degree of significance. We discuss in particular the influence of thermal effusivity, thermal diffusivity, and sample layer thickness on the significance and accuracy of this measurement technique. These fundamental thermal properties guide sample and substrate selection to allow for a feasible thermal transport characterization. Furthermore, our data evaluation allows us to directly extract the thermal conductivity from this transient technique, without separate determination of the volumetric heat capacity, when appropriate boundary conditions are fulfilled.
Using silica, poly(methyl methacrylate) (PMMA) thin films, and various substrates (quartz, steel, and silicon), we verify the quantitative correctness of our analytical approach.
KW - Thermal conductivity
KW - Photoacoustic characterization
KW - Thin film characterization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-528743
DO - https://doi.org/10.1016/j.pacs.2021.100246
SN - 2213-5979
VL - 22
SP - 100246
PB - Elsevier
AN - OPUS4-52874
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Pech May, Nelson Wilbur
A1 - Tabasco-Novelo, Carolina
A1 - Quintana, Patricia
A1 - Rodriguez-Gattorno, Geonel
A1 - Alvarado-Gil, Juan J.
T1 - Evidence of a Thermal Diffusivity Gap in Sintered Li–Co–Sb–O Solid Solutions
N2 - In this work, the thermal properties of ternary Li₃ₓCo₇₋₄ₓSb₂₊ₓO₁₂ solid solutions are studied for different concentrations in the range 0 ≤ x ≤ 0.7. Samples are elaborated at four different sintering temperatures: 1100, 1150, 1200 and 1250 °C. The effect of increasing the content of Li⁺ and Sb⁵⁺, accompanied by the reduction of Co²⁺, on the thermal properties is studied. It is shown that a thermal diffusivity gap, which is more pronounced for low values of x, can be triggered at a certain threshold sintering temperature (around 1150 °C in this study). This effect is explained by the increase of contact area between adjacent grains. Nevertheless, this effect is found to be less pronounced in the thermal conductivity. Moreover, a new framework for heat diffusion in solids is presented that establishes that both the heat flux and the thermal energy (or heat) satisfy a diffusion equation and therefore highlights the importance of thermal diffusivity in transient heat conduction phenomena.
KW - General Chemical Engineering
KW - General Chemistry
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-593248
DO - https://doi.org/10.1021/acsomega.2c07557
SN - 2470-1343
VL - 8
IS - 8
SP - 7808
EP - 7815
PB - American Chemical Society (ACS)
CY - Washington, DC
AN - OPUS4-59324
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lecompagnon, Julien
A1 - Ahmadi, Samim
A1 - Hirsch, Philipp Daniel
A1 - Rupprecht, C.
A1 - Ziegler, Mathias
T1 - Thermographic detection of internal defects using 2D photothermal super resolution reconstruction with sequential laser heating
N2 - Thermographic photothermal super resolution reconstruction enables the resolution of internal defects/inhomogeneities below the classical limit, which is governed by the diffusion properties of thermal wave propagation. Based on a combination of the application of special sampling strategies and a subsequent numerical optimization step in post-processing, thermographic super resolution has already proven to be superior to standard thermographic methods in the detection of one-dimensional defect/inhomogeneity structures. In our work, we report an extension of the capabilities of the method for efficient detection and resolution of defect cross sections with fully two-dimensional structured laser-based heating. The reconstruction is carried out using one of two different algorithms that are proposed within this work. Both algorithms utilize the combination of several coherent measurements using convex optimization and exploit the sparse nature of defects/inhomogeneities as is typical for most nondestructive testing scenarios. Finally, the performance of each algorithm is rated on reconstruction quality and algorithmic complexity. The presented experimental approach is based on repeated spatially structured heating by a high power laser. As a result, a two-dimensional sparse defect/inhomogeneity map can be obtained. In addition, the obtained results are compared with those of conventional thermographic inspection methods that make use of homogeneous illumination. Due to the sparse nature of the reconstructed defect/inhomogeneity map, this comparison is performed qualitatively.
KW - Thermography
KW - Super resolution
KW - NDT
KW - Inspection
KW - Internal defects
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-548351
DO - https://doi.org/10.1063/5.0088102
SN - 1089-7550
VL - 131
IS - 18
SP - 1
EP - 12
PB - AIP Publishing
AN - OPUS4-54835
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Bernegger, Raphael
A1 - Maierhofer, Christiane
A1 - Altenburg, Simon
T1 - Quantification of delaminations in semitransparent solids using pulsed thermography and mathematical 1D models
N2 - Material defects in fiber reinforced polymers such as delaminations can rapidly degrade the material properties or can lead to the failure of a component. Pulse thermography (PT) has proven to be a valuable tool to identify and quantify such defects in opaque materials. However, quantification of delaminations within semitransparent materials is extremely challenging. We present an approach to quantify delaminations within materials being semitransparent within the wavelength ranges of the optical excitation sources as well as of the infrared (IR) camera. PT experimental data of a glass fiber reinforced polymer with a real delamination within the material were reconstructed by one dimensional (1D) mathematical models. These models describe the heat diffusion within the material and consider semitransparency to the excitation source as well to the IR camera, thermal losses at the samples surfaces and a thermal contact resistance between the two layers describing the delamination. By fitting the models to the PT data, we were able to determine the depth of the delamination very accurately. Additionally, we analyzed synthetic PT data from a 2D simulation with our 1D-models to show how the thermal contact resistance is influenced by lateral heat flow within the material.
KW - Pulsed thermography
KW - Quantification
KW - Numerical simulation
KW - Analytical model
KW - Semitransparent
KW - GFRP
KW - Delamination
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-505766
DO - https://doi.org/10.1007/s10765-020-02642-7
VL - 41
IS - 5
SP - Article number: 67
PB - Springer
AN - OPUS4-50576
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Treiling, S.
A1 - Wang, Cui
A1 - Förster, C.
A1 - Reichenauer, F.
A1 - Kalmbach, J.
A1 - Boden, P.
A1 - Harris, J. P.
A1 - Carrella, L. M.
A1 - Rentschler, E.
A1 - Resch-Genger, Ute
A1 - Reber, C.
A1 - Seitz, M.
A1 - Gerhards, M.
A1 - Heinze, K.
T1 - Luminescence and Light-Driven Energy and Electron Transfer from an Exceptionally Long-Lived Excited State of a Non-Innocent Chromium(III) Complex
N2 - Photoactive metal complexes employing Earth‐abundant metal ions are a key to sustainable photophysical and photochemical applications. We exploit the effects of an inversion center and ligand non‐innocence to tune the luminescence and photochemistry of the excited state of the [CrN6] chromophore [Cr(tpe)2]3+ with close to octahedral symmetry (tpe=1,1,1‐tris(pyrid‐2‐yl)ethane). [Cr(tpe)2]3+ exhibits the longest luminescence lifetime (τ=4500 μs) reported up to date for a molecular polypyridyl chromium(III) complex together with a very high luminescence quantum yield of Φ=8.2 % at room temperature in fluid solution. Furthermore, the tpe ligands in [Cr(tpe)2]3+ are redox non‐innocent, leading to reversible reductive chemistry. The excited state redox potential and lifetime of [Cr(tpe)2]3+ surpass those of the classical photosensitizer [Ru(bpy)3]2+ (bpy=2,2′‐bipyridine) enabling energy transfer (to oxygen) and photoredox processes (with azulene and tri(n‐butyl)amine).
KW - Quantum yield
KW - Cr(III) complex
KW - Longst luminescence lifetime
KW - Electron transfer
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494870
DO - https://doi.org/10.1002/anie.201909325
VL - 58
SP - 2
EP - 13
PB - Wiley-VCH
AN - OPUS4-49487
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Ghasem Zadeh Khorasani, Media
A1 - Elert, Anna Maria
A1 - Hodoroaba, Vasile-Dan
A1 - Agudo Jácome, Leonardo
A1 - Altmann, Korinna
A1 - Silbernagl, Dorothee
A1 - Sturm, Heinz
T1 - Short- and long-range mechanical and chemical interphases caused by interaction of Boehmite (γ-AlOOH) with anhydride-cured epoxy resins
N2 - Understanding the interaction between boehmite and epoxy and the formation of their interphases with different mechanical and chemical structures is crucial to predict and optimize the properties of epoxy-boehmite nanocomposites. Probing the interfacial properties with atomic force microscopy (AFM)-based methods, especially particle-matrix long-range interactions, is challenging. This is due to size limitations of various analytical methods in resolving nanoparticles and their interphases, the overlap of interphases, and the effect of buried particles that prevent the accurate interphase property measurement. Here, we develop a layered model system in which the epoxy is cured in contact with a thin layer of hydrothermally synthesized boehmite. Different microscopy methods are employed to evaluate the interfacial properties. With intermodulation atomic force microscopy (ImAFM) and amplitude dependence force spectroscopy (ADFS), which contain information about stiffness, electrostatic, and van der Waals forces, a soft interphase was detected between the epoxy and boehmite. Surface potential maps obtained by scanning Kelvin probe microscopy (SKPM) revealed another interphase about one order of magnitude larger than the mechanical interphase. The AFM-infrared spectroscopy (AFM-IR) technique reveals that the soft interphase consists of unreacted curing agent. The long-range electrical interphase is attributed to the chemical alteration of the bulk epoxy and the formation of new absorption bands.
KW - Nanocomposites
KW - Interphase
KW - Intermodulation AFM
KW - Electron microscopy
KW - Infrared nano AFM
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483672
UR - https://www.mdpi.com/2079-4991/9/6/853/htm
DO - https://doi.org/10.3390/nano9060853
SN - 2079-4991
VL - 9
IS - 6
SP - 853, 1
EP - 20
PB - MDPI
AN - OPUS4-48367
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Munsch, Sarah Mandy
A1 - Strangfeld, Christoph
A1 - Kruschwitz, Sabine
ED - Kärger, J.
ED - Heitjans, P.
T1 - Determining the pore size distribution in synthetic and building materials using 1D NMR
N2 - NMR is gaining increasing interest in civil engineering applications for the use of microstructure characterization as e.g. pore size determination and monitoring of moisture transport in porous materials. In this study, the use of NMR as a tool for pore size characterization was investigated. For our study we used screed and synthetic materials at partial and full saturation. A successful determination could be achieved when having a reference or calibration method, although partly diffusion effects have been registered. Due to these diffusion effects, for the determination of pore size distributions of synthetic materials another NMR device was needed. Finally, the determination of the surface relaxivity of screed (50 μm/s) led to a higher value than first expected from literature.
T2 - 14th International Bologna Conference on Magnetic Resonance in Porous Media
CY - Gainesville, FL, USA
DA - 18.02.2018
KW - NMR relaxometry
KW - Pore size distribution
KW - Building materials
KW - Porous materials
KW - Surface relaxivity
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483680
UR - https://diffusion.uni-leipzig.de/pdf/volume31/diff_fund_31(2019)02.pdf
SN - 1862-4138
N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M.
VL - 31
IS - 2
SP - 1
EP - 9
PB - University of Leipzig
CY - Leipzig
AN - OPUS4-48368
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Tarantini, A.
A1 - Wegner, Karl David
A1 - Dussert, F.
A1 - Sarret, G.
A1 - Beal, D.
A1 - Mattera, L.
A1 - Lincheneau, C.
A1 - Proux, O.
A1 - Truffier-Boutry, D.
A1 - Moriscot, C.
A1 - Gallet, B.
A1 - Jouneau, P.-H.
A1 - Reiss, P.
A1 - Carriere, M.
T1 - Physicochemical alterations and toxicity of InP alloyed quantum dots aged in environmental conditions: A safer by design evaluation
N2 - Due to their unique optical properties, quantum dots (QDs) are used in a number of optoelectronic devices and are forecasted to be used in the near future for biomedical applications. The most popular QD composition consists of cadmium selenide (CdSe) or cadmium telluride (CdTe), which has been shown to pose health risks due to the release of toxic cadmium (Cd) ions. Due to similar optical properties but lower intrinsic toxicity, indium phosphide (InP) QDs have been proposed as a safer alternative. Nevertheless, investigations regarding their safety and possible toxicological effects are still in their infancy.
The fate and toxicity of seven different water-dispersible indium (In) based QDs, either pristine or after ageing in a climatic chamber, was evaluated. The core of these QDs was composed of indium, zinc and phosphorus (InZnP) or indium, zinc, phosphorus and sulfur (InZnPS). They were assessed either as core-only or as core-shell QDs, for which the core was capped with a shell of zinc, selenium and sulfur (Zn(Se,S)). Their Surface was functionalized using either penicillamine or glutathione.
In their pristine form, these QDs showed essentially no cytotoxicity. The particular case of InZnPS QD showed that core-shell QDs were less cytotoxic than core-only QDs. Moreover, surface functionalization with either penicillamine or glutathione did not appreciably influence cytotoxicity but affected QD stability. These QDs did not lead to over-accumulation of reactive oxygen species in exposed cells, or to any oxidative damage to cellular DNA. However, accelerated weathering in a climatic chamber led to QD precipitation and degradation, together with significant cytotoxic effects. Ageing led to dissociation of IneP and ZneS bonds, and to complexation of In Zn ions with carboxylate and/or phosphate moieties.
These results show that InZnP and InZnPS alloyed QDs are safer alternatives to CdSe QDs. They underline the necessity to preserve as much as possible the structural integrity of QDs, for instance by developing more robust shells, in order to ensure their safety for future applications.
KW - Indium phosphide
KW - Safe by design
KW - Toxicity
KW - EXAFS
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483070
DO - https://doi.org/10.1016/j.impact.2019.100168
VL - 14
SP - 100168-1
EP - 100168-13
PB - Elsevier
AN - OPUS4-48307
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - de Souza Machado, A. A.
A1 - Lau, C. W.
A1 - Kloas, W.
A1 - Bergmann, J.
A1 - Bachelier, J. B.
A1 - Faltin, E.
A1 - Becker, Roland
A1 - Görlich, A. S.
A1 - Rillig, M. C.
T1 - Microplastics can change soil properties and affect plant performance
N2 - Microplastics can affect biophysical properties of the soil. However, little is known about the cascade of events in fundamental levels of terrestrial ecosystems, i.e., starting with the changes in soil abiotic properties and propagating across the various components of soil−plant interactions, including soil microbial communities and plant traits. We investigated here the effects of six different microplastics (polyester fibers, polyamide beads, and four fragment types: polyethylene, polyester terephthalate, polypropylene, and polystyrene) on a broad suite of proxies for soil health and performance of spring onion (Allium fistulosum). Significant changes were observed in plant biomass, tissue elemental composition, root traits, and soil microbial activities. These plant and soil responses to microplastic exposure were used to propose a causal model for the mechanism of the effects. Impacts were dependent on particle type, i.e., microplastics with a shape similar to other natural soil particles elicited smaller differences from control. Changes in soil structure and water dynamics may explain the observed results in which polyester fibers and polyamide beads triggered the most pronounced impacts on plant traits and function. The findings reported here imply that the pervasive microplastic contamination in soil may have consequences for plant performance and thus for agroecosystems and terrestrial biodiversity.
KW - Mikroplastik
KW - Boden
KW - Pflanzenwachstum
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-484181
DO - https://doi.org/10.1021/acs.est.9b01339
SN - 0013-936X
SN - 1520-5851
VL - 53
IS - 10
SP - 6044
EP - 6052
PB - ACS
AN - OPUS4-48418
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Huang, J.
A1 - Tarábek, J.
A1 - Kulkarni, R.
A1 - Wang, Cui
A1 - Dračínský, M.
A1 - Smales, Glen Jacob
A1 - Pauw, Brian Richard
A1 - Resch-Genger, Ute
A1 - Bojdys, M. J.
T1 - A π-conjugated, covalent phosphinine framework
N2 - Structural modularity of polymer frameworks is a key advantage of covalent organic polymers, however, only C, N, O, Si and S have found their way into their building blocks so far. Here, we expand the toolbox available to polymer and materials chemists by one additional nonmetal, phosphorus. Starting with a building block that contains a λ⁵‐phosphinine (C₅P) moiety, we evaluate a number of polymerisation protocols, finally obtaining a π‐conjugated, covalent phosphinine‐based framework (CPF‐1) via Suzuki‐Miyaura coupling. CPF‐1 is a weakly porous polymer glass (72.4 m2 g‐1 N2 BET at 77 K) with green fluorescence (λmax 546 nm) and extremely high thermal stability. The polymer catalyzes hydrogen evolution from water under UV and visible light irradiation without the need for additional co‐catalyst at a rate of 33.3 μmol h‐¹ g‐¹. Our results demonstrate for the first time the incorporation of the phosphinine motif into a complex polymer framework. Phosphinine‐based frameworks show promising electronic and optical properties that might spark future interest in their applications in light‐emitting devices and heterogeneous catalysis.
KW - Phosphinine
KW - Fully aromatic frameworks
KW - Suzuki-Miyaura coupling
KW - Polymers
KW - Fluorescence
KW - Small-angle scattering
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-485330
DO - https://doi.org/10.1002/chem.201900281
SP - 2
EP - 10
PB - Wiley VCH-Verlag
CY - Weinheim
AN - OPUS4-48533
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Belenguer, A.
A1 - Michalchuk, Adam
A1 - Lampronti, G
A1 - Sanders, J
T1 - Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions
N2 - We here explore how ball-mill-grinding frequency affects the kinetics of a disulfide exchange reaction. Our kinetic data show that the reaction progress is similar at all the frequencies studied (15–30 Hz), including a significant induction time before the nucleation and growth process starts. This indicates that to start the reaction an initial energy accumulation is necessary. Other than mixing, the energy supplied by the mechanical treatment has two effects: (i) reducing the crystal size and (ii) creating defects in the structure. The crystal-breaking process is likely to be dominant at first becoming less important later in the process when the energy supplied is stored at the molecular level as local crystal defects. This accumulation is taken here to be the rate-determining step. We suggest that the local defects accumulate preferentially at or near the crystal surface. Since the total area increases exponentially when the crystal size is reduced by the crystal-breaking process, this can further explain the exponential dependence of the onset time on the milling frequency.
KW - Mechanochemistry
KW - Kinetics
KW - Diffraction
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483361
DO - https://doi.org/10.3762/bjoc.15.120
SN - 2195-951X
VL - 15
SP - 1226
EP - 1235
PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften
CY - Frankfurt, M.
AN - OPUS4-48336
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hahn, Marc Benjamin
T1 - Temperature in micromagnetism: Cell size and scaling effects of the stochastic Landau-Lifshitz equation
N2 - The movement of the macroscopic magnetic moment in ferromagnetic systems can be described by the Landau-Lifshitz (LL) or Landau-Lifshitz-Gilbert (LLG) equation. These equations are strictly valid only at absolute zero temperature. To include temperature effects a stochastic version of the LL or LLG equation for a spin density of one per unit cell can be used instead. To apply the stochastic LL to micromagnetic simulations, where the spin density per unit cell is generally higher, a conversion regarding simulation cell size and temperature has to be established. Based on energetic considerations, a conversion for ferromagnetic bulk and thin film systems is proposed. The conversion is tested in micromagnetic simulations which are performed with the Object Oriented Micromagnetic Framework (OOMMF). The Curie temperatures of bulk Nickel, Cobalt and Iron systems as well as Nickel thin-film systems with thicknesses between 6.3 mono layer (ML) and 31ML are determined from micromagnetic simulations. The results show a good agreement with experimentally determined Curie temperatures of bulk and thin film systems when temperature scaling is performed according to the presented model.
KW - Micromagnetism
KW - LLG
KW - LL equation
KW - Landau Lifshitz equation
KW - Landau Lifshitz Gilbert equation
KW - Stochastic Landau Lifshitz equation
KW - Stochastic Landau Lifshitz Gilbert equation
KW - Curie temperature
KW - Magnetic Nanoparticles
KW - Thin film systems
KW - Temeprature scaling
KW - Phase transition
KW - Magnet coupling
KW - Ferromagnetism
KW - Superparamagnetism
KW - Paramagnetism
KW - Ni
KW - Co
KW - Fe
KW - Steel
KW - Nickel
KW - Cobalt
KW - Iron
KW - Temperature effects
KW - Cell size
KW - Damping factor
KW - Gamma
KW - Alpha
KW - Spin
KW - Magnetic moment
KW - Magnetic interacion
KW - Magnetization dynamics
KW - Domain wall
KW - Exchange length
KW - temeprature dependent exchange length
KW - Bloch wall
KW - Neel wall
KW - Exchange interaction
KW - Magnetic anisotropy
KW - Simulation
KW - OOMMF
KW - Object oriented micromagnetic framework
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-484610
DO - https://doi.org/10.1088/2399-6528/ab31e6
VL - 3
IS - 7
SP - 075009-1
EP - 075009-8
PB - IOPscience
CY - England
AN - OPUS4-48461
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Diercks, Philipp
A1 - Gläser, Dennis
A1 - Lünsdorf, Ontje
A1 - Selzer, Michael
A1 - Flemisch, Bernd
A1 - Unger, Jörg F.
T1 - Evaluation of tools for describing, reproducing and reusing scientific workflows
N2 - In the field of computational science and engineering, workflows often entail the application of various software, for instance, for simulation or pre- and postprocessing.
Typically, these components have to be combined in arbitrarily complex workflows to address a specific research question. In order for peer researchers to understand, reproduce and (re)use the findings of a scientific publication, several challenges have to be addressed. For instance, the employed workflow has to be automated and information on all used software must be available for a reproduction of the results. Moreover, the results must be traceable and the workflow documented and readable to allow for external verification and greater trust.
In this paper, existing workflow management systems (WfMSs) are discussed regarding their suitability for describing, reproducing and reusing scientific workflows. To this end, a set of general requirements for WfMSs were deduced from user stories that we deem relevant in the domain of computational science and engineering. On the basis of an exemplary workflow implementation, publicly hosted at GitHub (https://github.com/BAMresearch/NFDI4IngScientificWorkflowRequirements), a selection of different WfMSs is compared with respect to these requirements, to support fellow scientists in identifying the WfMSs that best suit their requirements.
KW - FAIR
KW - Reproducibility
KW - Scientific workflows
KW - Tool comparison
KW - Workflow management
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-584832
DO - https://doi.org/10.48694/inggrid.3726
VL - 1
IS - 1
SP - 1
EP - 27
AN - OPUS4-58483
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Titscher, Thomas
A1 - van Dijk, T.
A1 - Kadoke, Daniel
A1 - Robens-Radermacher, Annika
A1 - Herrmann, Ralf
A1 - Unger, Jörg F.
T1 - Bayesian model calibration and damage detection for a digital twin of a bridge demonstrator
N2 - Using digital twins for decision making is a very promising concept which combines simulation models with corresponding experimental sensor data in order to support maintenance decisions or to investigate the reliability. The quality of the prognosis strongly depends on both the data quality and the quality of the digital twin. The latter comprises both the modeling assumptions as well as the correct parameters of these models. This article discusses the challenges when applying this concept to realmeasurement data for a demonstrator bridge in the lab, including the data management, the iterative development of the simulation model as well as the identification/updating procedure using Bayesian inference with a potentially large number of parameters. The investigated scenarios include both the iterative identification of the structural model parameters as well as scenarios related to a damage identification. In addition, the article aims at providing all models and data in a reproducibleway such that other researcher can use this setup to validate their methodologies.
KW - Damage detection
KW - Finite element analysis
KW - Load identification
KW - Model updating
KW - Estimation
KW - System identification
KW - Variational Bayesian statistics
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-574496
DO - https://doi.org/10.1002/eng2.12669
SN - 2577-8196
SP - 1
EP - 27
PB - Wiley
CY - Hoboken, NJ
AN - OPUS4-57449
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Diercks, Philipp
A1 - Veroy, K.
A1 - Robens-Radermacher, Annika
A1 - Unger, Jörg F.
T1 - Multiscale modeling of linear elastic heterogeneous structures via localized model order reduction
N2 - In this paper, a methodology for fine scale modeling of large scale linear elastic structures is proposed, which combines the variational multiscale method, domain decomposition and model order reduction. The influence of the fine scale on the coarse scale is modelled by the use of an additive split of the displacement field, addressing applications without a clear scale separation. Local reduced spaces are constructed by solving an oversampling problem with random boundary conditions. Herein, we inform the boundary conditions by a global reduced problem and compare our approach using physically meaningful correlated samples with existing approaches using uncorrelated samples. The local spaces are designed such that the local contribution of each subdomain can be coupled in a conforming way, which also preserves the sparsity pattern of standard finite element assembly procedures. Several numerical experiments show the accuracy and efficiency of the method, as well as its potential to reduce the size of the local spaces and the number of training samples compared to the uncorrelated sampling.
KW - Multiscale methods
KW - Variational multiscale method
KW - Localized model order reduction
KW - Domain decomposition methods
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-580671
DO - https://doi.org/10.1002/nme.7326
SN - 0029-5981
SP - 1
EP - 23
PB - Wiley online library
AN - OPUS4-58067
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lecompagnon, Julien
A1 - Hirsch, Philipp Daniel
A1 - Rupprecht, C.
A1 - Ziegler, Mathias
T1 - Nondestructive thermographic detection of internal defects using pixel-pattern based laser excitation and photothermal super resolution reconstruction
N2 - In this work, we present a novel approach to photothermal super resolution based thermographic resolution of internal defects using two-dimensional pixel pattern-based active photothermal laser heating in conjunction with subsequent numerical reconstruction to achieve a high-resolution reconstruction of internal defect structures. With the proposed adoption of pixelated patterns generated using laser coupled high-power DLP projector technology the complexity for achieving true two-dimensional super resolution can be dramatically reduced taking a crucial step forward towards widespread practical viability. Furthermore, based on the latest developments in high-power DLP projectors, we present their first application for structured pulsed thermographic inspection of macroscopic metal samples. In addition, a forward solution to the underlying inverse problem is proposed along with an appropriate heuristic to find the regularization parameters necessary for the numerical inversion in a laboratory setting. This allows the generation of synthetic measurement data, opening the door for the application of machine learning based methods for future improvements towards full automation of the method. Finally, the proposed method is experimentally validated and shown to outperform several established conventional thermographic testing techniques while conservatively improving the required measurement times by a factor of 8 compared to currently available photothermal super resolution techniques.
KW - Thermography
KW - Super resolution
KW - NDT
KW - Inspection
KW - Internal defects
KW - DMD
KW - DLP
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-570551
DO - https://doi.org/10.1038/s41598-023-30494-2
SN - 2045-2322
VL - 13
SP - 1
EP - 13
PB - Nature Research
AN - OPUS4-57055
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Straße, Anne
A1 - Rethmeier, Michael
A1 - Gumenyuk, Andrey
T1 - Influence of edge‑deposited layers on mechanical and corrosion properties of laser beam welds of 15 mm thick AISI 2205 duplex stainless steel
N2 - AISI 2205 duplex stainless steel is used in a variety of industries, including the chemical and petrochemical industries. This is due to its high tensile strength combined with good ductility and corrosion resistance. However, in laser beam welding, these properties are negatively afected by the high cooling rates typical of the welding process. The resulting higher ferrrite content in the weld metal than in the base material leads to a reduction in the ductility and corrosion resistance of the welded joint. To overcome this problem, in this study, thick plates were coated by direct energy deposition (DED) prior to laser beam welding, whereas a duplex powder mixture containing a higher nickel concentration was used as a coating material. To improve the weld quality for the proposed two-step process, a method of additional material deposition instead of conventional tack weld was investigated. The resulting welded joints showed a well-balanced austenite to ferrite ratio and their properties and microstructure were verifed by metallographic analysis, electron backscatter difraction and Charpy impact testing. Using the standard ASTM G48 test method, it was found that the corrosion resistance of the welds was improved by a factor of four in average compared to the conventionally welded joints. The resulting properties, such as good ductility and corrosion resistance, of the welds with pre-coated edges showed good agreement with those of the base metal and confrmed the proposed two-step process as a promising alternative to the conventional approaches for welding thick duplex stainless steel plates.
KW - Laser metal deposition
KW - Laser beam welding
KW - Duplex steels
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581731
UR - https://rdcu.be/dlb6E
DO - https://doi.org/10.1007/s40194-023-01567-7
SN - 0043-2288
SP - 1
EP - 12
PB - Springer
AN - OPUS4-58173
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Andrés Arcones, Daniel
A1 - Weiser, M.
A1 - Koutsourelakis, F.
A1 - Unger, Jörg F.
T1 - A Bayesian Framework for Simulation-based Digital Twins of Bridges
N2 - Simulation-based digital twins have emerged as a powerful tool for evaluating the mechanical response of bridges. As virtual representations of physical systems, digital twins can provide a wealth of information that complements traditional inspection and monitoring data. By incorporating virtual sensors and predictive maintenance strategies, they have the potential to improve our understanding of the behavior and performance of bridges over time. However, as bridges age and undergo regular loading and extreme events, their tructural characteristics change, often differing from the predictions of their initial design. Digital twins must be continuously adapted to reflect these changes. In this article, we present a Bayesian framework for updating simulation-based digital twins in the context of bridges. Our approach integrates information from measurements to account for inaccuracies in the simulation model and quantify uncertainties. Through its implementation and assessment, this work demonstrates the potential for digital twins to provide a reliable and up-to-date representation of bridge behavior, helping to inform decision-making for maintenance and management.
T2 - Eurostruct 2023
CY - Vienna, Austria
DA - 25.09.2023
KW - Digital Twins
KW - Bayesian Inference
KW - Bridge Monitoring
KW - Uncertainty Quantification
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-586803
UR - https://eurostruct.org/eurostruct-2023/
DO - https://doi.org/10.1002/cepa.2177
SN - 2509-7075
VL - 6
IS - 5
SP - 734
EP - 740
PB - Ernst & Sohn
CY - Berlin
AN - OPUS4-58680
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Strobl, Dominic
A1 - Unger, Jörg F.
A1 - Ghnatios, C.
A1 - Klawoon, Alexander
A1 - Pittner, Andreas
A1 - Rethmeier, Michael
A1 - Robens-Radermacher, Annika
T1 - Efficient bead-on-plate weld model for parameter estimation towards effective wire arc additive manufacturing simulation
N2 - Despite the advances in hardware and software techniques, standard numerical methods fail in providing real-time simulations, especially for complex processes such as additive manufacturing applications. A real-time simulation enables process control through the combination of process monitoring and automated feedback, which increases the flexibility and quality of a process. Typically, before producing a whole additive manufacturing structure, a simplified experiment in the form of a beadon-plate experiment is performed to get a first insight into the process and to set parameters suitably. In this work, a reduced order model for the transient thermal problem of the bead-on-plate weld simulation is developed, allowing an efficient model calibration and control of the process. The proposed approach applies the proper generalized decomposition (PGD) method, a popular model order reduction technique, to decrease the computational effort of each model evaluation required multiple times in parameter estimation, control, and optimization. The welding torch is modeled by a moving heat source, which leads to difficulties separating space and time, a key ingredient in PGD simulations. A novel approach for separating space and time is applied and extended to 3D problems allowing the derivation of an efficient separated representation of the temperature.
The results are verified against a standard finite element model showing excellent agreement. The reduced order model is also leveraged in a Bayesian model parameter estimation setup, speeding up calibrations and ultimately leading to an optimized real-time simulation approach for welding experiment using synthetic as well as real measurement data.
KW - Proper generalized decomposition
KW - Model order reduction
KW - Hardly separable problem
KW - Additive manufacturing
KW - Model calibration
KW - Wire arc additive manufacturing
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-596502
DO - https://doi.org/10.1007/s40194-024-01700-0
SN - 0043-2288
SP - 1
EP - 18
PB - Springer
AN - OPUS4-59650
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Strobl, Dominic
A1 - Unger, Jörg F.
A1 - Ghnatios, C.
A1 - Robens-Radermacher, Annika
T1 - PGD in thermal transient problems with a moving heat source: A sensitivity study on factors affecting accuracy and efficiency
N2 - Thermal transient problems, essential for modeling applications like welding and additive metal manufacturing, are characterized by a dynamic evolution of temperature. Accurately simulating these phenomena is often computationally expensive, thus limiting their applications, for example for model parameter estimation or online process control. Model order reduction, a solution to preserve the accuracy while reducing the computation time, is explored. This article addresses challenges in developing reduced order models using the proper generalized decomposition (PGD) for transient thermal problems with a specific treatment of the moving heat source within the reduced model. Factors affecting accuracy, convergence, and computational cost, such as discretization methods (finite element and finite difference), a dimensionless formulation, the size of the heat source, and the inclusion of material parameters as additional PGD variables are examined across progressively complex examples. The results demonstrate the influence of these factors on the PGD model’s performance and emphasize the importance of their consideration when implementing such models. For thermal example, it is demonstrated that a PGD model with a finite difference discretization in time, a dimensionless representation, a mapping for a moving heat source, and a spatial domain non-separation yields the best approximation to the full order model.
KW - Additive manufacturing
KW - Mapping for unseparable load
KW - Model order reduction (MOR)
KW - Thermal transient problem
KW - Sensitivity analysis
KW - Proper generalized decomposition (PGD)
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598001
DO - https://doi.org/10.1002/eng2.12887
IS - e12887
SP - 1
EP - 22
PB - John Wiley & Sons Ltd.
CY - Berlin
AN - OPUS4-59800
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Bartelmeß, Jürgen
A1 - Valderrey, Virginia
A1 - Rurack, Knut
T1 - Development of a “Turn-on” Fluorescent Probe-Based Sensing System for Hydrogen Sulfide in Liquid and Gas Phase
N2 - A “turn-on” fluorescence sensing system based on a BODIPY-cobaloxime complex for the detection of H2S in liquid and gas phase was developed. To that aim, two cobaloxime complexes bearing an axial pyridyl-BODIPY ligand were initially evaluated as sensitive fluorescent HS− indicators in aqueous solution. The sensing mechanism involves the selective substitution of the BODIPY ligand by the HS− anion at the cobalt center, which is accompanied by a strong fluorescence enhancement. The selection of a complex with an ideal stability and reactivity profile toward HS− relied on the optimal interaction between the cobalt metal-center and two different pyridyl BODIPY ligands. Loading the best performing BODIPY-cobaloxime complex onto a polymeric hydrogel membrane allowed us to study the selectivity of the probe for HS− against different anions and cysteine. Successful detection of H2S by the fluorescent “light-up” membrane was not only accomplished for surface water but could also be demonstrated for relevant H2S concentrations in gas phase.
KW - Sulfide sensing
KW - Fluorescence
KW - BODIPYs
KW - Cobaloxime complex
KW - Gas sensing
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-492186
DO - https://doi.org/10.3389/fchem.2019.00641
SN - 2296-2646
VL - 7
SP - Art. Nr. 641
PB - Frontiers Media
CY - Lausanne
AN - OPUS4-49218
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zocca, Andrea
A1 - Lüchtenborg, Jörg
A1 - Mühler, T.
A1 - Wilbig, Janka
A1 - Mohr, Gunther
A1 - Villatte, T.
A1 - Léonard, Fabien
A1 - Nolze, Gert
A1 - Sparenberg, M.
A1 - Melcher, J.
A1 - Hilgenberg, Kai
A1 - Günster, Jens
T1 - Enabling the 3D Printing of Metal Components in μ-Gravity
N2 - As humanity contemplates manned missions to Mars, strategies need to be developed for the design and operation of hospitable environments to safely work in space for years. The supply of spare parts for repair and replacement of lost equipment will be one key need, but in-space manufacturing remains the only option for a timely supply. With high flexibility in design and the ability to manufacture ready-to-use components directly from a computeraided model, additive manufacturing (AM) technologies appear extremely attractive. For the manufacturing of metal parts, laser-beam melting is the most widely used AM process. However, the handling of metal powders in the absence of gravity is one prerequisite for its successful application in space. A gas flow throughout the powder bed is successfully applied to compensate for missing gravitational forces in microgravity experiments. This so-called gas-flow-assisted powder deposition is based on a porous Building platform acting as a filter for the fixation of metal particles in a gas flow driven by a pressure difference maintained by a vacuum pump.
KW - Additive manufacturing
KW - µ-gravity
KW - Laser beam melting
KW - Parabolic flight
KW - 3D printing
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-492190
DO - https://doi.org/10.1002/admt.201900506
SP - 1900506
PB - WILEY-VCH Verlag GmbH
AN - OPUS4-49219
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Habib, Abdel Karim
A1 - Schalau, Bernd
T1 - Pool evaporation - experimental data collection and modelling
N2 - When handling flammable or toxic liquids or liquefied gases, the occurrence of a leakage and formation of a liquid pool is a scenario to be considered for risk assessment. Several models are available for the estimation of the evaporating mass flow, but only a very reduced number of experimental data is available for Validation purposes.
In the last years, the Federal Institute for Materials Research and Testing (BAM) in Berlin, Germany, carried out pool Evaporation experiments with different substances in basins with a Diameter ranging from 0,50 m to 1 m mainly on open air test sites with a built up (inner city) and a non-built-up (flat terrain) topography, but also in an enclosed space. The resulting experimental data sets cover a range of vapor pressures from 0,1 bar to 0,94 bar.
The aim of this work is to make the füll data set publicly available and to provide a description of the experimental boundary conditions.
Based on these data, a Validation of existing pool Evaporation models has been carried out and eventually led to a new formulation of an evaporation model, which is also presented here, covering the whole ränge from low wind speeds up to high vapor pressures.
KW - Lache
KW - Verdunstung
KW - Verdampfung
KW - Dampfdruck
KW - Windgeschwindigkeit
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-491826
DO - https://doi.org/10.1002/ceat.201800093
VL - 42
IS - 11
SP - 2450
EP - 2457
PB - WILEY‐VCH Verlag GmbH & Co. KGaA
CY - Weinheim
AN - OPUS4-49182
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schwibbert, Karin
A1 - Menzel, F.
A1 - Epperlein, N.
A1 - Bonse, Jörn
A1 - Krüger, Jörg
T1 - Bacterial adhesion on femtosecond laser-modified polyethylene
N2 - In this study, femtosecond laser-induced sub-micrometer structures are generated to modify polyethylene (PE) surface topographies. These surfaces were subjected to bacterial colonization studies with Escherichia coli and Staphylococcus aureus as test strains. The results reveal that the nanostructures do not influence S. aureus coverage, while the adhesion of E. coli is reduced.
KW - Bacterial adhesion
KW - Laser-modified surface
KW - Polyethylene
KW - Laser-induced nanostructures
KW - Biofilm
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-492280
DO - https://doi.org/10.3390/ma12193107
VL - 12
IS - 19
SP - 3107
PB - MDPI
CY - Basel, Schweiz
AN - OPUS4-49228
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Haustein, T.
A1 - Busweiler, Sabine
A1 - Haustein, V.
A1 - von Laar, C.
A1 - Plarre, Rüdiger
T1 - Laboratory breeding of Korynetes caeruleus (Coleoptera: Cleridae) for the biological of Anobium punctatum) (Coleoptera, Ptinidae)
N2 - Larvae and adults of Korynetes caeruleus (de Geer 1775) (Coleoptera: Cleridae) were collected from old churches and reared in the laboratory on Anobium punctatum (de Geer 1774) (Coleoptera: Ptinidae). Breeding success of K. caeruleus was low, but basic parameters of this species’ developmental cycle were identifi ed. At 21°C and 75% relative humidity and a fourmonth cold period at 4°C, the development of K. caeruleus from egg to adult appearance lasted 2 years. The pupal stage may be reached and completed after one and a half years. Feeding on larvae of A. punctatum by larvae of K. caeruleus was observed and consisted of a combination of sucking haemolymph and consuming body parts. The sickle-like mandibles of larvae of K. caeruleus penetrate the cuticle of prey larvae; this is followed by pumping and sucking body movements. Adult beetles of A. punctatum were not attacked by K. caeruleus larvae. Feeding behaviour of adult K. caeruleus was not investigated.
KW - Cultural heritage
KW - Coleoptera
KW - Korynetes caeruleus
KW - Cleridae
KW - Ptinidae
KW - Anobium punctatum
KW - Biological pest control
KW - Life history data
KW - Laboratory breeding
KW - Wood protection
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494999
DO - https://doi.org/10.14411/eje.2019.038
SN - 1802-8829
VL - 116
SP - 362
EP - 371
PB - České Budějovice
AN - OPUS4-49499
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Markwart, J. C.
A1 - Battig, Alexander
A1 - Velencoso, M. M.
A1 - Pollok, D.
A1 - Schartel, Bernhard
A1 - Wurm, F. R.
T1 - Aromatic vs. Aliphatic Hyperbranched Polyphosphoesters as Flame Retardants in Epoxy Resins
N2 - The current trend for future flame retardants (FRs) goes to novel efficient halogen-free materials, due to the ban of several halogenated FRs. Among the most promising alternatives are phosphorus-based FRs, and of those, polymeric materials with complex shape have been recently reported. Herein, we present novel halogen-free aromatic and aliphatic hyperbranched polyphosphoesters (hbPPEs), which were synthesized by olefin Metathesis polymerization and investigated them as a FR in epoxy resins. We compare their efficiency (aliphatic vs. aromatic) and further assess the differences between the monomeric compounds and the hbPPEs. The decomposition and vaporizing behavior of a compound is an important factor in its flame-retardant behavior, but also the interaction with the pyrolyzing matrix has a significant influence on the performance. Therefore, the challenge in designing a FR is to optimize the chemical structure and its decomposition pathway to the matrix, with regards to time and temperature. This behavior becomes obvious in this study, and explains the superior gas phase activity of the aliphatic FRs.
KW - Phosphorus
KW - Metathesis
KW - Dendritic
KW - Cone calorimeter
KW - Fire test
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494535
DO - https://doi.org/10.3390/molecules24213901
SN - 1420-3049
VL - 24
IS - 21
SP - 3901
PB - MDPI
AN - OPUS4-49453
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schütz, R.
A1 - Maragh, J.
A1 - Weaver, J.
A1 - Rabin, Ira
A1 - Masic, A.
T1 - The Temple Scroll: Reconstructing an ancient manufacturing practice
N2 - The miraculously preserved 2000-year-old Dead Sea Scrolls, ancient texts of invaluable historical significance, were discovered in the mid-20th century in the caves of the Judean desert. The texts were mainly written on parchment and exhibit vast diversity in their states of preservation. One particular scroll, the 8-m-long Temple Scroll is especially notable because of its exceptional thinness and bright ivory color. The parchment has a layered structure, consisting of a collagenous base material and an atypical inorganic overlayer. We analyzed the chemistry of the inorganic layer using x-ray and Raman spectroscopies and discovered a variety of evaporitic sulfate salts. This points toward a unique ancient production technology in which the parchment was modified through the addition of the inorganic layer as a writing surface. Furthermore, understanding the properties of these minerals is particularly critical for the development of suitable conservation methods for the preservation of these invaluable historical documents.
KW - Temple Scroll
KW - Dead Sea Scrolls
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-495314
DO - https://doi.org/10.1126/sciadv.aaw7494
VL - 5
IS - 9
SP - 1
EP - 9
PB - AAAS
AN - OPUS4-49531
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Bayerlein, Bernd
A1 - Hanke, T.
A1 - Muth, Thilo
A1 - Riedel, Jens
A1 - Schilling, Markus
A1 - Schweizer, C.
A1 - Skrotzki, Birgit
A1 - Todor, A.
A1 - Moreno Torres, Benjami
A1 - Unger, Jörg F.
A1 - Völker, Christoph
A1 - Olbricht, Jürgen
T1 - A Perspective on Digital Knowledge Representation in Materials Science and Engineering
N2 - The amount of data generated worldwide is constantly increasing. These data come from a wide variety of sources and systems, are processed differently, have a multitude of formats, and are stored in an untraceable and unstructured manner, predominantly in natural language in data silos. This problem can be equally applied to the heterogeneous research data from materials science and engineering. In this domain, ways and solutions are increasingly being generated to smartly link material data together with their contextual information in a uniform and well-structured manner on platforms, thus making them discoverable, retrievable, and reusable for research and industry. Ontologies play a key role in this context. They enable the sustainable representation of expert knowledge and the semantically structured filling of databases with computer-processable data triples.
In this perspective article, we present the project initiative Materials-open-Laboratory (Mat-o-Lab) that aims to provide a collaborative environment for domain experts to digitize their research results and processes and make them fit for data-driven materials research and development. The overarching challenge is to generate connection points to further link data from other domains to harness the promised potential of big materials data and harvest new knowledge.
KW - Data infrastructures
KW - Digital representations
KW - Digital workflows
KW - Knowledge graphs
KW - Materials informatics
KW - Ontologies
KW - Vocabulary providers
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546729
DO - https://doi.org/10.1002/adem.202101176
SN - 1438-1656
SP - 1
EP - 14
PB - Wiley-VCH GmbH
CY - Weinheim
AN - OPUS4-54672
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Ehlert, Christopher
A1 - Unger, Wolfgang
A1 - Saalfrank, P.
T1 - C K-edge NEXAFS spectra of graphene with physical and chemical defects: a study based on density functional theory
N2 - Recently, C K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of graphite (HOPG) surfaces have been measured for the pristine material, and for HOPG treated with either bromine or krypton plasmas (Lippitz et al., Surf. Sci., 2013, 611, L1). Changes of the NEXAFS spectra characteristic for physical (krypton) and/or chemical/physical modifications of the surface (bromine) upon plasma treatment were observed. Their molecular origin, however, remained elusive. In this work we study by density functional theory, the effects of selected point and line defects as well as chemical modifications on NEXAFS carbon K-edge spectra of single graphene layers. For Br-treated surfaces, also Br 3d X-ray Photoelectron Spectra (XPS) are simulated by a cluster approach, to identify possible chemical modifications. We observe that some of the defects related to plasma treatment lead to characteristic changes of NEXAFS spectra, similar to those in experiment. Theory provides possible microscopic origins for these changes.
KW - Graphene
KW - NEXAFS
KW - Spectrum simulation
KW - Density functional theory
PY - 2014
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-309658
DO - https://doi.org/10.1039/c4cp01106f
SN - 1463-9076
SN - 1463-9084
VL - 16
IS - 27
SP - 14083
EP - 14095
PB - The Royal Soc. of Chemistry
CY - Cambridge
AN - OPUS4-30965
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kaur, I.
A1 - Ellis, L.-J.
A1 - Romer, I.
A1 - Tantra, R.
A1 - Carriere, M.
A1 - Allard, S.
A1 - Mayne-L'Hermite, M.
A1 - Minelli, C.
A1 - Unger, Wolfgang
A1 - Potthoff, A.
A1 - Rades, Steffi
A1 - Valsami-Jones, E.
T1 - Dispersion of nanomaterials in aqueous media: Towards protocol optimization
N2 - The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and stability of the suspension. In this study, a systematic step-wise approach is carried out to identify optimal sonication conditions in order to achieve a stable dispersion. This approach has been adopted and shown to be suitable for several nanomaterials (cerium oxide, zinc oxide, and carbon nanotubes) dispersed in deionized (DI) water. However, with any change in either the nanomaterial type or dispersing medium, there needs to be optimization of the basic protocol by adjusting various factors such as sonication time, power, and sonicator type as well as temperature rise during the process. The approach records the dispersion process in detail. This is necessary to identify the time Points as well as other above-mentioned conditions during the sonication process in which there may be undesirable changes, such as damage to the particle surface thus affecting surface properties. Our goal is to offer a harmonized approach that can control the Quality of the final, produced dispersion. Such a guideline is instrumental in ensuring dispersion quality repeatability in the nanoscience community, particularly in the field of nanotoxicology.
KW - Dispersion of nanomaterials
KW - Aqueous media
KW - Protocol development
PY - 2017
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-435886
UR - https://www.jove.com/video/56074
DO - https://doi.org/10.3791/56074
SN - 1940-087X
IS - 130
SP - e560741, 1
EP - e560741, 23
PB - MyJove Corp.
CY - Cambridge, MA, USA
AN - OPUS4-43588
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Abbas, F.
A1 - Donskyi, Ievgen
A1 - Gholami, M.
A1 - Ziem, B.
A1 - Lippitz, Andreas
A1 - Unger, Wolfgang
A1 - Böttcher, C.
A1 - Rabe, J.
A1 - Haag, R.
A1 - Adeli, M.
T1 - Controlled covalent functionalization of thermally reduced graphene oxide to generate defined bifunctional 2D nanomaterials
N2 - A controlled, reproducible, gram-scale method is reported for the covalent functionalization of graphene Sheets by a one-pot nitrene [2+1] cycloaddition reaction under mild conditions. The reaction between commercially available 2,4,6-trichloro-1,3,5-triazine and sodium azide with thermally reduced graphene oxide (TRGO) results in defined dichlorotriazine-functionalized sheets. The different reactivities of the chlorine substituents on the functionalized graphene allow stepwise post-modification by manipulating the temperature.
This new method provides unique access to defined bifunctional 2D nanomaterials, as exemplified by chiral surfaces and multifunctional hybrid architectures.
KW - Graphene oxide
KW - Bifunctional 2D nanomaterials
KW - XPS
KW - NEXAFS
KW - AFM
PY - 2017
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-394789
DO - https://doi.org/10.1002/ange.201612422
SN - 1433-7851
VL - 56
IS - 10
SP - 2675
EP - 2679
PB - Wiley-VCH Verlag GmbH & Co. KGaA
CY - Weinheim
AN - OPUS4-39478
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Swaraj, S.
A1 - Dietrich, Paul
A1 - Unger, Wolfgang
T1 - Simultaneous surface and bulk sensitive XAS measurements of magnetic particle clusters
N2 - Magnetic iron oxide nanoparticle clusters (mnpc) coated with organic stabilizers were investigated using scanning transmission x-ray microscopy (STXM). Simultaneous surface and bulk sensitive Fe L₃ edge absorption spectra, obtained using a photomultiplier tube and a channeltron, were used to detect subtle changes in the oxidation state in the surface and bulk of Iron Oxide mnpc. The effectiveness of this mode of STXM operation is demonstrated for these nanoparticle clusters.
T2 - X-Ray Microscopy Conference 2016 (XRM 2016)
CY - Oxford, UK
DA - 15.08. 2016
KW - Fe L3 edge absorption spectra
KW - Scanning transmission x- ray microscopy
KW - Magnetic iron oxide nanoparticle clusters
KW - XAS
PY - 2017
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-410576
UR - http://iopscience.iop.org/article/10.1088/1742-6596/849/1/012014/pdf
DO - https://doi.org/10.1088/1742-6596/849/1/012014
SN - 1742-6588
VL - 849
SP - 012014, 1
EP - 012014, 5
PB - IOP Publishing
AN - OPUS4-41057
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Swaraj, S.
A1 - Dietrich, Paul
A1 - Unger, Wolfgang
T1 - Simultaneous surface and bulk sensitive XAS measurements of magnetic particle clusters
N2 - Magnetic iron oxide nanoparticle clusters (mnpc) coated with organic stabilizers were investigated using scanning transmission x-ray microscopy (STXM). Simultaneous surface and bulk sensitive Fe L3 edge absorption spectra, obtained using a photomultiplier tube and a channeltron, were used to detect subtle changes in the oxidation state in the surface and bulk of Iron Oxide mnpc.
The effectiveness of this mode of STXM operation is demonstrated for These nanoparticle clusters.
T2 - X-Ray Microscopy Conference 2016 (XRM 2016)
CY - Oxford, UK
DA - 15.08.2016
KW - Scanning transmission x-ray microscopy (STXM)
KW - Magnetic nanoparticles
KW - Fe L3 edge absorption spectra
PY - 2017
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-435907
UR - http://iopscience.iop.org/article/10.1088/1742-6596/849/1/012014/meta
DO - https://doi.org/10.1088/1742-6596/849/1/012014
VL - 849
SP - 012014, 1
EP - 012014, 4
PB - IOP Publishing
AN - OPUS4-43590
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Becker, Tina
A1 - Altenburg, Simon
A1 - Scheuschner, Nils
A1 - Breese, Philipp Peter
A1 - Metz, C.
A1 - Hilgenberg, Kai
A1 - Maierhofer, Christiane
T1 - In-situ monitoring of the Laser Powder Bed Fusion build process via bi- chromatic optical tomography
N2 - As metal additive manufacturing (AM) is entering industrial serial production of safety relevant components, the need for reliable process qualification is growing continuously. Especially in strictly regulated industries, such as aviation, the use of AM is strongly dependent on ensuring consistent quality of components. Because of its numerous influencing factors, up to now, the metal AM process is not fully controllable. Today, expensive part qualification processes for each single component are common in industry.
This contribution focusses on bi-chromatic optical tomography as a new approach for AM in-situ quality control. In contrast to classical optical tomography, the emitted process radiation is monitored simultaneously with two temperature calibrated cameras at two separate wavelength bands. This approach allows one to estimate the local maximum temperatures during the manufacturing process, thus increases the comparability of monitoring data of different processes. A new process information level at low investment cost is reachable, compared to, e.g., infrared thermography.
T2 - LANE 2022
CY - Fürth, Germany
DA - 04.08.2022
KW - Optical tomography
KW - Additive Manufacturing
KW - L-PBF
KW - In-process monitoring
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560270
DO - https://doi.org/10.1016/j.procir.2022.08.035
SN - 2212-8271
VL - 111
SP - 340
EP - 344
PB - Elsevier B.V.
CY - Amsterdam
AN - OPUS4-56027
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weigert, Florian
A1 - Müller, A.
A1 - Häusler, I.
A1 - Geißler, Daniel
A1 - Skroblin, D.
A1 - Unger, Wolfgang
A1 - Radnik, Jörg
A1 - Resch-Genger, Ute
T1 - Combining HR‑TEM and XPS to elucidate the core–shell structure of ultrabright CdSe/CdS semiconductor quantum dots
N2 - Controlling thickness and tightness of surface passivation shells is crucial for many applications of core–shell nanoparticles (NP). Usually, to determine shell thickness, core and core/shell particle are measured individually requiring the availability of both nanoobjects. This is often not fulfilled for functional nanomaterials such as many photoluminescent semiconductor quantum dots (QD) used for bioimaging, solid state lighting, and display technologies as the core does not show the applicationrelevant functionality like a high photoluminescence (PL) quantum yield, calling for a whole nanoobject approach. By combining high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), a novel whole nanoobject approach is developed representatively for an ultrabright oleic acid-stabilized, thick shell CdSe/CdS QD with a PL quantum yield close to unity. The size of this spectroscopically assessed QD, is in the range of the information depth of usual laboratory XPS. Information on particle size and monodispersity were validated with dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) and compared to data derived from optical measurements. In addition to demonstrating the potential of this novel whole nanoobject approach for determining architectures of small nanoparticles, the presented results also highlight challenges faced by different sizing and structural analysis methods and method-inherent uncertainties.
KW - Photoluminescence
KW - Single particle
KW - Microscopy
KW - Particle architecture
KW - Thickness
KW - SAXS
KW - Shell
KW - XPS
KW - TEM
KW - Semiconductor
KW - Quantum dot
KW - Photophysics
KW - Quantum yield
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-517911
DO - https://doi.org/10.1038/s41598-020-77530-z
VL - 10
IS - 1
SP - 20712
PB - Springer Nature
AN - OPUS4-51791
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Müller, Anja
A1 - Sparnacci, K.
A1 - Unger, Wolfgang
A1 - Tougaard, S.
T1 - Determining nonuniformities of core-shell nanoparticle coatings by analysis of the inelastic background of X-ray photoelectron spectroscopy survey spectra
N2 - Most real core-shell nanoparticle (CSNP) samples deviate from an ideal core-shell structure potentially having significant impact on the particle properties. An ideal structure displays a spherical core fully encapsulated by a shell of homogeneous thickness, and all particles in the sample exhibit the same shell thickness. Therefore,
analytical techniques are required that can identify and characterize such deviations.
This study demonstrates that by analysis of the inelastic background in X-ray photoelectron spectroscopy (XPS) survey spectra, the following types of deviations can be identified and quantified: the nonuniformity of the shell thickness within a nanoparticle sample and the incomplete encapsulation of the cores by the shell material. Furthermore, CSNP shell thicknesses and relative coverages can be obtained. These results allow for a quick and straightforward comparison between several batches of a specific CSNP, different coating approaches, and so forth. The presented XPS methodology requires a submonolayer distribution of CSNPs on a substrate.
Poly(tetrafluoroethylene)-poly(methyl methacrylate) and poly(tetrafluoroethylene)-polystyrene polymer CSNPs serve as model systems to demonstrate the applicability of the approach.
KW - Core-shell
KW - Nanoparticles
KW - Inelastic background
KW - Polymers
KW - QUASES
KW - XPS
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-511315
DO - https://doi.org/10.1002/sia.6865
SN - 0142-2421
SN - 1096-9918
VL - 52
SP - 1
EP - 8
PB - Wiley
CY - Chichester
AN - OPUS4-51131
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kovacevic, E.
A1 - Strunskus, T.
A1 - Santhosh, N. M.
A1 - Zavasnik, Z.
A1 - Unger, Wolfgang
A1 - Sauvage, T.
A1 - Ammar, M.-R.
A1 - Cvelbar, U.
A1 - Berndt, J.
T1 - Thermal stability studies of plasma deposited hydrogenated carbon nitride nanostructures
N2 - Thermally stable carbon nitride nanostructures have potential applications in surface coatings and automotive fields. In this work, hydrogenated nitrogen-rich carbon nitride nanoparticles have been synthesised via low-pressure low-power plasma vapour deposition technique from methane/Nitrogen gas mixture in a dry process. Thermal stability of the initially prepared hydrogenated carbon Nitride structures has been analysed by near-edge X-ray absorption fine-structure spectroscopy (NEXAFS, insitu), Raman spectroscopy, scanning and transmission electron microscopy and nuclear reaction Analysis (NRA). Thermal studies reveal the excellent stability of the material and nitrogen-rich characteristics (N/C ratio 0.5e0.2 ± 0.01). The obtained results suggest transformation of sp3-rich as-deposited carbon Nitride into sp2-carbon phase with more graphitic features upon thermal annealing. Such in-situ thermal studies of plasma deposited carbon nitrides confirm the conversion of sp3-rich phase to sp2-rich carbon phase at the critical temperature (about 450 K), without a huge loss in nitrogen content. The analysis revealed that the material is a stable plasma deposit after this critical temperature up to >1100 K. Additionally, super hydrophilic carbon nitride nanostructure transforms into a hydrophobic surface after thermal annealing.
These thermally stable hydrophobic carbon nitride nanoparticles could be used as a promising material for the hydrophobic coatings for various applications, especially for harsh conditions.
KW - Carbon nanoparticles
KW - Hydrogenated nanostructures
KW - Plasma deposition
KW - NEXAFS
KW - Thermal annealing
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-536163
DO - https://doi.org/10.1016/j.carbon.2021.08.008
SN - 0008-6223
VL - 184
SP - 82
EP - 90
PB - Elsevier Ltd.
AN - OPUS4-53616
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Pohl, Christoph
A1 - Smilauer, V.
A1 - Unger, Jörg F.
T1 - A three-phase transport model for high-temperature concrete simulations validated with X-ray CT data
N2 - Concrete exposure to high temperatures induces thermo-hygral phenomena, causing water phase changes, buildup of pore pressure and vulnerability to spalling. In order to predict these phenomena under various conditions, a three-phase transport model is proposed. The model is validated on X-ray CT data up to 320 ◦C, showing good agreement of the temperature profiles and moisture changes. A dehydration description, traditionally derived from thermogravimetric analysis, was replaced by a formulation based on data from neutron radiography. In addition, treating porosity and dehydration evolution as independent processes, previous approaches do not fulfil the solid mass balance. As a consequence, a new formulation is proposed that introduces the porosity as an independent variable, ensuring the latter condition.
KW - Concrete
KW - Porous media
KW - Spalling
KW - Dehydration
KW - Moisture transport
KW - Heat transfer
KW - Pore pressure
KW - Porosity
KW - Finite elements
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-532840
UR - https://doi.org/10.5281/zenodo.4890635
DO - https://doi.org/10.3390/ma14175047
SN - 1996-1944
VL - 14
IS - 17
SP - 1
EP - 21
PB - MDPI
CY - Basel
AN - OPUS4-53284
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Müller, Anja
A1 - Krahl, T.
A1 - Radnik, Jörg
A1 - Wagner, Andreas
A1 - Werner, W. S. M.
A1 - Ritter, B.
A1 - Kemnitz, E.
A1 - Unger, Wolfgang
T1 - Chemical in-depth analysis of (Ca/Sr)F2 core–shell like nanoparticles by X-ray photoelectron spectroscopy with tunable excitation energy
N2 - The fluorolytic sol–gel synthesis is applied with the intention to obtain two different types of core–shell nanoparticles, namely, SrF2–CaF2 and CaF2–SrF2. In two separate fluorination steps for core and shell formation, the corresponding metal lactates are reacted with anhydrous HF in ethylene glycol. Scanning transmission electron microscopy (STEM) and dynamic light scattering (DLS) confirm the formation of particles with mean dimensions between 6.4 and 11.5 nm. The overall chemical composition of the particles during the different reaction steps is monitored by quantitative Al Kα excitation X-ray photoelectron spectroscopy (XPS). Here, the formation of stoichiometric metal fluorides (MF2) is confirmed, both for the core and the final core–shell particles. Furthermore, an in-depth analysis by synchrotron radiation XPS (SR-XPS) with tunable excitation energy is performed to confirm the core–Shell character of the nanoparticles. Additionally, Ca2p/Sr3d XPS intensity ratio in-Depth profiles are simulated using the software Simulation of Electron Spectra for Surface Analysis (SESSA). In principle, core–shell like particle morphologies are formed but without a sharp interface between calcium and strontium containing phases.
Surprisingly, the in-depth chemical distribution of the two types of nanoparticles is equal within the error of the experiment. Both comprise a SrF2-rich core domain and CaF2-rich shell domain with an intermixing zone between them. Consequently, the internal morphology of the final nanoparticles seems to be independent from the synthesis chronology.
KW - Metal fluorides
KW - Sol-gel synthesis
KW - Synchrotron radiation
KW - X-ray photoelectron spectroscopy
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-522284
DO - https://doi.org/10.1002/sia.6937
SN - 0142-2421
VL - 53
IS - 5
SP - 494
EP - 508
PB - Wiley VCH
AN - OPUS4-52228
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kjaervik, Marit
A1 - Ramstedt, M.
A1 - Schwibbert, Karin
A1 - Dietrich, P. M
A1 - Unger, Wolfgang
T1 - Comparative Study of NAP-XPS and Cryo-XPS for the Investigation of Surface Chemistry of the Bacterial Cell-Envelope
N2 - Bacteria generally interact with the environment via processes involving their cell-envelope. Thus, techniques that may shed light on their surface chemistry are attractive tools for providing an understanding of bacterial interactions. One of these tools is Al Kα-excited photoelectron spectroscopy (XPS) with its estimated information depth of <10 nm. XPS-analyses of bacteria have been performed for several decades on freeze-dried specimens in order to be compatible with the vacuum in the analysis chamber of the spectrometer. A limitation of these studies has been that the freeze-drying method may collapse cell structure as well as introduce surface contaminants. However, recent developments in XPS allow for analysis of biological samples at near ambient pressure (NAP-XPS) or as frozen hydrated specimens (cryo-XPS) in vacuum. In this work, we have analyzed bacterial samples from a reference strain of the Gram-negative bacterium Pseudomonas fluorescens using both techniques. We compare the results obtained and, in general, observe good agreement between the two techniques. Furthermore, we discuss advantages and disadvantages with the two analysis approaches and the output data they provide. XPS reference data from the bacterial strain are provided, and we propose that planktonic cells of this strain (DSM 50090) are used as a reference material for surface chemical analysis of bacterial systems.
KW - P. Fluorescens
KW - Cryo XPS
KW - NAP-XPS
KW - DSM 5009
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-525640
DO - https://doi.org/10.3389/fchem.2021.666161
VL - 9
SP - Article 666161
PB - Frontiers
CY - Switzerland
AN - OPUS4-52564
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Unger, Wolfgang
A1 - Senoner, M.
A1 - Stockmann, Jörg M.
A1 - Fernandez, V.
A1 - Fairley, N.
A1 - Passiu, C.
A1 - Spencer, N. D.
A1 - Rossi, A.
T1 - Summary of ISO/TC 201 International Standard ISO 18516:2019 Surface chemical analysis - Determination of lateral resolution and sharpness in beam-based methods with a range from nanometres to micrometres and its implementation for imaging laboratory X-ray photoelectron spectrometers (XPS)
N2 - ISO 18516:2019 Surface chemical analysis—Determination of lateral resolution and sharpness in beam-based methods with a range from nanometres to micrometres revises ISO 18516:2006 Surface chemical analysis—Auger electron spectroscopy and X-ray photoelectron spectroscopy—Determination of lateral resolution. It implements three different methods delivering parameters useful to express the lateral resolution: (1) the straight edge method, (2) the narrow line method and (3) the grating method. The theoretical background of these methods is introduced in ISO/TR 19319:2013 Surface chemical analysis—Fundamental approaches to determination of lateral resolution and sharpness in beam-based methods. The revised International Standard ISO 18516 delivers standardized procedures for the determination of the (1) effective lateral resolution by imaging of square-wave gratings, the (2) lateral resolution expressed as the parameter D12–88 characterizing the steepness of the sigmoidal edge spread function (ESF) determined by imaging a straight edge and (3) the lateral resolution expressed as the full width of half maximum of the line spread function (LSF), wLSF, determined by imaging a narrow line. The last method also delivers information on the shape of the LSF, which characterizes an individual imaging instrument. Finally, the implementation of all three standardized methods in the field of imaging laboratory X-ray photoelectron spectroscopy (XPS) is shortly presented. This part of the letter is based on the use of a new test sample developed at ETH Zurich, Switzerland. This test sample displays a micrometre scaled pattern motivated by the resolving power of recent imaging XPS instruments.
KW - Grating method
KW - Imaging AES
KW - Imaging SIMS
KW - Imaging XPS
KW - Lateral resolution
KW - Narrow line method
KW - Noise in image
KW - Resolution criterion
KW - Straight edge method
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-536330
DO - https://doi.org/10.1002/sia.7025
SN - 1096-9918
VL - 54
IS - 4
SP - 320
EP - 327
PB - Wiley
CY - Chichester
AN - OPUS4-53633
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Steiner, S.
A1 - Heldt, J.
A1 - Sobol, Oded
A1 - Unger, Wolfgang
A1 - Frömeling, T.
T1 - Influence of oxygen vacancies on core-shell formation in solid solutions of (Na,Bi)TiO3 and SrTiO3
N2 - Solid solutions of (Na,Bi)TiO3 (NBT) and SrTiO3 (ST) are materials of interest for high-strain or high-energy density capacitor applications. Often, they exhibit chemical heterogeneity and develop core-shell structures during regular solid-state synthesis with an NBT-rich core. In this case, the NBT forms first so that the strontium needs to diffuse into the material to reach chemical homogeneity. Depending on the presence of core-shell structures, the electrical properties can vary drastically. In this work, we rationalize the effect of variations in oxygen vacancy concentration by Fe-acceptor and Nb-donor doping. It can be shown that a diffusion couple of strontium and oxygen is responsible for chemical homogenization and that the oxygen vacancy content can control the formation of a core-shell structure.
KW - Lead-free ceramics
KW - Bismuth titanates
KW - Core-shell structures
KW - Diffusion/diffusivity
KW - Ferroelectricity/ferroelectric materials
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-525988
DO - https://doi.org/10.1111/jace.17845
SP - 1
EP - 10
PB - Wiley Periodicals LLC, John Wiley & Sons, Inc.
AN - OPUS4-52598
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Robens-Radermacher, Annika
A1 - Held, Felix
A1 - Coelho Lima, Isabela
A1 - Titscher, Thomas
A1 - Unger, Jörg F.
T1 - Efficient identification of random fields coupling Bayesian inference and PGD reduced order model for damage localization
N2 - One of the main challenges regarding our civil infrastructure is the efficient operation over their complete design lifetime while complying with standards and safety regulations. Thus, costs for maintenance or replacements must be optimized while still ensuring specified safety levels. This requires an accurate estimate of the current state as well as a prognosis for the remaining useful life. Currently, this is often done by regular manual or visual inspections within constant intervals. However, the critical sections are often not directly accessible or impossible to be instrumented at all. Model‐based approaches can be used where a digital twin of the structure is set up. For these approaches, a key challenge is the calibration and validation of the numerical model based on uncertain measurement data. The aim of this contribution is to increase the efficiency of model updating by using the advantage of model reduction (Proper Generalized Decomposition, PGD) and applying the derived method for efficient model identification of a random stiffness field of a real bridge.”
KW - Model reduction
KW - Model updating
KW - Proper generalized decomposition
KW - Random field
KW - Variational Bayesian Inference
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521275
DO - https://doi.org/10.1002/pamm.202000063
VL - 20
IS - 1
SP - e202000063
PB - Wiley Online Libary
AN - OPUS4-52127
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wegner, Karl David
A1 - Dussert, F.
A1 - Truffier-Boutry, D.
A1 - Benayad, A.
A1 - Beal, D.
A1 - Mattera, L.
A1 - Ling, W. L.
A1 - Carrière, M.
A1 - Reiss, P.
T1 - Influence of the Core/Shell Structure of Indium Phosphide Based Quantum Dots on Their Photostability and Cytotoxicity
N2 - With the goal to improve their photostability, InP-based QDs are passivated with three types of inorganic shells, namely (i) a gradient ZnSexS1−x shell, (ii) an additional ZnS shell on top of the gradient shell with two different thicknesses (core/shell/shell, CSS), (iii) an alumina coating on top of ZnS. All three systems have photoluminescence Quantum yields (PLQY) > 50%and similar PL decay times (64–67 ns). To assess their photostability they are incorporated into a transparent poly (methyl methacrylate) (PMMA) matrix and exposed to continuous irradiation with simulated sunlight in a climate chamber. The alumina coated core/shell system exhibits the highest stability in terms of PLQY Retention as well as the lowest shift of the PL maximum and lowest increase of the PL linewidth, followed by the CSS QDs and finally the gradient shell system. By means of XPS studies we identify the degradation of the ZnS outer layer and concomitant xidation of the emissive InZnP core as the main origins of degradation in the gradient structure. These modifications do not occur in the case of the alumina-capped sample, which exhibits excellent chemical stability. The gradient shell and CSS systems could be transferred to the aqueous phase using surface ligand exchange with penicillamine. Cytotoxicity studies on human primary keratinocytes revealed that exposure for 24 h to 6.25–100 nM of QDs did not affect cell viability. However, a trend toward reduced cell proliferation is observed for higher concentrations of gradient shell and CSS QDs with a thin ZnS shell, while CSS QDs with a thicker ZnS shell do not exhibit any impact.
KW - Indium phosphide
KW - Quantum dots
KW - Cytotoxicity
KW - Photostability
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494249
DO - https://doi.org/10.3389/fchem.2019.00466
VL - 7
SP - Article Number: 466
PB - Frontiers Media SA
AN - OPUS4-49424
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Simon, Franz-Georg
A1 - Scholz, Philipp
T1 - Sequential Extraction of Incineration Bottom Ash: Conclusions Regarding Ecotoxicity
N2 - The classification of incineration bottom ash (IBA) as hazardous or non-hazardous according to ecotoxic hazard property HP14 is still under debate. In this context, only the compounds of Zn and Cu with the hazard statement code H410 are of relevance. With an approach based on the grouping of substances, it was shown that such substances are either readily water-soluble or slightly and sparingly soluble. The concentrations of readily soluble Cu and Zn compounds in IBA are far below the cut-off value of 0.1%. Slightly and sparingly soluble Zn and Cu compounds could be quantified in the first fraction of a four-step sequential extraction procedure. With the results from the complete sequence, the dimensionless synthesis toxicity index (STI) was calculated and was in the range of 494 to 1218 for the four investigated IBA samples. It was concluded that IBA can usually be classified as non-hazardous.
KW - Incineration bottom ash
KW - Hazard properties
KW - Ecotoxicity
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-605262
DO - https://doi.org/10.3390/app14135541
SN - 2076-3417
VL - 14
IS - 13
SP - 1
EP - 12
PB - MDPI
CY - Basel
AN - OPUS4-60526
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Mohr, Gunther
A1 - Altenburg, Simon
A1 - Ulbricht, Alexander
A1 - Heinrich, Ph.
A1 - Baum, D.
A1 - Maierhofer, Christiane
A1 - Hilgenberg, Kai
T1 - In-Situ Defect Detection in Laser Powder Bed Fusion by Using Thermography and Optical Tomography—Comparison to Computed Tomography
N2 - Among additive manufacturing (AM) technologies, the laser powder bed fusion (L-PBF) is one of the most important technologies to produce metallic components. The layer-wise build-up of components and the complex process conditions increase the probability of the occurrence of defects. However, due to the iterative nature of its manufacturing process and in contrast to conventional manufacturing technologies such as casting, L-PBF offers unique opportunities for in-situ monitoring. In this study, two cameras were successfully tested simultaneously as a machine manufacturer independent process monitoring setup: a high-frequency infrared camera and a camera for long time exposure, working in the visible and infrared spectrum and equipped with a near infrared filter. An AISI 316L stainless steel specimen with integrated artificial defects has been monitored during the build. The acquired camera data was compared to data obtained by computed tomography. A promising and easy to use examination method for data analysis was developed and correlations between measured signals and defects were identified. Moreover, sources of possible data misinterpretation were specified. Lastly, attempts for automatic data analysis by data Integration are presented.
KW - Laser powder bed fusion (L-PBF)
KW - Selective laser melting (SLM)
KW - Additive manufacturing (AM)
KW - Process monitoring
KW - Infrared thermography
KW - Optical tomography
KW - Computed tomography (CT)
KW - Data fusion
KW - Lack-of-fusion
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502417
DO - https://doi.org/10.3390/met10010103
VL - 10
IS - 1
SP - 103
PB - MDPI
CY - Basel, Schweiz
AN - OPUS4-50241
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Ehlert, Christopher
A1 - Holzweber, Markus
A1 - Lippitz, Andreas
A1 - Unger, Wolfgang
A1 - Saalfrank, Peter
T1 - A detailed assignment of NEXAFS resonances of imidazolium based ionic liquids
N2 - In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([CnC₁im]⁺[NTf₂]⁻ and [C₄C₁im]⁺[I]⁻). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
KW - Ionic liquids
KW - NEXAFS
KW - DFT spectrum simulations
PY - 2016
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-367223
DO - https://doi.org/10.1039/c5cp07434g
SN - 1463-9076
SN - 1463-9084
VL - 18
IS - 12
SP - 8654
EP - 8661
PB - Royal Society of Chemistry
CY - Cambridge, UK
AN - OPUS4-36722
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Unger, Wolfgang
A1 - Beiranvand, Z.
A1 - Kakanejadifard, A.
A1 - Donskyi, Ievgen
A1 - Faghani, A.
A1 - Tu, Z.
A1 - Lippitz, Andreas
A1 - Sasanpour, P.
A1 - Maschietto, F.
A1 - Paulus, B.
A1 - Haag, R.
A1 - Adeli, M.
T1 - Functionalization of fullerene at room temperature: toward new carbon vectors with improved physicochemical properties
N2 - In this work, fullerene has been functionalized with cyanuric Chloride at room temperature by a nitrene mediated [2 + 1] cycloaddition reaction. The adduct after functionalization is inherently in the form of azafulleroid and shows broad UV absorption in the wavelength range of 200–800 nm, as well as photothermal conversion and fluorescence with a high quantum yield.
KW - Functionalization of fullerenes
KW - XPS
KW - NEXAFS
PY - 2016
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-387076
DO - https://doi.org/10.1039/c6ra23419d
SN - 2046-2069
VL - 6
IS - 114
SP - 112771
EP - 112775
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-38707
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schwarz, F.
A1 - Heinrich, Thomas
A1 - Lippitz, Andreas
A1 - Unger, Wolfgang
A1 - Schalley, C.
T1 - A photoswitchable rotaxane operating in monolayers on solid support
N2 - A novel photoswitchable rotaxane was synthesised and its switching behaviour in solution was analysed with NMR and UV-Vis. A monolayer of rotaxanes was deposited on glass surfaces and the on-surface photoswitching was investigated. Angle-resolved NEXAFS spectra revealed a preferential orientation that reversibly changes upon switching.
KW - XPS
KW - NEXAFS
KW - Photoswitchable rotaxane
KW - Self assembly
PY - 2016
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-386814
DO - https://doi.org/10.1039/c6cc08586e
SN - 0022-4936
SN - 1364-548X
SN - 0009-241x
SN - 1359-7345
VL - 52
IS - 100
SP - 14458
EP - 14461
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-38681
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Röhsler, Andreas
A1 - Sobol, Oded
A1 - Unger, Wolfgang
A1 - Böllinghaus, Thomas
T1 - Comprehensive study of deuterium-induced effects in in austenitic stainless steel AISI 304L
N2 - The damaging impact of hydrogen on the austenitic stainless steel AISI 304 L was analysed.
To this aim, samples were charged electrochemically with the hydrogen isotope deuterium (2H, D) and examined with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD). The fusion of the obtained chemical and structural information revealed local enrichment of deuterium in austenite, transformation into martensite, crack formation and severe roughening of the specimen surface. The results indicated that martensite was not only formed during charging but also during Desorption and ToF-SIMS examinations. Furthermore, cross-sections of deuterium-charged samples revealed that in preferred deformation bands a g/ε/a 0 evolution is taking place.
By means of microscopic analyses and carrier gas hot extraction (CGHE), it was found that the use of NaAsO2 as recombination poison decreased the uptake of hydrogen significantly and resulted in severe precipitation on the specimen surfaces. This is in contrast to the popular presumption that NaAsO2 enhances the uptake of hydrogen (and
deuterium) during electrochemical charging by hampering its recombination from Atoms to molecules.
KW - AISI 304L
KW - Hydrogen
KW - ToF-SIMS
KW - Deuterium
KW - Martensite
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-477540
DO - https://doi.org/10.1016/j.ijhydene.2019.03.058
SN - 0360-3199
SN - 1879-3487
VL - 44
IS - 23
SP - 12228
EP - 12238
PB - Elsevier Ltd.
AN - OPUS4-47754
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Müller, Anja
A1 - Swaraj, S.
A1 - Sparnacci, K.
A1 - Unger, Wolfgang
T1 - Shell thickness determination for PTFE‐PS core‐shell nanoparticles using scanning transmission X‐ray microscopy (STXM)
N2 - A scanning transmission X‐ray microscopy (STXM)‐based methodology is introduced for determining the dimensions (shell thickness, core and total diameter) of core‐shell nanoparticles, which exhibit a strong X‐ray absorption contrast and a well‐defined interface between core and shell material. A low radiation dosage during data acquisition and, therefore, less X‐ray beam‐induced damage of the sample is achieved by recording STXM images only at 2 predetermined energies of maximum Absorption contrast, instead of recording a stack of images across the whole absorption edge.
A model core‐shell nanoparticle, polytetrafluoroethylene (PTFE) cores with polystyrene (PS) shell, is used for demonstration. Near‐edge X‐ray absorption fine structure spectroscopy confirms the significant difference in X‐ray absorption behavior between PTFE and PS. Additionally, because of the insolubility of styrene in PTFE a well‐defined interface between particle core and shell is expected. To validate the STXM results, both the naked PTFE cores as well as the complete core‐shell nanoparticles are examined by scanning electron microscopy (SEM). The introduced STXM‐based methodology yields particle dimensions in agreement with the SEM results and provides additional information such as the position of the particle core, which cannot be extracted from a SEM micrograph.
T2 - European conference on applications of surface and interface analysis (ECASIA'17)
CY - Montpellier, France
DA - 24.09.2017
KW - Core-shell nanoparticles
KW - Polymers
KW - PS
KW - PTFE
KW - SEM
KW - STXM
PY - 2018
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-449700
DO - https://doi.org/10.1002/sia.6464
SN - 1096-9918
SN - 0142-2421
VL - 50
IS - 11
SP - 1077
EP - 1082
PB - John Wiley & Sons
CY - Hoboken, New Jersey, USA
AN - OPUS4-44970
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kjaervik, Marit
A1 - Schwibbert, Karin
A1 - Dietrich, P.
A1 - Thissen, A.
A1 - Unger, Wolfgang
T1 - Surface characterisation of Escherichia coli under various conditions by near-ambient pressure XPS
N2 - Bacteria are inherently in a hydrated state and therefore not compatible to ultra-high vacuum techniques such as XPS without prior sample preparation involving freeze drying or fast freezing.
This has changed with the development of near-ambient pressure (NAP)-XPS, which makes it possible to characterise the bacterial surface with minimal sample preparation. This paper presents NAP-XPS measurements of Escherichia coli under various NAP conditions: at 11 mbar in a humid environment, at 2 mbar after drying in the chamber, pre-dried at 4 mbar, and at 1 mbar after overnight pumping at 10^−4 mbar. The high-resolution spectra of carbon, nitrogen, and oxygen are presented and found to be in general agreement with XPS measurements from freeze-dried and fast-frozen bacteria. However, it was found that the amount of carbon components associated with polysaccharides increases relative to aliphatic carbon during drying and increases further after overnight pumping. This implies that drying has an impact on the bacterial surface.
T2 - European conference on applications of surface and interface analysis (ECASIA'17)
CY - Montpellier, France
DA - 24.09.2018
KW - Bacteria
KW - E. coli
KW - NAP-XPS
PY - 2018
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-454047
DO - https://doi.org/10.1002/sia.6480
SN - 0142-2421
SN - 1096-9918
VL - 50
IS - 11
SP - 996
EP - 1000
PB - John Wiley & Sons
CY - Hoboken, New Jersey, USA
AN - OPUS4-45404
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Afantitis, A.
A1 - Melagraki, G.
A1 - Isigonis, P.
A1 - Tsoumanis, A.
A1 - Varsou, D. D.
A1 - Valsami-Jones, E.
A1 - Papadiamantis, A.
A1 - Ellis, L.-J. A.
A1 - Sarimveis, H.
A1 - Doganis, P.
A1 - Karatzas, P.
A1 - Tsiros, P.
A1 - Liampa, I.
A1 - Lobaskin, V.
A1 - Greco, D.
A1 - Serra, A.
A1 - Kinaret, P. A. S.
A1 - Saarimäki, L. A.
A1 - Grafström, R.
A1 - Kohonen, P.
A1 - Nymark, P.
A1 - Willighagen, E.
A1 - Puzyn, T.
A1 - Rybinska-Fryca, A.
A1 - Lyubartsev, A.
A1 - Jensen, K. A.
A1 - Brandenburg, J. G.
A1 - Lofts, S.
A1 - Svendsen, C.
A1 - Harrison, S.
A1 - Maier, D.
A1 - Tamm, K.
A1 - Jänes, J.
A1 - Sikk, L.
A1 - Dusinska, M.
A1 - Longhin, E.
A1 - Rundén-Pran, E.
A1 - Mariussen, E.
A1 - El Yamani, N.
A1 - Unger, Wolfgang
A1 - Radnik, Jörg
A1 - Tropsha, A.
A1 - Cohen, Y.
A1 - Lesczynski, J.
A1 - Hendren, C. O.
A1 - Wiesner, M.
A1 - Winkler, D.
A1 - Suzuki, N.
A1 - Yoon, T. H.
A1 - Choi, J.-S.
A1 - Sanabria, N.
A1 - Gulumian, M.
A1 - Lynch, I.
T1 - NanoSolveIT Project: Driving nanoinformatics research to develop innovative and integrated tools for in silico nanosafety assessment
N2 - Nanotechnology has enabled the discovery of a multitude of novel materials exhibiting unique physicochemical (PChem) properties compared to their bulk analogues. These properties have led to a rapidly increasing range of commercial applications; this, however, may come at a cost, if an association to long-term health and environmental risks is discovered or even just perceived. Many nanomaterials (NMs) have not yet had their potential adverse biological effects fully assessed, due to costs and time constraints associated with the experimental assessment, frequently involving animals. Here, the available NM libraries are analyzed for their suitability for integration with novel nanoinformatics approaches and for the development of NM specific Integrated Approaches to Testing and Assessment (IATA) for human and environmental risk assessment, all within the NanoSolveIT cloud-platform. These established and well-characterized NM libraries (e.g. NanoMILE, NanoSolutions, NANoREG, NanoFASE, caLIBRAte, NanoTEST and the Nanomaterial Registry (>2000 NMs)) contain physicochemical characterization data as well as data for several relevant biological endpoints, assessed in part using harmonized Organisation for Economic Co-operation and Development (OECD) methods and test guidelines.
Integration of such extensive NM information sources with the latest nanoinformatics methods will allow NanoSolveIT to model the relationships between NM structure (morphology), properties and their adverse effects and to predict the effects of other NMs for which less data is available. The project specifically addresses the needs of regulatory agencies and industry to effectively and rapidly evaluate the exposure, NM hazard and risk from nanomaterials and nano-enabled products, enabling implementation of computational ‘safe-by-design’ approaches to facilitate NM commercialization.
KW - Nanoinformatics
KW - Hazard assessment
KW - (Quantitative) Structure-Active Relationships
KW - Safe-by-design
KW - Predictive modelling
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-505952
DO - https://doi.org/10.1016/j.csbj.2020.02.023
VL - 18
SP - 583
EP - 602
PB - Elsevier B.V.
AN - OPUS4-50595
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Robens-Radermacher, Annika
A1 - Unger, Jörg F.
T1 - Efficient structural reliability analysis by using a PGD model in an adaptive importance sampling schema
N2 - One of the most important goals in civil engineering is to guarantee the safety of the construction. Standards prescribe a required failure probability in the order of 10−4 to 10−6. Generally, it is not possible to compute the failure probability analytically.
Therefore, many approximation methods have been developed to estimate the failure probability. Nevertheless, these methods still require a large number of evaluations of the investigated structure, usually finite element (FE) simulations, making full probabilistic design studies not feasible for relevant applications. The aim of this paper is to increase the efficiency of structural reliability analysis by means of reduced order models. The developed method paves the way for using full probabilistic approaches in industrial applications. In the proposed PGD reliability analysis, the solution of the structural computation is directly obtained from evaluating the PGD solution for a specific parameter set without computing a full FE simulation. Additionally, an adaptive importance sampling scheme is used to minimize the total number of required samples. The accuracy of the failure probability depends on the accuracy of the PGD model (mainly influenced on mesh discretization and mode truncation) as well as the number of samples in the sampling algorithm. Therefore, a general iterative PGD reliability procedure is developed to automatically verify the accuracy of the computed failure probability. It is based on a goal-oriented refinement of the PGD model around the adaptively approximated design point. The methodology is applied and evaluated for 1D and 2D examples. The computational savings compared to the method based on a FE model is shown and the influence of the accuracy of the PGD model on the failure probability is studied.
KW - Reliability
KW - Probability of failure
KW - Adaptive importance sampling
KW - Reduced order models
KW - Proper Generalized Decomposition
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-510345
DO - https://doi.org/10.1186/s40323-020-00168-z
VL - 7
SP - Article number: 29
PB - SpringerOpen
AN - OPUS4-51034
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Müller, Anja
A1 - Heinrich, Thomas
A1 - Tougaard, S.
A1 - Werner, W. S. M.
A1 - Hronek, M.
A1 - Kunz, Valentin
A1 - Radnik, Jörg
A1 - Stockmann, Jörg M.
A1 - Hodoroaba, Vasile-Dan
A1 - Benemann, Sigrid
A1 - Nirmalananthan-Budau, Nithiya
A1 - Geißler, Daniel
A1 - Sparnacci, K.
A1 - Unger, Wolfgang
T1 - Determining the thickness and completeness of the shell of polymer core-shell nanoparticles by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and transmission scanning electron microscopy
N2 - Core–shell nanoparticles (CSNPs) have become indispensable in various industrial applications. However, their real internal structure usually deviates from an ideal core–shell structure. To control how the particles perform with regard to their specific applications, characterization techniques are required that can distinguish an ideal from a nonideal morphology. In this work, we investigated poly(tetrafluoroethylene)–poly(methyl methacrylate) (PTFE–PMMA) and poly(tetrafluoroethylene)–polystyrene (PTFE–PS) polymer CSNPs with a constant core diameter (45 nm) but varying shell thicknesses (4–50 nm). As confirmed by transmission scanning electron microscopy (T-SEM), the shell completely covers the core for the PTFE–PMMA nanoparticles, while the encapsulation of the core by the shell material is incomplete for the PTFE–PS nanoparticles. X-ray photoelectron spectroscopy (XPS) was applied to determine the shell thickness of the nanoparticles. The software SESSA v2.0 was used to analyze the intensities of the elastic peaks, and the QUASES software package was employed to evaluate the shape of the inelastic background in the XPS survey spectra. For the first time, nanoparticle shell thicknesses are presented, which are exclusively based on the analysis of the XPS inelastic background. Furthermore, principal component analysis (PCA)-assisted time-of-flight secondary-ion mass spectrometry (ToF-SIMS) of the PTFE–PS nanoparticle sample set revealed a systematic variation among the samples and, thus, confirmed the incomplete encapsulation of the core by the shell material. As opposed to that, no variation is observed in the PCA score plots of the PTFE–PMMA nanoparticle sample set. Consequently, the complete coverage of the core by the shell material is proved by ToF-SIMS with a certainty that cannot be achieved by XPS and T-SEM.
KW - XPS
KW - T-SEM
KW - ToF-SIMS
KW - Core-shell nanoparticles
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-499165
DO - https://doi.org/10.1021/acs.jpcc.9b09258
VL - 123
IS - 49
SP - 29765
EP - 29775
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-49916
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Tu, Z.
A1 - Donskyi, Ievgen
A1 - Qiao, H.
A1 - Zhu, Z.
A1 - Unger, Wolfgang
A1 - Hackenberger, C. P. R.
A1 - Chen, W.
A1 - Adeli, M.
A1 - Haag, R.
T1 - Graphene Oxide-Cyclic R10 Peptide Nuclear Translocation Nanoplatforms for the Surmounting of Multiple-Drug Resistance
N2 - Multidrug resistance resulting from a variety of defensive pathways in Cancer has become a global concern with a considerable impact on the mortality associated with the failure of traditional chemotherapy. Therefore, further research and new therapies are required to overcome this challenge. In this work, a cyclic R10 peptide (cR10) is conjugated to polyglycerol-covered nanographene oxide to engineer a nanoplatform for the surmounting of multidrug resistance. The nuclear translocation of the nanoplatform, facilitated by cR10 peptide, and subsequently, a laser-triggered release of the loaded doxorubicin result in efficient anticancer activity confirmed by both in vitro and in vivo experiments. The synthesized nanoplatform with a combination of different features, including active nucleus-targeting, highloading capacity, controlled release of cargo, and photothermal property, provides a new strategy for circumventing multidrug resistant cancers.
KW - Graphen Oxide
KW - Nanoplatform
KW - Cancer
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-510061
DO - https://doi.org/10.1002/adfm.202000933
VL - 30
IS - 35
SP - 2000933
PB - Wiley VCH
AN - OPUS4-51006
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Otto, Peter
A1 - de Lorenzis, L.
A1 - Unger, Jörg F.
T1 - Explicit dynamics in impact simulation using a NURBS contact interface
N2 - In this paper, the impact problem and the subsequent wave Propagation are considered. For the contact discretization an intermediate non-uniform rational B-spline (NURBS) layer is added between the contacting finite element bodies, which allows a smooth contact formulation and efficient element-based integration.
The impact event is ill-posed and requires a regularization to avoid propagating stress oscillations. A nonlinear mesh-dependent penalty regularization is used, where the stiffness of the penalty regularization increases upon mesh refinement. Explicit time integration methods are well suited for wave propagation problems, but are efficient only for diagonal mass matrices. Using a spectral element discretization in combination with a NURBS contact layer the bulk part of the mass matrix is diagonal.
KW - Explicit dynamics
KW - Impact simulation
KW - Isogeometric analysis
KW - mortar method
KW - spectral elements
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506041
DO - https://doi.org/10.1002/nme.6264
VL - 121
IS - 6
SP - 1248
EP - 1267
PB - Wiley Online Libary
AN - OPUS4-50604
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Otto, Peter
A1 - Lorenzis, L.
A1 - Unger, Jörg F.
T1 - Explicit dynamics in impact simulation using a NURBS contact interface
N2 - In this paper, the impact problem and the subsequent wave propagation are considered. For the contact discretization an intermediate NURBS layer is added between the contacting finite element bodies, which allows a smooth contact formulation and efficient element‐based integration. The impact event is ill‐posed and requires a regularization to avoid propagating stress oscillations. A nonlinear mesh dependent penalty regularization is used, where the stiffness of the penalty regularization increases upon mesh refinement. Explicit time integration methods are well suited for wave propagation problems, but are efficient only for diagonal mass matrices. Using a spectral element discretization and the coupled FE‐NURBS approach the bulk part of the mass matrix is diagonal.
KW - Impact simulation
KW - Explicit dynamics
KW - Isogeometric analysis
KW - Spectral elements
KW - Mortar method
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494947
DO - https://doi.org/10.1002/nme.6264
SP - 1
EP - 21
PB - Wiley Online Libary
AN - OPUS4-49494
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Stockmann, Jörg M.
A1 - Radnik, Jörg
A1 - Bütefisch, S.
A1 - Busch, I.
A1 - Weimann, T.
A1 - Passiu, C.
A1 - Rossi, A.
A1 - Unger, Wolfgang
T1 - A new test specimen for the determination of the field of view of small-area X-ray photoelectron spectrometers
N2 - Small-area/spot photoelectron spectroscopy (SAXPS) is a powerful tool for the investigation of small surface features like microstructures of electronic devices, sensors or other functional surfaces, and so forth. For evaluating the quality of such microstructures, it is often crucial to know whether a small signal in a spectrum is an unwanted contamination of the field of view (FoV), defined by the instrument settings, or it originated from outside. To address this issue, the d80/20 parameter of a line scan across a chemical edge is often used. However, the typical d80/20 parameter does not give information on contributions from the long tails of the X-ray beam intensity distribution or the electron-optical system as defined by apertures. In the VAMAS TWA2 A22 project “Applying planar, patterned, multi-metallic samples to assess the impact of analysis area in surface-chemical analysis,” new test specimen was developed and tested. The here presented testing material consists of a silicon wafer substrate with an Au-film and embedded Cr circular and square spots with decreasing dimensions from 200 μm down to 5 μm. The spot sizes are traceable to the length unit due to size measurements with a metrological SEM. For the evaluation of the FoV, we determined the Au4f intensities measured with the center of the FoV aligned with the center of the spot and normalized to the Au4f intensity determined on the Au-film. With this test specimen, it was possible to characterize, as an example, the FoV of a Kratos AXIS Ultra DLD XPS instrument.
T2 - ECASIA 2019
CY - Dresden, Germany
DA - 15.09.2019
KW - Field of view
KW - Reference material
KW - Selected area XPS
KW - Small-area XPS
KW - Small-spot XPS
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-509902
DO - https://doi.org/10.1002/sia.6831
SN - 1096-9918
VL - 52
IS - 12
SP - 890
EP - 894
PB - John Wiley & Sons Ltd
AN - OPUS4-50990
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Ahmadi, Samim
A1 - Thummerer, G.
A1 - Breitwieser, S.
A1 - Mayr, G.
A1 - Lecompagnon, Julien
A1 - Burgholzer, P.
A1 - Jung, P.
A1 - Caire, G.
A1 - Ziegler, Mathias
T1 - Multi-dimensional reconstruction of internal defects in additively manufactured steel using photothermal super resolution combined with virtual wave based image processing
N2 - We combine three different approaches to greatly enhance the defect reconstruction ability of active thermographic testing. As experimental approach, laser-based structured illumination is performed in a step-wise manner. As an intermediate signal processing step, the virtual wave concept is used in order to effectively convert the notoriously difficult to solve diffusion-based inverse problem into a somewhat milder wavebased inverse problem. As a final step, a compressed-sensing based optimization procedure is applied which efficiently solves the inverse problem by making advantage of the joint sparsity of multiple blind measurements. To evaluate our proposed processing technique, we investigate an additively manufactured stainless steel sample with eight internal defects. The concerted super resolution approach is compared to conventional thermographic reconstruction techniques and shows an at least four times better spatial resolution.
KW - Active thermography
KW - Additive manufacturing
KW - Stainless steel
KW - ADMM
KW - Block regularization
KW - Internal defects
KW - Joint sparsity
KW - Laser excitation
KW - Multi-dimensional reconstruction
KW - Photothermal super resolution
KW - Virtual waves
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-525330
DO - https://doi.org/10.1109/tii.2021.3054411
SN - 1551-3203
SN - 1941-0050
VL - 17
IS - 11
SP - 7368
EP - 7378
PB - IEEE
CY - New York, NY
AN - OPUS4-52533
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Mohr, Gunther
A1 - Nowakowski, Susanna
A1 - Altenburg, Simon
A1 - Maierhofer, Christiane
A1 - Hilgenberg, Kai
T1 - Experimental Determination of the Emissivity of Powder Layers and Bulk Material in Laser Powder Bed Fusion Using Infrared Thermography and Thermocouples
N2 - Recording the temperature distribution of the layer under construction during laser powder bed fusion (L-PBF) is of utmost interest for a deep process understanding as well as for quality assurance and in situ monitoring means. While having a notable number of thermal monitoring approaches in additive manufacturing (AM), attempts at temperature calibration and emissivity determination are relatively rare. This study aims for the experimental temperature adjustment of an off-axis infrared (IR) thermography setup used for in situ thermal data acquisition in L-PBF processes. The temperature adjustment was conducted by means of the so-called contact method using thermocouples at two different surface conditions and two different materials: AISI 316L L-PBF bulk surface, AISI 316L powder surface, and IN718 powder surface. The apparent emissivity values for the particular setup were determined. For the first time, also corrected, closer to real emissivity values of the bulk or powder surface condition are published. In the temperature region from approximately 150 °C to 580 °C, the corrected emissivity was determined in a range from 0.2 to 0.25 for a 316L L-PBF bulk surface, in a range from 0.37 to 0.45 for 316L powder layer, and in a range from 0.37 to 0.4 for IN718 powder layer.
KW - Emisssivity
KW - Laser Powder Bed Fusion (L-PBF)
KW - Selective Laser Melting (SLM)
KW - Additive Manufacturing (AM)
KW - Process monitoring
KW - Infrared thermography
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-516148
DO - https://doi.org/10.3390/met10111546
VL - 10
IS - 11
SP - 1546
PB - MDPI
CY - Basel, Schweiz
AN - OPUS4-51614
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Ulbricht, Alexander
A1 - Mohr, Gunther
A1 - Altenburg, Simon
A1 - Oster, Simon
A1 - Maierhofer, Christiane
A1 - Bruno, Giovanni
ED - Czujko, T.
ED - Benedetti, M.
T1 - Can Potential Defects in LPBF Be Healed from the Laser Exposure of Subsequent Layers? A Quantitative Study
N2 - Additive manufacturing (AM) of metals and in particular laser powder bed fusion (LPBF) enables a degree of freedom in design unparalleled by conventional subtractive methods. To ensure that the designed precision is matched by the produced LPBF parts, a full understanding of the interaction between the laser and the feedstock powder is needed. It has been shown that the laser also melts subjacent layers of material underneath. This effect plays a key role when designing small cavities or overhanging structures, because, in these cases, the material underneath is feed-stock powder. In this study, we quantify the extension of the melt pool during laser illumination of powder layers and the defect spatial distribution in a cylindrical specimen. During the LPBF process, several layers were intentionally not exposed to the laser beam at various locations, while the build process was monitored by thermography and optical tomography. The cylinder was finally scanned by X-ray computed tomography (XCT). To correlate the positions of the unmolten layers in the part, a staircase was manufactured around the cylinder for easier registration. The results show that healing among layers occurs if a scan strategy is applied, where the orientation of the hatches is changed for each subsequent layer. They also show that small pores and surface roughness of solidified material below a thick layer of unmolten material (>200 µm) serve as seeding points for larger voids. The orientation of the first two layers fully exposed after a thick layer of unmolten powder shapes the orientation of these voids, created by a lack of fusion.
KW - Computed tomography
KW - Laser Powder Bed Fusion
KW - In situ monitoring
KW - infrared Thermography
KW - Optical Tomography
KW - Additive manufacturing
KW - AISI 316L
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-528778
DO - https://doi.org/10.3390/met11071012
VL - 11
IS - 7
SP - 1012
PB - MDPI
CY - Basel
AN - OPUS4-52877
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Altenburg, Simon
A1 - Straße, Anne
A1 - Gumenyuk, Andrey
A1 - Maierhofer, Christiane
T1 - In-situ monitoring of a laser metal deposition (LMD) process: comparison of MWIR, SWIR and high-speed NIR thermography
N2 - Additive manufacturing offers a range of novel applications. However, the manufacturing process is complex and the production of almost defect-free parts with high reliability and durability is still a challenge. Thermography is a valuable tool for process surveillance, especially in metal additive manufacturing processes. The high process temperatures allow one to use cameras usually operating in the visible spectral range. Here, we compare the results of measurements during the manufacturing process of a commercial laser metal deposition setup using a mid wavelength infrared camera with those from a short wavelength infrared camera and those from a visual spectrum high-speed camera with band pass filter in the near infrared range.
KW - Additive Manufacturing
KW - Process monitoring
KW - Thermography
KW - LMD
KW - Metal
KW - MWIR
KW - SWIR
KW - NIR
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-516318
DO - https://doi.org/10.1080/17686733.2020.1829889
VL - 19
IS - 2
SP - 97
EP - 114
PB - Taylor & Francis Group
CY - London, UK
AN - OPUS4-51631
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Ahmadi, Samim
A1 - Lecompagnon, Julien
A1 - Hirsch, Philipp Daniel
A1 - Burgholzer, P.
A1 - Jung, P.
A1 - Caire, G.
A1 - Ziegler, Mathias
T1 - Laser excited super resolution thermal imaging for nondestructive inspection of internal defects
N2 - A photothermal super resolution technique is proposed for an improved inspection of internal defects. To evaluate the potential of the laser-based thermographic technique, an additively manufactured stainless steel specimen with closely spaced internal cavities is used. Four different experimental configurations in transmission, reflection, stepwise and continuous scanning are investigated. The applied image post-processing method is based on compressed sensing and makes use of the block sparsity from multiple measurement events. This concerted approach of experimental measurement strategy and numerical optimization enables the resolution of internal defects and outperforms conventional thermographic inspection techniques.
KW - Super Resolution
KW - Laser Thermography
KW - Non Destructive Testing
KW - Comressed Sensing
KW - Inverse Problem
KW - Thermography
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-519016
DO - https://doi.org/10.1038/s41598-020-77979-y
VL - 10
IS - 1
SP - 22357
PB - Springer Nature
AN - OPUS4-51901
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Rothbart, Nick
A1 - Maierhofer, Christiane
A1 - Goldammer, M.
A1 - Hohlstein, F.
A1 - Koch, J.
A1 - Kryukov, I.
A1 - Mahler, G.
A1 - Stotter, B.
A1 - Oswald-Tranta, B.
A1 - Sengebusch, M.
T1 - A round robin test of flash thermography of CFRP and metal structures
N2 - Within the scope of a DIN INS project, a flash thermography round robin test that evaluates reliability, comparability and efficiency of different testing situations is organized. The results give information about the detectability of defects e.g. by their size and depth, the evaluation method and by the materials used. Besides, the influence of equipment and parameters used by the participants on the results were analysed. All of the quantitative results as well as the feedback given by the participants will be presented in a DIN committee in order to contribute to a flash thermography standard.
T2 - 7th International Symposium on NDT in Aerospace
CY - Bremen, Germany
DA - 16.11.2015
KW - Flash thermography
KW - Round robin test
KW - Metal
KW - Flat bottom holes
KW - SNR
PY - 2016
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-351070
UR - https://www.ndt.net/?id=18921
SN - 1435-4934
VL - 21
IS - 4
SP - 1
EP - 8
PB - NDT.net
CY - Kirchwald
AN - OPUS4-35107
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Stroh, Julia
A1 - Ali, Naveed Zafar
A1 - Maierhofer, Christiane
A1 - Emmerling, Franziska
T1 - Ettringite via Mechanochemistry: A Green and Rapid Approach for Industrial Application
N2 - Here, we report on a first mechanochemical synthesis of ettringite, an important cement hydrate phase. The mineral compound ettringite ([Ca3Al(OH)6]2·(SO4)3·26H2O) occurs rarely in nature, but is common for cement-based materials. Ettringite has wide technical application in the ceramic and paper industry. However, its typical wet-chemical synthesis is cumbersome and produces waste water and CO2 emissions. Here, we investigate the first mechanochemical synthesis of ettringite for developing an easy and sustainable alternative for industrial application. The mechanosynthesis was monitored in situ by coupled synchrotron X-ray diffraction (XRD) and infrared thermography (IRT). The consumption of the reactants and the formation of the reaction product were monitored with time-resolved XRD. IRT showed the temperature increase based on the exothermic reaction. The reaction conversion was significantly improved changing the strategy of the mechanosynthesis from a one- to a two-step process. The latter included neat pregrinding of solid reactants followed by a delayed addition of the stoichiometric amount of water. Thus, an increase of reaction conversion from 34 to 94% of ettringite could be achieved.
KW - XRD
KW - Mechanochemistry
KW - Ettringite
KW - In situ
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-479016
DO - https://doi.org/10.1021/acsomega.9b00560
SN - 2470-1343
VL - 4
IS - 4
SP - 7734
EP - 7737
PB - ACS Publications
CY - Washington, DC
AN - OPUS4-47901
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - da Costa, P. F. G. M.
A1 - Merízio, L. G.
A1 - Wolff, N.
A1 - Terraschke, H.
A1 - de Camargo, Andrea Simone Stucchi
T1 - Real-time monitoring of CdTe quantum dots growth in aqueous solution
N2 - Quantum dots (QDs) are remarkable semiconductor nanoparticles, whose optical properties are strongly size-dependent. Therefore, the real-time monitoring of crystal growth pathway during synthesis gives an excellent opportunity to a smart design of the QDs luminescence. In this work, we present a new approach for monitoring the formation of QDs in aqueous solution up to 90 °C, through in situ luminescence analysis, using CdTe as a model system. This technique allows a detailed examination of the evolution of their light emission. In contrast to in situ absorbance analysis, the in situ luminescence measurements in reflection geometry are particularly advantageous once they are not hindered by the concentration increase of the colloidal suspension. The synthesized particles were additionally characterized using X-ray diffraction analysis, transition electron microscopy, UV-Vis absorption and infrared spectroscopy. The infrared spectra showed that 3-mercaptopropionic acid (MPA)-based thiols are covalently bound on the surface of QDs and microscopy revealed the formation of CdS. Setting a total of 3 h of reaction time, for instance, the QDs synthesized at 70, 80 and 90 °C exhibit emission maxima centered at 550, 600 and 655 nm. The in situ monitoring approach opens doors for a more precise achievement of the desired emission wavelength of QDs.
KW - CdTe quantum dots
KW - In situ synthesis
KW - Real time growth control
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-603596
DO - https://doi.org/10.1038/s41598-024-57810-8
SN - 2045-2322
VL - 14
IS - 1
SP - 1
EP - 11
PB - Springer Science and Business Media LLC
AN - OPUS4-60359
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Becker, Tina
A1 - Breese, Philipp Peter
A1 - Metz, Christian
A1 - Altenburg, Simon
T1 - In-situ monitoring for PBF-LB/M processes: Does multispectral optical tomography add value in recognizing process deviations?
N2 - Laser powder bed fusion of metallic components (PBF-LB/M) is gaining acceptance in industry. However, the high costs and lengthy qualification processes required for printed components create the need for more effective in-situ monitoring and testing methods. This article proposes multispectral Optical Tomography (OT) as a new approach for monitoring the PBF-LB/M process. Compared to other methods, OT is a low-cost process monitoring method that uses long-time exposure imaging to observe the build process. However, it lacks time resolution compared to expensive thermographic sensor systems. Monochromatic OT (1C-OT) is already commercially available and observes the building process layer-wise using a single wavelength window in the NIR range. Multispectral OT (nC-OT) utilizes a similar setup but can measure multiple wavelength ranges per location simultaneously. By comparing the classical 1C-OT and nC-OT approaches, this article examines the advantages of nC-OT (two channel OT and RGB-OT) in reducing the false positive rate for process deviations and approximating maximum temperatures for a better comparison between different build processes and materials. This could ultimately reduce costs and time for part qualification. The main goal of this contribution is to assess the advantages of nC-OT compared to 1C-OT for in-situ process monitoring of PBF-LB/M.
T2 - Nolamp 2023
CY - Turku, Finland
DA - 22.08.2023
KW - Thermography
KW - Process Monitoring
KW - Additive manufacturing
KW - BPF-LB/M
KW - In-situ
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-592498
DO - https://doi.org/10.1088/1757-899X/1296/1/012008
VL - 1296
SP - 1
EP - 11
PB - IOP Publishing
CY - Bristol, UK
AN - OPUS4-59249
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Dopffel, N.
A1 - An Stepec, Biwen Annie
A1 - de Rezende, J.
A1 - Machado de Sousa, D.
A1 - Koerdt, Andrea
T1 - Microbiology of Underground Hydrogen Storage
N2 - Climate change is becoming one of the greatest challenges facing our society, particularly due to the continued use of fossil fuels. The steadily increasing demand for energy and the continuously growing world population will further intensify these challenges. The development of renewable energies is therefore of central importance. The 2020 EU Energy Roadmap aims to increase the share of renewable energies (gross energy consumption) to 55% by 2050.
Hydrogen (H2) has the highest potential to become the primary renewable energy source. It is envisioned that by 2050 up to 24% of the total energy demand of Europe is to be ensured by H2. However, a decisive disadvantage of the climate friendly alternatives is the massive containment demand, which needs to be highly secure, cost efficient and easily extractable.
Underground geological formations (UGF) represent a seemingly optimal alternative to meet the rapidly increasing storage demand. In this context, many studies are currently underway to determine the feasibility and risks of UGF. However, little or no consideration is being given to microbiology. Therefore, in this Research Topic we will focus on achieving a greater understanding of the impact microorganisms exert on UGF, with a particular emphasis on interdisciplinary studies.
As many subsurface microbial communities can use H2 as an electron donor, production of seemingly undesirable metabolic byproducts, such as hydrogen sulfide, methane, and acids, are also to be expected. However, the rate of the H2 conversion by the microorganisms, how their metabolic activities impact the UGF on a short-term and long-term scale, the extent of damages microorganisms exert on the infrastructure, or potential use of microorganisms to enhance UGF are just a few questions that require urgent research to assess the role of microorganisms in this new anthropogenic use of the subsurface environment. These and many questions can be addressed in this article collection. In particular, understanding microbial community changes and activity rates will help assess operational and environmental risks, develop mitigation strategies and provide new insights on life under extreme conditions (i.e., pressure, salinity).
In this Research Topic, the editorial team particularly welcomes Original Research, Hypothesis and Theory, Method, and Review manuscripts that deal with the latest advances in microbiology in formations that are planned or currently prepared for hydrogen storage, from both fundamental and practical points of view. The ultimate objective is to promote a deeper understanding into the sustainability of UGF and generate interdisciplinary research involving microbiologists, reservoir engineers, geologists, chemists, physicists.
The topics of interest include, but are not limited to:
• Microbial diversity in different underground hydrogen storage sites or formations currently being considered for hydrogen storage
• Mechanism and impact of microbial growth under high H2 pressure
• Potential role of microorganisms in the short-term and long-term storage of hydrogen
• Potential influences of microorganisms on the hydrogen storage infrastructure systems, e.g., microbiologically influenced corrosion, biofilm growth
• Hydrogen-solid-microorganism interactions, including the influence of microbial growth on UGF geological parameters
• Mechanism and modelling of microbial impact on hydrogen storage
UGF relevant for this Research Topic include porous media, salt caverns, deep aquifers, hard rock caverns and depleted oil/gas reservoirs.
KW - Biodeterioration and biodegradation
KW - Geology
KW - Anaerobic pathways
KW - Microbial simulation,
KW - Hydrogen storage
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-579042
DO - https://doi.org/10.3389/fenrg.2023.1242619
SN - 2296-598X
VL - 11
SP - 1
EP - 3
PB - Frontiers
CY - Frontiers in Energy Research
AN - OPUS4-57904
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Abel, Andreas
A1 - Rosalie, Julian M.
A1 - Reinsch, Stefan
A1 - Zapala, Pawel
A1 - Michels, Heiner
A1 - Skrotzki, Birgit
T1 - Influence of Mo and B additions in intermetallic near-Fe3Al alloys on microstructure and mechanical properties
N2 - Iron aluminides, already reported in the late 19th century, did not cease to attract the interest of scientists and engineers ever since. Besides good oxidation resistance, low density and resource availability, potentials for hightemperature strengths that compete with high-alloy steels were unlocked by low alloy contents. Still, research on alloy design continues, as alloying usually comes at the price of brittleness in low-temperature regimes. A potential candidate is the quinary Fe–Al–Mo–Ti–B system which is strengthened by solid solution and eutectic borides. It was shown to have good strength and outstanding creep resistance under compressive loading up to elevated temperatures. Although the individual effect of alloy additions is well understood in iron aluminides, little is known about the combined effects of alloying concentrations on microstructure, phase stability and mechanical properties. Therefore a systematic study of two Ti-doped near-Fe3Al alloys with varying contents of Mo (2–4 at.%) and B (0.5–1 at.%) was conducted. In total eight different alloys were fabricated by investment casting into ceramic shell molds. Alloys were characterized and compared by grain size, phase transitions, microstructure evolution as well as elemental compositions and volume fractions of phases. For mechanical characterization, macrohardness and microhardness tests as well as tensile tests at ambient and high tempera tures were conducted. Independent of alloy additions, alloys with 24–25 at.% Al exhibit superior proof strength due to a higher matrix hardness. Decreasing B content generally decreases strength by lower secondary phase fractions which contribute via particle hardening. Reducing Mo content decreases both the solute concentration in the matrix and secondary phase fractions. Surprisingly, strength is similar or even superior to alloys with higher Mo content. Strength relations are discussed with a focus on solid-solution hardening theory and other competing strengthening mechanisms.
KW - Materials Chemistry
KW - Metals and Alloys
KW - Mechanical Engineering
KW - Mechanics of Materials
KW - General Chemistry
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-585284
DO - https://doi.org/10.1016/j.intermet.2023.108074
VL - 163
SP - 1
EP - 11
PB - Elsevier Ltd.
AN - OPUS4-58528
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Jovičević-Klug, Matic
A1 - Souza Filho, Isnaldi R.
A1 - Springer, Hauke
A1 - Adam, Christian
A1 - Raabe, Dierk
T1 - Green steel from red mud through climate-neutral hydrogen plasma reduction
N2 - AbstractRed mud is the waste of bauxite refinement into alumina, the feedstock for aluminium production1. With about 180 million tonnes produced per year1, red mud has amassed to one of the largest environmentally hazardous waste products, with the staggering amount of 4 billion tonnes accumulated on a global scale1. Here we present how this red mud can be turned into valuable and sustainable feedstock for ironmaking using fossil-free hydrogen-plasma-based reduction, thus mitigating a part of the steel-related carbon dioxide emissions by making it available for the production of several hundred million tonnes of green steel. The process proceeds through rapid liquid-state reduction, chemical partitioning, as well as density-driven and viscosity-driven separation between metal and oxides. We show the underlying chemical reactions, pH-neutralization processes and phase transformations during this surprisingly simple and fast reduction method. The approach establishes a sustainable toxic-waste treatment from aluminium production through using red mud as feedstock to mitigate greenhouse gas emissions from steelmaking.
KW - Multidisciplinary
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-594424
DO - https://doi.org/10.1038/s41586-023-06901-z
SN - 0028-0836
VL - 625
IS - 7996
SP - 703
EP - 709
PB - Springer Science and Business Media LLC
AN - OPUS4-59442
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Machado Ferreira de Araujo, F.
A1 - Duarte-Ruiz, D.
A1 - Saßnick, H.-D.
A1 - Gentzmann, Marie C.
A1 - Huthwelker, T.
A1 - Cocchi, C.
T1 - Electronic Structure and Core Spectroscopy of Scandium Fluoride Polymorphs
N2 - Microscopic knowledge of the structural, energetic, and electronic properties of scandium fluoride is still incomplete despite the relevance of this material as an intermediate for the manufacturing of Al−Sc alloys. In a work based on first-principles calculations and X-ray spectroscopy, we assess the stability and electronic structure of six computationally predicted ScF3 polymorphs, two of which correspond to experimentally resolved single-crystal phases. In the theoretical analysis based on density functional theory (DFT), we identify similarities among the polymorphs based on their formation energies, chargedensity distribution, and electronic properties (band gaps and density of states). We find striking analogies between the results obtained for the ow- and high-temperature phases of the material, indirectly confirming that the transition occurring between them mainly consists of a rigid rotation of the lattice. With this knowledge, we examine the X-ray absorption spectra from the Sc and F K-edge contrasting firstprinciples results obtained from the solution of the Bethe−Salpeter equation on top of all-electron DFT with high-energy-resolution fluorescence detection measurements. Analysis of the computational results sheds light on the electronic origin of the absorption maxima and provides information on the prominent excitonic effects that characterize all spectra. A comparison with measurements confirms that the sample is mainly composed of the high- and low-temperature polymorphs of ScF3. However, some fine details in the experimental results suggest that the probed powder sample may contain defects and/or residual traces of metastable polymorphs.
KW - Scandium
KW - X-ray spectroscopy
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-570727
DO - https://doi.org/10.1021/acs.inorgchem.2c04357
SN - 0020-1669
VL - 62
IS - 10
SP - 4238
EP - 4247
PB - ACS Publications
CY - Washington DC
AN - OPUS4-57072
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Dombinov, V.
A1 - Herzel, Hannes
A1 - Meiller, M.
A1 - Müller, F.
A1 - Willbold, S.
A1 - Zang, J. W.
A1 - da Fonseca-Zang, W. A.
A1 - Adam, Christian
A1 - Klose, H.
A1 - Poorter, H.
A1 - Jablonowski, N. D.
A1 - Schrey, S. D.
T1 - Sugarcane bagasse ash as fertilizer for soybeans: Effects of added residues on ash composition, mineralogy, phosphorus extractability and plant availability
N2 - Sugarcane bagasse is commonly combusted to generate energy. Unfortunately, recycling strategies rarely consider the resulting ash as a potential fertilizer. To evaluate this recycling strategy for a sustainable circular economy, we characterized bagasse ash as a fertilizer and measured the effects of co-gasification and co-combustion of bagasse with either chicken manure or sewage sludge: on the phosphorus (P) mass fraction, P-extractability, and mineral P phases. Furthermore, we investigated the ashes as fertilizer for soybeans under greenhouse conditions. All methods in combination are reliable indicators helping to assess and predict P availability from ashes to soybeans. The fertilizer efficiency of pure bagasse ash increased with the ash amount supplied to the substrate. Nevertheless, it was not as effective as fertilization with triple-superphosphate and K2SO4, which we attributed to lower P availability. Co-gasification and co-combustion increased the P mass fraction in all bagasse-based ashes, but its extractability and availability to soybeans increased only when co-processed with chicken manure, because it enabled the formation of readily available Ca-alkali phosphates. Therefore, we recommend co-combusting biomass with alkali-rich residues to increase the availability of P from the ash to plants.
KW - Combustion and gasification
KW - Phosphate extractability and availability
KW - X-ray diffraction (XRD)
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-567632
DO - https://doi.org/10.3389/fpls.2022.1041924
SN - 1664-462X
VL - 13
SP - 1
EP - 13
PB - Frontiers Media
CY - Lausanne
AN - OPUS4-56763
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Winkler, Nicolas P.
A1 - Kotlyar, O.
A1 - Schaffernicht, E.
A1 - Matsukura, H.
A1 - Ishida, H.
A1 - Neumann, Patrick P.
A1 - Lilienthal, A. J.
T1 - Super-resolution for Gas Distribution Mapping
N2 - Gas Distribution Mapping (GDM) is a valuable tool for monitoring the distribution of gases in a wide range of applications, including environmental monitoring, emergency response, and industrial safety. While GDM is actively researched in the scope of gas-sensitive mobile robots (Mobile Robot Olfaction), there is a potential for broader applications utilizing sensor networks. This study aims to address the lack of deep learning approaches in GDM and explore their potential for improved mapping of gas distributions. In this paper, we introduce Gas Distribution Decoder (GDD), a learning-based GDM method. GDD is a deep neural network for spatial interpolation between sparsely distributed sensor measurements that was trained on an extensive data set of realistic-shaped synthetic gas plumes based on actual airflow measurements. As access to ground truth representations of gas distributions remains a challenge in GDM research, we make our data sets, along with our models, publicly available. We test and compare GDD with state-of-the-art models on synthetic and real-world data. Our findings demonstrate that GDD significantly outperforms existing models, demonstrating a 35% improvement in accuracy on synthetic data when measured using the Root Mean Squared Error over the entire distribution map. Notably, GDD appears to have superior capabilities in reconstructing the edges and characteristic shapes of gas plumes compared to traditional models. These potentials offer new possibilities for more accurate and efficient environmental monitoring, and we hope to inspire other researchers to explore learning-based GDM.
KW - Gas distribution mapping
KW - Spatial interpolation
KW - Sensor networks
KW - Deep learning
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-607786
DO - https://doi.org/10.1016/j.snb.2024.136267
SN - 0925-4005
VL - 419
SP - 1
EP - 12
PB - Elsevier B.V.
AN - OPUS4-60778
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Davison, Nathan
A1 - Hemingway, Jack M.
A1 - Wills, Corinne
A1 - Stolar, Tomislav
A1 - Waddell, Paul G.
A1 - Dixon, Casey M.
A1 - Barron, Luke
A1 - Dawson, James A.
A1 - Lu, Erli
T1 - Mechanochemical Synthesis of a Sodium Anion Complex [Na+(2,2,2-cryptand)Na–] and Studies of Its Reactivity: Two-Electron and One-Electron Reductions
N2 - Group 1 metal molecular chemistry is dominated by a +1 oxidation state, while a 0 oxidation state is widespread in the metals. A more exotic, yet still available, oxidation state of group 1 metal is −1, i.e., alkalide. Reported as early as the 1970s, the alkalides appear in every modern inorganic chemistry textbook as an iconic chemical curiosity, yet their reactivity remains unexplored. This is due to their synthetic hurdles. In this work, we report the first facile synthesis of the archetypical alkalide complex, [Na+(2,2,2-cryptand)Na–], which allows us to unveil a versatile reactivity profile of this once exotic species.
KW - Mechanochemistry
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-608632
DO - https://doi.org/10.1021/acs.inorgchem.4c02914
VL - 63
IS - 32
SP - 15247
EP - 15258
PB - American Chemical Society (ACS)
AN - OPUS4-60863
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schilling, Markus
A1 - Marschall, Niklas
A1 - Niebergall, Ute
A1 - Wachtendorf, Volker
A1 - Böhning, Martin
T1 - Characteristics of environmental stress cracking of PE-HD induced by biodiesel and diesel fuels
N2 - In the context of the increasing effect of carbon dioxide emissions on the global climate biodiesel produced from renewable sources has emerged as a promising contender replacing fossil fuels, especially in long-range transport vehicles, using existing engines and infrastructure.
High-density polyethylene is one of the prevailing materials for pipe and container applications for storage and transport of such fuels, both, from fossil and renewable resources. The contact with the respective fuels raises questions concerning material compatibility as biodiesel exhibits significant differences compared to conventional diesel fuel affecting its sorption and plasticization behavior in polyethylene. In this study, its behavior with respect to environmental stress cracking, considered one of the most frequent damage mechanisms leading to failure of polymer parts and packaging, was evaluated using the well-established Full Notch Creep Test. This
approach allows for a detailed fracture surface analysis using imaging techniques, such as optical and laser scanning microscopy, as well as infrared spectroscopy. Comparing the environmental stress cracking behavior in standard surfactant solutions with that in biodiesel and diesel, respective crack propagation rates, showing different levels of acceleration, were determined and details of the underlying mechanisms could be revealed.
Furthermore, the specific infrared absorption of the biodiesel’s ester functionality allows its semi-quantitative determination on the fracture surface of the tested specimens after failure. Thus, a preferred uptake of sorptive fluids in the fracture zone due to local morphological changes of the polyethylene could be directly evidenced by infrared spectroscopy.
KW - Environmental stress cracking (ESC)
KW - Full notch creep test (FNCT)
KW - Confocal laser scanning microscopy (LSM)
KW - Biodiesel
KW - Diesel
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-608591
DO - https://doi.org/10.1016/j.polymertesting.2024.108547
VL - 138
SP - 1
EP - 16
PB - Elsevier Ltd.
AN - OPUS4-60859
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zhuang, Y.
A1 - Spahr, S.
A1 - Lutze, H.V.
A1 - Reith, C.J.
A1 - Hagemann, N.
A1 - Paul, Andrea
A1 - Haderlein, S.B.
T1 - Persulfate activation by biochar and iron: Effect of chloride on formation of reactive species and transformation of N,N-diethyl-m-toluamide (DEET)
N2 - Fenton-like processes using persulfate for oxidative water treatment and contaminant removal can be enhanced by the addition of redox-active biochar, which accelerates the reduction of Fe(III) to Fe(II) and increases the yield of reactive species that react with organic contaminants. However, available data on the formation of non-radical or radical species in the biochar/Fe(III)/persulfate system are inconsistent, which limits the evaluation of treatment efficiency and applicability in different water matrices. Based on competition kinetics calculations, we employed different scavengers and probe compounds to systematically evaluate the effect of chloride in presence of organic matter on the formation of major reactive species in the biochar/Fe(III)/persulfate system for the transformation of the model compound N,N‑diethyl-m-toluamide (DEET) at pH 2.5. We show that the transformation of methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO2) cannot serve as a reliable indicator for Fe(IV), as previously suggested, because sulfate radicals also induce PMSO2 formation. Although the formation of Fe(IV) cannot be completely excluded, sulfate radicals were identified as the major reactive species in the biochar/Fe(III)/persulfate system in pure water. In the presence of dissolved organic matter, low chloride concentrations (0.1 mM) shifted the major reactive species likely to hydroxyl radicals. Higher chloride concentrations (1 mM), as present in a mining-impacted acidic surface water, resulted in the formation of another reactive species, possibly Cl2•−, and efficient DEET degradation. To tailor the application of this oxidation process, the water matrix must be considered as a decisive factor for reactive species formation and contaminant removal.
KW - Water treatment
KW - Organic contaminants
KW - Fenton-like systems
KW - Radicals
KW - ESR
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-608677
DO - https://doi.org/10.1016/j.watres.2024.122267
SN - 0043-1354
VL - 265
SP - 1
EP - 8
PB - Elsevier Ltd.
AN - OPUS4-60867
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -