TY - JOUR A1 - Baer, Wolfram A1 - Wossidlo, Peter T1 - Validation of a low blow specimen technique for R-curve determination using a drop tower N2 - Fracture mechanics based component design requires appropriate fracture mechanics toughness data with respect to both, loading rate as well as test temperature. Taking high-rate loading into account such as with accidental scenarios, different standards such as ASTM E 1820 or BS 7448-3 provide some information on dynamic fracture mechanics testing. Nevertheless, the designations differ so that a validation of the own material specific test method used for dynamic R-curve determination is mandatory. In order to address this for ductile cast iron materials an experimental method for the reliable determination of dynamic J-integral crack resistance curves at -40 °C following the multiple specimen approach has been established and validated. The experimental concept offers some additional valuable features. Single values of dynamic crack initiation toughness can be determined using a single specimen technique based on crack sensors. Furthermore, an experimentally independent method is provided according to which CTOD δ5 R-curves can be established. The focus of the present paper is on the validation of the experimental low blow technique using a drop tower test system. A drop tower test system was developed and set up to perform low blow tests at temperatures down to -40 °C. The system allows for a variation of the impact mass and height and was optimized for testing of ductile cast iron at stress intensity rates from approximately 5∙10⁴ to 3∙10⁵ MPa√ms⁻¹. This range of loading rate is characteristic for instance with crash scenarios of heavy sectioned DCI casks for radioactive materials. In order to address characteristic challenges of impact tests (test duration of microseconds up to milliseconds, inertial effects, signal oscillations), an appropriate full bridge strain gage method for the measurement of force directly on the specimen as well as a non-contact measurement of load line displacement using an optical extensometer have been developed and validated. The low blow test requires either to prevent bouncing strikes of the hammer by using the stop block technique or to catch the hammer after its first strike. Both options are not part of the experimental concept and setup which have been realized here. The paper describes investigations which have been performed in order to make sure that bouncing strikes of the hammer do not cause additional crack extension in the specimen. This is necessary to ensure a unique relation between the work done and the achieved crack extension. The investigations covered the analysis of limit loads of the specimen with respect to the measured force. The measured stiffness of the specimen was assessed and signals of crack sensors were analyzed. Furthermore, an analysis of the mechanical behavior of the loading system and the specimen by optical observation was performed. Corresponding results are discussed in the paper. It had finally been proven that additional crack extension in the specimen due to bouncing strikes of the hammer is not to be expected under the given conditions of test setup, material and loading. It can be seen as a major experimental advantage that the striker does not have to be catched after the low blow test. T2 - XXIV Italian Group of Fracture Conference CY - Urbino, Italy DA - 01.03.2017 KW - Dynamic fracture mechanics KW - R-curve KW - Low blow KW - Ductile cast iron PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-437686 DO - https://doi.org/10.1016/j.prostr.2017.04.005 SN - 2452-3216 VL - 3 SP - 25 EP - 32 AN - OPUS4-43768 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Agudo Jácome, Leonardo A1 - Göbenli, G. A1 - Eggeler, G. ED - Göken, M. T1 - Transmission electron microscopy study of the microstructural evolution during high-temperature and low-stress (011) [01-1] shear creep deformation of the superalloy single crystal LEK 94 N2 - The present work describes the shear creep behavior of the superalloy LEK 94 at temperatures between 980 and 1050 °C and shear stresses between 50 and 140 MPa for loading on the macroscopic crystallographic shear system (MCSS) (011)[01-1]. The strain rate versus strain curves show short primary and extended secondary creep regimes. We find an apparent activation energy for creep of Qapp = 466 kJ/mol and a Norton-law stress exponent of n = 6. With scanning transmission electron microscopy, we characterize three material states that differ in temperature, applied stress, and accumulated strain/time. Rafting develops perpendicular to the maximum principal stress direction, gamma channels fill with dislocations, superdislocations cut gamma' particles, and dislocation networks form at gamma/gamma' interfaces. Our findings are in agreement with previous results for high-temperature and low-stress [001] and [110] tensile creep testing, and for shear creep testing of the superalloys CMSX-4 and CMSX-6 on the MCSSs (111)[01-1] and (001)[100]. The parameters that characterize the evolving gamma/gamma' microstructure and the evolving dislocation substructures depend on creep temperature, stress, strain, and time. KW - Dislocations KW - Microstructure KW - Scanning transmission electron microscopy (STEM) KW - Creep KW - Shear test PY - 2017 DO - https://doi.org/10.1557/jmr.2017.336 SN - 0884-2914 SN - 2044-5326 VL - 32 IS - 24 SP - 4491 EP - 4502 PB - Cambridge University Press CY - Cambrigde AN - OPUS4-43756 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gottlieb, Cassian A1 - Millar, Steven A1 - Günther, Tobias A1 - Wilsch, Gerd T1 - Revealing hidden spectral information of chlorine and sulfur in data of a mobile Laser-induced Breakdown Spectroscopy system using chemometrics N2 - For the damage assessment of reinforced concrete structures the quantified ingress profiles of harmful species like chlorides, sulfates and alkali need to be determined. In order to provide on-site analysis of concrete a fast and reliable method is necessary. Low transition probabilities as well as the high ionization energies for chlorine and sulfur in the near-infrared range makes the detection of Cl I and S I in low concentrations a difficult task. For the on-site analysis a mobile LIBS-system (k = 1064 nm, Epulse ≤ 3 mJ, t = 1.5 ns) with an automated scanner has been developed at BAM. Weak chlorine and sulfur signal intensities do not allow classical univariate analysis for process data derived from the mobile system. In order to improve the analytical performance multivariate analysis like PLS-R will be presented in this work. A comparison to standard univariate analysis will be carried out and results covering important parameters like detection and quantification limits (LOD, LOQ) as well as processing variances will be discussed (Allegrini and Olivieri, 2014 [1]; Ostra et al., 2008 [2]). It will be shown that for the first time a low cost mobile system is capable of providing reproducible chlorine and sulfur analysis on concrete by using a low sensitive system in combination with multivariate evaluation. KW - LIBS KW - Chemometrics KW - Building materials PY - 2017 DO - https://doi.org/10.1016/j.sab.2017.04.001 SN - 0584-8547 VL - 132 SP - 43 EP - 49 PB - Elsevier B.V. AN - OPUS4-40066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weltschev, Margit T1 - Auswahl eines Kennwertes für den Vergleich des mechanischen Leistungsniveaus von Polyethylenformstoffen für Gefahrgutverpackungen T1 - Parameter selection for the comparison of the mechanical level of performance of polyethylene molding materials for packagings of dangerous goods N2 - Zum Vergleich der Polyethylenformstoffe für eine Bauart von Gefahrgutverpackungen und IBC wurden die Materialkennwerte: Schmelze-Massefließrate MFR, Dichte D, Kerbschlag-zähigkeit acN bei -30 °C, Spannungsrissbeständigkeit (bestimmt mit dem Full Notch Creep Test) und Beständigkeit gegen oxidativen Abbau Ox (bestimmt durch den prozentualen Anstieg des MFR in Salpetersäure) in der DIN EN 15507 – Verpackung – Verpackungen zur Beförderung gefährlicher Güter – Vergleichende Werkstoffprüfung von Polyethylensorten ausgewählt. Das Ziel der Untersuchungen war die Auswahl eines Kennwertes für die Bestimmung des mechanischen Leistungsniveaus von Polyethylenformstoffen, da unter Druck Verpackungen beulen oder knicken. Zur Auswahl standen drei Prüfverfahren: a) Bestimmung der Biegesteifigkeit S nach DIN 53 350 (Prinzip von Ohlsen). b) Bestimmung der Biegefestigkeit σfM und Biegedehnung ɛfM nach DIN EN ISO 178 c) Bestimmung der Druckkraft Fmax und Verformung dL bei Fmax nach DIN EN ISO 604. Die Prüfmethode zur Bestimmung der Biegesteifigkeit nach DIN 53 350 eignet sich zum Vergleich des mechanischen Leistungsniveaus der Formstoffe. Zur Verbesserung der Reproduzierbarkeit der Ergebnisse sollte der Skalierungsbereich der Prüfapparatur erweitert wer-den, um genauere Messergebnisse zu erzielen. Der Dreipunktbiegeversuch nach DIN EN ISO 178 eignet sich bei verformungsfähigen Kunststoffen, wie dem Polyethylen, zur Bestimmung der Biegefestigkeit σfM. Dieser Ver-such besitzt den Nachteil, dass am Ort des maximalen Biegemoments in der Randschicht, wo auch die maximale Biegespannung erzeugt wird, zusätzlich der Biegestempel angreift. Die Messergebnisse haben gezeigt, dass die Druckprüfung nach DIN EN ISO 604 sich sehr gut zur Bewertung des mechanischen Verhaltens der Polyethylenformstoffe unter Druckbelastung (Stapeldruckprüfung der Verpackungen) eignet. KW - Gefahrgutverpackung KW - Polyethylen KW - Biegesteifigkeit KW - Biegefestigkeit KW - Druckkraft PY - 2017 DO - https://doi.org/10.3139/120.111025 SN - 0025-5300 VL - 59 IS - 5 SP - 466 EP - 471 PB - Carl Hanser Verlag GmbH & Co.KG CY - München AN - OPUS4-40145 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Joester, Maike A1 - Seifert, Stephan A1 - Emmerling, Franziska A1 - Kneipp, Janina T1 - Physiological influence of silica on germinating pollen as shown by Raman spectroscopy N2 - The process of silicification in plants and the biochemical effects of silica in plant tissues are largely unknown. To study the molecular changes occurring in growing cells that are exposed to higher than normal concentration of silicic acid, Raman spectra of germinating pollen grains of three species (Pinus nigra, Picea omorika, and Camellia japonica) were analyzed in a multivariate classification approach that takes into account the variation of biochemical composition due to species, plant tissue structure, and germination condition. The results of principal component analyses of the Raman spectra indicate differences in the utilization of stored lipids, a changed mobilization of storage carbohydrates in the pollen grain bodies, and altered composition and/or structure of cellulose of the developing pollen tube cell walls. These biochemical changes vary in the different species. KW - Silica KW - Raman spectroscopy KW - Principal component analysis PY - 2017 DO - https://doi.org/10.1002/jbio.201600011 SN - 1864-063X SN - 1864-0648 VL - 10 IS - 4 SP - 542 EP - 552 AN - OPUS4-40090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bender, P. A1 - Bogart, L.K. A1 - Posth, O. A1 - Szczerba, Wojciech A1 - Rogers, S.E. A1 - Castro, A. A1 - Nilsson, L. A1 - Zeng, L. J. A1 - Sugunan, A. A1 - Sommertune, J. A1 - Fornara, A. A1 - Gonzales-Alonso, D. A1 - Fernandez Barquin, L. A1 - Johansson, C. T1 - Structural and magnetic properties of multi-core nanoparticles analysed using a generalised numerical inversion method N2 - The structural and magnetic properties of magnetic multi-core particles were determined by numerical inversion of small angle scattering and isothermal magnetisation data. The investigated particles consist of iron oxide nanoparticle cores (9 nm) embedded in poly(styrene) spheres (160 nm). A thorough physical characterisation of the particles included transmission electron microscopy, X-ray diffraction and asymmetrical flow field-flow fractionation. Their structure was ultimately disclosed by an indirect Fourier transform of static light scattering, small angle X-ray scattering and small angle neutron scattering data of the colloidal dispersion. The extracted pair distance distribution functions clearly indicated that the cores were mostly accumulated in the outer surface layers of the poly(styrene) spheres. To investigate the magnetic properties, the isothermal magnetisation curves of the multi-core particles (immobilised and dispersed in water) were analysed. The study stands out by applying the same numerical approach to extract the apparent moment distributions of the particles as for the indirect Fourier transform. It could be shown that the main peak of the apparent moment distributions correlated to the expected intrinsic moment distribution of the cores. Additional peaks were observed which signaled deviations of the isothermal magnetisation behavior from the non-interacting case, indicating weak dipolar interactions. KW - Numerical inversion KW - Magnetic nanoparticles KW - Iron oxides KW - Magnetic properties KW - Structural properties PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-400952 DO - https://doi.org/10.1038/srep45990 SN - 2045-2322 VL - 7 SP - Article 45990, 1 EP - 14 AN - OPUS4-40095 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rodrigues, A.C.P. A1 - Österle, Werner A1 - Gradt, Thomas A1 - Azevedo, César Roberto de Farias T1 - Impact of copper nanoparticles on tribofilm formation determined by pin-on-disc tests with powder supply: Addition of artificial third body consisting of Fe3O4, Cu and graphite N2 - Copper, magnetite and graphite particles were mixed in order to observe their impact on the coefficient of friction (CoF) during pin-on-disc tests and on the tribofilm formation after testing. Pure magnetite powder provided a value of CoF of 0.4. Magnetite-copper mixtures tested at 400 °C revealed lower CoF values (~0.4) than those at room temperature (~0.6). Magnetite-graphite and magnetite-graphite-copper mixtures presented lower CoF values (~0.3). All systems formed a magnetite-based tribofilm and patches of metallic copper were found on the tribosurfaces of the mixtures containing copper. Carbon layers and graphite nanoinclusions were observed in the graphite mixtures. The incorporation of zirconia particles, a by-product of ball milling mixing, prevented the selective transfer of graphite and copper to the tribosurfaces of some of the samples. KW - Brake pad materials KW - Sliding friction KW - Transfer layer KW - Surface analysis KW - Model friction tests PY - 2017 DO - https://doi.org/10.1016/j.triboint.2017.02.014 SN - 0301-679X VL - 110 SP - 103 EP - 112 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-40104 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Joseph, A. A1 - Bernardes, C. E. S. A1 - Druzhinina, A. I. A1 - Varushchenko, R. M. A1 - Nguyen, Thi Yen A1 - Emmerling, Franziska A1 - Yuan, L. A1 - Dupray, V. A1 - Coquerel, G. A1 - Minas da Piedade, M. E. T1 - Polymorphic phase transition in 4′-hydroxyacetophenone: Equilibrium temperature, kinetic barrier, and the relative stability of Z′=1 and Z′=2 forms N2 - Particularly relevant in the context of polymorphism is understanding how structural, thermodynamic, and kinetic factors dictate the stability domains of polymorphs, their tendency to interconvert through phase transitions, or their possibility to exist in metastable states. These three aspects were investigated here for two 4′-hydroxyacetophenone (HAP) polymorphs, differing in crystal system, space group, and number and conformation of molecules in the asymmetric unit. The results led to a ΔfGm°-T phase diagram highlighting the enantiotropic nature of the system and the fact that the Z′=1 polymorph is not necessarily more stable than its Z′=2 counterpart. It was also shown that the form II → form I transition is entropy driven and is likely to occur through a nucleation and growth mechanism, which does not involve intermediate phases, and is characterized by a high activation energy. Finally, although it has been noted that conflicts between hydrogen bond formation and close packing are usually behind exceptions from the hypothesis of Z′=1 forms being more stable than their higher Z′ analogues, in this case, the HAP polymorph with stronger hydrogen bonds (Z′=2) is also the one with higher density. KW - Polymorphism KW - Polymorphic transition KW - 4'-hydroxyacetophenone PY - 2017 DO - https://doi.org/10.1021/acs.cgd.6b01876 SN - 1528-7483 SN - 1528-7505 VL - 17 IS - 4 SP - 1918 EP - 1932 PB - ACS AN - OPUS4-40167 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Jan P. A1 - Götschel, S. A1 - Maierhofer, Christiane A1 - Weiser, M. T1 - Determining the Material Parameters for the Reconstruction of Defects in Carbon Fiber Reinforced Polymers from Data Measured by Flash Thermography N2 - Flash thermography is a fast and reliable non-destructive testing method for the investigation of defects in carbon fiber reinforced polymer (CFRP) materials. In this paper numerical simulations of transient thermography data are presented, calculated for a quasi-isotropic flat bottom hole sample. They are compared to experimental data. These simulations are one important step towards the quantitative reconstruction of a flaw by assessing thermographic data. The applied numerical model is based on the finite-element method, extended by a semi-analytical treatment of the boundary of the sample, which is heated by the flash light. A crucial part for a reliable numerical model is the prior determination of the material parameters of the specimen as well as of the experimental parameters of the set-up. The material parameters in plane and in depth diffusivity are measured using laser line excitation. In addition, the absorption and heat transfer process of the first layers is investigated using an IR microscopic lens. The performance of the two distinct components of CFRP during heating – epoxy resin and carbon fibers – is examined. Finally, the material parameters are optimized by variation and comparison of the simulation results to the experimental data. The optimized parameters are compared to the measured ones and further methods to ensure precise material parameter measurements are discussed. T2 - 43rd Review of Progress in Quantitative Nondestructive Evaluation CY - Atlanta, GA, USA DA - 17.07.2016 KW - Aktive Thermografie KW - Thermische Diffusivität KW - Zerstörungsfreie Prüfung KW - Kohlenstofffaserverstärkter Kunststoff KW - CFK KW - Active thermography KW - Thermal diffusivity KW - Non-Destructive testing KW - Carbon fiber reinforced polymer KW - CFRP PY - 2017 SN - 978-0-7354-1474-7 DO - https://doi.org/10.1063/1.4974671 SN - 0094-243X VL - 1806 IS - 1 SP - UNSP 100006-1 EP - 11 PB - AIP Publishing CY - Melville, NY, USA AN - OPUS4-39332 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Billing, Mark A1 - Gräfe, Christine A1 - Saal, Adrian A1 - Biehl, Philip A1 - Clement, Joachim A1 - Dutz, silvio A1 - Weidner, Steffen A1 - Schacher, Felix T1 - Zwitterionic Iron Oxide (γ-Fe2O3) Nanoparticles Based on P(2VP-grad-AA) Copolymers N2 - This study presents the synthesis and characterization of zwitterionic core–shell hybrid nanoparticles consisting of a core of iron oxide multicore nanoparticles (MCNPs, γ-Fe2O3) and a shell of sultonated poly(2-vinylpyridine-grad-acrylic acid) copolymers. The gradient copolymers are prepared by reversible addition fragmentation chain transfer polymerization of 2-vinylpyridine (2VP), followed by the addition of tert-butyl acrylate and subsequent hydrolysis. Grafting of P(2VP-grad-AA) onto MCNP results in P(2VP-grad-AA)@MCNP, followed by quaternization using 1,3-propanesultone-leading to P(2VPS-grad-AA)@MCNP with a zwitterionic shell. The resulting particles are characterized by transmission electron microscopy, dynamic light scattering, and thermogravimetric analysis measurements, showing particle diameters of ≈70–90 nm and an overall content of the copolymer shell of ≈10%. Turbidity measurements indicate increased stability toward secondary aggregation after coating if compared to the pristine MCNP and additional cytotoxicity tests do not reveal any significant influence on cell viability. KW - Blockcopolymer KW - Controlled radical polymerization KW - Hybrid nanoparticles KW - Iron oxide nanoparticles KW - Sulfobetaines PY - 2017 DO - https://doi.org/10.1002/marc.201600637 SN - 1022-1336 SN - 1521-3927 VL - 38 IS - 4 SP - 1600637-1 EP - 1600637-8 PB - Wiley-VCH AN - OPUS4-39339 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Babutzka, Martin A1 - Heyn, A. T1 - Dynamic tafel factor adaption for the evaluation of instantaneous corrosion rates on zinc by using gel-type electrolytes N2 - The paper presents a new method for the determination and evaluation of tafel factors using gel-type electrolytes and electrochemical frequency modulation technique (EFM). This relatively new electrochemical method offers the possibility to determine both polarization resistances and tafel factors within one measurement and in short measuring intervals. Starting from a comprehensive parameter study it is shown that a direct relationship between the two values exists that can be described mathematically. This contribution presents the determined tafel factors for the system gel-type electrolyte/zinc and discusses their applicability and their limits. T2 - 19th Chemnitz Seminar on Materials Engineering – 19. Werkstofftechnisches Kolloquium CY - Chemnitz, Germany DA - 16.03.2017 KW - Gel-type electrolytes KW - Gelartige Elektrolyte KW - Zinc KW - Zink KW - Stern Geary constant KW - Stern-Geary-Konstante PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-394324 UR - http://iopscience.iop.org/article/10.1088/1757-899X/181/1/012021/pdf DO - https://doi.org/10.1088/1757-899X/181/1/012021 SN - 1757-899X SN - 1757-8981 VL - 181 IS - Conference 1 SP - Article UNSP 012021, 1 EP - 11 PB - IOP Publishing CY - Bristol, UK AN - OPUS4-39432 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Asadujjaman, Asad A1 - Kent, B. A1 - Bertin, Annabelle T1 - Phase transition and aggregation behaviour of an UCST-type copolymer poly(acrylamide-coacrylonitrile) in water: effect of acrylonitrile content, concentration in solution, copolymer chain length and presence of electrolyte N2 - An UCST-type copolymer of acrylamide (AAm) and acrylonitrile (AN) (poly(AAm-co-AN)) was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization and its temperature-induced phase transition and aggregation behaviour studied by turbidimetry, static and dynamic light scattering, small angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM) measurements. The phase transition temperature was found to increase with increasing AN content in the copolymer, concentration of the solutions and copolymer chain length. A significant effect was observed onto the phase transition temperature by addition of different electrolytes into the copolymer solution. The copolymer chains were aggregated below the phase transition temperature and disaggregated above it. The size of the aggregates increases with increasing AN contents and concentration of the copolymer solutions below the phase transition temperature. The copolymer chains were expanded and weekly associated in solution above the phase transition temperature. A model is proposed to explain such association–aggregation behaviour of poly(AAm-co-AN) copolymers depending on AN contents and concentration of the copolymer solutions as a function of temperature. KW - Thermoresponsive polymers KW - UCST-type copolymer PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-394636 DO - https://doi.org/10.1039/c6sm02262f SN - 1744-683X SN - 1744-6848 VL - 13 IS - 3 SP - 658 EP - 669 PB - RSC AN - OPUS4-39463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Philippen, Jan A1 - Guguschev, Christo A1 - Klimm, Detlef ED - Kuech, Thomas F. ED - Feigelson, Robert R. ED - Nakajima, K. ED - Stringfellow, G.B. T1 - Single crystal fiber growth of cerium doped strontium yttrate, SrY2O4:Ce3+ N2 - First single crystal fibers of cerium doped Strontium yttrate were fabricated using the laser-heated pedestal growth technique. Through thermodynamic Equilibrium calculations and by high-temperature mass spectrometry suitable growth conditions could be determined. The atmosphere played an important role during crystallization. It affected the composition shift, on the one hand, and the valence state of cerium, on the other hand. These dependencies can be explained by combining X-ray diffraction, elemental analysis, and optical spectroscopy. Crystallization in slightly reducing nitrogen atmosphere proved to be a reasonable choice, because evaporation is suppressed and trivalent cerium is stabilized. Strong green emission that depends on the Oxygen fugacity during crystallization could be excited using UV light. Optical properties of SrY2O4:Ce3+ were measured for the first time. KW - Laser heated pedestal growth KW - Oxides KW - Strontium yttrate KW - Single crystal fiber KW - LED phosphors PY - 2017 DO - https://doi.org/10.1016/j.jcrysgro.2016.11.033 SN - 0022-0248 SN - 1873-5002 VL - 459 SP - 17 EP - 22 PB - Elsevier CY - Amsterdam AN - OPUS4-39496 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maenz, S. A1 - Brinkmann, O. A1 - Kunisch, E. A1 - Horbert, V. A1 - Gunella, F. A1 - Bischoff, S. A1 - Schubert, H. A1 - Sachse, A. A1 - Xin, L. A1 - Günster, Jens A1 - Illerhaus, Bernhard A1 - Jandt, K. D. A1 - Bossert, J. A1 - Kinne, R. W. A1 - Bungartz, M. T1 - Enhanced bone formation in sheep vertebral bodies after minimally invasive treatment with a novel, PLGA fiber-reinforced brushite cement. N2 - Injectable, brushite-forming calcium phosphate cements (CPC) show potential for bone replacement, but they exhibit low mechanical strength. This study tested a CPC reinforced with poly(l-lactide-co-glycolide) acid (PLGA) fibers in a minimally invasive, sheep lumbar vertebroplasty model. The study aimed to test the in vivo biocompatibility and osteogenic potential of a PLGA fiber-reinforced, brushite-forming CPC in a sheep large animal model. KW - µCT KW - Vertebral KW - PLGA cement PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S152994301631066X DO - https://doi.org/10.1016/j.spinee.2016.11.006 SN - 1529-9430 SN - 1878-1632 VL - 17 IS - 5 SP - 709 EP - 719 PB - Elsevier Science direct AN - OPUS4-40462 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yilmaz, M. A1 - Kilinc, Y. A1 - Nadar, G. A1 - Tasdemir, Z. A1 - Wollschläger, Nicole A1 - Österle, Werner A1 - Leblebici, Y. A1 - Alaca, B. E. T1 - Top-down technique for scaling to nano in silicon MEMS N2 - Nanoscale building blocks impart added functionalities to microelectromechanical systems (MEMS). The integration of silicon nanowires with MEMS-based sensors leading to miniaturization with improved sensitivity and higher noise immunity is one example highlighting the advantages of this multiscale approach. The accelerated pace of research in this area gives rise to an urgent need for batch-compatible solutions for scaling to nano. To address this challenge, a monolithic fabrication approach of silicon nanowires with 10-lm-thick silicon-on-insulator (SOI) MEMS is developed in this work. A two-step Si etching approach is adopted, where the first step creates a shallow surface protrusion and the second step releases it in the form of a nanowire. It is during this second deep etching step that MEMS—with at least a 2-order-of-magnitude scale difference - is formed as well. The technique provides a pathway for preserving the lithographic resolution and transforming it into a very high mechanical precision in the assembly of micro- and nanoscales with an extreme topography. Validation of the success of integration is carried out via in situ actuation of MEMS inside an electron microscope loading the nanowire up to its fracture. The technique yields nanowires on the top surface of MEMS, thereby providing ease of access for the purposes of carrying out surface processes such as doping and contact formation as well as in situ observation. As the first study demonstrating such monolithic integration in thick SOI, the work presents a pathway for scaling down to nano for future MEMS combining multiple scales. KW - Nanowires KW - Silicon KW - Top-down KW - MEMS PY - 2017 DO - https://doi.org/10.1116/1.4978047 SN - 1071-1023 VL - 35 IS - 2 SP - 022001-1 EP - 022001-7 PB - America Vacuum Society AN - OPUS4-39370 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Seuthe, T. A1 - Mermillod-Blondin, A. A1 - Grehn, M. A1 - Bonse, Jörn A1 - Wondraczek, L. A1 - Eberstein, M. T1 - Structural relaxation phenomena in silicate glasses modifed by irradiation with femtosecond laser pulses N2 - Structural relaxation phenomena in binary and multicomponent lithium silicate glasses were studied upon irradiation with femtosecond (fs) laser pulses (800 nm central wavelength, 130 fs pulse duration) and subsequent thermal annealing experiments. Depending on the annealing temperature, micro-Raman spectroscopy analyses evidenced different relaxation behaviours, associated to bridging and non-bridging oxygen structures present in the glass network. The results indicate that the mobility of lithium ions is an important factor during the glass modification with fs-laser pulses. Quantitative phase contrast imaging (spatial light interference microscopy) revealed that these fs-laser induced structural modifications are closely related to local changes in the refractive index of the material. The results establish a promising strategy for tailoring fs-laser sensitivity of glasses through structural mobility. KW - Femtosecond laser KW - Silicate glasses KW - Raman spectroscopy KW - Structural relaxation KW - Refractive index PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-393045 DO - https://doi.org/10.1038/srep43815 SN - 2045-2322 VL - 7 SP - 43815, 1 EP - 43815, 10 PB - Nature Publishing Group CY - London, UK AN - OPUS4-39304 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Lohse, V. A1 - Negendank, D. A1 - Kormunda, M. A1 - Esser, N. T1 - Thin SnOx films for surface plasmon resonance enhanced ellipsometric gas sensing (SPREE) N2 - Background: Gas sensors are very important in several fields like gas monitoring, safety and environmental applications. In this approach, a new gas sensing concept is investigated which combines the powerful adsorption probability of metal oxide conductive sensors (MOS) with an optical ellipsometric readout. This concept Shows promising results to solve the problems of cross sensitivity of the MOS concept. Results: Undoped tin oxide (SnOx) and iron doped tin oxide (Fe:SnOx) thin add-on films were prepared by magnetron sputtering on the top of the actual surface plasmon resonance (SPR) sensing gold layer. The films were tested for their sensitivity to several gas species in the surface plasmon resonance enhanced (SPREE) gas measurement. It was found that the undoped tin oxide (SnOx) shows higher sensitivities to propane (C3H8) then to carbon monoxide (CO). By using Fe:SnOx, this relation is inverted. This behavior was explained by a change of the amount of binding sites for CO in the layer due to this iron doping. For hydrogen (H2) no such relation was found but the sensing ability was identical for both layer materials. This observation was related to a different sensing mechanism for H2 which is driven by the Diffusion into the layer instead of adsorption on the surface. Conclusion: The gas sensing selectivity can be enhanced by tuning the properties of the thin film overcoating. A relation of the binding sites in the doped and undoped SnOx films and the gas sensing abilities for CO and C3H8 was found. This could open the path for optimized gas sensing devices with different coated SPREE sensors. KW - Doped tin oxide KW - Ellipsometry KW - Gas sensing KW - Surface plasmon KW - Resonance KW - Thin films KW - Transparent conductive oxides PY - 2017 DO - https://doi.org/10.3762/bjnano.8.56 SN - 2190-4286 VL - 8 SP - 522 EP - 529 AN - OPUS4-39391 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kulla, Hannes A1 - Greiser, Sebastian A1 - Benemann, Sigrid A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Knowing When To Stop-Trapping Metastable Polymorphs in Mechanochemical Reactions N2 - The cocrystal formation of pyrazinamide (PZA) with malonic acid (MA) was studied in situ. The mechanochemical reaction proceeds via conversion of a crystalline intermediate (PZA:MA II) into the thermodynamically more stable form (PZA:MA I) upon further grinding. The information derived from in situ powder X-ray diffraction (PXRD) enabled the isolation of this new metastable polymorph. On the basis of the PXRD data, the crystal structure of the 1:1 cocrystal PZA:MA II was solved. The polymorphs were further characterized and compared by Raman spectroscopy, solid-state NMR spectroscopy, differential thermal analysis/thermogravimetric analysis, and scanning electron microscopy. Our study demonstrates how monitoring mechanochemical reactions by in situ PXRD can direct the discovery and isolation of even short-lived intermediates not yet accessed by conventional methods. KW - Mechanochemistry KW - Polymorphs KW - Metastable KW - In situ PXRD KW - Cocrystal KW - Pyrazinamide PY - 2017 DO - https://doi.org/10.1021/acs.cgd.6b01572 SN - 1528-7483 SN - 1528-7505 VL - 17 IS - 3 SP - 1190 EP - 1196 AN - OPUS4-39420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Huang, S. G. A1 - Vleugels, J. A1 - Mohrbacher, H. A1 - Woydt, Mathias T1 - Microstructure and tribological performance of NbC-Ni cermets modified by VC and Mo2C N2 - The current study reports on the influence of the Addition of 5–15 vol% VC or/and Mo2C carbide on the microstructure and mechanical properties of nickel bonded NbC cermets, which are compared to cobalt bonded NbC cermets. The NbC, Ni and secondary carbides powder mixtures were liquid phase sintered for 1 h at 1420 °C in vacuum. The fully densified cermets are composed of a cubic NbC grains matrix and an evenly distributed fcc Ni binder. NbC grain growth was significantly inhibited and a homogeneous NbC grain size distribution was obtained in the cermets with VC/Mo2C additions. The mechanical properties of the NbC-Ni matrix cermets are strongly dependent on the carbide and Ni binder content and are directly compared to their NbC-Co equivalents. The liquid phase sintered NbC-12 vol% Ni cermet had a modest Vickers hardness (HV30) of 1077 ± 22 kg/mm2 and an indentation toughness of 9.1 ± 0.5 MPa·m1/2. With the addition of 10–15 vol% VC, the hardness increased to 1359 ± 15 kg/mm2, whereas the toughness increased to 11.3 ± 0.1 MPa·m1/2. Addition of 5 and 10 vol% Mo2C into a NbC-12 vol% Ni mixtures generated the same values in HV30 and KIC when compared to VC additions. A maximum flexural strength of 1899 ± 77 MPa was obtained in the cermet with 20 vol% Ni binder and 4 vol% VC+4 vol% Mo2C addition, exhibiting a high fracture toughness of 15.0 ± 0.5 MPa·m1/2, but associated with a loss in hardness due to the high Ni content. The dry sliding wear behaviour was established at room temperature and 400 °C from 0.1 to 10 m/s. KW - Cermet KW - Liquid phase sintering KW - Grain growth KW - Wear KW - Niobium carbide PY - 2017 DO - https://doi.org/10.1016/j.ijrmhm.2017.03.012 SN - 0263-4368 VL - 66 SP - 188 EP - 197 AN - OPUS4-40505 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Kirner, Sabrina A1 - Koter, Robert A1 - Pentzien, Simone A1 - Spaltmann, Dirk A1 - Krüger, Jörg T1 - Femtosecond laser-induced periodic surface structures on titanium nitride coatings for tribological applications N2 - Titanium nitride (TiN) was coated on different substrate materials, namely pure titanium (Ti), titanium alloy (Ti6Al4V) and steel (100Cr6), generating 2.5 μm thick TiN layers. Using femtosecond laser pulses (30 fs, 790 nm, 1 kHz pulse repetition rate), large surface areas (5 mm × 5 mm) of laser-induced periodic surface structures (LIPSS) with sub-wavelength periods ranging between 470 nm and 600 nm were generated and characterized by optical microscopy (OM), white light interference microscopy (WLIM) and scanning electron microscopy (SEM). In tribological tests, coefficients of friction (COF) of the nanostructured surfaces were determined under reciprocating sliding conditions (1 Hz, 1.0 N normal load) against a 10-mm diameter ball of hardened 100Cr6 steel during 1000 cycles using two different lubricants, namely paraffin oil and engine oil. It turned out that the substrate material, the laser fluence and the lubricant are crucial for the tribological performance. However, friction and wear could not be significantly reduced by LIPSS on TiN layers in comparison to unstructured TiN surfaces. Finally, the resulting wear tracks on the nanostructured surfaces were investigated with respect to their morphology (OM, SEM), depth (WLIM) and chemical composition by energy dispersive X-ray spectroscopy (EDX) and, on one hand, compared with each other, on the other hand, with non-structured TiN surfaces. KW - Laser-induced periodic surface structures (LIPSS) KW - Femtosecond laser ablation KW - Titanium nitride films KW - Friction KW - Wear PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0169433216322486 DO - https://doi.org/10.1016/j.apsusc.2016.10.132 SN - 0169-4332 SN - 1873-5584 VL - 418 IS - Part B SP - 572 EP - 579 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-40507 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hermens, U. A1 - Kirner, Sabrina A1 - Emonts, C. A1 - Comanns, P. A1 - Skoulas, E. A1 - Mimidis, A. A1 - Mescheder, H. A1 - Winands, K. A1 - Krüger, Jörg A1 - Stratakis, E. A1 - Bonse, Jörn T1 - Mimicking lizard-like surface structures upon ultrashort laser pulse irradiation of inorganic materials N2 - Inorganic materials, such as steel, were functionalized by ultrashort laser pulse irradiation (fs- to ps-range) to modify the surface’s wetting behavior. The laser processing was performed by scanning the laser beam across the surface of initially polished flat sample material. A systematic experimental study of the laser processing parameters (peak fluence, scan velocity, line overlap) allowed the identification of different regimes associated with characteristic surface morphologies (laser-induced periodic surface structures, grooves, spikes, etc.). Analyses of the surface using optical as well as scanning electron microscopy revealed morphologies providing the optimum similarity to the natural skin of lizards. For mimicking skin structures of moisture-harvesting lizards towards an optimization of the surface wetting behavior, additionally a two-step laser processing strategy was established for realizing hierarchical microstructures. In this approach, micrometer-scaled capillaries (step 1) were superimposed by a laser-generated regular array of small dimples (step 2). Optical focus variation imaging measurements finally disclosed the three dimensional topography of the laser processed surfaces derived from lizard skin structures. The functionality of these surfaces was analyzed in view of wetting properties. KW - Femtosecond laser ablation KW - Laser-induced periodic surface structures KW - Lizard KW - Surface wetting KW - Fluid transport KW - Steel PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0169433216328306 DO - https://doi.org/10.1016/j.apsusc.2016.12.112 SN - 0169-4332 SN - 1873-5584 VL - 418 IS - Part B SP - 499 EP - 507 PB - Elsevier, North-Holland CY - Amsterdam AN - OPUS4-40509 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Carstensen, J. A1 - Bergmann, L. A1 - dos Santos, J. F. A1 - Wu, C. S. A1 - Rethmeier, Michael T1 - Numerical simulation of thermally induced residual stresses in friction stir welding of aluminum alloy 2024-T3 at different welding speeds N2 - The paper deals with a numerical finite element simulation of the residual stress evolution in friction stir welding of 6 mm thick aluminum alloy AA2024-T3. The transient thermal field during the welding process was calculated with the commercial code COMSOL Multiphysics 5.0. Therefore, a thermal-pseudo-mechanical (TPM) heat source was implemented. A subsequent mechanical simulation was performed with varying hardening models for different welding speeds of 60 and 300 mm/min. The influence of softening of the material, which was due to hardening precipitation dissolution associated to the heating, was also investigated. Experiments in terms of thermocouple measurements as well as Vickers hardness and X-ray measurements of the residual stresses were conducted and compared to numerically obtained results. A qualitatively as well as quantitatively good agreement was found for different applied welding speeds. KW - Friction stir welding KW - Residual stress KW - Finite element simulation KW - Thermal softening KW - Aluminum alloy 2024-T3 PY - 2017 DO - https://doi.org/10.1007/s00170-016-9793-8 SN - 0268-3768 SN - 1433-3015 VL - 91 SP - 1443 EP - 1452 PB - Springer CY - London AN - OPUS4-40511 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Olejko, Lydia A1 - Bald, Ilko T1 - FRET efficiency and antenna effect in multi-color DNA origami-based light harvesting systems N2 - Artificial light harvesting complexes find applications in artificial photosynthesis, photovoltaics and light harvesting chemical sensors. They are used to enhance the absorption of light of a reaction center which is often represented by a single acceptor. Here, we present different light harvesting systems on DNA origami structures and analyze systematically the light harvesting efficiency. By changing the number and arrangement of different fluorophores (FAM as donor, Cy3 as transmitter and Cy5 as acceptor molecules) the light harvesting efficiency is optimized to create a broadband absorption and to improve the antenna effect 1 (including two energy transfer steps) from 0.02 to 1.58, and the antenna effect 2 (including a single energy transfer step) from 0.04 to 8.7, i.e. the fluorescence emission of the acceptor is significantly higher when the light-harvesting antenna is excited at lower wavelength compared to direct excitation of the acceptor. The channeling of photo energy to the acceptor proceeds by Förster Resonance Energy Transfer (FRET) and we carefully analyze also the FRET efficiency of the different light harvesting systems. Accordingly, the antenna effect can be tuned by modifying the stoichiometry of donor, transmitter and acceptor dyes, whereas the FRET efficiency is mainly governed by the spectroscopic properties of dyes and their distances. KW - DNA origami KW - Light-harvesting KW - FRET KW - Antenna effect PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-405867 UR - http://pubs.rsc.org/en/content/articlelanding/2017/ra/c7ra02114c#!divAbstract DO - https://doi.org/10.1039/C7RA02114C VL - 7 IS - 39 SP - 23924 EP - 23934 PB - The Royal Soc. of Chemistry AN - OPUS4-40586 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heck, Christian A1 - Prinz, Julia A1 - Dathe, A. A1 - Merck, V. A1 - Stranik, O. A1 - Fritzsche, W. A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Gold nanolenses self-assembled by DNA origami N2 - Nanolenses are self-similar chains of metal nanoparticles, which can theoretically provide extremely high field enhancements. Yet, the complex structure renders their synthesis challenging and has hampered closer analyses so far. Here, DNA origami is used to self-assemble 10, 20, and 60 nm gold nanoparticles as plasmonic gold nanolenses (AuNLs) in solution and in billions of copies. Three different geometrical arrangements are assembled, and for each of the three designs, surface-enhanced Raman scattering (SERS) capabilities of single AuNLs are assessed. For the design which shows the best properties, SERS signals from the two different internal gaps are compared by selectively placing probe dyes. The highest Raman enhancement is found for the gap between the small and medium nanoparticle, which is indicative of a cascaded field enhancement. KW - DNA origami KW - SERS KW - Gold nanoparticles KW - Plasmonics PY - 2017 UR - http://pubs.acs.org/doi/pdf/10.1021/acsphotonics.6b00946 DO - https://doi.org/10.1021/acsphotonics.6b00946 SN - 2330-4022 VL - 4 IS - 5 SP - 1123 EP - 1130 AN - OPUS4-40587 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Caricato, A.P. A1 - Focsa, C. A1 - Krüger, Jörg A1 - Palla Papavlu, A. T1 - European materials research society spring meeting 2016 symposium "Laser - materials interactions for tailoring future's applications" Preface N2 - This Conference Proceedings volume contains a selection of the contributions presented in Symposium C “Laser-material interactions for tailoring future applications” organized during the annual Spring Meeting of the European Materials Research Society (E-MRS) held from May 2nd to 6th 2016 in the Lille Grand Palais, France. T2 - EMRS Spring Meeting 2016, Symposium "“Laser-material interactions for tailoring future applications” CY - Lille, France DA - 02.05.2016 KW - European Materials Research Society (E-MRS) KW - Laser-material interactions KW - Spring Meeting 2016 PY - 2017 DO - https://doi.org/10.1016/j.apsusc.2017.04.089 SN - 0169-4332 SN - 1873-5584 VL - 418 IS - Part B SP - 419 EP - 419 PB - Elsevier B.V. AN - OPUS4-40570 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cabeza, Sandra A1 - Mishurova, Tatiana A1 - Garces, G. A1 - Requena, G. A1 - Bruno, Giovanni A1 - Sevostianov, I. T1 - Stress-induced damage evolution in cast AlSi12CuMgNi alloy with one- and two ceramic reinforcements N2 - Two composites, consisting of an as-cast AlSi12CuMgNi alloy reinforced with 15%vol. Al2O3 short fibres and with 7%vol. Al2O3 short fibres + 15%vol. SiC particles were studied. Synchrotron computed tomography disclosed distribution, orientation, and volume fraction of the different phases. In-situ compression tests during neutron diffraction in direction parallel to the fibres plane revealed the load partition between phases. Internal damage (fragmentation) of the Si phase and Al2O3 fibres was directly observed in CT reconstructions. Significant debonding between Al-matrix and SiC particles was also found. Finally, based on the Maxwell scheme, a micro-mechanical model was utilized for the new composite with two ceramic reinforcements; it rationalizes the experimental data, and predicts the evolution of all internal stress components in each phase. KW - Computed tomography KW - Metal matrix composite KW - Load partition KW - Neutron diffraction PY - 2017 DO - https://doi.org/10.1007/s10853-017-1182-7 SN - 0022-2461 SN - 1573-4803 VL - 52 IS - 17 SP - 10198 EP - 10216 PB - Springer AN - OPUS4-40572 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Miccoli, Lorenzo A1 - Müller, U. A1 - Pospisil, S. T1 - Rammed earth walls strengthened with polyester fabric strips: Experimental analysis under in-plane cyclic loading N2 - This study analyses the mechanical behaviour under pseudo-dynamic loading of structural elements built in rammed earth and strengthened with polyester fabric strips. This strengthening technique was developed to exploit the strength potential of rammed earth and to solve its lack of tensile strength. For this reason, in-plane cyclic tests were carried out to investigate the shear behaviour of unstrengthened and strengthened walls. The strengthening technique requires low-tech equipment and workmanship, uses readily available, not expensive and industrially standardised materials. The experimental results were analysed in terms of stiffness degradation, energy dissipation capacity and equivalent viscous damping. Although the unstrengthened and strengthened walls confirmed a limited ductile behaviour, the findings confirm that the strengthening contributes to limit the spread of the diagonal cracks and provide an increase of strength in terms of horizontal load and displacement capacity. KW - Rammed earth KW - Pseudo-dynamic loads KW - Shear-compression tests KW - Strengthening KW - Polyester fabric strips PY - 2017 DO - https://doi.org/10.1016/j.conbuildmat.2017.05.115 IS - 149 SP - 29 EP - 36 PB - Elsevier Ltd. AN - OPUS4-40497 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Epperlein, Nadja A1 - Menzel, Friederike A1 - Schwibbert, Karin A1 - Koter, Robert A1 - Bonse, Jörn A1 - Sameith, Janin A1 - Krüger, Jörg A1 - Toepel, Jörg T1 - Influence of femtosecond laser produced nanostructures on biofilm growth on steel N2 - Biofilm formation poses high risks in multiple industrial and medical settings. However, the robust nature of biofilms makes them also attractive for industrial applications where cell biocatalysts are increasingly in use. Since tailoring material properties that affect bacterial growth or its inhibition is gaining attention, here we focus on the effects of femtosecond laser produced nanostructures on bacterial adhesion. Large area periodic surface structures were generated on steel surfaces using 30-fs laser pulses at 790 nm wavelength. Two types of steel exhibiting a different corrosion resistance were used, i.e., a plain structural steel (corrodible) and a stainless steel (resistant to corrosion). Homogeneous fields of laser-induced periodic surface structures (LIPSS) were realized utilizing laser fluences close to the ablation threshold while scanning the sample under the focused laser beam in a multi-pulse regime. The nanostructures were characterized with optical and scanning electron microscopy. For each type of steel, more than ten identical samples were laser-processed. Subsequently, the samples were subjected to microbial adhesion tests. Bacteria of different shape and adhesion behavior (Escherichia coli and Staphylococcus aureus) were exposed to laser structures and to polished reference surfaces. Our results indicate that E. coli preferentially avoids adhesion to the LIPSS-covered areas, whereas S. aureus favors these areas for colonization. KW - Laser-induced periodic surface structures KW - Femtosecond laser KW - Steel KW - Biofilms KW - Microbial adhesion tests PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0169433217305470 DO - https://doi.org/10.1016/j.apsusc.2017.02.174 SN - 0169-4332 SN - 1873-5584 VL - 418 IS - Part B SP - 420 EP - 424 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-40565 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pasternak, H. A1 - Launert, B. A1 - Kannengießer, Thomas A1 - Rhode, Michael T1 - Advanced residual stress assessment of plate girders through welding simulation N2 - This article provides an impression on potentials in applying nowadays welding simulation tools in construction design. This is carried out exemplary on plate girders from two structural steel grades. The calculated residual stresses are compared with measurements by sectioning method. It has been repeatedly stated that present Eurocode models fail to approximate the residual stresses. Especially for high strength steel (HSS) only limited information is available on realistic occurring residual stresses in typical I-girders. The investigations are aimed to give further guidance on these values. A few proposals on advanced models are discussed. T2 - MBST 2016 - Modern Building Materials, Structures and Techniques CY - Vilnius, Litunia DA - 26.05.2016 KW - Residual stresses KW - Plate girders KW - I-shape sections KW - High-strength steel KW - Welding simulation PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-392177 UR - http://www.sciencedirect.com/science/article/pii/S1877705817305192 DO - https://doi.org/10.1016/j.proeng.2017.02.013 SN - 1877-7058 IS - 172 SP - 23 EP - 30 PB - Elsevier CY - Amsterdam, Niederlande AN - OPUS4-39217 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaupp, Thomas A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Welding residual stresses in 960 MPa grade QT and TMCP high-strength steels N2 - High-strength steels with yield strengths ≥ 690 MPa are becoming increasingly significant for modern steel constructions. Both quenched and tempered (QT) high-strength steels and steels produced by the thermo-mechanically controlled process (TMCP) are currently available. TMCP-steels are usually provided with a typical mill scale. Apart from the manufacturing process these steels differ also in their chemical composition. The influence of these differences are investigated here with focus on the residual stresses formed during TIG welding. Bead on plate welds have shown characteristic residual stress distributions depending on the type of steel as well as on the heat input and preheat temperature. The following work demonstrates that the fluid flow, induced by the elements present in the mill scale, leads to a deeper penetration of the material. This can also lead to increased residual stresses in the surface of the weld and the HAZ. Furthermore, higher heat input and preheat temperature can induce higher tensile residual stresses − which are evident in the present study. KW - Residual stresses KW - High-strength steel KW - Welding KW - Mill scale KW - Phase transformation PY - 2017 DO - https://doi.org/10.1016/j.jmapro.2017.05.006 SN - 1526-6125 VL - 27 SP - 226 EP - 232 PB - ELSEVIER AN - OPUS4-40312 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kulla, Hannes A1 - Wilke, Manuel A1 - Fischer, Franziska A1 - Röllig, Mathias A1 - Maierhofer, Christiane A1 - Emmerling, Franziska T1 - Warming up for mechanosynthesis – temperature development in ball mills during synthesis N2 - We present a first direct measurement of the temperature during milling combined with in situ Raman spectroscopy monitoring. The data reveal a low temperature increase due to the mechanical impact and clear temperature increases as a consequence of the reaction heat. Based on the data, temperature rises as postulated in the magma plasma and hot spot theory can be excluded for soft matter milling syntheses. KW - Thermography KW - Milling KW - Mechanochemistry KW - Soft matter PY - 2017 DO - https://doi.org/10.1039/c6cc08950j SN - 1364-548X SN - 1359-7345 SN - 0009-241X VL - 53 IS - 10 SP - 1664 EP - 1667 AN - OPUS4-39251 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wilke, Manuel A1 - Bach, S. A1 - Gorelik, T. A1 - Kolb, U. A1 - Tremel, W. A1 - Emmerling, Franziska T1 - Divalent metal phosphonates – new aspects for syntheses, in situ characterization and structure solution N2 - Divalent metal phosphonates are promising hybrid materials with a broad field of application. The rich coordination chemistry of the phosphonate linkers enables the formation of structures with different dimensionalities ranging from isolated complexes and layered structures to porous frameworks incorporating various functionalities through the choice of the building blocks. In brief, metal phosphonates offer an interesting opportunity for the design of multifunctional materials. Here, we provide a short review on the class of divalent metal phosphonates discussing their syntheses, structures, and applications. We present the advantages of the recently introduced mechanochemical pathway for the Synthesis of divalent phosphonates as a possibility to generate new, in certain cases metastable compounds. The benefits of in situ investigation of synthesis mechanisms as well as the implementation of sophisticated methods for the structure analysis of the resulting compounds are discussed. KW - Metal phosphonate KW - Mechanochemistry PY - 2017 DO - https://doi.org/10.1515/zkri-2016-1971 SN - 2194-4946 SN - 2196-7105 VL - 232 IS - 1-3 SP - 209 EP - 222 PB - De Gruyter AN - OPUS4-40003 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schulz, K. A1 - Schmack, R. A1 - Klemm, H. W. A1 - Kabelitz, Anke A1 - Schmidt, T. A1 - Emmerling, Franziska A1 - Kraehnert, R. T1 - Mechanism and kinetics of hematite crystallization in air: Linking bulk and surface models via mesoporous films with defined nanostructure N2 - Iron can form numerous oxides, hydroxides, and oxide−hydroxides. Despite their relevance, many of the transformation processes between these phases are still poorly understood. In particular the crystallization of quasi-amorphous hydroxides and oxide−hydroxides is difficult to assess, since typical diffraction and scattering methods provide only sampleaveraged information about the crystallized phases. We report a new approach for the investigation of the crystallization of oxide−hydroxides. The approach relies on model-type films that comprise a defined homogeneous nanostructure. The nanostructure allows quantitative linking of Information obtained by bulk-averaging diffraction techniques (XRD, SAXS) with locally resolved information, i.e., Domain sizes (SEM, TEM, LEEM) and phase composition (SAED). Using time-resolved imaging and diffraction we deduce mechanism and kinetics for the crystallization of ferrihydrite into hematite. Hematite forms via nucleation of hematite domains and subsequent Domain growth that terminates only upon complete transformation. A Johnson−Mehl−Avrami−Kolmogorov model describes the kinetics over a wide temperature range. The derived understanding enables the first synthesis of ferrihydrite films with ordered mesoporosity and quantitative control over the films’ hematite and ferrihydrite content. KW - Iron oxide KW - Crystallization KW - Mesoporous films KW - Nanostructure PY - 2017 DO - https://doi.org/10.1021/acs.chemmater.6b05185 SN - 0897-4756 SN - 1520-5002 VL - 29 IS - 4 SP - 1724 EP - 1734 AN - OPUS4-39690 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Asadujjaman, Asad A1 - Bertin, Annabelle A1 - Schönhals, Andreas T1 - Dielectric analysis of the upper critical solution temperature behaviour of a poly(acrylamide-coacrylonitrile) copolymer system in water N2 - A copolymer consisting of acrylamide (AAm) and acrylonitrile (AN) in aqueous solution was investigated using broadband dielectric spectroscopy at frequencies between 10⁻¹ Hz and 10⁶ Hz in the temperature range from 2 °C to 60 °C. This system shows an UCST phase behavior. The phase transition and aggregation behavior is monitored by both the temperature and frequency dependence of the complex conductivity σ*(f, T), where the AN fraction and the concentration of the solution were varied. Additionally, the dielectric data are compared with the results obtained from dynamic light scattering measurements. The temperature dependence of the DC conductivity (σDC) of the copolymer solution is monitored and the phase transition temperature (PTT) of the poly(AAm-co-AN) copolymer is deduced from a change in the T-dependence of the DC conductivity. The change in σDC can be explained by decreased effective charge carrier mobility and a reduction of the effective charge number density at temperatures below the phase Transition temperature of the poly(AAm-co-AN) solution. A pronounced interfacial polarization effect on the frequency dependence of the real part of the conductivity (σ') is observed at temperatures below the phase Transition temperature. The charge carriers are blocked at the formed aggregates giving rise to this interfacial polarization. The dependence of the interfacial polarization on the acrylonitrile fraction in the copolymer and the concentration of the solution is studied in detail and conclusions concerning the internal structures of the copolymer aggregates are drawn. KW - Thermoresponsive polymres PY - 2017 DO - https://doi.org/10.1039/c6sm02684b SN - 1744-6848 SN - 1744-683X VL - 13 IS - 12 SP - 2384 EP - 2393 PB - Royl Society of Chemistry Publishing AN - OPUS4-39556 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Schick, Ch. A1 - Schönhals, Andreas T1 - Unexpected behavior of ultra-thin films of blends of polystyrene/poly(vinyl methyl ether) studied by specific heat spectroscopy N2 - Specific heat spectroscopy (SHS) employing AC nanochip calorimetry was used to investigate the glassy dynamics of ultra-thin films (thicknesses: 10 nm–340 nm) of a polymer blend, which is miscible in the bulk. In detail, a Poly(vinyl methyl ether) (PVME)/Polystyrene (PS) blend with the composition of 25/75 wt. % was studied. The film thickness was controlled by ellipsometry while the film topography was checked by atomic force microscopy. The results are discussed in the framework of the balance between an adsorbed and a free surface layer on the glassy dynamics. By a self-assembling process, a layer with a reduced mobility is irreversibly adsorbed at the polymer/substrate interface. This layer is discussed employing two different scenarios. In the first approach, it is assumed that a PS-rich layer is adsorbed at the substrate. Whereas in the second approach, a PVME-rich layer is suggested to be formed at the SiO2 substrate. Further, due to the lower surface tension of PVME, with respect to air, a nanometer thick PVME-rich surface layer, with higher molecular mobility, is formed at the polymer/air interface. By measuring the glassy dynamics of the thin films of PVME/PS in dependence on the film thickness, it was shown that down to 30 nm thicknesses, the dynamic Tg of the whole film was strongly influenced by the adsorbed layer yielding a systematic increase in the dynamic Tg with decreasing the film thickness. However, at a thickness of ca. 30 nm, the influence of the mobile surface layer becomes more pronounced. This results in a systematic decrease in Tg with the further decrease of the film thickness, below 30 nm. These results were discussed with respect to thin films of PVME/PS blend with a composition of 50/50 wt.%as well as literature results. KW - Ultra thin polymer films PY - 2017 DO - https://doi.org/10.1063/1.4978505 SN - 0021-9606 SN - 1089-7690 VL - 146 IS - 20 SP - 203321-1 EP - 203321-9 PB - AIP Publishing AN - OPUS4-39558 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sproesser, G. A1 - Chang, Y.-J. A1 - Pittner, Andreas A1 - Finkbeiner, M. A1 - Rethmeier, Michael T1 - Energy efficiency and environmental impacts of high power gas metal arc welding N2 - Single-wire gas metal arc welding (SGMAW) and high power tandem GMAW (TGMAW) are evaluated with respect to energy efficiency. The key performance indicator electrical deposition efficiency is applied to reflect the energy efficiency of GMAW in different material transfer modes. Additionally, the wall-plug efficiency of the equipment is determined in order to identify the overall energy consumption. The results show that energy efficiency can be increased by 24% and welding time is reduced over 50% by application of the tandem processes. A comparative life cycle assessment of a 30-mm-thick weld is conducted to investigate the influences of the energy efficiency on the environmental impacts. The environmental impacts on the categories global warming potential, acidification potential, eutrophication potential, and photochemical ozone creation potential can be reduced up to 11% using an energy-efficient TGMAW process. KW - Tandem gas metal arc welding KW - Life cycle assessment (LCA) KW - Energy efficiency KW - High power welding PY - 2017 DO - https://doi.org/10.1007/s00170-017-9996-7 SN - 0268-3768 SN - 1433-3015 VL - 91 IS - 9-12 SP - 3503 EP - 3513 PB - Springer CY - London AN - OPUS4-39564 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ho, Y.T. A1 - Adriani, G A1 - Beyer, Sebastian A1 - Nhan, P.-T. A1 - Kamm, R. D. A1 - Kah, J.C.Y. T1 - A facile method to probe the vascular permeability of nanoparticles in nanomedicine applications N2 - The effectiveness of nanoparticles (NP) in nanomedicine depends on their ability to extravasate from vasculature towards the target tissue. This is determined by their permeability across the endothelial barrier. Unfortunately, a quantitative study of the diffusion permeability coefficients (Pd) of NPs is difficult with in vivo models. Here, we utilize a relevant model of vascular-tissue interface with tunable endothelial permeability in vitro based on microfluidics. Human umbilical vein endothelial cells (HUVECs) grown in microfluidic devices were treated with Angiopoietin 1 and cyclic adenosine monophosphate (cAMP) to vary the Pd of the HUVECs monolayer towards fluorescent polystyrene NPs (pNPs) of different sizes, which was determined from image analysis of their fluorescence intensity when diffusing across the monolayer. Using 70 kDa dextran as a probe, untreated HUVECs yielded a Pd that approximated tumor vasculature while HUVECs treated with 25 μg/mL cAMP had Pd that approximated healthy vasculature in vivo. As the size of pNPs increased, its Pd decreased in tumor vasculature, but remained largely unchanged in healthy vasculature, demonstrating a trend similar to tumor selectivity for smaller NPs. This microfluidic model of vascular-tissue interface can be used in any laboratory to perform quantitative assessment of the tumor selectivity of nanomedicine-based systems. KW - Nanoparticle PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-397053 DO - https://doi.org/10.1038/s41598-017-00750-3 SN - 2045-2322 VL - 7 IS - 1 SP - Article 707, 1 EP - 13 PB - Macmillan AN - OPUS4-39705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nguyen, Thi Yen A1 - Roessler, Ernst A1 - Rademann, Klaus A1 - Emmerling, Franziska T1 - Control of organic polymorph formation: crystallization pathways in acoustically levitated droplets N2 - Theoretical and experimental studies indicate that crystal nucleation can take more complex pathways than expected on the ground of the classical nucleation theory. Among these pathways are the formation of pre-nucleation clusters and amorphous precursor phases. A direct in situ observation of the different pathways of nucleation from solution is challenging since the paths can be influenced by heterogeneous nucleation sites, such as container walls. Here, we provide insights into the crystallization process using the in situ combination of an acoustic levitator, Raman spectroscopy, and X-ray scattering. The contactless sample holder enables the observation of homogeneous crystallization processes and the detection of intermediates and final crystalline forms. We provide evidence for the existence of multiple pathways of nucleation based on the investigation of the crystallization of organic molecules from different solvents. Starting from a diluted solution, a supersaturation is reached during the experiment due to the evaporation of the solvent. The highly supersaturated solution reveals different pathways of crystallization. Depending on the degree of supersaturation either the thermodynamically stable or the metastable crystal form is observed. KW - Crystallization KW - In situ XRD KW - Polymorphism KW - Polyamorphism KW - Raman spectroscopy PY - 2017 DO - https://doi.org/10.1515/zkri-2016-1964 SN - 2194-4946 SN - 2196-7105 VL - 232 IS - 1-3 SP - 15 EP - 24 PB - De Gruyter CY - Berlin AN - OPUS4-39708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zocca, Andrea A1 - Lima, Pedro A1 - Günster, Jens T1 - LSD-based 3D printing of alumina ceramics N2 - An improved method of powder 3D printing leading to dense ceramic parts is presented. The application of powder-based binder jetting 3D printing technologies to technical ceramics is generally limited by the low packing density of the powder and by the need to use a flowable powder. With layer-wise slurry deposition, it is, however, possible to deposit powder beds with high particle packing and furthermore using submicron powders. This method was combined with the binder jetting technology to develop a novel process, named LSD-print. By means of LSD-print, a submicron Al2O3 powder could be processed to produce samples with a density comparable with that of standard pressed samples, both in the green state and after sintering. KW - Additive manufacturing KW - Layer-wise slurry deposition KW - Dense alumina KW - 3D printing PY - 2017 DO - https://doi.org/10.4416/JCST2016-00103 SN - 2190-9385 VL - 8 IS - 1, SI SP - 141 EP - 147 PB - Göller Verlag GmbH CY - Baden Baden AN - OPUS4-39672 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hennig, C. A1 - Weiss, S. A1 - Kraus, Werner A1 - Kretzschmar, J. A1 - Scheinost, A.C. T1 - Solution species and crystal structure of Zr(IV) acetate N2 - Complex formation and the coordination of zirconium with acetic acid were investigated with Zr K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) and single-crystal diffraction. Zr K-edge EXAFS spectra show that a stepwise increase of acetic acid in aqueous solution with 0.1 M Zr(IV) leads to a structural rearrangement from initial tetranuclear hydrolysis species [Zr4(OH)8(OH2)16]8+ to a hexanuclear acetate species Zr6(O)4(OH)4(CH3COO)12. The solution species Zr6(O)4(OH)4(CH3COO)12 was preserved in crystals by slow evaporation of the aqueous solution. Single-crystal diffraction reveals an uncharged hexanuclear cluster in solid Zr6(μ3-O)4(μ3-OH)4(CH3COO)12·8.5H2O. EXAFS measurements show that the structures of the hexanuclear zirconium acetate cluster in solution and the solid state are identical. KW - Complex formation KW - Crystal structure KW - Zr(iV) compounds PY - 2017 DO - https://doi.org/10.1021/acs.inorgchem.6b01624 SN - 0020-1669 SN - 1520-510X VL - 56 IS - 5 SP - 2473 EP - 2480 PB - ACS AN - OPUS4-39677 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mitova, M. A1 - Iliev, M. A1 - Nováková, A. A1 - Gorbushina, Anna A1 - Groudeva, V.I. A1 - Martin-Sanchez, Pedro Maria T1 - Diversity and biocide susceptibility of fungal assemblages dwelling in the Art Gallery of Magura Cave, Bulgaria N2 - Magura Cave, north-western Bulgaria, possesses valuable rock-art paintings made with bat guano and dated from the period between the Eneolithic and Bronze Ages. Since 2008, the Art Gallery is closed to the general public in order to protect the paintings from vandalism, microclimatic changes caused by visitors and artificial illumination, and the consequent growth of fungi and phototrophs. Nevertheless, some tourist visits are allowed under the supervision of cave managers. This study provides the first scientific report on cultivable fungal assemblages dwelling different substrata in the Art Gallery. A total of 78 strains, belonging to 37 OTUs (Ascomycota 81%, Zygomycota 13%, Basidiomycota 5%), were isolated in the study. This fungal diversity was clearly dominated by Penicillium (50% of strains) and Aspergillus (13%). The most relevant visible fungal colonies were detected in sediments rich in bat guano, where, besides Penicillium, other guanophilic fungi such as Mucor, Mortierella, Trichosporon and Trichoderma were dominant. Conversely, scarce fungi were detected on rock surface of painted walls. Based on the biocide susceptibility assay, octylisothiazolinone (OIT) and benzalkonium chloride (BAC) were effective inhibiting the in vitro growth of dominant fungal species in Magura Cave, when applied at concentrations ranged from 100 to 1,000 mg/L. These data provide a valuable knowledge about Magura fungi, and exemplify a type of preliminary test that may be conducted before planning any biocide treatment. However, considering the irreversible effects of biocides on the ecological balance in caves, and the low fungal contamination in painted walls of Magura Cave, there is no reason to use conventional biocides in this cave. Further studies, monitoring microbial communities and microclimatic parameters, should be conducted to improve the knowledge on microbial ecology in Magura Cave and possible human impacts, as well as to allow the early detection of potential microbial outbreaks. KW - Fungi KW - Rock-art caves KW - Biocides PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-397436 DO - https://doi.org/10.5038/1827-806X.46.1.2061 SN - 0392-6672 VL - 46 IS - 1 SP - 67 EP - 80 PB - Scholar Commons CY - Tampa, FL, USA AN - OPUS4-39743 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 - Cyclic poly(L-lactide)s via ring-expansion polymerizations catalysed by 2,2-dibutyl-2- stanna-1,3-dithiolane N2 - L-Lactides were polymerized in bulk at 120 or 160 °C with cyclic dibutyltin catalysts derived from 1,2-dimercaptoethane or 2-mercaptoethanol. Only linear chains having one benzyl ester and one OH-end group were obtained when benzyl alcohol was added. When L-lactides were polymerized with neat dibutyl-2-stanna-1,3-dithiolane, exclusively cyclic polylactides were formed even at 120 °C. The temperature, time and monomer/catalyst ratio (M/C) were varied. These results are best explained by a combination of ring-expansion polymerization and ring-extrusion of cyclic oligo- or polylactides with Elimination of the cyclic catalyst. Neither syntheses of linear polylactides nor of cyclic lactides involved racemization up to 20 h at 160 °C. KW - Ring-expansion polymerization KW - MALDI KW - Polylactides PY - 2017 DO - https://doi.org/10.1039/C6PY02166B SN - 1759-9954 SN - 1759-9962 VL - 8 IS - 9 SP - 1589 EP - 1596 PB - Royal Society of Chemistry AN - OPUS4-39748 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dietzsch, Michael A1 - Andrusenko, Iryna A1 - Branscheid, Robert A1 - Emmerling, Franziska A1 - Kolb, Ute A1 - Tremel, Wolfgang T1 - Snapshots of calcium carbonate Formation - a step by step analysis N2 - Recent advances in our understanding of CaCO, nucleation from solution have provoked new and challenging questions. We have studied CaC03 formation using precipitation by carbonate ester hydrolysis which ensures precipitation from a strictly homogeneous solution state and allows “titrating” carbonate to a solution with a given Ca2+ concentration on a timescale suited for kinetic studies. Nucleation and crystallization were traced by combining dynamic light Scattering (DLS) and transmission electron microscopy (TEM). DLS served as in situ technique to identify the nucleation time, to monitor particle size evolution, to discriminate different precipitation mechanisms and to validate reproducibility. TEM snapshots taken during different stages of the precipitation process identified different phases and morphologies. At a high level of supersaturation homogeneous nucleation in solution led to the formation of amorphous CaC03 particles (diameter=30 nm), which transformed via vaterite to calcite. Nucleation occurred uniformly in solution which appears to be unique for the CaC03 System. In the presence of Na-polymethacrylate (Na-PMA), heterogeneous nucleation was suppressed and Ca-polymer aggregates were formed in the prenucleation stage. Beyond a critical threshold supersaturation CaC03 particles formed in solution outside of these aggregates. The nucleation process resembled that without additive, indicating that Na-PMA exerts only a minor effect on the CaC03 nucleation. In the postnucleation stage, the polymer led to the formation of extended liquid-like networks, which served as a precursor phase for solid ACC particles that formed alongside the network. KW - biomineralization KW - calcium carbonate KW - nucleation KW - polymer additives PY - 2017 DO - https://doi.org/10.1515/zkri-2016-1973 SN - 2194-4946 SN - 2196-7105 VL - 232 IS - 1-3 SP - 255 EP - 265 PB - De Gruyter CY - Berlin AN - OPUS4-39863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Miccoli, Lorenzo A1 - Gerrard, C. A1 - Perrone, C. A1 - Gardei, André A1 - Ziegert, C. T1 - A collaborative engineering and archaeology project to investigate decay in historic rammed earth structures: The case of the Medieval preceptory in Ambel N2 - This study assesses the structural vulnerability of part of a later medieval earthen building at Ambel (near Zaragoza, Spain), once a preceptory or monastic house belonging to the Military Orders. An inspection of its morphology and materials coupled with the results of an extensive campaign of static monitoring reveals marked structural inhomogeneities, the product of more than a thousand years of construction, failure, and repair from the 10th century to the present day. Building materials are inappropriately juxtaposed, there are discontinuities between construction phases and fundamental concerns remain over the long-term stability of the structure. The current condition of the structure is mainly influenced by structural discontinuities introduced at the time of construction, the unintended consequences of repair and modification and the material decay that has affected the base of the rammed earth walls. The overall findings of the static monitoring show that there is no related damage, variations in crack widths are related to the building seasonal cycle. While static analysis is an essential prerequisite before a suitable maintenance program can be fully defined, this study argues that no evaluation of the structural behavior of any historic building can afford to ignore its archaeological “biography” of modification and repair. KW - Archaeology KW - Historical earthen building KW - Materials characterization KW - Rammed earth KW - Static monitoring PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-396274 DO - https://doi.org/10.1080/15583058.2016.1277283 VL - 11 IS - 5 SP - 636 EP - 655 PB - Taylor & Francis Group AN - OPUS4-39627 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sproesser, G. A1 - Chang, Y.-J. A1 - Pittner, Andreas A1 - Finkbeiner, M. A1 - Rethmeier, Michael T1 - Environmental energy efficiency of single wire and tandem gas metal arc welding N2 - This paper investigates gas metal arc welding (GMAW) with respect to energy consumption and its associated environmental impacts. Different material transfer modes and power levels for single wire GMAW (SGMAW) and tandem GMAW (TGMAW) are evaluated by means of the indicator electrical deposition efficiency. Furthermore, the wall-plug efficiency of the equipment is measured in order to describe the total energy consumption from the electricity grid. The results show that the energy efficiency is highly affected by the respective process and can be significantly enhanced by a TGMAW process. The wall-plug efficiency of the equipment shows no significant dependency on the power range or the material transfer mode. Moreover, the method of life cycle assessment (LCA) is adopted in order to investigate the influences of energy efficient welding on the environmental impacts. In the comparative LCA study, the demand of electrical energy is reduced up to 24%. In consequence, the indicator values for global warming potential (100), acidification potential, eutrophication potential, and photochemical ozone creation potential are reduced up to 11%. KW - Energy input KW - Tandem welding KW - MAG welding KW - Environment KW - Lifetime PY - 2017 DO - https://doi.org/10.1007/s40194-017-0460-y SN - 0043-2288 SN - 1878-6669 VL - 61 IS - 4 SP - 733 EP - 743 PB - Springer CY - Heidelberg AN - OPUS4-39877 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Heídari, M. A1 - von Klitzing, R. A1 - Schönhals, Andreas T1 - Unveiling the dynamics of self-assembled layers of thin films of poly(vinyl methyl ether) (PVME) by nanosized relaxation spectroscopy N2 - A combination of nanosized dielectric relaxation (BDS) and thermal spectroscopy (SHS) was utilized to characterize the dynamics of thin films of Poly(vinyl methyl ether) (PVME) (thicknesses: 7 nm – 160 nm). For the BDS measurements, a recently designed nano-structured electrode system is employed. A thin film is spin-coated on an ultra-flat highly conductive silicon wafer serving as the bottom electrode. As top electrode, a highly conductive wafer with non-conducting nanostructured SiO2 nano-spacers with heights of 35 nm or 70 nm is assembled on the bottom electrode. This procedure results in thin supported films with a free polymer/air interface. The BDS measurements show two relaxation processes, which are analyzed unambiguously for thicknesses smaller than 50 nm. The relaxation rates of both processes have different temperature dependencies. One process coincidences in its position and temperature dependence with the glassy dynamics of bulk PVME and is ascribed to the dynamic glass transition of a bulk-like layer in the middle of the film. The relaxation rates were found to be thickness independent as confirmed by SHS. Unexpectedly, the relaxation rates of the second process obey an Arrhenius-like temperature dependence. This process was not observed by SHS and was related to the constrained fluctuations in a layer, which is irreversibly adsorbed at the substrate with a heterogeneous structure. Its molecular fluctuations undergo a confinement effect resulting in the localization of the segmental dynamics. To our knowledge, this is the first report on the molecular dynamics of an adsorbed layer in thin films. KW - Broadband dielectric spectroscopy KW - AC-nanochip calorimetry KW - Nanostructured capacitors KW - Thin films PY - 2017 UR - http://pubs.acs.org/doi/pdf/10.1021/acsami.6b14404 DO - https://doi.org/10.1021/acsami.6b14404 SN - 1944-8244 VL - 9 IS - 8 SP - 7535 EP - 7546 PB - ACS Publications CY - Washington DC AN - OPUS4-39291 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Artzt, Katia A1 - Haubrich, J. A1 - Klaus, M. A1 - Genzel, Ch. A1 - Requena, G. A1 - Bruno, Giovanni T1 - An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V N2 - Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. High tensile strain gradients were found at the frontal surface for samples in an as-built condition. The geometry of the samples promotes increasing strains towards the pillar of the bridges. We observed that the higher the laser energy density during fabrication, the lower the lattice strains. A relief of lattice strains takes place after heat treatment. KW - Selective laser melting KW - Additive manufacturing KW - Heat treatment KW - Ti-6Al-4V KW - Synchrotron X-ray diffraction KW - Residual stress PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-395759 DO - https://doi.org/10.3390/ma10040348 SN - 1996-1944 VL - 10 IS - 4 SP - Article 348, 1 EP - 14 AN - OPUS4-39575 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dieck, S. A1 - Rosemann, Paul A1 - Kromm, Arne A1 - Halle, T. T1 - Reversed austenite for enhancing ductility of martensitic stainless steel N2 - The novel heat treatment concept, “quenching and partitioning” (Q&P) has been developed for high strength steels with enhanced formability. This heat treatment involves quenching of austenite to a temperature between martensite start and finish, to receive a several amount of retained austenite. During the subsequent annealing treatment, the so called partitioning, the retained austenite is stabilized due to carbon diffusion, which results in enhanced formability and strength regarding strain induced austenite to martensite transformation. In this study a Q&P heat treatment was applied to a Fe-0.45C-0.65Mn-0.34Si-13.95Cr stainless martensite. Thereby the initial quench end temperature and the partitioning time were varied to characterize their influence on microstructural evolution. The microstructural changes were analysed by dilatometer measurements, X-ray diffraction and scanning electron microscopy, including electron backscatter diffraction. Compression testing was made to examine the mechanical behaviour. It was found that an increasing partitioning time up to 30 min leads to an enhanced formability without loss in strength due to a higher amount of stabilized retained and reversed austenite as well as precipitation hardening. T2 - 19th Chemnitz Seminar on Materials Engineering – 19. Werkstofftechnisches Kolloquium CY - Chemnitz, Germany DA - 16.03.2017 KW - Quenching and partitioning KW - Martensitic stainless steels KW - Heat treatment KW - Transformation induced plasticity KW - High ductility PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-395328 DO - https://doi.org/10.1088/1757-899X/181/1/012034 SN - 1757-899X SN - 1757-8981 VL - 181 IS - Conference 1 SP - Article UNSP 012034, 1 EP - 8 PB - IOP Publishing CY - Bristol, UK AN - OPUS4-39532 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rosemann, Paul A1 - Müller, C. A1 - Baumann, O. A1 - Modersohn, W. A1 - Halle, T. T1 - Influence of the post-weld surface treatment on the corrosion resistance of the duplex stainless steel 1.4062 N2 - The duplex stainless steel 1.4062 (X2CrNiN22-2) is used as alternative material to austenitic stainless steels in the construction industry. The corrosion resistance of welded seams is influenced by the base material, the weld filler material, the welding process and also by the final surface treatment. The scale layer next to the weld seam can be removed by grinding, pickling, electro-polished or blasting depending on the application and the requested corrosion resistance. Blasted surfaces are often used in industrial practice due to the easier and cheaper manufacturing process compared to pickled or electro-polished surfaces. Furthermore blasting with corundum-grain is more effective than blasting with glass-beads which also lower the process costs. In recent years, stainless steel surfaces showed an unusually high susceptibility to pitting corrosion after grinding with corundum. For this reason, it is now also questioned critically whether the corrosion resistance is influenced by the applied blasting agent. This question was specifically investigated by comparing grinded, pickled, corundum-grain- and glass-bead-blasted welding seams. Results of the SEM analyses of the blasting agents and the blasted surfaces will be presented and correlated with the different performed corrosion tests (potential measurement, KorroPad-test and pitting potential) on welding seams with different surface treatments. T2 - 19th Chemnitz Seminar on Materials Engineering – 19. Werkstofftechnisches Kolloquium CY - Chemnitz, Germany DA - 16.03.2017 KW - Corrosion resistance KW - Welding KW - Duplex stainless steels KW - Pitting corrosion KW - Surface treatment PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-395374 DO - https://doi.org/10.1088/1757-899X/181/1/012019 SN - 1757-899X SN - 1757-8981 VL - 181 IS - Conference 1 SP - Article UNSP 012019, 1 EP - 9 PB - IOP Publishing CY - Bristol, UK AN - OPUS4-39537 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gottlieb, Cassian A1 - Millar, Steven A1 - Grothe, S. A1 - Wilsch, Gerd T1 - 2D evaluation of spectral LIBS data derived from heterogeneous materials using cluster algorithm N2 - Laser-induced Breakdown Spectroscopy (LIBS) is capable of providing spatially resolved element maps in regard to the chemical composition of the sample. The evaluation of heterogeneous materials is often a challenging task, especially in the case of phase boundaries. In order to determine information about a certain phase of a material, the need for a method that offers an objective evaluation is necessary. This paper will introduce a cluster algorithm in the case of heterogeneous building materials (concrete) to separate the spectral information of non-relevant aggregates and cement matrix. In civil engineering, the information about the quantitative ingress of harmful species like Cl−, Na+ and SO2−4 is of great interest in the evaluation of the remaining lifetime of structures (Millar et al., 2015; Wilsch et al., 2005). These species trigger different damage processes such as the alkali-silica reaction (ASR) or the chloride-induced corrosion of the reinforcement. Therefore, a discrimination between the different phases, mainly cement matrix and aggregates, is highly important (Weritz et al., 2006). For the 2D evaluation, the expectation-maximizationalgorithm (EM algorithm; Ester and Sander, 2000) has been tested for the application presented in this work. The method has been introduced and different figures of merit have been presented according to recommendations given in Haddad et al. (2014). Advantages of this method will be highlighted. After phase separation, non-relevant information can be excluded and only the wanted phase displayed. Using a set of samples with known and unknown composition, the EM-clustering method has been validated regarding to Gustavo González and Ángeles Herrador (2007). KW - LIBS KW - Concrete KW - EM-clustering KW - Heterogeneity PY - 2017 DO - https://doi.org/10.1016/j.sab.2017.06.005 SN - 0584-8547 VL - 2017 IS - 134 SP - 58 EP - 68 PB - Elsevier B.V. AN - OPUS4-40644 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 - Cyclic Polylactides via Simultaneous Ring-Opening Polymerization and Polycondensation Catalyzed by Dibutyltin Mercaptides N2 - L-Lactide is polymerized in bulk at 160 8C either with dibutyltin bis(benzylmercaptide) (SnSBzl), dibutyltin bis(benzothiazole 2-mercaptide) (SnMBT), or with dibutyltin bis(pentafluorothiophenolate) (SnSPF) as catalysts. SnSBzl yields linear polylactides having benzylthio-ester end groups in addition to cyclic polylactides, whereas SnMBT and SnSPF mainly or exclusively yield cyclic polylactides. This finding, together with model reactions, indicates that the SnS catalysts promote a combined ring-opening polymerization and polycondensation process including end-to-end cyclization. SnMBT caused slight racemization (3%–5%), when used at 160 8C. With SnSPF optically pure cyclic poly(L-lactide)s with high-molecular weights can be prepared at 160 8C. KW - Cyclopolymerization KW - Catalysts KW - MALDI-TOF MS KW - Polyester KW - Ring-opening polymerization PY - 2017 DO - https://doi.org/10.1002/pola.28762 VL - 55 IS - 22 SP - 3767 EP - 3775 PB - Wiley Periodicals AN - OPUS4-42600 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Resch-Genger, Ute ED - Mousavi, M. ED - Thomasson, B. ED - Li, M. ED - Kraft, Marco ED - Würth, Christian ED - Andersson-Engels, S. T1 - Beam-profile-compensated quantum yield measurements of upconverting nanoparticles N2 - The quantum yield is a critically important parameter in the development of lanthanide-based upconverting nanoparticles (UCNPs) for use as novel contrast agents in biological imaging and optical reporters in assays. The present work focuses on the influence of the beam Profile in measuring the quantum yield (f) of nonscattering dispersions of nonlinear upconverting probes, by establishing a relation between f and excitation light power density from a rate equation analysis. A resulting 60% correction in the measured f due to the beam profile utilized for excitation underlines the significance of the beam profile in such measurements, and its impact when comparing results from different Setups and groups across the world. KW - Fluorescence KW - Lanthanide KW - Upconversion KW - Brithtness KW - Quantification KW - Nanoparticle KW - Absolute fluoreometry KW - NIR KW - IR KW - Quantum yield KW - Integrating sphere spectroscopy KW - Method PY - 2017 DO - https://doi.org/10.1039/c7cp03785f SN - 1463-9076 SN - 1463-9084 VL - 19 IS - 33 SP - 22016 EP - 22022 PB - Royal Society of Chemistry AN - OPUS4-42583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Haferkamp, Sebastian A1 - Fischer, Franziska A1 - Kraus, Werner A1 - Emmerling, Franziska T1 - Mechanochemical Knoevenagel condensation investigated in situ N2 - The mechanochemical Knoevenagel condensation of malononitrile with p-nitrobenzaldehyde was studied in situ using a tandem approach. X-ray diffraction and Raman spectroscopy were combined to yield time-resolved information on the milling process. Under solvent-free conditions, the reaction leads to a quantitative conversion to p-nitrobenzylidenemalononitrile within 50 minutes. The in situ data indicate that the process is fast and proceeds under a direct conversion. After stopping the milling process, the reaction continues until complete conversion. The continuous and the stopped milling process both result in crystalline products suitable for single crystal X-ray diffraction. KW - Mechanochemistry KW - Ball milling KW - C–C coupling KW - In situ KW - Knoevenagel condensation PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-425388 DO - https://doi.org/10.3762/bjoc.13.197 VL - 13 SP - 2010 EP - 2014 PB - Beilstein-Institut AN - OPUS4-42538 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Resch-Genger, Ute ED - Otto, S. ED - Scholz, Norman ED - Behnke, Thomas ED - Heinze, K. T1 - Thermo-Chromium: A Contactless Optical Molecular Thermometer N2 - The unparalleled excited-state potential-energy landscape of the chromium(III)-based dye [1]3+ ([Cr(ddpd)2]3+; ddpd=N,N’-dimethyl-N,N’-dipyridin-2-ylpyridin-2,6-diamine) enables a strong dual emission in the near infrared region. The temperature dependence of this dual emission allows the use of [1]3+ as an unprecedented molecular ratiometric thermometer in the 210–373 K temperature range in organic and in aqueous media. Incorporation of [1]3+ in biocompatible nanocarriers, such as 100 nm-sized polystyrene nanoparticles and solutol micelles, provides nanodimensional thermometers operating under physiological conditions. KW - Temperature KW - Sensor KW - Dual emission KW - Fluorescence KW - Cr complex KW - Nano KW - Particle KW - Micelle KW - Probe KW - Environment PY - 2017 DO - https://doi.org/10.1002/chem.201701726 SN - 0947-6539 VL - 23 IS - 50 SP - 12131 EP - 12135 PB - Wiley-VCH AN - OPUS4-42539 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Vormwald, M. T1 - Fatigue strength and fracture mechanics N2 - If fracture mechanics shall be applied to the total lifetime respectively the fatigue limit of components (within the meaning of the S-N curve approach) it has to address four challenges: (a) It has to adequately describe so-called short crack propagation, which cannot be based on the common long crack concepts for principle reasons. Since the crack size is in the order of the plastic zone size, the modelling of short crack propagation cannot be based on the common linear elastic Delta K concept. Instead, an elastic-plastic parameter such as the cyclic J integral has to be applied. A second point is that the crack closure concept has to be modified in that the crack opening stress is not a constant, crack size- independent parameter but shows a transient behaviour with increasing short crack size. (b) It has to provide a meaningful definition of the initial crack dimensions as the starting point for an S-N curve relevant (residual) lifetime analysis. This can be based either on the (statistical) size of material defects which can be treated as cracks or by the size of the crack which would arrest subsequent to early crack propagation, whatever is larger. (c) It has to cope with the problem of multiple cracks for load levels higher than the fatigue limit such as it occurs in many applications in the absence of very large initial defects. (d) This requires consequent statistical treatment taking into account variations in the local geometry of the area where crack initiation has to be expected as well as the scatter in the initial crack size and in the material data used for the analyses. T2 - 2nd International Conference on Structural Integrity CY - Funchal, Madeira, Portugal DA - 04.09.2017 KW - Fatigue strength KW - Fracture mechanics KW - Initial crack size KW - Short crack propagation KW - Multiple crack propagation PY - 2017 DO - https://doi.org/10.1016/j.prostr.2017.07.065 SN - 2452-3216 VL - 5 SP - 745 EP - 752 AN - OPUS4-42545 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hertwig, Andreas A1 - Hinrichs, K. A1 - Beck, Uwe A1 - Esser, N. T1 - Editorial to the proceedings of the 7th conference on spectroscopic N2 - The 7th International Conference on Spectroscopic Ellipsometry (ICSE-7) was held in Berlin in June 2016, jointly organised by ICSE and BAM. The publication of the proceedings special issue in Applied Surface Science follows this event. In the special issue, about 100 articles on current topics of optics and surface science related to ellipsometry, polarimetry, and similar techniques are presented, underpinning the high significance of these techniques for many fields of materials science. T2 - 7th International Conference on Spectroscopic Ellipsometry, ICSE-7 CY - Berlin, Germany DA - 06.06.2016 KW - Spectroscopic ellipsomety PY - 2017 DO - https://doi.org/10.1016/j.apsusc.2017.04.081 SN - 0169-4332 VL - 2017 IS - 421 SP - 269 EP - 270 PB - Elsevier B.V. AN - OPUS4-42554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Léonard, Fabien A1 - Stein, J. A1 - Soutis, C. A1 - Withers, P. J. T1 - The quantification of impact damage distribution in composite laminates by analysis of X-ray computed tomograms N2 - One of the great strengths of X-ray computed tomography over conventional inspection methods (ultrasound, thermography, radiography) is that it can image damage in 3D. However for curved ordeformed composite panels it can be difficult to automatically ascribe the damage to specific plies or inter-ply interfaces. An X-ray computed tomography (CT) data processing methodology is developed to extract the through-thickness distribution of damage in curved or deformed composite panels. The method is applied to [(0°/90°)2]s carbon fibre reinforced polymer (CFRP) panels subjected low velocity impact damage (5 J up to 20 J) providing 3D ply-by-ply damage visualisation and analysis. Our distance transform approach allows slices to be taken that approximately follow the composite curvature allowing the impact damage to be separated, visualised and quantified in 3D on a ply-by-ply basis. In this way the interply delaminations have been mapped, showing characteristic peanut shaped delaminations with the major axis oriented with the fibres in the ply below the interface. This registry to the profile of the panel constitutes a significant improvement in our ability to characterise impact damage in composite laminates and extract relevant measurements from X-ray CT datasets. KW - Delamination KW - Impact behaviour KW - Non-destructive testing KW - X-ray computed tomography KW - Distance transform PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0266353817307157?via%3Dihub DO - https://doi.org/10.1016/j.compscitech.2017.08.034 SN - 0266-3538 SN - 1879-1050 VL - 152 SP - 139 EP - 148 PB - Elsevier Ltd. AN - OPUS4-42556 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Beier, T. A1 - Tchoffo Ngoula, D. T1 - Approximation of the crack driving force for cracks at notches under static and cyclic loading N2 - The work deals with the efficient calculation of the elastic-plastic crack driving force (J-integral for monotonic loading andΔJ-integral under cyclic loading) for short cracks at notches as essential parameter for the reliable static and fatigue assessment of notched structures. The J- or ΔJ-integral is calculated based on analytical solutions for stress intensity factors, estimated by means of well-known weight function solutions in the case of cracks under power-law stress distributions. A plasticity-correction function is applied to the stress intensity factors to obtain the final expression of the crack driving force. The comparison between analytical solutions and finite element calculations in case of cracks at the weld toe in welded joints shows good agreement. T2 - 2nd International Conference on Structural Integrity CY - Funchal, Madeira, Portugal DA - 04.09.2017 KW - Structural integrity KW - Fracture mechanics KW - Crack driving force KW - Notches PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-425577 DO - https://doi.org/10.1016/j.prostr.2017.07.111 SN - 2452-3216 VL - 5 SP - 875 EP - 882 PB - Elsevier B.V. AN - OPUS4-42557 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Giebson, C. A1 - Voland, K. A1 - Ludwig, H.-M. A1 - Meng, Birgit T1 - Alkali-silica reaction performance testing of concrete considering external alkalis and preexisting microcrack N2 - In concrete elements, simultaneously subjected to cyclic loadings and external alkalis, the risk for damage caused by or under participation of an alkali-silica reaction (ASR) is particularly high. This is of particular concern for concrete pavements due to the increasing heavy vehicle traffic and the application of sodium chloride (NaCl) de-icer during winter. Since 2004, the climate simulation concrete prism test (CS-CPT) has been used successfully to evaluate job mixtures for pavements by considering the impact of alkali-containing de-icers. However, the role of mechanical predamage on ASR is largely unclear. In a joint research project, the CS-CPT has been used to investigate the influence of preexisting microcracks on ASR. It was evident that an ASR initiated earlier in the predamaged concrete prisms due to the more rapid ingress of NaCl solution through the microcracks. KW - Alkali-silica reaction KW - Climate simulation concrete prism test KW - External alkalis KW - Laser-induced breakdown spectroscopy KW - Microcracks KW - Pavement concrete PY - 2017 DO - https://doi.org/10.1002/suco.201600173 SN - 1464-4177 SN - 1751-7648 VL - 18 IS - 4 SP - 528 EP - 538 PB - Ernst & Sohn AN - OPUS4-42574 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Naresh-Kumar, G. A1 - Vilalta-Clemente, A. A1 - Jussila, H. A1 - Winkelmann, Aimo A1 - Nolze, Gert A1 - Vespucci, S. A1 - Nagarajan, S. A1 - Wilkinson, A. J. A1 - Trager-Cowan, C. T1 - Quantitative imaging of anti-phase domains by polarity sensitive orientation mapping using electron backscatter diffraction N2 - Advanced structural characterisation techniques which are rapid to use, non-destructive and structurally definitive on the nanoscale are in demand, especially for a detailed understanding of extended-defects and their influence on the properties of materials. We have applied the electron backscatter diffraction (EBSD) technique in a scanning electron microscope to non-destructively characterise and quantify antiphase domains (APDs) in GaP thin films grown on different (001)Si substrates with different offcuts. We were able to image and quantify APDs by relating the asymmetrical intensity distributions observed in the EBSD patterns acquired experimentally and comparing the same with the dynamical electron diffraction simulations. Additionally mean angular error maps were also plotted using automated cross-correlation based approaches to image APDs. Samples grown on substrates with a 4° offcut from the [110] do not show any APDs, whereas samples grown on the exactly oriented substrates contain APDs. The procedures described in our work can be adopted for characterising a wide range of other material systems possessing non-centrosymmetric point groups. KW - Polarity KW - Semiconductor KW - Antiphase boundary PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-420167 SN - 2045-2322 VL - 7 SP - Article 10916, 1 EP - 10 AN - OPUS4-42016 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sobol, Oded A1 - Nolze, Gert A1 - Saliwan Neumann, Romeo A1 - Eliezer, D. A1 - Böllinghaus, Thomas A1 - Unger, Wolfgang T1 - Novel approach to image hydrogen distribution and related phase transformation in duplex stainless steels at the sub-micron scale N2 - The effect of electrochemical charging of hydrogen on the structure of a lean duplex stainless steel LDX 2101® (EN 1.4162, UNS S32101) was examined by both Time-of-Flight secondary ion mass spectrometry and electron back-scatter diffraction. The goal is to correlate hydrogen concentration and induced structural changes. Chemical and structural characterizations were done for the same region at the sample's surface with sub-micron spatial resolution. Regions of interest were varying in size between 50 × 50 μm and 100 × 100 μm. The results show a phase transformation of austenite to mainly a defect-rich BCC and scarcely a HCP phase. The phase transformation occurred in deuterium rich regions in the austenite. KW - Time-of-flight secondary ion mass spectrometry KW - ToF-SIMS KW - Electron backscatter diffraction KW - EBSD KW - Hydrogen-assisted cracking KW - Data fusion KW - Lean duplex stainless steel PY - 2017 DO - https://doi.org/10.1016/j.ijhydene.2017.08.016 SN - 0360-3199 VL - 42 IS - 39 SP - 25114 EP - 25120 AN - OPUS4-42022 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maierhofer, Christiane A1 - Krankenhagen, Rainer A1 - Röllig, Mathias A1 - Unnikrishnakurup, Sreedhar A1 - Monte, C. A1 - Adibekyan, A. A1 - Gutschwager, B. A1 - Knazowicka, L. A1 - Blahut, A. A1 - Gower, M. A1 - Lodeiro, M. A1 - Baker, G. A1 - Aktas, A. T1 - Einfluss thermischer und optischer Materialeigenschaften auf die Charakterisierung von Fehlstellen in Faserverbundwerkstoffen mit aktiven Thermografieverfahren T1 - Influence of thermal and optical material properties on the characterization of defects in fiber reinforced composites with active thermography methods N2 - In diesem Beitrag werden zerstörungsfreie Untersuchungen mittels aktiver Thermografie an Probekörpern aus CFK und GFK mit unterschiedlichen künstlichen Fehlstellen vorgestellt. Dabei wird die zeitliche und örtliche Temperaturverteilung nach der Erwärmung mit Blitzlampen oder mit einem Infrarot-Strahler mit einer Infrarot-Kamera erfasst. Zur späteren Rekonstruktion der Messdaten wurde ein numerisches Modell entwickelt. Dazu war die Bestimmung der thermophysikalischen und optischen Materialeigenschaften erforderlich, was in diesem Beitrag ebenfalls beschrieben wird. Die Ergebnisse der numerischen Modellierung werden mit den experimentellen Untersuchungen der aktiven Thermografie verglichen. Weiterhin werden die experimentellen Untersuchungen hinsichtlich der beiden Materialsysteme CFK und GFK und unter Berücksichtigung der Teiltransparenz des GFK-Materials sowie der unterschiedlichen Anregungsquellen bewertet. N2 - This paper presents results of the non-destructive evaluation of CFRP and GFRP test specimens with various artificial defects using active thermography. After heating the specimens with flash lamps or with an infrared radiator, the temporal and spatial resolved temperature distribution is recorded with an infrared camera. For the reconstruction of the experimental data, a numerical model was developed. For the numerical simulations, the thermal and optical material parameters had to be determined, which is described in this contribution as well. The results of numerical modelling are compared to experimental data of active thermography. Additionally, the experimental results are assessed related to the two materials CFRP and GFRP by considering the partial transmissivity of the GFRP material, and to the different excitation sources. T2 - Temperatur 2017 CY - Berlin, Germany DA - 17.05.2017 KW - Zerstörungsfreie Prüfung KW - Aktive Thermografie KW - Faserverbundwerkstoffe (CFK, GFK) KW - Numerische Simulation PY - 2017 DO - https://doi.org/10.1515/teme-2017-0078 SN - 0171-8096 SN - 2196-7113 VL - 85 IS - 1 SP - 13 EP - 27 PB - DE GRUYTER CY - Oldenburg AN - OPUS4-42395 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Al-Terkawi, Abdal-Azim A1 - Scholz, G. A1 - Emmerling, Franziska A1 - Kemnitz, E. T1 - Strontium-coordination polymers based on tetrafluorophthalic and phthalic acids: mechanochemical synthesis, ab initio structures determination, and spectroscopic characterization N2 - Two strontium-based dicarboxylate systems [Sr(oBDC-F4)(H2O)2] (1) and [{Sr(oBDC)(H2O)2)·H2O] (2) were synthesized mechanochemically via milling of Sr(OH)2·8H2O with tetrafluorophthalic acid (H2oBDC-F4) or phthalic acid (H2oBDC), respectively. The new structures were determined ab initio from the powder X-ray diffraction (PXRD) data. Both compounds 1 and 2 crystallize in the monoclinic space group P21 /c as two-dimensional coordination polymers (2D-CPs). The determined structures were validated by extended X-ray absorption (EXAFS) data. Compounds 1 and 2 show different thermal stabilities. The fluorinated CP 1 is decomposed at 300 °C while the nonfluorinated CP 2 transforms into a new phase after thermal treatment at 400 °C. The two hydrated CPs exhibit small surface areas which increase after the thermal posttreatment for 1 but remains unchanged for the dehydrated sample of 2. Dynamic vapor sorption (DVS) experiments indicate that both the dehydrated and hydrated samples of 2 depict no significant differences in their adsorption isotherms. The DVS of water indicates that the phase transition after thermal posttreatment of 2 is irreversible. KW - Mechanochemistry KW - XRD KW - NMR PY - 2017 DO - https://doi.org/10.1039/c7dt02564e SN - 1477-9226 SN - 1477-9234 VL - 46 IS - 37 SP - 12574 EP - 12587 PB - The Royal Society of Chemistry CY - Cambridge AN - OPUS4-42261 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Hertwig, Andreas A1 - Heidari, M. A1 - von Klitzing, R. A1 - Napolitano, S. A1 - Sferrazza, M. A1 - Schönhals, Andreas T1 - Decoupling of dynamic and thermal glass transition in thin films of a PVME/PS blend N2 - The discussions on the nanoconfinement effect on the glass transition and glassy dynamics phenomena have yielded many open questions. Here, the thickness dependence of the thermal glass transition temperature of thin films of a PVME/PS blend is investigated by ellipsometry. Its thickness dependence was compared to that of the dynamic glass transition (measured by specific heat spectroscopy), and the deduced Vogel temperature (T0). While and T0 showed a monotonous increase, with decreasing the film thickness, the dynamic glass transition temperature () measured at a finite frequency showed a non-monotonous dependence that peaks at 30 nm. This was discussed by assuming different cooperativity length scales at these temperatures, which have different sensitivities to composition and thickness. This non-monotonous thickness dependence of disappears for frequencies characteristic for T0. Further analysis of the fragility parameter, showed a change in the glassy dynamics from strong to fragile, with decreasing film thickness. KW - Thin polymeric films KW - Ellipsometry KW - Specific heat spectroscopy PY - 2017 DO - https://doi.org/10.1021/acsmacrolett.7b00625 SN - 2161-1653 VL - 6 IS - 10 SP - 1156 EP - 1161 PB - ACS Publications AN - OPUS4-42266 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Chatzigiannakis, E. A1 - Beckmann, Jörg A1 - Wachtendorf, Volker A1 - von der Ehe, Kerstin A1 - Braun, Ulrike A1 - Jaunich, Matthias A1 - Schade, U. A1 - Wolff, Dietmar T1 - Discoloration Effects of High-Dose gamma-Irradiation and Long-Term Thermal Aging of (U) HMW-PE N2 - Two polyethylene types with ultra-high (UHMWPE) and high molecular weight (HMW-PE) used as neutron radiation shielding materials in casks for radioactive waste were irradiated with doses up to 600 kGy using a 60Co gammasource. Subsequently, thermal aging at 125∘C was applied for up to one year. Degradation effects in the materials were characterized using colorimetry, UV-Visspectroscopy, IR spectroscopy, and DSC. Both materials exhibited a yellowing upon irradiation.The discoloration of UHMW-PE disappeared again after thermal aging.Therefore, the yellowing is assumed to originate fromannealable color centers in the formof free radicals that are trapped in the crystalline regions of the polymer and recombine at elevated temperatures. For the antioxidantcontaining HMWPE, yellowing was observed after both irradiation and thermal aging. The color change was correlated mainly to decomposition products of the antioxidant in addition to trapped radicals as in UHMW-PE. Additionally, black spots appeared after thermal aging of HMW-PE. KW - Irradiation KW - UHMWPE KW - Colour center KW - Yellowness index PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-423992 DO - https://doi.org/10.1155/2017/1362491 SN - 1687-9422 VL - 2017 IS - Article ID 1362491 SP - 1 EP - 10 PB - Hindawi AN - OPUS4-42399 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. A1 - Weidner, Steffen A1 - Scheliga, F. ED - Shaplov, A. T1 - Cyclization and dispersity of polyesters N2 - Two classes of polyesters were prepared by irreversible polycondensations. The dependence of the dispersities on the experimental parameters such as synthetic method, chemical structure, molecular weight and initial monomer concentration was determined. At first it was demonstrated that it is essential for a correct calculation of Mn and Mw to include all oligomers down to the dimers in the evaluation of SEC curves. Furthermore, it was demonstrated for poly(e-caprolactone)s and polylactides that reversible polycondensations and ring-opening polymerizations with equilibration yield identical products. Finally, the dependence of the dispersity on various experimental Parameters was determined for equilibrated poly(e-caprolactone)s and polylactides. KW - Irreversible polycondensation KW - Polycaprolactone KW - Polylactide KW - Dispersity KW - MALDI-TOF MS PY - 2017 DO - https://doi.org/10.1002/masy.201600169 SN - 1022-1360 SN - 1521-3900 VL - 375 IS - 1 SP - Article 1600169, 1 EP - 6 PB - Wiley-VCH AN - OPUS4-42407 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Cheng-Chieh A1 - Weisbrich, S. A1 - Neitzel, F. ED - Emri, Igor T1 - Approximate model for geometrical complex structures N2 - Many engineering structures are nowadays made of composite materials or metal foam. These modern engineering materials contain very complex inner geometry. To simulate the deformational behaviour of these structures often requires a high number of discretisation elements. This in turn yields a very large system of linear equations that are extremely time and memory consuming or practically impossible to solve. It is therefore desirable to find an approach to overcome this obstacle. In this paper a numerical method is proposed to find an approximate substitute model for geometrical complex structures. T2 - 33rd Danubia Adria Symposium on Advances in Experimental Mechanics CY - Portorož, Slovenia DA - 20.09.2016 KW - Adjustment calculation KW - Finite element method KW - Substitute model KW - Complex structures PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S2214785317308593 DO - https://doi.org/10.1016/j.matpr.2017.06.084 SN - 2214-7853 VL - 4 IS - 5, Part 1 SP - 5995 EP - 6000 PB - Elsevier CY - Amsterdam, Netherlands AN - OPUS4-42794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Le, Quynh Hoa A1 - Vestergaard, M.C. A1 - Tamiya, E T1 - Carbon-based nanomaterials in biomass-based fuel-fed fuel cells N2 - Environmental and sustainable economical concerns are generating a growing interest in biofuels predominantly produced from biomass. It would be ideal if an energy conversion device could directly extract energy from a sustainable energy resource such as biomass. Unfortunately, up to now, such a direct conversion device produces insufficient power to meet the demand of practical applications. To realize the future of biofuel-fed fuel cells as a green energy conversion device, efforts have been devoted to the development of carbon-based nanomaterials with tunable electronic and surface characteristics to act as efficient metal-free electrocatalysts and/or as supporting matrix for metal-based electrocatalysts. We present here a mini review on the recent advances in carbon-based catalysts for each type of biofuel-fed/biofuel cells that directly/indirectly extract energy from biomass resources, and discuss the challenges and perspectives in this developing field KW - Carbon-based nanomaterials KW - Biofuel cells KW - Biomass KW - Carbon nanotubes KW - Graphene KW - Carbon nanodots PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-428226 UR - http://www.mdpi.com/1424-8220/17/11/2587/htm DO - https://doi.org/10.3390/s17112587 SN - 1424-8220 VL - 17 IS - 11 SP - 2587, 1 EP - 2587, 21 PB - MDPI AG CY - Basel, Switzerland AN - OPUS4-42822 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heitz, J. A1 - Plamadeala, C. A1 - Muck, M. A1 - Armbruster, O. A1 - Baumgartner, W. A1 - Weth, A. A1 - Steinwender, C. A1 - Plessberger, H. A1 - Kellermair, J. A1 - Kirner, Sabrina V. A1 - Krüger, Jörg A1 - Bonse, Jörn A1 - Guntner, A. S. A1 - Hassel, A. W. T1 - Femtosecond laser-induced microstructures on Ti substrates for reduced cell adhesion N2 - Miniaturized pacemakers with a surface consisting of a Ti alloy may have to be removed after several years from their implantation site in the heart and shall, therefore, not be completely overgrown by cells or tissue. A method to avoid this may be to create at the surface by laser-ablation self-organized sharp conical spikes, which provide too little surface for cells (i.e., fibroblasts) to grow on. For this purpose, Ti-alloy substrates were irradiated in the air by 790 nm Ti:sapphire femtosecond laser pulses at fluences above the ablation threshold. The laser irradiation resulted in pronounced microstructure formation with hierarchical surface morphologies. Murine fibroblasts were seeded onto the laser-patterned surface and the coverage by cells was evaluated after 3–21 days of cultivation by means of scanning electron microscopy. Compared to flat surfaces, the cell density on the microstructures was significantly lower, the coverage was incomplete, and the cells had a clearly different morphology. The best results regarding suppression of cell growth were obtained on spike structures which were additionally electrochemically oxidized under acidic conditions. Cell cultivation with additional shear stress could reduce further the number of adherent cells. KW - Laser Processing KW - Femtosecond laser KW - Titanium alloy KW - Cell adhesion KW - Anodic oxidation KW - Pacemaker PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-427681 UR - https://link.springer.com/article/10.1007/s00339-017-1352-0 DO - https://doi.org/10.1007/s00339-017-1352-0 SN - 0947-8396 SN - 1432-0630 VL - 123 IS - 12 SP - 734, 1 EP - 9 PB - Springer-Verlag CY - Berlin AN - OPUS4-42768 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, Rui A1 - Russo, Patrícia A. A1 - de Oliveira Guilherme Buzanich, Ana A1 - Jeon, Taeyeol A1 - Pinna, Nicola T1 - Hybrid organic–inorganic transition-metal phosphonates as precursors for water oxidation electrocatalysts N2 - Efficient water oxidation catalysts are required for the development of water splitting technologies. Herein, the synthesis of layered hybrid NiFephenylphosphonate compounds from metal acetylacetonate precursors and phenylphosphonic acid in benzyl alcohol, and their Oxygen evolution reaction performance in alkaline medium, are reported. The hybrid particles are formed by inorganic layers of NiO6 and FeO6 distorted octahedra separated by bilayers of the organic group, and template the Formation in situ of NiFe hydroxide nanosheets of sizes between 5 and 25 nm and thicknesses between 3 and 10 nm. X-ray absorption spectroscopy measurements suggest that the hybrid also acts as a template for the local structure of the metal sites in the active catalyst, which remain distorted after the transformation. Optimum electrocatalytic activity is achieved with the hybrid compound with a Fe content of 16%. The combination of the synergistic effect between Ni and Fe with the structural properties of the hybrid results in an efficient catalyst that generates a current density of 10 mA cm−2 at an overpotential of 240 mV, and also in a stable catalyst that operates continuously at low overpotentials for 160 h. KW - Water oxydation catalysis KW - EXAFS PY - 2017 DO - https://doi.org/10.1002/adfm.201703158 SN - 1616-301X SN - 1616-3028 VL - 27 IS - 40 SP - Article 1703158, 1 EP - 11 PB - WILEY-VCH Verlag CY - Weinheim AN - OPUS4-42783 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cooper, R. A1 - Bruno, Giovanni A1 - Shyam, A. A1 - Watkins, T. A1 - Pandey, A. A1 - Wheeler, M. T1 - Effect of microcracking on the uniaxial tensile response of beta-eucryptite ceramics: Experiments and constitutive model N2 - A constitutive model for the nonlinear or “pseudoplastic” mechanical behavior in a linear-elastic solid with thermally induced microcracks is developed and applied to experimental results. The model is termed strain dependent microcrack density approximation (SDMDA) and is an extension of the modified differential scheme that describes the slope of the stress-strain curves of microcracked solids. SDMDA allows a continuous variation in the microcrack density with tensile loading. Experimental uniaxial tensile response of β-eucryptite glass and ceramics with controlled levels of microcracking is reported. It is demonstrated that SDMDA can well describe the extent of non-linearity in the experimental uniaxial tensile response of β-eucryptite with varying levels of microcracking. The advantages of the SDMDA are discussed in regard to tensile loading. KW - Microcracking KW - β-eucryptite KW - Young's modulus KW - Modeling KW - Tensile behavior PY - 2017 DO - https://doi.org/10.1016/j.actamat.2017.06.033 SN - 1359-6454 SN - 1873-2453 VL - 135 SP - 361 EP - 371 PB - Elsevier Ltd. AN - OPUS4-40859 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kingelhöffer, Hellmuth A1 - Affeldt, E. E. A1 - Bache, M. A1 - Bartsch, M. A1 - Beck, T. A1 - Christ, H. J. A1 - Fedelich, Bernard A1 - Hähner, P. A1 - Holdsworth, S. R. A1 - Lang, K.-H. A1 - McGaw, M. A1 - Olbricht, Jürgen A1 - Remy, L. A1 - Skrotzki, Birgit A1 - Stekovich, S. T1 - Editorial - Special issue: Recent developments in thermo-mechanical fatigue N2 - Components in the Aerospace, Power and Automotive engineering sectors are frequently subjected to cyclic stresses induced by thermal fluctuations and mechanical loads. For the design of such components, reliable material property data are required which need to be acquired using well accepted and reproducible test procedures for thermo-mechanical fatigue (TMF) loading. There is limited availability of proven TMF data indicating there is need for further research and testing. The TMF behaviour of materials is often desired to be simulated in models which describe the cyclic stress-strain behaviour, the fatigue life and the cyclic crack growth behaviour. There is a continuous need for the development and amendment of such models. Models can be validated by using materials in industrial applications which are subjected to TMF loading. The 3rd Workshop on Thermo-Mechanical Fatigue was held on 27–29 April 2016 at BAM, Berlin, Germany. The workshop was attended by 90 attendees coming from 17 countries in the world. 38 presentations including five poster presentations were held. The following topics were covered by the workshop: – TMF of materials coated with Thermal Barrier Coatings. – Thermal Gradient Mechanical Fatigue. – TMF crack growth. – TMF + High Cycle Fatigue. – TMF Modelling and Lifetime Prediction. – TMF Properties of steels, cast iron, Al-, Mg- and Ni-alloys – Advanced TMF Testing Techniques. – Industrial Applications. A panel discussion was held regarding the present state of TMF testing standards (ISO and ASTM) and their potential for improvement. The discussion and contributions were summarized and forwarded to the standard committees. The 3rd TMF-Workshop ensured the continuation of international exchange of knowledge providing a forum to present and discuss all recent developments in the field of thermo-mechanical fatigue. The current special issue publishes eleven selected papers of the 3rd TMF-Workshop 2016. The papers were peer reviewed by a number of experts in the Thermo-Mechanical Fatigue sector. I hope you will enjoy reading papers of this special issue. T2 - 3rd International Workshop on Thermo-Mechanical Fatigue (TMF-Workshop 2016) CY - Berlin, Germany DA - 27.04.2016 KW - Fatigue damage KW - Thermo-mechanical fatigue KW - Fatigue life time KW - Life time prediction KW - TMF PY - 2017 DO - https://doi.org/10.1016/j.ijfatigue.2017.02.002 SN - 0142-1123 VL - 99 IS - 2 SP - 215 PB - Elsevier CY - Oxford AN - OPUS4-40895 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Geißler, Daniel A1 - Würth, Christian A1 - Wolter, C. A1 - Weller, H. A1 - Resch-Genger, Ute T1 - Excitation wavelength dependence of the photoluminescence quantum yield and decay behavior of CdSe/CdS quantum dot/quantum rods with different aspect ratios N2 - The excitation wavelength (lexc) dependence of the photoluminescence (PL) quantum yield (FPL) and decay behavior (tPL) of a series of CdSe/CdS quantum dot/Quantum rods (QDQRs), consisting of the same spherical CdSe core and rod-shaped CdS shells, with aspect ratios ranging from 2 to 20 was characterized. lexc between 400–565 nm were chosen to cover the first excitonic absorption band of the CdSe core material, the onset of absorption of the CDs shell, and the region of predominant shell absorption. A strong lexc dependence of relative and absolutely measured FPL and tPL was found particularly for the longer QDQRs with higher aspect ratios. This is attributed to combined contributions from a length-dependent shell-to-core exciton localization efficiency, an increasing number of defect states within the shell for the longest QDQRs, and probably also the presence of absorbing, yet non-emitting shell material. Although the FPL values of the QDQRs decrease at shorter wavelength, the extremely high extinction coefficients introduced by the shell outweigh this effect, leading to significantly higher brightness values at wavelengths below the absorption onset of the CdS Shell compared with direct excitation of the CdSe cores. Moreover, our results present also an interesting example for the comparability of absolutely measured FPL using an integrating sphere setup and FPL values measured relative to common FPL standards, and underline the Need for a correction for particle scattering for QDQRs with high aspect ratios. KW - Quantum dot KW - Quantum rod KW - Quantum yield KW - Integrating sphere KW - Decay time PY - 2017 DO - https://doi.org/10.1039/C7CP02142A SN - 1463-9076 SN - 1463-9084 VL - 19 IS - 19 SP - 12509 EP - 12516 PB - Royal Society of Chemistry (RSC) AN - OPUS4-40814 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Daly, M. A1 - Burnett, T. L. A1 - Pickering, E. J. A1 - Tuck, O. C. G. A1 - Léonard, Fabien A1 - Kelley, R. A1 - Withers, P. J. A1 - Sherry, A. H. T1 - A multi-scale correlative investigation of ductile fracture N2 - The use of novel multi-scale correlative methods, which involve the coordinated characterisation of matter across a range of length scales, are becoming of increasing value to materials scientists. Here, we describe for the first time how a multi-scale correlative approach can be used to investigate the nature of ductile fracture in metals. Specimens of a nuclear pressure vessel steel, SA508 Grade 3, are examined following ductile fracture using medium and high-resolution 3D X-ray computed tomography (CT) analyses, and a site-specific analysis using a dual beam plasma focused ion beam scanning electron microscope (PFIB-SEM). The methods are employed sequentially to characterise damage by void nucleation and growth in one volume of interest, allowing for the imaging of voids that ranged in size from less than 100 nm to over 100 mm. This enables the examination of voids initiated at carbide particles to be detected, as well as the large voids initiated at inclusions. We demonstrate that this multi-scale correlative approach is a powerful tool, which not only enhances our understanding of ductile failure through detailed characterisation of microstructure, but also provides quantitative information about the size, volume fractions and spatial distributions of voids that can be used to inform models of failure. It isfound that the vast majority of large voids nucleated at MnS inclusions, and that the volume of a void varied according to the volume of its initiating inclusion raised to the power 3/2. The most severe voiding was concentrated within 500 mm of the fracture surface, but measurable damage was found to extend to a depth of at least 3 mm. Microvoids associated with carbides (carbide-initiated voids) were found to be concentrated around larger inclusion-initiated voids at depths of at least 400 mm. Methods for quantifying X-ray CT void data are discussed, and a procedure for using this data to calibrate parameters in the Gurson-Tvergaard Needleman (GTN) model for ductile failure is also introduced. KW - Gurson model KW - SA508 KW - Correlative tomography KW - Void nucleation & growth KW - X-ray computed tomography PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-414547 UR - http://www.sciencedirect.com/science/article/pii/S1359645417302203?via%3Dihub DO - https://doi.org/10.1016/j.actamat.2017.03.028 VL - 130 SP - 56 EP - 68 PB - Elsevier AN - OPUS4-41454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wilke, Manuel A1 - Kabelitz, Anke A1 - Zimathies, Annett A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Crystal structure and in situ investigation of a mechanochemical synthesized 3D zinc N-(phosphonomethyl)glycinate N2 - The mechanochemical synthesis of the zinc N-(phosphonomethyl)glycinate Zn(O₃PCH₂NH₂CH₂CO₂) H₂O is presented. The structure was solved from powder X-ray diffraction (PXRD) data. In the three-dimensional pillared structure, the Zn atoms are coordinated tetrahedrally. In situ investigations of the reaction process with synchrotron PXRD and Raman spectroscopy reveal a two-step process including the formation of an intermediate. KW - Mechanochemistry KW - Metal phosphonate KW - In situ PY - 2017 DO - https://doi.org/10.1007/s10853-017-1121-7 SN - 0022-2461 SN - 1573-4803 VL - 52 IS - 20 SP - 12013 EP - 12020 PB - Springer CY - New York AN - OPUS4-41490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schumacher, David A1 - Antin, K.-N. A1 - Zscherpel, Uwe A1 - Vilaça, P. T1 - Application of different X-ray techniques to improve in-service carbon fiber reinforced rope inspection N2 - Carbon fiber reinforced polymer ropes are gaining in significance in the fields of civil engineering and hoisting applications. Thus, methods of non-destructive testing (NDT) need to be developed and evaluated with respect to new challenges and types of defects. Particularly important is the development of in-service testing solutions which allow the integration in global online monitoring systems. Conventional methods like electrical resistivity or strain measurements using optical fibers are already in use. This study investigates the possibility of using various X-ray techniques to increase the reliability and significance of NDT and their applicability to in-service testing. Conventional film radiography is the most common technique; however, even after image enhancement of the digitized film, this technique lacks contrast sensitivity and dynamic range compared to digital detector array (DDA) radiography. The DDA radiography is a highly sensitive method; yet, the limitation is that it delivers 2D images of 3D objects. By the use of co-planar translational laminography the detectability of planar defects is superior to 2D methods due to multiple projection angles. Apart from this, it can be used on-site due to a rather simple setup and robust equipment. In this work two photon counting detectors (PCD) with different sensor materials (Si and CdTe) were used. The results show that the resolution and defect recognition is lower in case of DDA radiography and laminography using PCDs compared to high-resolution computed tomography. However, the DDA radiography and laminography are sensitive enough to both fiber breakage and delaminations and can be significantly advantageous in terms of measurement time and adaptability for on-site monitoring. KW - X-ray imaging KW - Digital radiography KW - Co-planar translational laminography KW - Computed tomography KW - Photon counting detectors KW - Carbon fiber reinforced polymer KW - Rope PY - 2017 DO - https://doi.org/10.1007/s10921-017-0441-5 SN - 0195-9298 SN - 1573-4862 VL - 36 IS - 4 SP - Paper 62, 1 PB - Springer International Publishing AG CY - Cham, Switzerland AN - OPUS4-41781 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Radunz, Sebastian A1 - Tschiche, Harald Rune A1 - Moldenhauer, Daniel A1 - Resch-Genger, Ute T1 - Broad range ON/OFF pH sensors based on pKa tunable fluorescent BODIPYs N2 - A set of highly fluorescent, pH-responsive boron dipyrromethene dyes covering the pH range of 5-12 is presented for broad range pH measurements in mixed aqueous-organic median and polymer matrices. Readout in the intensity Domain with low cost and miniaturized Instrumentation utilizes reversible protonation induced switching ON of their initially completely quenched flourescence mediated by photoinduced electron Transfer. All dyes, rationally designed to reveal closely matching Absorption and Emission properties, are accessible via facile two-step reactions in Overall yields of up to 20%. By modifying the Substitution pattern of the meso-Aryl substiuent, the pKa values could be fine-tuned from 6 to 11. Integration of these molecules into polymeric films by a simple mixing procedure yielded reversible and longterm stable pH sensors for naked eye detection. KW - Fluorescence KW - Sensor KW - PH KW - Dye KW - BODIPY KW - Synthesis KW - Quantification KW - Film KW - Quantum yield KW - Lifetime KW - PET PY - 2017 DO - https://doi.org/10.1016/j.snb.2017.05.080 SN - 0925-4005 VL - 251 SP - 490 EP - 494 PB - Elsevier AN - OPUS4-41782 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pauli, Jutta A1 - Hoffmann, Katrin A1 - Würth, Christian A1 - Behnke, Thomas A1 - Resch-Genger, Ute T1 - Standardization of fluorescence measurements in the UV/vis/NIR/IR N2 - Photoluminescence techniques are amongst the most widely used Tools in the life sciences, with new and exciting applications in medical diagnostics and molecular Imaging continuously emerging. Advantages include their comparative ease of use, unique sensitivity, non-invasive character, and potential for Multiplexing, remote sensing, and miniaturization. General drawbacks are, however, signals, that contain unwanted wavelength- and polarization contributions from Instrument-dependent effects, which are also time-dependent due to aging of Instrument-components, and difficulties to measure absolute flourescence entensities. Moreover, scattering Systems require Special measurement geometries and the interest in new optical Reporters with Emission > 1000 nm strategies for reliable measurements in the second diagnostic for the comparison of material Performance and the rational designg of new flourophores with improved properties. Here, we present strategies to versatile method-adaptable liquid and solid flourescence Standards for different flourescence paramters including traceable Instrument calibration procedures and the design of integrating spere setups for the absolute measurements of emission spectra and Quantum yields in the wavelength Region of 350 to 1600 nm. Examples are multi-Emitter glasses, spectral flourescence Standards, and quantum yield Standards for the UV/vis/NIR. T2 - Conference on Molecular-Guided Surgery - Molecules, Devices, and Applications III CY - San Francisco, CA, USA DA - 28.01.2017 KW - Fluorescence KW - Reference material KW - Standard KW - Calibration KW - Nanoparticle KW - Absolute flourometry KW - Integrating sphere spectroscopy KW - NIR KW - IR KW - Quantum yield standard KW - Emission standards PY - 2017 SN - 978-1-5106-0539-8 DO - https://doi.org/10.1117/12.2255728 SN - 0277-786X VL - 10049 SP - 1 PB - Proceedings of SPIE AN - OPUS4-41783 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Poyet, S. A1 - Dridi, W. A1 - L'Hostis, V. A1 - Meinel, Dietmar T1 - Microstructure and diffusion coefficient of an old corrosion product layer and impact on steel rebar corrosion in carbonated concrete N2 - Corrosion is the major degradation pathway affecting reinforced concrete structures. In the long-term, the rust layer might become thick and slow down the diffusion of oxygen from the atmosphere to the steel. With this in mind, the mineralogy, microstructure and diffusion properties of an old and thick corrosion product layer were investigated. Despite the presence of macropores, the gas diffusion coefficient was found to be low. The impact of the layer on the oxygen diffusion was evaluated using Fick’s law. The results showed that the layer could reduce the flux of oxygen only in a specific configuration. KW - Steel reinforced concrete KW - Rust KW - X-ray computed tomography KW - Micro-CT PY - 2017 DO - https://doi.org/10.1016/j.corsci.2017.06.002 VL - 2017 IS - 125 SP - 48 EP - 58 PB - Elsevier B.V. CY - Radarweg 29, 1043 NX Amsterdam, The Netherlands AN - OPUS4-41784 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wachtendorf, Volker A1 - Kalbe, Ute A1 - Krüger, O. A1 - Bandow, Nicole ED - Brown, R. ED - Gedde, U.W. ED - Hedenqvist, M.S. T1 - Influence of weathering on the leaching behaviour of zinc and PAH from synthetic sports surfaces N2 - Synthetic materials used for outdoor sports grounds consist of a mix of inorganic, organic and polymeric compounds that show ageing due to weathering and a complex leaching behaviour by percolation of rainwater, which can limit its lifetime. Additionally, weathering exposure induces degradation processes in the polymers, which leads to the formation of new surfaces allowing water to access additional reservoirs of leachable compounds. A laboratory test comprising artificial weathering, ozonisation and subsequent leaching was developed to investigate this behaviour in a reproducible and controllable way. The experiments showed a general decline of Zn, polycyclic aromatic hydrocarbons (PAH) and total organic carbon (TOC) concentrations after an initial increase. Within this general trend, the course of concentration over exposure duration is very specific for individual sample materials and the analyte under investigation. The results indicate that weathering and degradation behaviour cannot be predicted from initial material conditions. Thus, weathering experiments are recommended to fill this gap of knowledge. KW - Athletic tracks KW - Artificial turf KW - Ageing KW - Artificial weathering KW - Polymer degradation KW - Rubber granules KW - Leaching KW - Contamination PY - 2017 DO - https://doi.org/10.1016/j.polymertesting.2017.09.021 SN - 0142-9418 SN - 1873-2348 VL - 63 IS - October SP - 621 EP - 631 PB - Elsevier Ltd. CY - Amsterdam, The Netherlands AN - OPUS4-42205 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, Luman A1 - de Greef, Nils A1 - Kalinka, Gerhard A1 - Van Bilzen, Bart A1 - Locquet, Jean-Pierre A1 - Verpoest, Ignaas A1 - Won Seo, Jin T1 - Carbon nanotube-grafted carbon fiber polymer composites: Damage characterization on the micro scale N2 - Multiwall carbon nanotubes (CNTs) e carbon fibers (CFs)hybrid materials were produced by directly growing CNTs on CFs by means of chemical vapor deposition. For the latter, the oxidative dehydrogenation reaction of C2H2 and CO2 was applied, which allows growing CNTs without damaging the CF surface. Uni-directional nano-engineered carbon fiber reinforced composites (nFRCs) were fabricated by impregnating these hybrid materials with epoxy. The nFRCs subjected to single fiber push-out tests revealed a decrease of the interfacial shear strength (IFSS) of about 36% compared to the carbon fiber composites without CNTs. By means of transverse three-point bending tests performed on pre-notched composite beams inside a scanning electron microscope, the fracturing behavior parallel to the fibers was studied in-situ. The nFRCs showed significantly reduced fiber/matrix debonding while CNTs pull-out, CNTs bridging as well as matrix failure occurred. These results demonstrate that the presence of CNTs in nFRCs affects the stress distribution and consequently the damage Initiation as well as the damage propagation. The presence of CNTs suppresses the stress concentration at the fiber/Matrix interface and reduces the debonding of CFs from the matrix. However, our results indicate that the stress concentration shifts towards the CNTs' ends/matrix interface and causes promoted matrix failure leading to lower IFSS. KW - Carbon fibres nanotubes interface PY - 2017 DO - https://doi.org/10.1016/j.compositesb.2017.06.004 SN - 1359-8368 SN - 1879-1069 VL - 126 SP - 202 EP - 210 PB - Elsevier CY - Niederlande AN - OPUS4-42202 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wilrich, Cordula A1 - Brandes, Elisabeth A1 - Michael-Schulz, Heike A1 - Schröder, Volkmar A1 - Schwarz, Silke A1 - Wehrstedt, Klaus-Dieter T1 - UN GHS ‒ Physical hazard classifications of chemicals: A critical review of combinations of hazard classes N2 - One of the fundamental principles of the UN-GHS (Globally Harmonized System of Classification and Labelling of Chemicals) is that all hazards of a chemical should be assigned and communicated. There is no general prioritization of hazards in the sense that certain hazard classes are not applicable if another one has been assigned. In contrast to health and environmental hazards, there are physical or chemical factors which preclude certain combinations of physical hazard classes. So far, there is no common understanding as to which combinations are relevant and which not. For example, should a pyrophoric liquid be classified as flammable liquid in addition, or is this redundant and unnecessary? In the course of the implementation of the GHS by countries or sectors and the actual application by industry all over the world, such questions become more and more important. This publication systematically discusses all combinations of the UN-GHS physical hazard classes and assesses them with regard to the relevance of possible simultaneous assignment to a chemical. For many of the combinations an unambiguous decision based on theGHS alone is not possible, thus confirming that the question which physical hazard classes might be assigned simultaneously to a chemical is not trivial. As one more milestone on the path to a globally harmonized system for the classification of hazardous chemicals, this should be discussed and ultimately solved on a global basis. It is the hope that this publication might serve as an impetus for such discussions. KW - UN-GHS KW - Globally Harmonized System of Classification and Labelling of Chemicals KW - Hazardous chemicals KW - Chemicals classification KW - Physical hazards PY - 2017 UR - https://www.sciencedirect.com/science/article/pii/S1871553217300336 DO - https://doi.org/10.1016/j.jchas.2017.03.005 SN - 1871-5532 VL - 24 IS - 6 SP - 15 EP - 28 PB - Elsevier Inc. AN - OPUS4-42704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wessig, P. A1 - Schulze, T. A1 - Pfennig, A. A1 - Weidner, Steffen A1 - Prentzel, S. A1 - Schlaad, H. T1 - Thiol–ene polymerization of oligospiroketal rods N2 - The nucleophilic thiol–ene (thia-Michael) reaction between molecular rods bearing terminal thiols and bis-maleimides was investigated. The molecular rods have oligospiroketal (OSK) and oligospirothioketal (OSTK) backbones. Contrary to the expectations, cyclic oligomers were always obtained instead of linear rigid-rod polymers. Replacing the OS(T)K rods with a flexible chain yielded polymeric products, suggesting that the OS(T)K structure is responsible for the formation of cyclic products. The reason for the preferred formation of cyclic products is due to the presence of folded conformations, which have already been described for articulated rods. KW - Oligospiroketals KW - Polymerization KW - MALDI-TOF MS PY - 2017 DO - https://doi.org/10.1039/C7PY01569K SN - 1759-9954 SN - 1759-9962 VL - 8 IS - 44 SP - 6879 EP - 6885 PB - Royal Society of Chemistry AN - OPUS4-42685 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Negendank, Detlef A1 - Lohse, Volkmar A1 - Kormunda, M. A1 - Esser, N. T1 - Dependence of the optical constants and the performance in the SPREE gas measurement on the thickness of doped tin oxide over coatings N2 - In this study, thickness related changes of the optical properties of doped tin oxide were studied. Two different sets of samples were prepared. The first set was doped with iron or nickel on silicon substrate with thicknesses of 29–56 nm, the second was iron doped on gold/glass substrate with 1.6–6.3 nm. The optical constants were determined by using spectral ellipsometry (SE) followed by modelling of the dielectric function with an oscillator model using Gaussian peaks. The analysis of the optical constants shows a dependence of the refraction and the absorption on the thickness of the doped tin oxide coating. In addition to the tin oxide absorption in the UV, one additional absorption peak was found in the near-IR/red which is related to plasmonic effects due to the doping. This peak shifts from the near-IR to the red part of the visible spectrum and becomes stronger by reducing the thickness, probably due to the formation of metal nanoparticles in this layer. These results were found for two different sets of samples by using the same optical model. Afterwards the second sample set was tested in the Surface Plasmon Resonance Enhanced Ellipsometric (SPREE) gas measurement with CO gas. It was found that the thickness has significant influence on the sensitivity and thus the adsorption of the CO gas. By increasing the thickness from 1.6 nm to 5.1 nm, the sensing ability is enhanced due to a higher coverage of the surface with the over coating. This is explained by the high affinity of CO molecules to the incorporated Fe-nanoparticles in the tin oxide coating. By increasing the thickness further to 6.3 nm, the sensing ability drops because the layer disturbs the SPR sensing effect too much. T2 - 7th International Conference on Spectroscopic Ellipsometry (ICSE-7) DA - 06.06.2016 KW - Surface plasmon resonance KW - Spectroscopic ellipsometry KW - Doped tin oxide KW - Gas sensing KW - Plasmonic absorption PY - 2017 DO - https://doi.org/10.1016/j.apsusc.2016.11.188 SN - 0169-4332 VL - 421, Teil B SP - 480 EP - 486 PB - Elsevier B.V. AN - OPUS4-42692 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kowarik, Stefan A1 - Weber, C. A1 - Pithan, L. A1 - Zykov, A. A1 - Bommel, S. A1 - Carla, F. A1 - Felici, R. A1 - Knie, C. A1 - Bléger, D. T1 - Multiple timescales in the photoswitching kinetics of crystalline thin films of azobenzene-trimers N2 - Functional materials that exhibit photoinduced structural phase transitions are highly interesting for applications in optomechanics and mechanochemistry. It is, however, still not fully understood how photochemical reactions, which are often accompanied by molecular motion, proceed in confined and crystalline environments. Here we show that thin films of azobenzene trimers exhibit high structural order and determine the crystallographic unit cell. We demonstrate that thin film can be switched partially reversibly between a crystalline and an amorphous phase. The time constant of the photoinduced amorphisation as measured with real-time x-ray diffraction ($\approx $ 220 s) lies between the two time constants (120 s and 2870 s) of the ensemble photoisomerisation processes that are measured via optical spectroscopy. Our observation of a photoinduced shrinking of the crystalline domains indicates a cascading process, in which photoisomerisation starts at the surface of the thin film and propagates deeper into the crystalline layer by introducing disorder and generating free volume. This finding is important for the rapidly evolving research field of photoresponsive thin films and smart crystalline materials in general. KW - Azobenzene PY - 2017 DO - https://doi.org/10.1088/1361-648X/aa8654 SN - 0953-8984 SN - 1361-648X VL - 29 IS - 43 SP - Article 434001, 1 EP - 8 AN - OPUS4-42501 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rosu, Dana-Maria A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan A1 - Kraehnert, R. A1 - Hertwig, Andreas ED - Hertwig, Andreas ED - Hinrichs, K. ED - Beck, Uwe ED - Esser, N. T1 - Ellipsometric porosimetry on pore-controlled TiO2 layers N2 - The practical performance of surface coatings in applications like catalysis, water splitting or batteries depends critically on the coating materials’ porosity. Determining the porosity in a fast and nondestructive way is still an unsolved problem for industrial thin-films technology. As a contribution to calibrated, non-destructive, optical layer characterisation, we present a multi-method comparison study on porous TiO2 films deposited by sol-gel synthesis on Si wafers. The ellipsometric data were collected on a range of samples with different TiO2 layer thickness and different porosity values. These samples were produced by templated sol-gel synthesis resulting in layers with a well-defined pore size and pore density. The ellipsometry measurement data were analysed by means of a Bruggeman effective medium approximation (BEMA), with the aim to determine the mixture ratio of void and matrix material by a multi-sample analysis strategy. This analysis yielded porosities and layer thicknesses for all samples as well as the dielectric function for the matrix material. Following the idea of multi-method techniques in metrology, the data was referenced to imaging by electron microscopy (SEM) and to a new EPMA (electron probe microanalysis) porosity approach for thin film analysis. This work might lead to a better metrological understanding of optical porosimetry and also to better-qualified characterisation methods for nano-porous layer systems. 1. IntroductionPorous materials, especially porous thin films play an importantrole in chemical and physical technology in every case where thecontact area between two media has to be maximised. From cataly-sis to photochemistry and photovoltaics, the applications of porouslayer materials are diverse and numerous [1–6].The accurate and non-destructive characterisation of porousfilms for layered systems poses a challenge. This applies especiallyfor the key parameter of porous films, their porosity, i.e. the mix-ing ratio between the Matrix of the film (host material) and thepore volume which is empty or filled with a fluid medium (inclu-sions). This parameter influences most of the physical and chemicalproperties of a porous thin film and is therefore essential for theunderstanding as well as the optimisation of this class of materials. T2 - International Conference on Spectroscopic Ellipsometry (ICSE-7) CY - Berlin, Germany DA - 06.06.2016 KW - Spectroscopic ellipsometry KW - Porous materials KW - Porosimetry KW - Multi-sample analysis KW - Thin film metrology PY - 2017 DO - https://doi.org/10.1016/j.apsusc.2016.11.055 SN - 0169-4332 SN - 1873-5584 VL - 421 IS - Part B SP - 487 EP - 493 PB - Elsevier B.V. AN - OPUS4-42517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schilling, Markus A1 - Niebergall, Ute A1 - Böhning, Martin T1 - Full notch creep test (FNCT) of PE-HD – Characterization and differentiation of brittle and ductile fracture behavior during environmental stress cracking (ESC) N2 - The damage mechanisms slow crack growth (SCG) and environmental stress cracking (ESC), relevant for PE-HD materials are characterized based on improved full notch creep testing (FNCT) of two selected typical PE-HD materials for container applications. In this context, a distinction of the failure mechanisms as well as a categorization of involved media is suggested. Employing a novel FNCT device, elongation data were obtained in addition to conventional time-to-failure results of stress-dependent as well as temperature-dependent measurements. Changes in failure behavior, as determined by fracture surface analysis based on light microscopy (LM) and laser scanning microscopy (LSM), are correlated with FNCT results and used to introduce an additional possibility for the identification of brittle/ductile fracture behavior. KW - Environmental stress cracking (ESC) KW - Slow crack growth (SCG) KW - Full notch creep test (FNCT) KW - High-density polyethylene (PE-HD) PY - 2017 DO - https://doi.org/10.1016/j.polymertesting.2017.09.043 SN - 0142-9418 SN - 1873-2348 VL - 64 SP - 156 EP - 166 PB - Elsevier CY - Amsterdam AN - OPUS4-42484 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cabeza, Sandra A1 - Garces, G. A1 - Adeva, Paloma A1 - Kabra, S. A1 - Gan, W. T1 - Effect of Extrusion Temperature on the Plastic Deformation of an Mg-Y-Zn Alloy Containing LPSO Phase Using In Situ Neutron Diffraction N2 - The evolution of the internal strains during in situ tension and compression tests has been measured in an MgY2Zn1 alloy containing long-period stacking ordered (LPSO) phase using neutron diffraction. The alloy was extruded at two different temperatures to study the influence of the microstructure and texture of the magnesium and the LPSO phases on the deformation mechanisms. The alloy extruded at 623 K (350 °C) exhibits a strong fiber texture with the basal plane parallel to the extrusion direction due to the presence of areas of coarse non-recrystallised grains. However, at 723 K (450 °C), the magnesium phase is fully recrystallised with grains randomly oriented. On the other hand, at the two extrusion temperatures, the LPSO phase orients their basal plane parallel to the extrusion direction. Yield stress is always slightly higher in compression than in tension. Independently on the stress sign and the extrusion temperature, the beginning of plasticity is controlled by the activation of the basal slip system in the dynamic recrystallized grains. Therefore, the elongated fiber-shaped LPSO phase which behaves as the reinforcement in a metal matrix composite is responsible for this tension–compression asymmetry. KW - Mg-Y-Zn Alloy KW - LPSO Phase KW - Neutron Diffraction PY - 2017 DO - https://doi.org/10.1007/s11661-017-4284-6 VL - 48A IS - 11 SP - 5332 EP - 5343 PB - Spinger AN - OPUS4-42935 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wollschläger, Nicole A1 - Palasse, L. A1 - Häusler, Ines A1 - Dirscherl, K. A1 - Oswald, F. A1 - Narbey, S. A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan T1 - Characterization of the inner structure of porous TiO2 nanoparticle films in dye sensitive solar cells (DSSC) by focused ion beam (FIB) tomography and transmission Kikuchi diffraction (TKD) in the scanning electron microscope (SEM) N2 - A combined methodical approach is tested for the first time with respect to the characterization of the inner structure of porous TiO2 layers infiltrated with ruthenium molecular sensitizer as typically used in modern dye sensitized solar cells (DSSC). Their performance is directly linked to the surface area ‘offered’ by the pore Network to the dye. The micrometer thick layer employed was manufactured by screen-printing of a starting TiO2 powder constituted of shape-controlled, bipyramidal anatase nanoparticles (NPs) on FTO/glass substrates. The analytical methods exploited in our study are Focused Ion Beam (FIB) slicing followed by 3D reconstruction as well as the new approach transmission Kikuchi diffraction (TKD) technology in the scanning electron microscope (SEM). While the first method results in the visualization of the 3D pore network within the TiO2 layer, the second one can be successfully applied to analyze the crystal orientation of grains (i.e. NPs in our case) in nanometer resolution. Moreover, size and shape distribution of the TiO2 NPs within the layer can be extracted. SEM in transmission mode and atomic force microscopy (AFM) have been used to verify the dimensional data obtained by the new combined methodical approach. Its analytical benefits but also the challenges and limitations are highlighted. KW - Transmission Kikuchi diffraction KW - Focused ion beam tomography KW - Titanium dioxide KW - Nanoparticles KW - Porosity KW - Particle size KW - DSSC PY - 2017 DO - https://doi.org/10.1016/j.matchar.2017.06.030 SN - 1044-5803 SN - 1873-4189 VL - 131 SP - 39 EP - 48 PB - Elsevier AN - OPUS4-40875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - Chapala, P. A1 - Bermeshev, M. A1 - Schönhals, Andreas A1 - Böhning, Martin T1 - Molecular Mobility and Physical Aging of a Highly Permeable Glassy Polynorbornene as Revealed by Dielectric Spectroscopy N2 - Polymeric membranes represent a cost- and energy efficient solution for gas separation. Recently superglassy polymers with high free volume outperform many conventional dense polymers in terms of gas permeability and selectivity. However, such polymers are prone to pronounced physical aging, resulting in a dramatic reduction in the gas permeability. Molecular mobility of polymer segments plays an important role in the physical aging and the gas transport performance of polymeric membranes. Molecular mobility and physical aging of a representative superglassy polynorbornene with very high gas permeability, PTCNSi2g, was monitored by using dielectric spectroscopy with state-of-the-art high-resolution analyzers. This work helps to shed some light on the structure−property relationship of superglassy polymers on a molecular level and to provide practical “design rules” for the development of high performance polymers for gas separation. KW - Molecular mobility KW - Gas separation membrane KW - Broadband dielectric spectroscopy KW - Polymer KW - Physical ageing PY - 2017 DO - https://doi.org/10.1021/acsmacrolett.7b00456 SN - 2161-1653 VL - 6 IS - 8 SP - 813 EP - 818 PB - ACS CY - Washington DC, USA AN - OPUS4-41354 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ward, H. A1 - Burger, M. A1 - Chang, Y.-J. A1 - Fürstmann, P. A1 - Neugebauer, S. A1 - Radebach, A. A1 - Sproesser, G. A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Uhlmann, E. A1 - Steckel, J. Ch. T1 - Assessing carbon dioxide emission reduction potentials of improved manufacturing processes using multiregional input output frameworks N2 - Evaluating innovative process technologies has become highly important within the last decades. As standard tools different Life Cycle Assessment methods have been established, which are continuously improved. While those are designed for evaluating single processes they run into difficulties when it comes to assessing environmental impacts of process innovations at macroeconomic level. In this paper we develop a multi-step evaluation framework building on multi regional inputeoutput data that allows estimating macroeconomic impacts of new process technologies, considering the network characteristics of the global economy. Our procedure is as follows: i) we measure differences in material usage of process alternatives, ii) we identify where the standard processes are located within economic networks and virtually replace those by innovative process technologies, iii) we account for changes within economic systems and evaluate impacts on emissions. Within this paper we exemplarily apply the methodology to two recently developed innovative technologies: longitudinal large diameter steel pipe welding and turning of high-temperature resistant materials. While we find the macroeconomic impacts of very specific process innovations to be small, its conclusions can significantly differ from traditional process based approaches. Furthermore, information gained from the methodology provides relevant additional insights for decision makers extending the picture gained from traditional process life cycle assessment. KW - Economic wide technology replacement KW - Sustainability assessment KW - Multi-regional inputeoutput data KW - Life-cycle assessment KW - Greenhouse gas mitigation KW - Process innovations PY - 2017 DO - https://doi.org/10.1016/j.jclepro.2016.02.062 SN - 0959-6526 SN - 1879-1786 VL - 163 SP - 154 EP - 165 PB - Elsevier Ltd. AN - OPUS4-41356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Woydt, Mathias T1 - VGP 2013 - Propelling marine lubricants N2 - This letter to the Editor directs attention to EN 16807-2016:12, Liquid Petroleum products - Bio lubricants - Criteria and requirements of bio lubricants and bio-based lubricants. KW - Bio lubricants KW - Liquid petroleum products KW - EN 16807-2016:12 PY - 2017 SN - 1545-858X VL - 73 IS - 7 SP - 7 PB - Society of Tribologists and Lubrication Engineers CY - Park Ridge, IL AN - OPUS4-41342 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hernández-Nava, E. A1 - Tammas-Williams, S. A1 - Smith, C. A1 - Léonard, Fabien A1 - Withers, P. J. A1 - Todd, I. A1 - Goodall, R. T1 - X-ray tomography characterisation of lattice structures processed by selective electron beam melting N2 - Metallic lattice structures intentionally contain open porosity; however, they can also contain unwanted closed porosity within the structural members. The entrained porosity and defects within three different geometries of Ti-6Al-4V lattices, fabricated by Selective Electron Beam Melting (SEBM), is assessed from X-ray computed tomography (CT) scans. The results suggest that horizontal struts that are built upon loose powder show particularly high (~20 x 10⁻³ vol %) levels of pores, as do nodes at which many (in our case 24) struts meet. On the other hand, for struts more closely aligned (0° to 54°) to the build direction, the fraction of porosity appears to be much lower (~0.17 x 10⁻³%) arising mainly from pores contained within the original atomised powder particles. KW - Cellular solids KW - Aqdditive manufacturing KW - Computed tomography KW - Titanium alloys PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-413689 UR - http://www.mdpi.com/2075-4701/7/8/300 DO - https://doi.org/10.3390/met7080300 SN - 2075-4701 VL - 7 IS - 8 SP - Article 300, 1 EP - 12 PB - MDPI AN - OPUS4-41368 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Al-Terkawi, Abdal-Azim A1 - Scholz, G. A1 - de Oliveira Guilherme Buzanich, Ana A1 - Reinsch, Stefan A1 - Kemnitz, E. A1 - Emmerling, Franziska T1 - Ca- and Sr- tetrafluoroisophthalates: mechanochemical synthesis, characterization, and ab initio structure determination N2 - New fluorinated coordination polymers were prepared mechanochemically by milling the alkaline earth metal hydroxides MII(OH)2·xH2O (MII: Ca, Sr) with tetrafluoroisophthalic acid (H2mBDC-F4). The structures of [{Ca(mBDC-F4)(H2O)2}·H2O] and [{Sr(mBDC-F4)(H2O)2}·H2O] were determined based on ab initio calculations and their powder X-ray diffraction (PXRD) data. The compounds are isomorphous and crystallize in the orthorhombic space group P212121. The determined structures were validated by using extended X-ray absorption (EXAFS) data. The new materials were thoroughly characterized using elemental analysis, thermal analysis, magic angle spinning NMR, and attenuated total reflection-infrared spectroscopy. Further characterization methods such as BET, dynamic vapor sorption, and scanning electron microscopy imaging were also used. Our investigations indicate that mechanochemistry is an efficient method for preparing such materials. KW - Mechanochemistry KW - In situ KW - XRD KW - Coordination polymers PY - 2017 UR - http://pubs.rsc.org/-/content/articlehtml/2017/dt/c7dt00734e DO - https://doi.org/10.1039/c7dt00734e VL - 46 IS - 18 SP - 6003 EP - 6012 AN - OPUS4-41516 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Matoga, D. A1 - Roztocki, K. A1 - Wilke, Manuel A1 - Emmerling, Franziska A1 - Oszajca, M. A1 - Fitta, M. A1 - Bałanda, M. T1 - Crystalline bilayers unzipped and rezipped: solid-state reaction cycle of a metal–organic framework with triple rearrangement of intralayer bonds N2 - We present a series of remarkable structural transformations for a family of layered metal–organic frameworks (MOFs) in a three-step solid-state reaction cycle. The cycle represents new dynamic behavior of 2D coordination polymers and involves the sequence of reactions: {[Mn2(ina)4(H2O)2]·2EtOH}n (JUK-1) → {(NH4)2[Mn(ina)2(NCS)2]}n·xH2O (JUK-2) → {[Mn2(ina)2(Hina)2(NCS)2]}n (JUK-3) → JUK-1 (Hina = isonicotinic acid), each accompanied by rearrangement of intralayer coordination bonds and each induced by a different external stimulus. In situ investigation of the first step of the cycle by combined synchrotron X-ray diffraction and Raman spectroscopy reveals direct mechanochemical unzipping of JUK-1 bilayers to respective JUK-2 layers with reaction rates dependent on the milling conditions. In contrast, the reverse zipping of JUK-2 layers involves two steps and proceeds through a new MOF (JUK-3) whose structure was elucidated by powder X-ray diffraction. Magnetic measurements confirm conversions of manganese nodes in the reaction cycle. The findings indicate the possibility of developing coordination-based assemblies with large structural responses for use in smart stimuli-responsive systems and sensor technologies. KW - Mechanochemistry KW - In situ KW - XRD KW - MOF PY - 2017 UR - http://pubs.rsc.org/is/content/articlehtml/2017/ce/c7ce00655a DO - https://doi.org/10.1039/C7CE00655A VL - 19 SP - 2987 EP - 2995 AN - OPUS4-41517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pavlovic, Mato A1 - Zoëga, Andreas A1 - Kurz, J. H. A1 - Zanotelli, Christina T1 - Investigations to introduce the probability of detection method for ultrasonic inspection of hollow axles at Deutsche Bahn N2 - The vast experience with the automated, ultrasonic system for the inspection of hollow railway axles used by Deutsche Bahn shows that much smaller flaws are detectable than required. This results in a number of false calls. False calls lead to unnecessary demounting and disassembling of wheelsets, which generates unnecessary additional costs. In order to adjust the sensitivity of the inspection system to reduce the number of false calls without compromising safety, the capability of the system to detect cracks needs to be comprehensively established. This capability can be quantified by using probability of detection (POD) curves for the system. The multi-parameter POD model makes it possible to include several factors that influence the crack detection in the analysis. The analysis presented in this paper shows that crack position, orientation, depth extension, and shape as well as the geometry of the axle all have influence on the ultrasonic response amplitude. For future work, calculation of the POD using multi-parameter POD model with these parameters is planned. T2 - ESIS TC24 Workshop "Integrity of Railway Structures" CY - Leoben, Austria DA - 24.10.2016 KW - Crack KW - Reliability KW - POD KW - Axle KW - Ultrasonic PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-415201 DO - https://doi.org/10.1016/j.prostr.2017.07.002 SN - 2452-3216 VL - 4 SP - 79 EP - 86 PB - Elsevier, B.V. AN - OPUS4-41520 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Moldenhauer, Laura A1 - Helmerich, Rosemarie A1 - Köppe, Enrico A1 - Haamkens, Frank A1 - Wittmann, Jochen ED - Emri, Igor T1 - Experimental feasibility study about moisture in building materials measured with Bluetooth N2 - Structural health monitoring contributes to early damage detection in the built infrastructure. During the last two decades, sensor networks transferred from wired to wireless sensor networks. Several methods exist to measure moisture in building materials. Most of the introduced commercial moisture measurement methods provide information about the local or near surface moisture. A feasibility study is presented to demonstrate, how the Received Signal Strength Indicator (RSSI) of a Bluetooth Low Energy (BLE) signal, transmitted from the BLE-module embedded in building materials, correlate with changing moisture content. The feasibility of this influence was investigated in the presented study. The maximum and minimum RSSI were systematically recorded and analysed. T2 - 33nd Danubia Adria Symposium on Advances in Experimental Mechanics CY - Portoroz, Slovenia DA - 20.09.2016 KW - BLE KW - Long-Term Monitoring KW - Network KW - Structural Health Monitoring KW - Moisture Measurement KW - RSSI KW - Bluetooth Low Energy KW - Sensor PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S2214785317308398 DO - https://doi.org/10.1016/j.matpr.2017.06.053 SN - 2214-7853 VL - 4 IS - 5, Part 1 SP - 5889 EP - 5892 PB - Elsevier Ltd. AN - OPUS4-41585 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weltschev, Margit A1 - Heming, Frank A1 - Haufe, Manuela A1 - Heyer, Martina T1 - The influence of the age of biodiesel and heating oil with 10 % biodiesel on the resistance of sealing materials at different temperatures T1 - Der Einfluss des Alters von Biodiesel und Heizöl mit 10 % Biodiesel auf die Beständigkeit der Dichtungswerkstoffe bei verschiedenen Temperaturen N2 - The objective of this research was to determine the resistance of frequently used sealing materials such as fluorocarbon rubber (FKM), fluorosilicone rubber (FVMQ), silicone rubber (VMQ), ethylene-propylene-diene rubber (EPDM), chloroprene rub-ber (CR), chlorosulfonated polyethylene (CSM), butyl rubber (IIR), acrylonitrile buta-diene rubber (NBR), polyester urethane rubber (PUR) and polyamide (PA) in non-aged/aged biodiesel and heating oil with 10 % biodiesel at 20 °C, 40 °C and 70 °C. Mass, tensile properties and Shore hardness A/D (for polyamide) of the test speci-mens were determined before and after the exposure for 84/42 days in the aged and non-aged fuels of different age. Biodiesel fuels are easily oxidized and contain acids and water. The sealing materi-als: acrylonitrile butadiene rubber, butyl rubber, chloroprene rubber, chlorosulfonated polyethylene and ethylene-propylene-diene rubber and were generally not resistant to biodiesel and heating oil with 10 % biodiesel. Fluorocarbon rubber, fluorosilicone rubber and polyamide were the most resistant materials in all tested fuels up to 70 °C. The degree of damage to the sealing materials increased with higher test temperatures and the age of the fuels. KW - Sealing materials KW - Biofuels KW - Tensile properties KW - Shore hardness PY - 2017 DO - https://doi.org/10.1002/mawe.201700058 SN - 0933-5137 SN - 1521-4052 VL - 48 IS - 9 SP - 837 EP - 845 PB - Wiley-VCH Verlag GmbH & Co.KGaA CY - Weinheim AN - OPUS4-42077 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krütt, Enno T1 - Ermüdungsbedingte Degradation von Fahrbahnbeton - Einfluss auf den Stofftransport T1 - Fatigue-induced degradation of deck concrete influence on the material transport N2 - In den letzten 15 Jahren hat im deutschen Autobahnnetz die Anzahl von Schäden an Betonfahrbahnen, die vor 2005 er-richtet wurden zugenommen. Dies führt oft zu einer Vermin-derung der Lebensdauer von 30 auf 10 bis 15 Jahre. Trotz umfassender Untersuchungen wurde die Ursache bis jetzt nicht eindeutig geklärt, jedoch scheint die Alkali-Kieselsäure-Reaktion (AKR) hierbei eine Rolle zu spielen. Vor diesem Hintergrund wurden AKR-Performance-Tests entwickelt, die jedoch die mechanischen Einwirkungen aus Klima und Ver-kehr nicht berücksichtigen. Aus diesem Grund wurde eine AKR-Forschergruppe von der Deutschen Forschungsgemein-schaft ins Leben gerufen, welche sich experimentell und auf Simulationsebene mit diesem Thema befasst. Inhalt dieses Beitrages sind ausgewählte Ergebnisse des an der BAM bear-beiteten experimentellen Projektteils, welche in eine auf die Auswirkung einer mechanischen Degradation fokussierte Promotionsarbeit einfließen. Ziel der ausgewählten Untersuchung ist es, den Einfluss einer mechanisch induzierten Betondegradation auf den Stofftrans-port herauszuarbeiten. Hierzu wird ein großformatiger Balken einem zyklischen Vier-Punkt Biegezugversuch mit einer Anzahl von 5 Mio. Lastwechseln unterzogen. Während des Versuches findet ein Schadensmonitoring mit verschiedenen zerstörungsfreien Prüftechniken statt. Hierzu zählen Deh-nungsmessungen, Schallemissionsanalyse und Ultraschall-messungen. Nach dem zyklischen Belastungs-versuch werden kleinformatige Probekörper aus dem belasteten Balken entnommen. Als Referenz dienen unbelas-tete Probekörper aus der gleichen Herstellungscharge. Die Oberflächen der entnommenen Probekörper werden in einem kapillaren Saugversuch zum einen mit deionisiertem Wasser und zum anderen mit einer 3,6 %igen NaCl-Lösung beauf-schlagt. Während der Saugversuche dienen verschiedene zerstörungsfreie bzw. -arme Messmethoden dazu, die Feuch-teaufnahme bzw. -verteilung in den Probekörpern zu messen. Hierzu gehören neben der Gravimetrie die Messung mit NMR (Nuclear-Magnetic-Resonance) sowie TDR (Time-Domain-Reflectometry). Nach den Saugversuchen wird die Na- und Cl-Verteilung an den mit NaCl-Lösung beaufschlagten Pro-bekörpern zerstörend mittels LIBS (Laser-Induced-Breakdown-Spectroscopy) ermittelt. Erste Ergebnisse zeigen, dass die zyklische Ermüdungsdegradation den Stofftransport tendenziell verstärkt. KW - Degradation KW - Stofftransport KW - Fahrbahnbeton PY - 2017 SN - 0005-9900 SN - 1437-1006 VL - 112 IS - 7 SP - 458 EP - 458 AN - OPUS4-41097 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bochnig, M. S. A1 - Oh, M.-J. A1 - Nagel, T. A1 - Jost-Brinkmann, P.-G. A1 - Ziegler, Fred T1 - Comparison of the shock absorption capacities of different mouthguards N2 - In this in vitro study, the protective qualities of different mouthguard types were examined during small hard object collisions. The aim was to investigate inconclusive aspects of hard inserts, nylon nets, and air spaces as reinforcements in the anterior region and the protection qualities of ethylene vinyl acetate (EVA). Five different mouthguards with a labial thickness between 2 mm and 11 mm made of materials of varying stiffness were investigated. As a negative control, the same experiments were performed without a mouthguard. Different combinations of EVA and labial inserts ((polyethylene terephthalate glycol-modified [PETG]), nylon mesh, air space) were tested. Using a stainless steel pendulum device, blows of different energy (0.07-2.85 joules) were applied to the center of the crown of a pivoted tooth in a custom-built jaw model. A laser Doppler vibrometer measured the tooth deflection, while an acceleration sensor attached to the pendulum measured the braking accelerations. Tooth deflection was reduced up to 99.7% compared to no mouthguard, and the braking acceleration was reduced up to 72.2% by increasing the mouthguards' labial thickness in combination with labial inserts of different stiffness and a built-in air space between the front teeth and the mouthguard. The mouthguards made of soft materials (EVA with nylon mesh) showed slightly better protection qualities than the more rigid mouthguards of similar thickness (PETG; P<.05). However, with increasing impact energy, their protective capacities decreased to a greater extent than the stiffer mouthguards. The combination of increased labial thickness and labial inserts of varying stiffness and eventually an air space offers the best protection capacities for hard, small object collisions. KW - Shock absorbtion KW - Hard object collisions KW - Mouthguard PY - 2017 DO - https://doi.org/10.1111/edt.12324 SN - 1600-4469 VL - 33 IS - 3 SP - 205 EP - 213 PB - John Wiley & Sons, Ltd CY - Hoboken, NJ, USA AN - OPUS4-41098 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -