TY - JOUR A1 - Hentrich, D. A1 - Taabache, Soraya A1 - Brezesinski, G. A1 - Lange, Nele A1 - Unger, Wolfgang A1 - Kübel, C. A1 - Bertin, Annabelle A1 - Taubert, A. T1 - A dendritic amphiphile for efficient control of biomimetic calcium phosphate mineralization N2 - The phase behavior of a dendritic amphiphile containing a Newkome-type dendron as the hydrophilic moiety and a cholesterol unit as the hydrophobic segment is investigated at the air–liquid interface. The amphiphile forms stable monomolecular films at the air–liquid interface on different subphases. Furthermore, the mineralization of calcium Phosphate beneath the monolayer at different calcium and phosphate concentrations versus mineralization time shows that at low calcium and Phosphate concentrations needles form, whereas flakes and spheres dominate at higher concentrations. Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron diffraction confirm the formation of calcium phosphate. High-resolution transmission electron microscopy and electron diffraction confirm the predominant formation of octacalcium phosphate and hydroxyapatite. The data also indicate that the final products form via a complex multistep reaction, including an association step, where nano-needles aggregate into larger flake-like objects. KW - Dendritic amphiphile KW - Calcium phosphate KW - Biomineralization PY - 2017 DO - https://doi.org/10.1002/mabi.201600524 SN - 1616-5187 SN - 1616-5195 VL - 17 IS - 8 SP - Article 1600524, 1 EP - 14 AN - OPUS4-41825 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Swaraj, S. A1 - Dietrich, Paul A1 - Unger, Wolfgang T1 - Simultaneous surface and bulk sensitive XAS measurements of magnetic particle clusters N2 - Magnetic iron oxide nanoparticle clusters (mnpc) coated with organic stabilizers were investigated using scanning transmission x-ray microscopy (STXM). Simultaneous surface and bulk sensitive Fe L₃ edge absorption spectra, obtained using a photomultiplier tube and a channeltron, were used to detect subtle changes in the oxidation state in the surface and bulk of Iron Oxide mnpc. The effectiveness of this mode of STXM operation is demonstrated for these nanoparticle clusters. T2 - X-Ray Microscopy Conference 2016 (XRM 2016) CY - Oxford, UK DA - 15.08. 2016 KW - Fe L3 edge absorption spectra KW - Scanning transmission x- ray microscopy KW - Magnetic iron oxide nanoparticle clusters KW - XAS PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-410576 UR - http://iopscience.iop.org/article/10.1088/1742-6596/849/1/012014/pdf DO - https://doi.org/10.1088/1742-6596/849/1/012014 SN - 1742-6588 VL - 849 SP - 012014, 1 EP - 012014, 5 PB - IOP Publishing AN - OPUS4-41057 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silverstein, R. A1 - Sobol, Oded A1 - Böllinghaus, Thomas A1 - Unger, Wolfgang A1 - Eliezer, D. T1 - Hydrogen behavior in SAF 2205 duplex stainless steel N2 - This paper describes austenitic-ferritic duplex stainless steels, SAF 2205, in the presence of hydrogen. The duplex stainless steels (DSS) properties include excellent resistance to stress corrosion cracking, high strength and good weldability. Those steels are preferably used in industries combining hydrogen and loads. Hydrogen location in addition to hydrogen binding energy with the steel's defects are of great importance for the analysis of hydrogen embrittlement model in that steel. It is known from previously published works that the susceptibility to hydrogen embrittlement will depend on the competition between reversible and irreversible traps; meaning a direct relation to the hydrogen's state and position in the steel. In this work, we examine the local hydrogen concentration, trapping and distribution by two modern and advanced techniques: thermal desorption spectrometry (TDS) and we support it by time of flight-secondary ion mass spectrometer (ToF-SIMS). In this paper, we support and give for the first time new insights and better understanding to the hydrogen embrittlement mechanism in SAF 2205. The trapping energies levels were calculated using TDS and Lee and Lee's model. This model revealed reversible in addition to irreversible trapping sites. Also the trapping controlling mechanism was found to be a combination of detrapping controlled mechanism and diffusion controlled mechanism. The use of ToF-SIMS for local imaging the distribution of hydrogen species supports the discussion of the different hydrogen traps in this type of steel. The hydrogen embrittlemet phenomenon in SAF 2205 will be discussed in details in that paper. KW - Hydrogen trapping KW - Duplex stainless steel KW - Thermal desorption spectrometry (TDS) KW - ToF-SIMS PY - 2017 DO - https://doi.org/10.1016/j.jallcom.2016.11.184 SN - 0925-8388 SN - 1873-4669 VL - 695 SP - 2689 EP - 2695 PB - Elsevier B.V. AN - OPUS4-38856 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sobol, Oded A1 - Böllinghaus, Thomas A1 - Wirth, Thomas A1 - Unger, Wolfgang A1 - Eliezer, D. T1 - High resolution ToF-SIMS imaging of deuterium permeation and cracking in duplex stainless steels N2 - Fundamental understanding and elucidation of hydrogen assisted degradation and trapping mechanisms is dependent on sufficient imaging techniques for respective hydrogen interactions, in particular with multi-phase metallic microstructures. The present work shows the progress in elucidating the deuterium behavior in austenitic-ferritic duplex stainless steels under the consideration that deuterium behaves in many ways similarly to hydrogen. A novel combination of deuterium permeation and in-situ Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) imaging technique is compared with post charging ToF-SIMS imaging experiments. As a step beyond state-of-the-art, integration of chemo-metric and high resolution structural characterization techniques with computational multivariate data analysis (MVA) and data fusion is presented. T2 - 2016 International Hydrogen Conference CY - Grand Teton National Park, Jackson Lake Lodge, Wyoming, USA DA - 11.09.2016 KW - DSS KW - ToF-SIMS KW - Data-fusion KW - EBSD PY - 2017 SN - 978-0-7918-6138-7 SP - 407 EP - 415 PB - ASME Press CY - Two Park Ave. New-York, NY 10016, USA AN - OPUS4-42647 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Tof-SIMS imaging of Deuterium in DSS steel microstructures and data fusion with SEM topography data: Towards a better understanding of hydrogen assisted cracking in steel N2 - The use of duplex stainless steels (DSS) in energy related applications is well known. Nowadays, DSS steels become more favorable than austenitic steels due to the outstanding mechanical properties, the good corrosion resistance and the lower nickel content. However, the use of the duplex grade in acidic environments such as seawater often leads to severe degradation of the structural integrity of the steel by hydrogen-induced/assisted cracking (HAC) phenomena, which can eventually result in premature failure. Hydrogen assisted degradation and cracking of steels are active fields of research even though this topic is intensively studied for more than a century. A bottleneck is the analytical validation of the theoretical models proposed ion the literature at the sub-micron scale. Industrial and the research communities see a need for an accurate analytical method by which it is possible to image the distribution of hydrogen in the microstructure of a steels or and other alloys. Among the very few available methods hydrogen imaging methods, Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) has the principal capability for mapping of hydrogen in a steel’s microstructure. The combination of ToF-SIMS with multivariate data analysis (MVA), electron microscopy (SEM) and electron-backscattered diffraction (EBSD) is a powerful approach for providing chemical and structural information. The use of data fusion techniques has been shown recently to enhance the better understanding of the hydrogen induced degradation processes in in a DSS steel. T2 - The Scientific International Symposium on SIMS and Related Techniques Based on Ion-Solid Interactions (SISS19) CY - Kyoto, Japan DA - 11.5.17 KW - Hydrogen KW - DSS steel KW - ToF SIMS KW - SEM KW - EDX KW - EBSD KW - Data fusion PY - 2017 AN - OPUS4-40276 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 - CONF A1 - Unger, Wolfgang T1 - Low pressure plasma, UV photo and wet chemical modification of graphite, graphene and carbon nano tubes N2 - Graphene is a two-dimensional carbon network with unique properties, including high mechanical stiffness, strength, and elasticity, outstanding electrical and thermal conductivity, and many others. Despite these advantages, its low solubility, poor reactivity and the limited accessibility of a well-defined basal plane are major challenges for applications. An ideal method to overcome these problems is the covalent attachment of functional molecules to its surface which enables further reactive modifications for specific applications. There is a number of different technologies for surface functionalization of graphene and related CNT materials. However, to get control on the functionalization process and to optimize the performance of the modified surfaces analytical tools for surface chemical characterization are required. X-ray absorption (NEXAFS) and photoelectron spectroscopy (XPS) have been identified to be rather powerful here. Specifically NEXAFS spectroscopy underpinned by quantum chemical spectrum simulations is unique in a way to address changes of aromaticity and defect formation at the graphene surface during functionalization. For relevant surface modification technologies, we present examples on how NEXAFS and XPS can perform well. All presented modifications aim on the production of platforms for defined functional 2D nanomaterials, as for example multifunctional hybrid architectures. In detail, we investigated: • Graphene and carbon nanotube functionalized by a Vacuum-Ultraviolet (VUV) induced photochemical process in NH3 or O2 atmospheres in order to introduce amino or hydroxy functionalities, respectively. • Br bonding on r.f. cw low pressure plasma brominated graphite surfaces by using Br2 and bromoform as plasma gases. • A wet chemical method for covalent functionalization of graphene sheets by a one-pot nitrene [2+1] cycloaddition reaction under mild conditions. Here a reaction between 2,4,6-trichloro-1,3,5-triazine and sodium azide with thermally reduced graphene oxide (TRGO) results in defined dichlorotriazine-functionalized graphene sheets. T2 - The 17th European Conference on Applications of Surface and Interface Analysis CY - Montpellier, France DA - 24.09.2017 KW - Graphene KW - XPS KW - NEXAFS PY - 2017 AN - OPUS4-42787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Harald A1 - Unger, Wolfgang A1 - Schulte, Petra T1 - Nanotechnologie Aktivitäten der BAM N2 - Die Präsentation gibt einen Überblick über die verschiedenen Aktivitäten der BAM im Bereich der Nanotechnologie mit den Schwerpunkten Nanopartikel und Nanosicherheit. Es wird sowohl die Transportsicherheit, als auch die Sicherheit von Batterien mit Nanopartikeln angesprochen. Verschiedene BAM-Projekte zum Thema Nano werden vorgestellt, beginnend mit relevanten REFOPlanprojekten über die Erstellung der OECD nanoTG110 bis hin zu EU-Projekten zur Standardisierung von Messungen an Nanomaterialien, hier insbesondere AEROMET, NanoDefine, NanoValid und EC4SafeNano. T2 - Nano-Behördenklausur der Bundesoberbehörden CY - Berlin, Germany DA - 02.11.2017 KW - Nano KW - Nanotechnologie KW - Nanopartikel KW - Nanosicherheit KW - Nanoanalytik PY - 2017 AN - OPUS4-42793 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Swaraj, S. A1 - Dietrich, Paul A1 - Unger, Wolfgang T1 - Simultaneous surface and bulk sensitive XAS measurements of magnetic particle clusters N2 - Magnetic iron oxide nanoparticle clusters (mnpc) coated with organic stabilizers were investigated using scanning transmission x-ray microscopy (STXM). Simultaneous surface and bulk sensitive Fe L3 edge absorption spectra, obtained using a photomultiplier tube and a channeltron, were used to detect subtle changes in the oxidation state in the surface and bulk of Iron Oxide mnpc. The effectiveness of this mode of STXM operation is demonstrated for These nanoparticle clusters. T2 - X-Ray Microscopy Conference 2016 (XRM 2016) CY - Oxford, UK DA - 15.08.2016 KW - Scanning transmission x-ray microscopy (STXM) KW - Magnetic nanoparticles KW - Fe L3 edge absorption spectra PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-435907 UR - http://iopscience.iop.org/article/10.1088/1742-6596/849/1/012014/meta DO - https://doi.org/10.1088/1742-6596/849/1/012014 VL - 849 SP - 012014, 1 EP - 012014, 4 PB - IOP Publishing AN - OPUS4-43590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kaur, I. A1 - Ellis, L.-J. A1 - Romer, I. A1 - Tantra, R. A1 - Carriere, M. A1 - Allard, S. A1 - Mayne-L'Hermite, M. A1 - Minelli, C. A1 - Unger, Wolfgang A1 - Potthoff, A. A1 - Rades, Steffi A1 - Valsami-Jones, E. T1 - Dispersion of nanomaterials in aqueous media: Towards protocol optimization N2 - The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and stability of the suspension. In this study, a systematic step-wise approach is carried out to identify optimal sonication conditions in order to achieve a stable dispersion. This approach has been adopted and shown to be suitable for several nanomaterials (cerium oxide, zinc oxide, and carbon nanotubes) dispersed in deionized (DI) water. However, with any change in either the nanomaterial type or dispersing medium, there needs to be optimization of the basic protocol by adjusting various factors such as sonication time, power, and sonicator type as well as temperature rise during the process. The approach records the dispersion process in detail. This is necessary to identify the time Points as well as other above-mentioned conditions during the sonication process in which there may be undesirable changes, such as damage to the particle surface thus affecting surface properties. Our goal is to offer a harmonized approach that can control the Quality of the final, produced dispersion. Such a guideline is instrumental in ensuring dispersion quality repeatability in the nanoscience community, particularly in the field of nanotoxicology. KW - Dispersion of nanomaterials KW - Aqueous media KW - Protocol development PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-435886 UR - https://www.jove.com/video/56074 DO - https://doi.org/10.3791/56074 SN - 1940-087X IS - 130 SP - e560741, 1 EP - e560741, 23 PB - MyJove Corp. CY - Cambridge, MA, USA AN - OPUS4-43588 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Abbas, F. A1 - Donskyi, Ievgen A1 - Gholami, M. A1 - Ziem, B. A1 - Lippitz, Andreas A1 - Unger, Wolfgang A1 - Böttcher, C. A1 - Rabe, J. A1 - Haag, R. A1 - Adeli, M. T1 - Controlled covalent functionalization of thermally reduced graphene oxide to generate defined bifunctional 2D nanomaterials N2 - A controlled, reproducible, gram-scale method is reported for the covalent functionalization of graphene Sheets by a one-pot nitrene [2+1] cycloaddition reaction under mild conditions. The reaction between commercially available 2,4,6-trichloro-1,3,5-triazine and sodium azide with thermally reduced graphene oxide (TRGO) results in defined dichlorotriazine-functionalized sheets. The different reactivities of the chlorine substituents on the functionalized graphene allow stepwise post-modification by manipulating the temperature. This new method provides unique access to defined bifunctional 2D nanomaterials, as exemplified by chiral surfaces and multifunctional hybrid architectures. KW - Graphene oxide KW - Bifunctional 2D nanomaterials KW - XPS KW - NEXAFS KW - AFM PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-394789 DO - https://doi.org/10.1002/ange.201612422 SN - 1433-7851 VL - 56 IS - 10 SP - 2675 EP - 2679 PB - Wiley-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-39478 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -