TY - JOUR A1 - Winkelmann, A. A1 - Nolze, Gert A1 - Cios, G. A1 - Tokarski, T. A1 - Bala, P. T1 - Refined Calibration Model for Improving the Orientation Precision of Electron Backscatter Diffraction Maps N2 - For the precise determination of orientations in polycrystalline materials, electron backscatter diffraction (EBSD) requires a consistent calibration of the diffraction geometry in the scanning electron microscope (SEM). In the present paper, the variation of the projection center for the Kikuchi diffraction patterns which are measured by EBSD is calibrated using a projective transformation model for the SEM beam scan positions on the sample. Based on a full pattern matching approach between simulated and experimental Kikuchi patterns, individual projection center estimates are determined on a subgrid of the EBSD map, from which least-square fits to affine and projective transformations can be obtained. Reference measurements on single-crystalline silicon are used to quantify the orientation errors which result from different calibration models for the variation of the projection center. KW - Scanning electron microscopy KW - Electron backscatter diffraction KW - Kikuchi diffraction KW - Projection center KW - Orientation precision PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-509342 DO - https://doi.org/10.3390/ma13122816 VL - 13 IS - 12 SP - 2816 PB - MDPI AN - OPUS4-50934 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scheuerlein, C. A1 - Andrieux, J. A1 - Michels, M. A1 - Lackner, F. A1 - Chiriac, R. A1 - Hagner, M. A1 - Di Michiel, M. A1 - Meyer, Christian A1 - Toche, F. ED - Foley, C. P. T1 - Effect of the fabrication route on the phase and volume changes during the reaction heat treatment of Nb3Sn superconducting wires N2 - Accelerator magnets that can reach magnetic fields well beyond the Nb-Ti performance limits are presently being built and developed, using Nb3Sn superconductors. This technology requires reaction heat treatment (RHT) of the magnet coils, during which Nb3Sn is formed from its ductile precursor materials (a “wind and react” approach). The Nb3Sn microstructure and microchemistry are strongly influenced by the conductor fabrication route, and by the Phase changes during RHT. By combining in situ differential scanning calorimetry, high Energy synchrotron x-ray diffraction, and micro-tomography experiments, we have acquired a unique data set that describes in great detail the phase and microstructure changes that take place during the processing of restacked rod process (RRP), powder-in-tube (PIT), and internal tin (IT) Nb3Sn wires. At temperatures below 450 ° the phase evolutions in the three wire types are similar, with respectively solid state interdiffusion of Cu and Sn, Cu6Sn5 formation, and Cu6Sn5 peritectic transformation. Distinct differences in phase evolutions in the wires are found when temperatures exceed 450 °C. The volume changes of the conductor during RHT are a difficulty in the production of Nb3Sn accelerator magnets. We compare the wire diameter changes measured in situ by dilatometry with the phase and void volume evolution of the three types of Nb3Sn wire. Unlike the Nb3Sn wire length changes, the wire diameter evolution is characteristic for each Nb3Sn wire type. The strongest volume increase, of about 5%, is observed in the RRP wire, where the main diameter increase occurs above 600 °C upon Nb3Sn formation. KW - Nb3Sn KW - Microstructure KW - Phase transformations KW - Volume changes KW - X-ray diffraction KW - Differential scanning calorimetry KW - Synchrotron micro-tomography PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-505128 DO - https://doi.org/10.1088/1361-6668/ab627c VL - 33 IS - 3 SP - 034004 PB - IOP Publishing CY - Bristol (UK) AN - OPUS4-50512 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nolze, Gert A1 - Tokarski, T. A1 - Cios, G. A1 - Winkelmann, A. T1 - Manual measurement of angles in backscattered and transmission Kikuchi diffraction patterns N2 - A historical tool for crystallographic analysis is provided by the Hilton net, which can be used for manually surveying the crystal lattice as it is manifested by the Kikuchi bands in a gnomonic projection. For a quantitative analysis using the Hilton net, the projection centre as the relative position of the signal source with respect to the detector plane needs to be known. Interplanar angles are accessible with a precision and accuracy which is estimated to be ≤0.3o. Angles between any directions, e.g. zone axes, are directly readable. Finally, for the rare case of an unknown projection-centre position, its determination is demonstrated by adapting an old approach developed for photogrammetric applications. It requires the indexing of four zone axes [uvw]i in a backscattered Kikuchi diffraction pattern of a known phase collected under comparable geometric conditions. KW - Electron backscatter diffraction KW - EBSD KW - Angle measurement KW - Gnomonic projections KW - Kikuchi patterns PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-507625 DO - https://doi.org/10.1107/S1600576720000692 VL - 53 SP - 435 EP - 443 AN - OPUS4-50762 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Matz, R. A1 - Rabe, Torsten A1 - Töpfer, J. A1 - Ziesche, S. T1 - Circuit-Board-Integrated Transformers Design and Manufacture N2 - Transformers couple two sections of a circuit by electromagnetic induction. They are widely used to either transform alternating voltage levels or to transmit power or signals across galvanic isolation. Both of these functions are essential for the operation of sensors and controllers. Covering all aspects from idea to circuit performance and from design to manufacture, this paper presents the first comprehensive description of the making of miniaturized, rugged, up-to-100W transformers for embedding into multilayer circuit boards. For circular coils, the well-manageable Ampere-Laplace law is shown to yield reliable designs, predicting correctly the performance of manufactured hardware. This enables fast design without lengthy finite element modelling. In the low-power linear regime, basic relations describe how the device’s characteristics evolve from the material properties and device structure. While scattering Parameters are useful for the analysis of isolated transformers with their intrinsic parasitics, the interaction with the components of the final circuit and the aspects of power and efficiency are addressed by chain matrixes. While these design rules are similar for multilayer boards of different material (like epoxy, Teflon, ceramics), the manufacturing of ceramic board transformers is considered here in detail. Low-temperature-cofired ceramic (LTCC) boards being sintered at 900 °C are particularly suited for harsh environments with chemical or thermal stress as frequently found at sensor positions. The transformer performance usually benefits from or even requires an integrated ceramic core of higher permeability, a ferrite, to shape the magnetic flux. Methods to sinter ferrites inside a dielectric ceramic multilayerandto measure their performance are therefore described in detail.Asthe sintering behaviour of dielectricandmagnetic ceramics differs considerably, their simultaneous sintering is challenging.However, the sintering temperatures of the usefulMnZnand NiZnCu ferrites can be lowered to that of the dielectric material with only moderate loss of permeability by glass additives. Furthermore, thermal mismatch between materials causes catastrophic failure or at least stress and loss of magnetic performance during cooling to room temperature after sintering. This is avoidable by either adjusting the thermal expansion coefficient of the ferrite or by enclosing the ferrite between stressreleasing separation layers.We present the state of the art in materials development according to the first approach as well as fully functional devices made with the second technique. Other applications not directly addressed but well related to this work are characterized by low load resistance in relation to the coil resistance of the transformer. Efficient power transmission then requires that technological solutions are applied to achieve the lowest possible resistive loss inside the coils by an enlarged conductor cross-section. As this is particularly challenging for LTCC boards, a technique is discussed to fabricate conductor traces with a thickness larger than their width. KW - Multilayer ceramic technology KW - LTCC KW - Transformer PY - 2020 DO - https://doi.org/10.4416/JCST2019-00071 SN - 2190-9385 VL - 11 IS - 1 SP - 44 EP - 61 PB - Göller Verlag CY - Baden-Baden AN - OPUS4-50751 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Winkelmann, A. A1 - Cios, G. A1 - Tokarski, T. A1 - Nolze, Gert A1 - Hielscher, R. A1 - Koziel, T. T1 - EBSD orientation analysis based on experimental Kikuchi reference patterns N2 - Orientation determination does not necessarily require complete knowledge of the local atomic arrangement in a crystalline phase. We present a method for microstructural phase discrimination and orientation analysis of phases for which there is only limited crystallographic information available. In this method, experimental Kikuchi diffraction patterns are utilized to generate a self-consistent master reference for use in the technique of Electron Backscatter Diffraction (EBSD). The experimentally derived master data serves as an application-specific reference in EBSD pattern matching approaches. As application examples, we map the locally varying orientations in samples of icosahedral quasicrystals observed in a Ti40Zr40Ni20 alloy, and we analyse AlNiCo decagonal quasicrystals. KW - EBSD KW - Quasicrystal KW - Crystal orientation KW - Pattern matching PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-507611 DO - https://doi.org/10.1016/j.actamat.2020.01.053 VL - 188 SP - 376 EP - 385 PB - Elsevier Ltd. AN - OPUS4-50761 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cios, G. A1 - Nolze, Gert A1 - Winkelmann, A. A1 - Tokarski, T. A1 - Hielscher, R. A1 - Strzalka, R. A1 - Buganski, I. A1 - Wolny, J. A1 - Bala, P. T1 - Approximant-based orientation determination of quasicrystals using electron backscatter diffraction N2 - Orientation mapping of quasicrystalline materials is demonstrated using crystalline approximant structures in the technique of electron backscatter diffraction (EBSD). The approximant-based orientations are symmetrised according to the rotational point group of the quasicrystal, including the visualization of orientation maps using proper colour keys for quasicrystal symmetries. Alternatively, approximant-based orientation data can also be treated using pseudosymmetry post-processing options in the EBSD system software, which enables basic grain size estimations. Approximant-based orientation analyses are demonstrated for icosahedral and decagonal quasicrystals. KW - EBSD KW - Quasicrystal KW - Approximant KW - Chrystal orientation KW - Data processing PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514221 DO - https://doi.org/10.1016/j.ultramic.2020.113093 VL - 218 SP - 113093 PB - Elsevier B.V. AN - OPUS4-51422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Koclega, Damian A1 - Radziszewska, A. A1 - Dymek, S. A1 - Morgiel, J. A1 - Maj, L. A1 - Kranzmann, Axel T1 - Improvement of Corrosion Resistance of 13CrMo4-5 Steel by Ni-Based Laser Cladding Coatings N2 - The 13CrMo4-5 ferritic steel is commonly used in power plants, due to its favorable mechanical properties. According to EN 10028-2, this steel can be used at temperatures up to 570°C because of its creep behavior. The inefficient corrosion resistance limits the application of this steel to lower temperatures depending on the gas temperature and slag formation. Therefore, the application of a highly resistant Ni-based coating is proposed to extend the corrosion resistance of elements made of ferritic steel. The corrosion test was performed in an environment containing a mixture of gases, like O2, COx, and SOx, and deposited ashes with elements, e.g., Na, Cl, Ca, Si, C, Fe, and Al. The exposure time was, respectively, 240 h, 1000 h and 4500 h at a temperature of 600°C. The oxide scale formed on the 13CrMo4-5 steel was significantly thicker than on the IN686 coating. The microstructure and chemical and phase compositions of the oxide scale were investigated using light optical microscopy together with scanning and transmission electron microscopy techniques. Energy dispersive x-ray analyses were performed when appropriate. KW - Aggressive environments KW - Corrosion resistance KW - High - temperature KW - Inconel 686 KW - Laser cladding PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514289 DO - https://doi.org/10.1007/s11665-020-04867-x SN - 1059-9495 VL - 29 IS - 6 SP - 3702 EP - 3713 PB - Springer AN - OPUS4-51428 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scherb, T. A1 - Fantin, Andrea A1 - Checcia, S. A1 - Stephan-Scherb, Christiane A1 - Escolástico, S. A1 - Franz, A. A1 - Seeger, J. A1 - Meulenberg, W. A. A1 - d'Acapito, F. A1 - Serra, J. M. T1 - Unravelling the crystal structure of Nd5.8WO12-d and Nd5.7W0.75Mo0.25O12-d mixed ionic electronic conductors N2 - Mixed ionic electronic conducting ceramics Nd6-yWO12-d (d is the Oxygen deficiency) provide excellent stability in harsh environments containing strongly reactive gases such as CO2, CO, H2, H2O or H2S. Due to this chemical stability, they are promising and cost-efficient candidate materials for gas separation, catalytic membrane reactors and protonic ceramic fuel cell technologies. As in La6-yWO12-d, the ionic/electronic transport mechanism in Nd6-yWO12-d is expected to be largely controlled by the crystal structure, the conclusive determination of which is still lacking. This work presents a crystallographic study of Nd5.8WO12-d and molybdenum-substituted Nd5.7W0.75Mo0.25O12-d prepared by the citrate complexation route. High-resolution synchrotron and neutron powder diffraction data were used in combined Rietveld refinements to unravel the crystal structure of Nd5.8WO12-d and Nd5.7W0.75Mo0.25O12-d. Both investigated samples crystallize in a defect fluorite crystal structure with space group Fm3m and doubled unit-cell parameter due to cation ordering. Mo replacesWat bothWyckoff sites 4a and 48h and is evenly distributed, in contrast with La6-yWO12-d. X-ray absorption spectroscopy as a function of partial pressure pO2 in the near-edge regions excludes oxidation state changes of Nd (Nd3+) and W(W6+) in reducing conditions: the enhanced hydrogen permeation, i.e. ambipolar conduction, observed in Mo-substituted Nd6-yWO12-d is therefore explained by the higher Mo reducibility and the creation of additional – disordered – oxygen vacancies. KW - Powder diffraction KW - Mixed conductors KW - X-ray absorption spectroscopy PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514607 DO - https://doi.org/10.1107/S1600576720012698 VL - 53 SP - 1471 EP - 1483 AN - OPUS4-51460 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duarte, Larissa A1 - Andrade, Ana Carolina A1 - Bettge, Dirk T1 - Fractographic Analysis of Fatigue Striations Formation under different Microstructures and Loading Conditions T1 - Fraktographische Untersuchung der Bildung von Schwingstreifen bei unterschiedlichen Gefügezuständen und Belastungsbedingungen N2 - Fatigue failure of a component can occur at service loads considerably lower than the yield strength of the material. Under fatigue loading condition, the material in the vicinity of the tip of a propagating crack repeatedly deforms plastically, leaving microscopic marks on the crack surface, commonly known as fatigue striations. Counting and measuring fatigue striations is a method in estimating the number of loading cycles a component went through until fracture. Some studies suggest a one-to-one relation between the number of fatigue striations and the number of load cycles, but this relation is still debatable, given that there are many factors influencing the formation of those striations. The main purpose of this work is to analyze the influence of microstructure and mechanical strength on the formation of fatigue striations in structural steels, in order to understand how these material properties are related to the fatigue crack behavior. For such, standard Charpy-V samples were subjected to hardness, fatigue and impact testing. Metallography was performed to characterize the microstructure, and a fractographic analysis by using optical and scanning electron microscopy was carried out to investigate the fracture surface. This study shows that steels with higher ductility have a closer one-to-one relation than those with a higher tensile strength. Above a certain level of tensile strength, fatigue striations do form rarely or completely disappear. N2 - Weit unterhalb der Streckfestigkeit des Werkstoffs kann es durch Schwingbruch zum Bauteilversagen kommen. Unter Schwingbeanspruchung wird der Werkstoff in der Nähe der Spitze eines sich ausbreitenden Risses wiederholt plastisch verformt. Dabei entstehen allgemein als Schwingstreifen bekannte mikroskopische Spuren. Das Zählen und Vermessen von Schwingstreifen ist ein Verfahren zum Schätzen der Anzahl von Belastungszyklen, denen ein Bauteil bis zum Bruch ausgesetzt war. Einige Studien legen hier eine 1 : 1-Beziehung zwischen der Anzahl von Schwingstreifen und der Anzahl von Lastspielen nahe. Dies erscheint angesichts der zahlreichen, die Bildung solcher Streifen beeinflussenden Faktoren allerdings fraglich. Hauptziel dieser Arbeit ist die Untersuchung der Auswirkungen des Gefüges und der mechanischen Festigkeit auf die Bildung von Schwingstreifen in Baustählen, um Zusammenhänge zwischen diesen Werkstoffeigenschaften und dem Schwingbruchverhalten verstehen zu können. Dafür wurden an Standard-Charpy-V-Proben Härte- sowie Schwing- und Schlagprüfungen durchgeführt. Zur Gefügecharakterisierung wurden die Proben metallographisch untersucht. Die Bruchfläche wurde zur Analyse fraktographisch licht- und rasterelektronenmikroskopisch untersucht. Die vorliegende Untersuchung zeigt dabei auf, dass Stähle mit einer höheren Duktilität näher an eine solche 1 : 1-Beziehung herankommen als solche mit einer höheren Zugfestigkeit. Oberhalb einer bestimmten Zugfestigkeit bilden sich selten oder gar keine Schwingstreifen. KW - Schwingstreifen KW - Fatigue striations PY - 2020 DO - https://doi.org/10.3139/147.110668 VL - 57 IS - 12 SP - 869 EP - 886 PB - Carl Hanser Verlag CY - München AN - OPUS4-51952 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nolze, Gert A1 - Winkelmann, A. T1 - About the reliability of EBSD measurements: Data enhancement N2 - An extensive set of information about the diffracting volume is carried by EBSD patterns: the crystal lattice, the reciprocal lattice, the crystal structure, the crystal symmetry, the mean periodic number of the diffracting phase, the source point from where it has been projected (projection centre), the crystal orientation, the sample topography (local tilt), the (preparation) quality of defect density of the crystal, and possible pattern overlaps. Some of this information is used regularly in conventional EBSD analyses software while others are still waiting for a more widespread application. Despite the wealth of information available, the accuracy and precision of the data that are presently extracted from conventional EBSD patterns are often well below the actual physical limits. Using a selection of example applications, we will demonstrate the gain in angular resolution possible using relatively low-resolution patterns of approximately 20k pixels in combination with pattern matching (PM) approaches. In this way, fine details in a microstructure can be revealed which would otherwise be hidden in the orientation noise. KW - EBSD KW - Orientation precision KW - Disorientation KW - Grain boundary KW - Phase transformation PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521618 DO - https://doi.org/10.1088/1757-899X/891/1/012018 VL - 891 SP - 012018 PB - IOP Science AN - OPUS4-52161 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Taketa, I. A1 - Kalinka, Gerhard A1 - Gorbatikh, L. A1 - Lomov, S. A1 - Verpoest, I. T1 - Influence of cooling rate on the properties of carbon fiber unidirectional composites with polypropylene, polyamide 6, and polyphenylene sulfide matrices N2 - The longitudinal and transverse strength of three unidirectional thermoplastic prepreg systems: carbon fiber/polypropylene (CF/PP), polyamide 6 (CF/PA6), and polyphenylene sulfide (CF/PPS) are studied and analytical formulas are proposed for the estimation of matrix and fiber/matrix interface properties from composites properties. Since the matrices are semi-crystalline thermoplastics, the influence of cooling rate on the strength is statistically evaluated. While the 0° tensile strength is found to be independent of the cooling rate, the 90° tensile strength is strongly influenced by the matrix type and cooling rate. The matrix modulus increases as the cooling rate is decreased; the degree of crystallinity also increases. The matrix residual stress, interfacial shear strength, and mode II interlaminar fracture toughness are also found to depend on the cooling rate, with the trends different for different matrices. KW - Matrix residual stress KW - Thermoplastic prepreg KW - Unidirectional composites KW - Cooling rate KW - Interfacial strength PY - 2020 DO - https://doi.org/10.1080/09243046.2019.1651083 SN - 0924-3046 SN - 1568-5519 N1 - Die originale japanische Version des Artikels erschien in: Journal of the Japan Society for Composite Materials, Jg. 44, Nr. 4 (2018), S. 123-128. - The original Japanese version of the article was published in: Journal of the Japan Society for Composite Materials, vol. 44, no. 4 (2018), pp. 123-128. VL - 29 IS - 1 SP - 101 EP - 113 PB - Taylor & Francis CY - London AN - OPUS4-45433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stephan-Scherb, Christiane A1 - Schulz, Wencke A1 - Schneider, M. A1 - Karafiludis, Stephanos A1 - Laplanche, G. T1 - High-Temperature Oxidation in Dry and Humid Atmospheres of the Equiatomic CrMnFeCoNi and CrCoNi High- and Medium-Entropy Alloys N2 - Surface degradation phenomena of two model equiatomic alloys from the CrMnFeCoNi alloy system were investigated in 2% O2 and 10% H2O (pO2 = 0.02 and 10−7 atm, respectively) at 800 °C for times up to 96 h. The crystallographic structures, morphologies, and chemical compositions of the corrosion layers developing on CrMnFeCoNi and CrCoNi were comparatively analyzed by mass gain analysis, X-ray diffraction, and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and electron backscatter diffraction. The oxidation resistance of CrMnFeCoNi is relatively poor due to the fast growth of porous Mnoxide(s). CrCoNi forms an external chromia layer that is dense and continuous in a dry 2% O2 atmosphere. This layer buckles and spalls off after exposure to 10% H2O atmosphere. Beneath the chromia layer, a Cr-depleted zone forms in the CrCoNi alloy in both environments. As the oxide scale spalls off in the H2O-containing atmosphere, a secondary chromia layer was observed and correspondingly enlarges the Cr-depleted zone. In contrast, as the chromia layer remains without significant spallation when CrCoNi is exposed to a dry oxidizing atmosphere, the region depleted in Cr is narrower. KW - High temperature oxidation KW - High entropy alloys KW - Medium entropy alloys KW - CrMnFeCoNi KW - CrCoNi KW - Mn-oxides PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-517859 DO - https://doi.org/10.1007/s11085-020-10014-7 SN - 0030-770X VL - 95 IS - 1-2 SP - 105 EP - 133 PB - Springer AN - OPUS4-51785 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lüders, C. A1 - Kalinka, Gerhard A1 - Li, Wei A1 - Sinapius, M. A1 - Wille, T. T1 - Experimental and numerical multiscale approach to thermally cycled FRP N2 - Due to the different thermal expansion of the constituent materials, cyclic thermal loading of FRP induces alternating stresses in the material at two scales: at the micro scale (level of fibre–matrix-interaction) and at the macro scale (level of the multidirectional laminate). Especially the micro scale effect is not comprehensively investigated yet. Additionally, computational investigations mostly neglect this effect due to the homogenous modelling of the composite material. As this effect is assumed to significantly contribute to the fatigue of FRP at thermal loads, the present paper suggests an experimental and numerical multiscale approach including Experiments at the different involved material scales to separately observe the effects acting at these scales. The approach also includes numerical modelling for each scale to complement the knowledge gained from the Experiments and to create a basis for the consideration of the micro effect even in macroscopic fatigue models treating homogeneous modelled composites. The main focus of the contribution is to bring the overall Approach up for discussion, rather than to present the multiscale modelling details. KW - Fatigue KW - Thermal cycling KW - Fibre reinforced plastic KW - Cryogenic KW - Carbon Fibre KW - Epoxy Resin PY - 2020 DO - https://doi.org/10.1016/j.compstruct.2020.112303 SN - 0263-8223 VL - 244 SP - 112303 PB - Elsevier Ltd. CY - Niederlande AN - OPUS4-50844 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Waurischk, Tina A1 - Thieme, C. A1 - Rüssel, C. T1 - Crystal growth velocities of a highly anisotropic phase obtained via surface and volume crystallization of barium–strontium–zinc silicate glasses N2 - In the past few years, a new phase, Ba0.5Sr0.5Zn2Si2O7 with negative thermal expansion has been described in the literature. Some excess of SiO2 is necessary to produce glasses from which the Ba0.5Sr0.5Zn2Si2O7 phase can be crystallized. Unfortunately, in such glasses usually surface crystallization occurs; however, the addition of nucleating agents such as trace quantities of platinum or relatively high quantities of ZrO2 is necessary to achieve bulk nucleation. These additional components also affect the crystal growth velocity, which furthermore is different for crystal growth from the surface and in the bulk. In this paper, three different chemical compositions containing different ZrO2 concentrations, where one composition additionally contains 100 ppm platinum, are studied with respect to their crystallization behaviour. Although the compositions do not differ much, the crystallization behaviour and also the Crystal growth velocities are surprisingly different. KW - Glass ceramic KW - Crystal growth velocity KW - Low expansion PY - 2020 DO - https://doi.org/10.1007/s10853-020-04773-6 SN - 0022-2461 VL - 55 SP - 10364 EP - 10374 PB - Springer AN - OPUS4-50853 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erdmann, Maren A1 - Niebergall, Ute A1 - Wachtendorf, Volker A1 - Böhning, Martin T1 - Evaluation of UV-induced embrittlement of PE-HD by Charpy impact test N2 - The impact fracture behavior of two common high-density polyethylene grades for container applications were intensively studied by the instrumented Charpy impact test after well-defined exposure to UV-irradiation. Individual stages of the impact event, such as crack initiation and crack propagation energy as well as maximum impact load, were investigated from the recorded load–deflection curves. UV-induced material property changes were further investigated by infrared spectroscopy, differential scanning calorimetry, and dynamic-mechanical analysis as well as density measurements. Based on the results of the Charpy impact test, three indicators were identified to describe the extend of photooxidation on high-density polyethylene: (a) a reduced Charpy impact strength—at least to half of its initial value for a distinctly brittle impact fracture, (b) a marked decrease in the crack propagation contribution to the impact strength, and (c) an increase of the brittle features of the fracture surface. KW - Degradation KW - Mechanical properties KW - Packaging KW - Polyolefins KW - Polyethylene PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-509130 DO - https://doi.org/10.1002/APP.49069 SN - 0021-8995 VL - 137 IS - 36 SP - 49069 PB - Wiley AN - OPUS4-50913 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Xu, F. A1 - Ren, H. A1 - Zheng, M. A1 - Shao, X. A1 - Dai, T. A1 - Wu, Y. A1 - Tian, L. A1 - Liu, Y. A1 - Liu, B. A1 - Günster, Jens A1 - Liu, Y. A1 - Liu, Y. T1 - Development of biodegradable bioactive glass ceramics by DLP printed containing EPCs/BMSCs for bone tissue engineering of rabbit mandible defects N2 - Bioactive glass ceramics have excellent biocompatibility and osteoconductivity; and can form direct chemical bonds with human bones; thus, these ceramic are considered as “Smart” materials. In this study, we develop a new type of bioactive glass ceramic (AP40mod) as a scaffold containing Endothelial progenitor cells (EPCs) and Mesenchymal stem cells (BMSCs) to repair critical-sized bone defects in rabbit mandibles. For in vitro experiments: AP40mod was prepared by Dgital light processing (DLP) system and the optimal ratio of EPCs/BMSCs was screened by analyzing cell proliferation and ALP activity, as well as the influence of genes related to osteogenesis and angiogenesis by direct inoculation into scaffolds. The scaffold showed suitable mechanical properties, with a Bending strength 52.7 MPa and a good biological activity. Additionally, when EPCs/BMSCs ratio were combined at a ratio of 2:1 with AP40mod, the ALP activity, osteogenesis and angiogenesis were significantly increased. For in vivo experiments: application of AP40mod/EPCs/BMSCs (after 7 days of in vitro spin culture) to repair and reconstruct critical-sized mandible defect in rabbit showed that all scaffolds were successfully accurately implanted into the defect area. As revealed by macroscopically and CT at the end of 9 months, defects in the AP40mod/EPCs/BMSCs group were nearly completely covered by normal bone and the degradation rate was 29.9% compared to 20.1% in the AP40mod group by the 3D reconstruction. As revealed by HE and Masson staining analyses, newly formed blood vessels, bone marrow and collagen maturity were significantly increased in the AP40mod/EPCs/BMSCs group compared to those in the AP40mod group. We directly inoculated cells on the novel material to screen for the best inoculation ratio. It is concluded that the AP40mod combination of EPCs/BMSCs is a promising approach for repairing and reconstructing large load bearing bone defect. KW - Three-dimensional Bone tissue engineering KW - Endothelial progenitor cell KW - Bone marrow-derived mesenchymal stem cell KW - Bioactive glass scaffold PY - 2020 DO - https://doi.org/10.1016/j.jmbbm.2019.103532 SN - 1751-6161 VL - 103 SP - 103532 EP - 103532 PB - Elsevier Ltd. AN - OPUS4-50491 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pu, Y. A1 - Lawrence, M. J. A1 - Celorrio, V. A1 - Wang, Q. A1 - Gu, M. A1 - Sun, Z. A1 - Agudo Jácome, Leonardo A1 - Russell, A. E. A1 - Huang, L. A1 - Rodriguez, P. T1 - Nickel confined in 2D earth-abundant oxide layers for highly efficient and durable oxygen evolution catalysts N2 - Low cost, high-efficiency catalysts towards water splitting are urgently required to fulfil the increasing demand for energy. In this work, low-loading (<20 wt%) Ni-confined in layered metal oxide anode catalysts (birnessite and lepidocrocite titanate) have been synthesized by facile ion exchange methodology and subjected to systematic electrochemical studies. It was found that Ni-intercalated on K-rich birnessite (Ni-KMO) presents an onset overpotential (ηonset) as low as 100 mV and overpotential at 10 mA cm−2 (η10) of 206 mV in pH = 14 electrolyte. By combining electrochemical methods and X-ray absorption and emission spectroscopies (XAS and XES), we demonstrate Ni sites are the active sites for OER catalysis and that the Mn3+ sites facilitate Ni intercalation during the ion-exchange process, but display no observable contribution towards OER activity. The effect of the pH and the nature of the supporting electrolyte on the electrochemical performance was also evaluated. KW - Confined catalyst KW - Low-loading KW - Layered manganese oxide KW - Oxygen evolution reaction KW - Transmission electron microscopy (TEM) PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515027 DO - https://doi.org/10.1039/D0TA04031B SN - 2050-7496 SN - 2050-7488 VL - 8 IS - 26 SP - 13340 EP - 13350 PB - Royal Society of Chemistry CY - London AN - OPUS4-51502 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gadelmeier, C. A1 - Haas, S. A1 - Lienig, T. A1 - Manzoni, Anna Maria A1 - Feuerbacher, M. A1 - Glatzel, U. T1 - Temperature Dependent Solid Solution Strengthening in the High Entropy Alloy CrMnFeCoNi in Single Crystalline State N2 - The main difference between high entropy alloys and conventional alloys is the solid solution strengthening effect, which shifts from a single element to a multi-element matrix. Little is known about the effectiveness of this effect at high temperatures. Face-centered cubic, equiatomic, and single crystalline high entropy alloy CrMnFeCoNi was pre-alloyed by arc-melting and cast as a single Crystal using the Bridgman process. Mechanical characterization by creep testing were performed at temperatures of 700, 980, 1100, and 1200°C at different loads under vacuum and compared to single-crystalline pure nickel. The results allow a direct assessment of the influence of the chemical composition without any disturbance by grain boundary sliding or diffusion. The results indicate different behaviors of single crystalline pure nickel and CrMnFeCoNi. At 700°C CrMnFeCoNi is more creep-resistant than Ni, but at 980°C both alloys show a nearly similar creep strength. Above 980°C the creep behavior is identical and the solid solution strengthening effect of the CrMnFeCoNi alloy disappears. KW - High entropy alloys KW - Single crystal PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514572 DO - https://doi.org/10.3390/met10111412 VL - 10 IS - 11 SP - 1412 PB - MDPI AN - OPUS4-51457 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Famy, A. A1 - Agudo Jácome, Leonardo A1 - Schönhals, Andreas T1 - Effect of Silver Nanoparticles on the Dielectric Properties and the Homogeneity of Plasma Poly(acrylic acid) Thin Films N2 - For the first time, structure−electrochemical relationships of thin films of a plasma-polymerized acrylic acid/carbon dioxide AA/CO2 (75/25%) copolymer modified by implanted silver nanoparticles are discussed. The pulsed plasma polymerization of AA/CO2 was utilized and adjusted to obtain a maximal amount of COOH Groups forming an almost uncross-linked polymer structure. The prepared polymer layer is rinsed by a silver nitrate solution to impregnate Ag+ ions. This step is followed by its reduction of Ag+ with NaBH4 as a chemical route in comparison to the reduction by sunlight as an ecofriendly photoreduction method. The chemical composition and morphology of the topmost surface layer of the AA/CO2 polymer thin film were investigated by X-ray photoelectron spectroscopy and atomic force microscopy. Moreover, the molecular mobility, conductivity, and thermal stability of the polymer layer were analyzed using broadband dielectric spectroscopy. The dielectric properties of the AA/ CO2 polymer thin film were studied in the presence of Ag+ ions or Ag0. It was found that a cross-linked polymer layer with a smooth surface and high conductivity was obtained in the presence of Ag+/ Ag0. KW - Nanoparticles PY - 2020 DO - https://doi.org/10.1021/acs.jpcc.0c06712 SN - 1932-7447 VL - 124 IS - 41 SP - 22817 EP - 22826 PB - ACS AN - OPUS4-51468 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Waurischk, Tina A1 - Müller, Ralf A1 - Reinsch, Stefan A1 - Kiefer, P. A1 - Deubener, J. A1 - Balzer, R. A1 - Behrens, H. T1 - Crack Growth in Hydrous Soda-Lime Silicate Glass N2 - Stable crack growth was measured for nominal dry and water-bearing (6 wt%) soda-lime silicate glasses in double cantilever beam geometry and combined with DMA studies on the effects of dissolved water on internal friction and glass transition, respectively. In vacuum, a decreased slope of logarithmic crack growth velocity versus stress intensity factor is evident for the hydrous glass in line with an increase of b-relaxation intensity indicating more energy Dissipation during fracture. Further, inert crack growth in hydrous glass is found to be divided into sections of different slope, which indicates different water related crack propagation mechanism. In ambient air, a largely extended region II is observed for the hydrous glass, which indicates that crack growth is more sensitive to ambient water. KW - Internal friction KW - Soda-lime silicate glass KW - Water content KW - Stable crack growth KW - DCB geometry KW - Stress intensity factor PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506829 DO - https://doi.org/10.3389/fmats.2020.00066 VL - 7 SP - Articel 66 AN - OPUS4-50682 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -