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 - 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 - 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 - Dong, S. A1 - Leng, J. A1 - Feng, Y. A1 - Liu, M. A1 - Stackhouse, C. J. A1 - Schönhals, Andreas A1 - Chiappisi, L. A1 - Gao, L. A1 - Chen, W. A1 - Shang, J. A1 - Jin, L. A1 - Qi, Z. A1 - Schalley, C. A. T1 - Structural water as an essential comonomer in supramolecular polymerization N2 - Although the concept of structural water that is bound inside hydrophobic pockets and helps to stabilize protein structures is well established, water has rarely found a similar role in supramolecular polymers. Water is often used as a solvent for supramolecular polymerization, however without taking the role of a comonomer for the supramolecular polymer structure. We report a low–molecular weight monomer whose supramolecular polymerization is triggered by the incorporation of water. The presence of water molecules as comonomers is essential to the polymerization process. The supramolecular polymeric material exhibits strong adhesion to surfaces, such as glass and paper. It can be used as a water-activated glue, which can be released at higher temperatures and reused many times without losing its performance. KW - Supra molecular polymerization PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-432728 DO - https://doi.org/10.1126/sciadv.aao0900 SN - 2375-2548 VL - 3 IS - 11 SP - eaao0900, 1 EP - eaao0900, 8 PB - American Association for the Advancement of Science AN - OPUS4-43272 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leng, Jing A1 - Kang, Nianjun A1 - Wang, De-Yi A1 - Falkenhagen, Jana A1 - Thünemann, Andreas A1 - Schönhals, Andreas T1 - Structure–Property Relationships of Nanocomposites Based on Polylactide and Layered Double Hydroxides – Comparison of MgAl and NiAl LDH as Nanofiller N2 - Nanocomposites based on poly(L-lactide) (PLA) and organically modified Ni/Al layered double hydroxides (NiAl/LDHs) are prepared by melt blending and investigated by a combination of size exclusion chromatography, differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), wide-angle X-ray scattering, and broadband dielectric spectroscopy. A detailed comparison to the behavior of the corresponding MgAl/LDH–PLA nanocomposites is made. SAXS investigations show that the morphology of the NiAl/LDH–PLA nanocomposites is more intercalated compared to the MgAl/LDH based PLA nanocomposite, which is more exfoliated. The DSC investigation gives a different dependence of the degree of crystallization on the concentration of LDH for NiAl/LDH–PLA than for MgAl/LDH–PLA nanocomposite system. These differences are discussed taking the differences of the morphologies of both systems into account. Broadband dielectric spectroscopy reveals information about the molecular dynamics where essential differences are observed for all relaxation processes taking place in both systems which were related to the different morphologies. KW - Nanocomposites KW - Polylactide PY - 2017 DO - https://doi.org/10.1002/macp.201700232 SN - 1022-1352 SN - 1521-3935 VL - 218 IS - 20 SP - Article 1700232, 1 EP - 12 PB - Wiley-VCH Verlag AN - OPUS4-42597 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yilmaz, M. A1 - Wollschläger, Nicole A1 - Esfahani, M. N. A1 - Österle, Werner A1 - Leblebici, Y. A1 - Alaca, B. E. T1 - Superplastic behavior of silica nanowires obtained by direct patterning of silsesquioxane-based precursors N2 - Silica nanowires spanning 10 μm-deep trenches are fabricated from different types of silsesquioxane-based precursors by direct e-beam patterning on silicon followed by release through deep reactive ion etching. Nanowire aspect ratios as large as 150 are achieved with a critical dimension of about 50 nm and nearly rectangular cross-sections. In situ bending tests are carried out inside a scanning electron microscope, where the etch depth of 10 mm provides sufficient space for deformation. Silica NWs are indeed observed to exhibit superplastic behavior without fracture with deflections reaching the full etch depth, about two orders of magnitude larger than the nanowire thickness. A large-deformation elastic bending model is utilized for predicting the deviation from the elastic behavior. The results of forty different tests indicate a critical stress level of 0.1–0.4 GPa for the onset of plasticity. The study hints at the possibility of fabricating silica nanowires in a monolithic Fashion through direct e-beam patterning of silsesquioxane-based resins. The fabrication technology is compatible with semiconductor manufacturing and provides silica nanowires with a very good structural integrity. KW - Silica nanowires KW - HSQ KW - Superplasticity KW - In situ bending tests PY - 2017 DO - https://doi.org/10.1088/1361-6528/aa5b80 SN - 0957-4484 SN - 1361-6528 VL - 28 IS - 11 SP - Article 115302, 1 EP - 10 AN - OPUS4-39166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hilgenberg, Kai A1 - Rethmeier, Michael A1 - Steinhoff, K. T1 - Surface structuring by pulsed laser implantation N2 - Micrometric surface topologies are required for a wide range of technical applications. While lowered surface features have been used for many years to improve the tribological behavior of contacting surfaces, there are also other fields of application, where the potential of elevated surface features is known, e. g. for metal forming tools. However, the demand for a high wear resistance of these structures often inhibits an industrial application. A solution is offered by structuring techniques that use additional material. A promising approach is the localized dispersing of hard ceramic particles by pulsed laser radiation, the so-called laser implantation. This paper describes the potential to adjust the geometry as well as the mechanical properties of laser implanted surfaces by means of microstructural and topological investigations. Afterwards, results of a wear test are given and different applications for this structuring technique are discussed. It can be shown that dome-shaped or ring-shaped structures on a micrometric scale can be produced with high hardness and wear resistance. KW - Laser implantation KW - Surface structuring PY - 2017 DO - https://doi.org/10.4028/www.scientific.net/MSF.879.750 SN - 0255-5476 SN - 1662-9752 VL - 879 SP - 750 EP - 755 PB - Trans Tech Publications AN - OPUS4-38263 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Launert, B. A1 - Szczerba, R. A1 - Gajewski, M. A1 - Rhode, Michael A1 - Pasternak, H. A1 - Gizejowski, M. T1 - The buckling resistance of welded plate girders taking into account the influence of post-welding imperfections - Part 1: Parameter study N2 - Welding is the most important joining technique and offers the advantage of customizable plate thicknesses. On the other hand, welding causes residual stresses and deformations influencing the load carrying capacity. Their consideration in the design requires simple and fast models. Though welding simulation has contributed to accurately access to these values nowadays, their application to large components remains still in a less practicable range. Nevertheless, many studies emphasized the need to make corrections in recently available simplified models. Especially the influence of residual stresses seems somewhat overestimated in many cases if comparing conventional structural steel S355 and high-strength steel S690. In the age of computer-aided design, an improved procedure to implement weld-inducted imperfections appears overdue. This will be presented in two parts. The first part illustrates the potential influence of post-welding imperfections exemplified for weak axis buckling in comparison with the general method in accordance with Eurocode 3. Residual stresses and initial crookedness were varied systematically in order to produce a scatter band of capacities. An approach to characterize the borders of these imperfections was untertaken before that. The excessive scattering of reduction factors for the load bearing capacity demonstrates the importance of these variables. Results were finally evaluated against advanced simulation models which will be further detailed in part two of this contribution. KW - Welded Plate Girders KW - Stability KW - Post-welding Imperfections KW - Residual Stresses KW - Parameter Study PY - 2017 DO - https://doi.org/10.3139/120.110964 SN - 0025-5300 SN - 2195-8572 VL - 59 IS - 1 SP - 47 EP - 56 PB - Carl Hanser Verlag CY - München AN - OPUS4-38922 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Martin, S. A1 - Walnsch, A. A1 - Nolze, Gert A1 - Leineweber, A. A1 - Léaux, F. A1 - Scheuerlein, C. T1 - The crystal structure of (Nb0.75Cu0.25)Sn-2 in the Cu-Nb-Sn system N2 - During the processing of superconducting Nb3Sn wire, several intermediate intermetallic phases including a previously encountered Cu-Nb-Sn phase show up. The yet unknown crystal structure of this phase is now identified by a combination of different experimental techniques and database search to be of the hexagonal NiMg2 type with a proposed composition of about (Nb0.75Cu0.25)Sn2. The structure determination started from an evaluation of the lattice parameters from EBSD Kikuchi patterns from quenched material suggesting hexagonal or orthorhombic symmetry. A database search then led to the hexagonal NiMg2 type structure, the presence of which was confirmed by a Rietveld analysis on the basis of high energy synchrotron X-ray powder diffraction data. Assuming a partial substitution of Nb in orthorhombic NbSn2 by Cu, the change of the valence electron concentration provokes a structural transformation from the CuMg2 type for NbSn2 to the NiMg2 type for (Nb0.75Cu0.25)Sn2. In the previous literature the (Nb0.75Cu0.25)Sn2 phase described here has occasionally been referred to as Nausite. KW - Electron backscatter diffraction KW - X-ray diffraction KW - Intermetallic compound KW - Structure solution KW - Superconductor PY - 2017 DO - https://doi.org/10.1016/j.intermet.2016.09.008 SN - 0966-9795 SN - 1879-0216 VL - 80 SP - 16 EP - 21 PB - Elsevier Ltd. AN - OPUS4-37874 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Martins, M. S. S. A1 - Schartel, Bernhard A1 - Magalhães, F. D. A1 - Pereira, C. M. C. T1 - The effect of traditional flame retardants, nanoclays and carbon nanotubes in the fire performance of epoxy resin composites N2 - The effectiveness of distinct fillers, from micro to nano-size scaled, on the fire behaviour of an epoxy resin and its carbon fibre reinforced composites was assessed by cone calorimetry. The performance was compared not only regarding the reaction to fire performance, but also in terms of thermal stability, glass transition temperature and microstructure. Regarding the fire reaction behaviour of nanofilled epoxy resin, anionic nanoclays and thermally oxidized carbon nanotubes showed the best results, in agreement with more compact chars formed on the surface of the burning polymer. For carbon fibre reinforced composite plates, the cone calorimeter results of modified resin samples did not show significant improvements on the heat release rate curves. Poorly dispersed fillers in the resin additionally caused reductions on the glass transition temperature of the composite materials. KW - Epoxy resin KW - Carbon fibre reinforced composite KW - Nanoclays KW - Carbon nanotubes KW - Flame retardants PY - 2017 DO - https://doi.org/10.1002/fam.2370 SN - 1099-1018 SN - 0308-0501 VL - 41 IS - 2 SP - 111 EP - 130 PB - Wiley & Sons, Ltd. AN - OPUS4-39085 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 - Pauw, Brian Richard A1 - Smith, A. J. A1 - Snow, T. A1 - Terril, N. J. A1 - Thünemann, Andreas T1 - The modular small-angle X-ray scattering data correction sequence N2 - Data correction is probably the least favourite activity amongst users experimenting with small-angle X-ray scattering: if it is not done sufficiently well, this may become evident only during the data analysis stage, necessitating the repetition of the data corrections from scratch. A recommended comprehensive sequence of elementary data correction steps is presented here to alleviate the difficulties associated with data correction, both in the laboratory and at the synchrotron. When applied in the proposed order to the raw signals, the resulting absolute scattering cross section will provide a high degree of accuracy for a very wide range of samples, with its values accompanied by uncertainty estimates. The method can be applied without modification to any pinhole-collimated instruments with photon-counting direct-detection area detectors. KW - Small-angle X-ray scattering KW - SAXS KW - Accuracy KW - Methodology KW - Data correction PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-432114 DO - https://doi.org/10.1107/S1600576717015096 SN - 1600-5767 VL - 50 IS - 6 SP - 1800 EP - 1811 PB - International Union of Crystallography AN - OPUS4-43211 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nolze, Gert A1 - Dietrich, D. A1 - Lampke, T. A1 - Del-Solar-Velarde, N. A1 - Nickel, D. A1 - Chapoulie, R. A1 - Castillo Butters, L.J. T1 - The potential of EBSD and EDS for ceramics investigations - Case studies on sherds of pre-Columbian pottery N2 - The work focuses on the potential of structural and chemical examinations by scanning electron microscopy based methods for archaeometric studies on ceramics. Achieved by a single preparation technique (polished block sections), the feasibility and benefits of electron backscatter diffraction are demonstrated as case studies using polychrome examples of pre-Columbian pottery (Wari, Moche and Cajamarca). Elemental and phase maps allow for separate consideration of clay and temper. Identification of mineral phases and intergrowths of temper particles provide information for clarifying clay procurement and firing techniques with respect to local versus non-local pottery to enlighten trade relations, technological transfer and shared heritage of pre-Columbian cultures. KW - SEM–EDS/EBSD KW - Pre-Columbian ceramics KW - Temper KW - Pseudobrookite KW - Titanite PY - 2017 VL - 60 IS - 3 SP - 489 EP - 501 AN - OPUS4-45096 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mushtaq, S. A1 - Steers, E.B.M. A1 - Barnhart, D. A1 - Churchill, G. A1 - Kasik, M. A1 - Richter, Silke A1 - Pfeifer, Jens A1 - Putyera, K. T1 - The production of doubly charged sample ions by “charge transfer and ionization” (CTI) in analytical GD-MS N2 - Normally, in analytical GD-MS, the doubly charged metallic ion signals from the sample are several orders of magnitude less than the corresponding singly charged signals. However, we have observed that using a neon plasma, the M++ signals of some elements, which have double ionization energies close to the first ionization energy of neon, are of the same order as the M+ signal. Doubly charged ions may be produced directly in the discharge cell by electron ionization (EI), and also by two electron Penning ionization (TEP), but these processes cannot explain the above effect. In this paper, we suggest that an additional process named as ‘Charge Transfer and Ionization’ (CTI) produces such ions either in their ionic ground state or in an excited state. To confirm that this process is typical of the discharges used in GD-MS and not an artefact of any particular form of cell and ion extraction system, we have carried out comprehensive experimental measurements using three different GD-MS instruments, viz., Nu Astrum, VG9000 and ELEMENT GD and our results provide clear evidence for CTI. This is the first time the process has been identified as an ionization process in analytical GD-MS. CTI must be differentiated from Asymmetric Charge Transfer (ACT), which is a “selective” process and requires a close energy match (e.g. ΔE < 0.5 eV for a strong effect). On the other hand, CTI is “non-selective” in the sense that a close energy match is not required (e.g. a strong effect is observed with ΔE ∼ 2 eV), although the process only occurs for a limited number of elements, depending on the plasma gas used and the total energy required to doubly ionize the metallic atom. KW - Titanium KW - Glow discharge processes KW - Doubly charged ions KW - The charge transfer and ionization process (CTI) KW - Krypton KW - Neon PY - 2017 DO - https://doi.org/10.1039/C6JA00415F SN - 0267-9477 SN - 1364-5544 VL - 32 IS - 9 SP - 1721 EP - 1729 PB - Royal Society of Chemistry AN - OPUS4-41108 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 - Weidner, Steffen A1 - Kricheldorf, H. R. T1 - The Role of Transesterification in SnOct 2 - Catalyzed Polymerizations of Lactides N2 - l-lactide or meso-lactide are polymerized either at 120 °C where the polymerization process of l-lactide is accompanied by crystallization, or at 180 °C where poly(l-lactide) remains in the molten state. Polymerizations at 120 °C initially yield even-numbered chains (with respect to lactic acid units) having relatively low dispersity, but the fraction of odd-numbered chains increases with time and the entire molecular weight distribution changes. Traces of cyclics are only formed after 7 d. Polymerizations at 180 °C yield equilibrium of even and odd-numbered chains from the beginning, but at low monomer/initiator ratios and short reaction times (<4 h) cyclics are again not formed. They appear at longer reaction times and entail higher dispersities. The results are discussed in terms of five different transesterification mechanisms. KW - Polylactides KW - MALDI KW - Transesterification KW - Sn catalysts PY - 2017 DO - https://doi.org/10.1002/macp.201600331 SN - 1022-1352 VL - 218 IS - 3 SP - 1600331 PB - Wiley AN - OPUS4-39753 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Steppan, Enrico A1 - Mantzke, Philipp A1 - Steffens, Benjamin A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Thermal desorption analysis for hydrogen trapping in microalloyed high-strength steels N2 - Hydrogen can have an extreme degradation effects in steels, particularly concerning the mechanical properties. These effects can lead to hydrogen-assisted cracking in microalloyed high-strength steels during fabrication and/or operation in industrial applications. In order to study these effects, electrochemically charged tensile specimens were tested to elucidate the degradation of their properties. The carrier gas hot extraction (CGHE) method, which functionally combines a mass spectrometer with a thermal desorption analysis (TDA) process, was used for the detection of ultra-low diffusible hydrogen concentrations in the material specimens. The mass spectrometer provided rapid and automatic determination of hydrogen concentration, whereas the TDA presented the activation energy within the respective test specimen at the specific temperature. Additionally, specimen temperature was carefully monitored to reduce the evaluation error for local effusion peaks. A quenching and deformation dilatometer was used for the analysis of typical heat-affected zones during the welding process for a high reproducibility of the homogenous microstructures that were studied. The present work shows the interaction between hydrogen and lattice defects in different microalloyed materials and heat-affected zones of weldable fine-grained steels. These steels were prepared in a quenched and tempered condition and in a thermo-mechanically rolled condition. These preparations were made according to German standard DIN EN 10025-6 and to DIN EN 10149-2, respectively. The trapping characteristics of two steel grades, S690QL and S700MC, were studied with respect to the activation energy dependent on carbon content and microalloying elements such as Ti, Nb, Mo, Cr, and V. The two steel grades exhibited several types of traps: carbide formations, dislocations, and/or grain boundaries were common, which can influence activation energy and hydrogen solubility. The type and dimension of inclusions or particles also affected the hydrogen trapping behavior. A decrease of carbon and specific alloying elements in thermo-mechanically hot rolled steels led to a change in the activation energy binding the trapped hydrogen. This thermo-mechanically hot rolled steel revealed an increased interaction between hydrogen and precipitations. The higher carbon content in the quenched and tempered steel led to a higher interaction between hydrogen and iron carbide, specifically in the martensitic phase. Furthermore, the trapping behavior in heat-affected zones showed a significant increase in activation energy, especially in the coarse-grained microstructure. These previously mentioned various effects were studied to better understand the degradation of mechanical properties in these two steels. KW - Microalloyed steels KW - Hydrogen embrittlement KW - Heating KW - Chemical analysis KW - Microstructure KW - Heat-affected zone PY - 2017 DO - https://doi.org/10.1007/s40194-017-0451-z SN - 0043-2288 SN - 1878-6669 VL - 61 IS - 4 SP - 637 EP - 648 PB - Springer CY - Berlin Heidelberg AN - OPUS4-40190 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stelzner, Ludwig A1 - Powierza, Bartosz T1 - Thermisch induzierter Feuchtetransport in HPC T1 - Thermally induced Moisture Transport in structure density High-performance Concrete N2 - Die Entwicklung von leistungsfähigen Fließmitteln in den letzten Jahrzehnten ermöglicht die Herstellung von Beton mit sehr geringem w/z-Wert, bei gleichzeitig guter Verarbeitbar-keit. Die Reduzierung des w/z-Wertes geht dabei mit einer Erhöhung der Festigkeit und einer Verdichtung der Gefü-gestruktur einher. Aufgrund der hohen Druckfestigkeit finden diese Hochleistungsbetone vermehrten Einsatz im Hoch-, Brücken-, und Tunnelbau. Unter Brandbeanspruchung neigen diese Hochleistungsbetone allerdings zu explosionsartigen Abplatzungen. Diese werden nach derzeitigem Stand auf thermomechanische und thermohydraulische Prozesse zurückgeführt. Letztere beruhen auf der Generierung hoher Wasserdampfdrücke in einseitig brandbeanspruchten Beton-bauteilen, die zum einen auf die geringe Permeabilität des Hochleistungsbetons und zum anderen auf die Bildung einer wassergesättigten Zone, der sogenannten „moisture clog“ zurückzuführen sind. Dabei spielen Verdampfungs- und Kondensationsvorgänge sowie der vorhandene Temperatur-gradient eine wichtige Rolle. Die Interaktion des Feuchtetra-nsportes mit den Gefügeveränderungen während der thermi-schen Beanspruchung soll im Rahmen weiterer Versuche eingehend untersucht werden. Zur Analyse des Feuchtetransports während der thermischen Beanspruchung wurden miniaturisierte Prüfkörper aus Hoch-leistungsbeton hergestellt, die mit Hilfe eines elektrischen Heizelements einseitig erwärmt wurden. Zur Sicherstellung eines eindimensionalen Wärme- und Feuchtetransportes ist der Betonprüfkörper mit einer speziellen Glaskeramik und einer Hochtemperaturwolle ummantelt. Simultan zur Erwär-mung werden eine Reihe röntgentomographischer Aufnah-men durchgeführt. Durch Differenzbildung aufeinanderfol-gender Aufnahmen können Dichteveränderungen lokal und zeitlich aufgelöst werden. Diese lassen Rückschlüsse auf Än-derungen der Feuchteverteilung im Prüfkörper während der Erwärmung zu. Parallel dazu werden Untersuchungen mittels NMR-Relaxometrie (nuclear magnetic resonance) vor und nach der thermischen Beanspruchung durchgeführt. Diese Prüfmethodologie ermöglicht es erstmals, die Veränderungen der Feuchteverteilung infolge thermischer Beanspruchung im Hochleistungsbeton von den Gelporen bis hin zu vorhande-nen Verdichtungsporen abzubilden. So zeigen erste Ergebnis-se, dass die gewählten Untersuchungsmethoden Veränderun-gen der Feuchteverteilung im Prüfkörper räumlich und zeitlich auflösen können. KW - Abplatzen KW - Spalling KW - Brand KW - Feuchtetransport KW - Hochleistungsbeton KW - Röntgen-3D-Computertomographie KW - NMR KW - Fire KW - Moisture clog KW - Moisture transport KW - HPC KW - HSC KW - X-ray CT PY - 2017 DO - https://doi.org/10.1002/best.201700022 SN - 0005-9900 SN - 1437-1006 VL - 112 IS - 7 SP - 486 EP - 486 PB - Ernst & Sohn CY - Berlin AN - OPUS4-41826 LA - deu 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 - Kühn, Hans-Joachim A1 - Rehmer, Birgit A1 - Skrotzki, Birgit T1 - Thermomechanical fatigue of heat-resistant austenitic cast iron EN-GJSA-XNiSiCr35-5-2 (Ni-Resist D-5S) N2 - TMF tests were carried out on EN-GJSA-XNiSiCr35-5-2 at constant minimum temperature (400 °C) and varying maximum temperatures (Tmax = 700 °C, 800 °C, 900 °C) with hold times of 180 s at Tmax and two phase angles (in-phase (IP), 180° out-of-phase (OP)). The results showed a comparable strength under OP- and IP-TMF loading. At Tmax = 700 °C and 900 °C, the lifetime in IP-tests was slightly longer than that of OP-tests, while it is vice versa at Tmax = 800 °C. The IP-tests at Tmax = 900 °C showed a similar lifetime as OP-tests at Tmax = 700 °C and 800 °C, which was unexpected for such a high testing temperature. All IP-tests at Tmax = 900 °C showed a continuous cyclic softening from the beginning on, which was different from all other testing conditions. Complementary metallographic investigations indicated that under this test condition, intergranular creep damage is present in the volume of the test pieces. T2 - 3rd International Workshop on Thermo-Mechanical Fatigue (TMF-Workshop 2016) CY - Berlin, Germany DA - 27.04.2016 KW - Cast iron KW - Cracks KW - Cyclic softening KW - Microscopy KW - Thermomechanical fatigue PY - 2017 DO - https://doi.org/10.1016/j.ijfatigue.2017.01.009 SN - 0142-1123 SN - 1879-3452 VL - 99 IS - 2 (Special issue: Recent developments in thermo-mechanical fatigue) SP - 295 EP - 302 PB - Elsevier CY - Oxford AN - OPUS4-39680 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -