TY - JOUR A1 - Zocca, Andrea A1 - Colombo, P. A1 - Günster, Jens A1 - Mühler, T. A1 - Heinrich, J.G. T1 - Selective laser densification of lithium aluminosilicate glass ceramic tapes JF - Applied surface science N2 - Tapes, cast by blade deposition of a lithium aluminosilicate glass slurry, were sintered using a YAG-fiber laser, with the aim of finding suitable parameters for an additive manufacturing process based on layer-wise slurry deposition and selective laser densification. The influence of the laser parameters (output power and scan velocity) on the sintering was evaluated, by scanning electron microscopy and by X-ray diffraction, on the basis of the quality of the processed layer. Well densified samples could be obtained only in a small window of values for the output power and the scan velocity. The measurement of the width of a set of single scanned lines allowed also to estimate the minimum resolution of the system along the layer plane. KW - Selective laser sintering (SLS) KW - Laserwise-slurry-deposition (LSD) KW - Glass-ceramic KW - LAS PY - 2013 UR - http://ac.els-cdn.com/S0169433212020168/1-s2.0-S0169433212020168-main.pdf?_tid=4ba0c92c-31d4-11e4-84f1-00000aab0f02&acdnat=1409575040_15d5256291262aca99cc5321374ab879 DO - https://doi.org/10.1016/j.apsusc.2012.11.058 SN - 0169-4332 SN - 1873-5584 VL - 265 SP - 610 EP - 614 PB - North-Holland CY - Amsterdam AN - OPUS4-31283 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhou, Z. A1 - Han, Q. A1 - Wang, D. A1 - Macé, T. A1 - Kipphardt, Heinrich A1 - Maiwald, Michael A1 - Tuma, Dirk A1 - Uehara, S. A1 - Akima, D. A1 - Shimosaka, T. A1 - Jung, J. A1 - Oh, S.-H. A1 - van der Veen, A. A1 - van Wijk, J.I.T. A1 - Ziel, P. R. A1 - Konopelko, L. A1 - Valkova, M. A1 - Mogale, D.M. A1 - Botha, A. A1 - Brewer, P. A1 - Murugan, A. A1 - Minnaro, M.D. A1 - Miller, M. A1 - Guenther, F. A1 - Kelly, M.E. T1 - CCQM K101 Final report international comparison CCQM-K101:Oxygen in nitrogen-a track B comparison and that the matrix contains argon JF - Metrologia N2 - This key comparison aims to assess the capabilities of the participants to determine the amount-of-substance fraction oxygen in nitrogen. The GAWG has classified this as a track B comparison, due to the unexpected 50 μmol/mol argon mole fraction content of the transfer standards, which effects the achievable performance of some measurement techniques such a GC-TCD. The separation of oxygen and argon is challenging, and not all systems in use are equally well designed for it. As this analytical challenge due to a substantial fraction of argon in the transfer standards became a reality, the Gas Analysis Working Group (GAWG) decided to qualify this key comparison as a regular key comparison and not as a core comparison, which may be used to support calibration and measurement capabilities (CMCs) for oxygen in nitrogen, or for oxygen in nitrogen mixtures containing argon only (see also the section on support to CMCs). KW - CCQM-K101 KW - Gas analysis PY - 2016 UR - http://iopscience.iop.org/article/10.1088/0026-1394/53/1A/08013 SN - 1681-7575 SN - 0026-1394 VL - 53 IS - Techn Suppl SP - 08013, 1 EP - 71 PB - IOP publishing AN - OPUS4-40013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zehbe, R. A1 - Riesemeier, Heinrich A1 - Kirkpatrick, C.J. A1 - Brochhausen, C. T1 - Imaging of articular cartilage - data matching using X-ray tomography, SEM, FIB slicing and conventional histology JF - Micron N2 - The study was aimed at demonstrating a true cellular resolution for articular cartilage using synchrotron radiation-based X-ray microcomputed tomography (SR-µCT) with a sample-specific optimization of the phase contrast. The generated tomographic data were later used to prepare a matching histological sample from the full volume specimen. We used highly coherent and monochromatic X-rays from a synchrotron source to image a tissue sample of bovine articular cartilage after deparaffinization. Phase contrast enhancement was achieved by using five different sample to detector distances for the same X-ray energy. After tomography, the sample was re-embedded into resin while retaining a dedicated sample orientation for subsequent sectioning and polishing, which was conducted until a previously defined spatial position was achieved. The protocol for resin embedding was developed to inhibit morphological changes during embedding. Giemsa staining was applied for better structural and morphological discrimination. Data from tomography and lightmicroscopy were exactly matched and finally compared to results from FIB/SEM imaging. Image detail was achieved at a single cell resolution. Image detail was achieved at a single cell resolution, which has been estimated to be 0.833 µm/voxel in the tomographic data. SR-µCT with optimized phase contrast properties represents a method to investigate biological tissues in certain areas of interest, where true cellular resolution or enhanced volumetric imaging is needed. In this study, we demonstrate that this method can compete with conventional histology using light microscopy but even surpasses it due to the possibility of retrieving volumetric data. KW - Synchrotron radiation-based µCT KW - Phase contrast KW - FIB/SEM imaging KW - Histology KW - Articular cartilage KW - Data matching PY - 2012 DO - https://doi.org/10.1016/j.micron.2012.05.001 SN - 0047-7206 SN - 0968-4328 VL - 43 IS - 10 SP - 1060 EP - 1067 PB - Pergamon Press CY - Oxford AN - OPUS4-26435 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zehbe, R. A1 - Haibel, A. A1 - Riesemeier, Heinrich A1 - Gross, U. A1 - Kirkpatrick, C.J. A1 - Schubert, H. A1 - Brochhausen, C. T1 - Going beyond histology. Synchrotron micro-computed tomography as a methodology for biological tissue characterization: from tissue morphology to individual cells JF - Interface : journal of the Royal Society N2 - Current light microscopic methods such as serial sectioning, confocal microscopy or multiphoton microscopy are severely limited in their ability to analyse rather opaque biological structures in three dimensions, while electron optical methods offer either a good three-dimensional topographic visualization (scanning electron microscopy) or high-resolution imaging of very thin samples (transmission electron microscopy). However, sample preparation commonly results in a significant alteration and the destruction of the three-dimensional integrity of the specimen. Depending on the selected photon energy, the interaction between X-rays and biological matter provides semi-transparency of the specimen, allowing penetration of even large specimens. Based on the projection-slice theorem, angular projections can be used for tomographic imaging. This method is well developed in medical and materials science for structure sizes down to several micrometres and is considered as being non-destructive. Achieving a spatial and structural resolution that is sufficient for the imaging of cells inside biological tissues is difficult due to several experimental conditions. A major problem that cannot be resolved with conventional X-ray sources are the low differences in density and absorption contrast of cells and the surrounding tissue. Therefore, X-ray monochromatization coupled with a sufficiently high photon flux and coherent beam properties are key requirements and currently only possible with synchrotron-produced X-rays. In this study, we report on the three-dimensional morphological characterization of articular cartilage using synchrotron-generated X-rays demonstrating the spatial distribution of single cells inside the tissue and their quantification, while comparing our findings to conventional histological techniques. KW - Cartilage KW - Chondrocyte KW - Synchrotron micro-computed tomography KW - Histology KW - Scanning electron microscopy KW - Three-dimensional imaging PY - 2010 DO - https://doi.org/10.1098/rsif.2008.0539 SN - 1742-5689 SN - 1742-5662 VL - 7 SP - 49 EP - 59 PB - The Royal Society CY - London AN - OPUS4-22123 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zabler, S. A1 - Rueda, A. A1 - Rack, A. A1 - Riesemeier, Heinrich A1 - Zaslansky, P. A1 - Manke, I. A1 - Garcia-Moreno, F. A1 - Banhart, J. T1 - Coarsening of grain-refined semi-solid Al-Ge32 alloy: X-ray microtomography and in situ radiography JF - Acta materialia KW - Microtomography KW - Radiography KW - 2D/3D imageanalysis KW - Technical binary alloys KW - LSW PY - 2007 DO - https://doi.org/10.1016/j.actamat.2007.05.028 SN - 1359-6454 SN - 1873-2453 VL - 55 IS - 15 SP - 5045 EP - 5055 PB - Elsevier Science CY - Kidlington AN - OPUS4-20583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zabler, S. A1 - Rack, A. A1 - Manke, I. A1 - Thermann, K. A1 - Tiedemann, J. A1 - Harthill, N. A1 - Riesemeier, Heinrich T1 - High-resolution tomography of cracks, voids and micro-structure in greywacke and limestone JF - Journal of structural geology N2 - Rocks are commonly very heterogeneous materials. Randomly distributed micro-flaws inside the rock are believed to initiate tensile cracks from which shear fractures develop and coalescence through en echelon interactions leads to fracture. In this paper, we describe the results of applying high-resolution X-ray tomography to samples of greywacke and limestone experimentally deformed under unconfined axial shortening at various loads equivalent to different fractions of the sample strength. Mineral grains, pores, micro-cracks and other voids were imaged with a resolution of 10 µm. 3D image analysis enabled us to monitor the initial state of the samples and the changes in them due to compression. Crack morphology is characterized and compared to the micro-structure of the sample before and after deformation. In the greywacke, formation of a macro-crack ~10° oblique to the stress direction is observed. It initiated in fine intergranular material at the top tip of the sample and is composed of tensile fractures connected by wing cracks. None of the voids defined in the initial state fractured, and the crack is interpreted to have started either as a micro-crack which was smaller than the resolution of the tomography, or, as a completely new crack. In the limestone, cracks are observed to initiate in features that are too small to be imaged by the tomography, or also in newly created cracks. KW - Rock porosity KW - Crack formation KW - X-ray imaging KW - Micro-tomography KW - 3D image analysis PY - 2008 DO - https://doi.org/10.1016/j.jsg.2008.03.002 SN - 0191-8141 SN - 1873-1201 VL - 30 IS - 7 SP - 876 EP - 887 PB - Pergamon Press CY - Oxford AN - OPUS4-18566 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yao, Dongxu A1 - Xia, Y. A1 - Zuo, K.-h. A1 - Zeng, Y.-P. A1 - Jiang, D. A1 - Günster, Jens A1 - Heinrich, J.G. T1 - Gradient porous silicon nitride prepared via vacuum foaming and freeze drying JF - Materials letters N2 - Gradient porous silicon nitride (Si3N4) was fabricated by a novel vacuum foaming and freeze drying process. Aqueous Si3N4 slurries were foamed at vacuum pressure of 50–90 kPa, the green body was obtained by the freeze drying process, a gradient pore structure with porosities of 72–90% was achieved after pressureless sintering at 1680 °C. The porosity was increased with decreasing vacuum pressure. The pore structure consists of large pores (~100 μm) on top, medium pores (~45 μm) on the wall of the large pores, and small pores (~0.7 μm) in the matrix. Such gradient porous Si3N4 with macro- and micro-pores has potential application as high temperature filters. KW - Silicon nitride KW - Graded PY - 2015 DO - https://doi.org/10.1016/j.matlet.2014.11.067 SN - 0167-577x SN - 1873-4979 VL - 141 SP - 138 EP - 140 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-35177 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yao, Dongxu A1 - Xia, Y. A1 - Zuo, K.-h. A1 - Jiang, D. A1 - Günster, Jens A1 - Zeng, Y.-P. A1 - Heinrich, J.G. T1 - Porous Si3N4 ceramics prepared via partial nitridation and SHS JF - Journal of the European Ceramic Society N2 - Porous Si3N4 ceramics were prepared via partial nitridation and self-propagating high temperature synthesis (SHS) process. Raw Si and additive Y2O3 were mixed and molded under 10 MPa into a compact, the compact was partial nitridation at 1300 °C to form a porous Si/Si3N4, and then it was buried in a Si/Si3N4 bed for SHS to obtain porous Si3N4 with rod-like β-Si3N4 morphology. The processing combined the advantages of the nitridation of Si and SHS with low cost, low shrinkage and time saving. Porous Si3N4 with a porosity of 47%, a strength of 143 MPa were obtained by this method. KW - Si3N4 KW - Strength KW - Porosity PY - 2013 DO - https://doi.org/10.1016/j.jeurceramsoc.2012.08.033 SN - 0955-2219 SN - 1873-619X VL - 33 IS - 2 SP - 371 EP - 374 PB - Elsevier CY - Oxford AN - OPUS4-31282 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yao, Dongxu A1 - Xia, Y. A1 - Zuo, K.-h. A1 - Jiang, D. A1 - Günster, Jens A1 - Zeng, Y.-P. A1 - Heinrich, J.G. T1 - The effect of fabrication parameters on the mechanical properties of sintered reaction bonded porous Si3N4 ceramics JF - Journal of the European Ceramic Society N2 - Porous silicon nitride ceramics were prepared via sintered reaction bonded silicon nitride at 1680 °C. The grain size of nitrided Si3N4 and diameter of post-sintered ß-Si3N4 are controlled by size of raw Si. Porosity of 42.14–46.54% and flexural strength from 141 MPa to 165 MPa were obtained. During post-sintering with nano Y2O3 as sintering additive, nano Y2O3 can promote the formation of small ß-Si3N4 nuclei, but the large amount of ß-Si3N4 (>20%) after nitridation also works as nuclei site for precipitation, in consequence the growth of fine ß-Si3N4 grains is restrained, the length is shortened, and the improvement on flexural strength is minimized. The effect of nano SiC on the refinement of the ß-Si3N4 grains is notable because of the pinning effect, while the effect of nano C on the refinement of the ß-Si3N4 grains is not remarkable due to the carbothermal reaction and increase in viscosity of the liquid phase. KW - Porous ceramics KW - Silicon nitride KW - Reaction bonding KW - Anisotropic grain growth KW - Ceramic PY - 2014 DO - https://doi.org/10.1016/j.jeurceramsoc.2014.06.018 SN - 0955-2219 SN - 1873-619X VL - 34 IS - 15 SP - 3461 EP - 3467 PB - Elsevier CY - Oxford AN - OPUS4-32542 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yao, Dongxu A1 - Wirth, Cynthia A1 - Zeng, Y.-P. A1 - Jiang, D. A1 - Günster, Jens A1 - Heinrich, J. T1 - Near zero shrinkage porous Al2O3 prepared via 3D-printing and reaction bonding JF - Materials letters N2 - Porous Al2O3 with high porosity (~45%), remarkable flexural strength (~70 MPa), and low dimensional change (~1–2%), was produced by indirect 3D printing and reaction bonding. Coarse Al with good flowability was carried out printing green body. The green body was heat treated to get fully oxidized, volume expansion during oxidation simultaneously formed strong neck bonding, not only brought good strength, but also restricted shrinkage. Porous Al2O3 with architecture of macro pores designed by 3D printing and micro pores in the strut formed by packing of particles was obtained. The near zero shrinkage can facilitate precise design of product with complex shape. KW - Al2O3 reaction bonding PY - 2015 DO - https://doi.org/10.1016/j.matlet.2015.02.037 SN - 0167-577x SN - 1873-4979 VL - 147 SP - 116 EP - 118 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-34960 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -