Papers by Keyword: X-Ray Diffraction (XRD)

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Authors: Sylvain Jacques, Houssam Fakih
Abstract: Thin (SiC/Ti3SiC2)n multi-layered coatings were deposited at 1100°C on ceramic substrates by chemical vapour deposition (CVD) methods. Each SiC sub-layer was classically processed from H2/CH3SiCl3. Each Ti3SiC2 sub-layer was obtained by reactive CVD (RCVD) from a H2/TiCl4 gaseous mixture reacting on each SiC solid sub-layer that was previously deposited. The growth of Ti3SiC2 by RCVD involves partial or total SiC consumption. The H2/TiCl4 ratio was chosen on the basis of a thermodynamic study. Using a sufficiently high H2/TiCl4 ratio and limiting the sub-layer thickness allowed the formation of TiC or binary titanium silicides to be avoided. By using a constant low gas pressure in the CVD reactor, it was possible to obtain nearly pure Ti3SiC2 sub-layers as thin as 0.8 μm. In that case, the ternary compound exhibits basal planes oriented perpendicular to the substrate surface. A way to obtain thinner sub-layers was the use of a pressurepulsed CVD method. In addition, the pressure-pulsed method allowed the preferential orientation to be prevented in the Ti3SiC2 coating.
Authors: Christoph Seitz, Z.G. Herro, Boris M. Epelbaum, Albrecht Winnacker, Rainer Hock, Andreas Magerl
Abstract: A structural characterisation of the first [01-15] grown 6H SiC crystals is presented. They show a different micro domain structure outside the facetted region as compared to conventionally [0001] grown crystals. It is imposed by the reduced rotational symmetry for this direction which favours the activation of a low number of glide systems.
Authors: Ian C. Madsen, Ian E. Grey, Stuart J. Mills
Abstract: A study of the thermal decomposition sequence of a sample of natural arsenian plumbojarosite has been undertaken using in situ X-ray diffraction. The sample was heated to 900°C using an Anton-Paar heating stage fitted to an INEL CPS120 diffractometer. The data were analysed using a whole-pattern, Rietveld based approach for the extraction of quantitative phase abundances. The instrument configuration used required the development and application of algorithms to correct for aberrations in the (i) peak intensities due to differing path lengths of incident and diffracted beams in the sample and (ii) peak positions due to sample displacement. Details of the structural models used were refined at selected steps in the pattern and then fixed for subsequent analysis. The data sequence consists of some 110 individual data sets which were analysed sequentially with the output of each run forming the input for analysis of the next data set. The results of the analysis show a complex breakdown and recrystallisation sequence including the formation of a major amount of amorphous material after initial breakdown of the plumbojarosite.
Authors: Liang Xu, Chuan Zhen Huang, Han Lian Liu, Bin Zou, Hong Tao Zhu, Jun Wang
Abstract: The TiB2 whiskers were fabricated in TiB2/TiCx composites by the in-situ synthesis process. The phase composition, thermodynamics, weight loss and lattice parameters of the obtained phases were studied. The obtained TiB2 whiskers showed an aspect ratio of 10-20 and a diameter of 0.5-1.5 μm. The synthesized TiC was a non-stoichiometric phase with a lattice parameter of 4.274 Å. Most of the whiskers had the cylinder shape, whereas, a few whiskers showed a bead-necklace morphology. The growth mechanisms of TiB2 whiskers were governed by the solid-liquid-solid (S-L-S) mechanism and the particle-to-particle connection mechanism.
Authors: Alain Jacques, Laura Dirand, Jean Philippe Chateau, Thomas Schenk, Olivier Ferry, Pierre Bastie
Abstract: The combination of high temperature (1050°C -1150°C) testing and in situ high energy X-Ray diffraction measurements using synchrotron Three Crystal Diffractometry may give various insights into the mechanical behaviour of superalloys: measurement of the lattice mismatch, order within the ' phase, elastic constants, and dynamic response to changes in the experimental conditions. Several examples are given on the rafted AM1 superalloy, resulting from experiments at the ID15A (ESRF) and BW5 (DESY) high energy beamlines.
Authors: C. M. Hefferan, S. F. Li, J. Lind, Ulrich Lienert, Anthony D. Rollett, R.M. Suter
Abstract: We have used high energy x-ray diffraction microscopy (HEDM) to study annealing behavior in high purity aluminum. In-situ measurements were carried out at Sector 1 of the Advanced Photon Source. The microstructure in a small sub-volume of a 1 mm diameter wire was mapped in the as-received state and after two differential anneals. Forward modeling analysis reveals three dimensional grain structures and internal orientation distributions inside grains. The analysis demonstrates increased ordering with annealing as well as persistent low angle internal boundaries. Grains that grow from disordered regions are resolution limited single crystals. Together with this recovery behavior, we observe subtle motions of some grain boundaries due to annealing.
Authors: Masahito Watanabe, Akitoshi Mizuno, Toshihiko Akimoto, Shinji Kohara
Abstract: It is well known that multi-component alloys form bulk metallic glasses (BMGs) from the supercooled liquid state without rapid quenching. However, the mechanism of phase selection between crystal and glass states has not been fully clarified. To obtain an insight into the glass-forming processes, we carried out in-situ observation on the solidification of Zr-based BMG-forming alloys from its supercooled liquids by time-resolved X-ray diffraction combined with the conical nozzle levitation (CNL) technique to achieve a containerless melting. For Zr-based alloys, we succeeded in detecting the X-ray diffraction patterns during glass formation from the supercooled liquid state as well as the crystallization from the liquid state. Furthermore we performed the precise structure analysis of supercooled state of Zr-based binary liquids. Based on the liquid structure and in-situ observation results, we discussed about the phase selection mechanism between crystal and glass states.
Authors: Arne Kromm, Thomas Kannengiesser
Abstract: Results obtained from laboratory tests mostly need to be verified under fabrication conditions in order to incorporate design specifics (joint configuration and restraint), which effect the residual stress state considerably. For this purpose, multi-pass sub merged arc welding was performed in a special large-scale testing facility. The impact of varying interpass temperatures could be proven in-situ by means of a pronounced stress accumulation during welding and subsequent heat treatment accompanied by stress determination using X-ray diffraction.
Authors: Dong Ying Ju, J.G. Wang, Minoru Abe
Abstract: The purpose of this investigation is to detect damage from stress distribution in the surface of near pre-crack tip by using X-ray diffraction technique during biaxial tension test. An measurements apparatus to measure stress distribution along pre-crack direction was fabrication by use of a biaxial tensile test device and a stress analyzer based on single exposure technique with one position sensitive proportional counter. Stress distribution with different tensile applied stress ratios were measured during biaxial tension test. As results, the shape of actual stress was keeping increase with increasing tensile applied stress. At maximum applied stress, the residual stress increases with the increasing distance from the crack tip; after reaching a maximum it gradually diminish.
Authors: Francisco Manuel Braz Fernandes, Karimbi Koosappa Mahesh, Corneliu Marius Crăciunescu, João Pedro Oliveira, Norbert Schell, Rosa Maria Miranda, Luisa Quintino, José Luis Ocaña
Abstract: The demand of emerging joining techniques for shape memory alloys (SMA) has become of great importance, as their functional properties, namely shape memory effect (SME) and superelasticity (SE) present unique solutions for state-of-the-art applications. Literature shows that significant efforts have been conducted on laser welding of these alloys, although very limited results concerning mechanical properties are repeatedly achieved. A better understanding of the mechanical behaviour of these welded joints may be got through a detailed analysis of the structural characteristics of the material from the base metal to the weld bead. Such studies have been carried out on a series of Ni-rich Ni-Ti SMA laser welded plates using synchrotron radiation.
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