Papers by Keyword: Synchrotron Radiation (XRD)

Abstract: The quantitative evaluation of the preferential orientation of crystallites by the synchrotron and neutron diffraction techniques during regeneration at the interface with implant gives a good prediction of the mechanical properties of the bone. During the process of bone healing after implantation, the speed and quality of regeneration is affected by the nature of the implant surface. Titanium alloy (Ti-Al-4V) is currently coating with the hydroxyapatite (HAp), Ca10(PO4)6 (OH)2, in order to obtain a stable and functional direct connection between bone and implant. At the interface implant-bone, the new bone reconstituted after implantation must have the same mechanical properties of bone in order to accept the implant. Therefore, it is necessary to study by means of two non destructive techniques: neutron diffraction and synchrotron radiation, the crystal growth and texture of this new bone crystals reconstituted at the interface.

Abstract: Residual stresses near the grain boundary of a bicrystal were measured by synchrotron radiation of SPring-8 at Japan Synchrotron Radiation Research Institute. A copper bicrystal specimen with a 90-degree tilt boundary was deformed 30% in tension. After the plastic extension, kink bands developed in a deformed matrix along the grain boundary. In this study, we focused on the residual stresses in the deformed matrix and the kink band. Residual stresses were evaluated by the X-ray single crystal measurement method. Stereographic projections were used to determine crystal orientations of deformed regions. Our observation showed that crystal orientations were different between the deformed matrix and the kink band. Residual stresses in the direction along the grain boundary in the deformed matrix and kink band were compressive. Residual stresses in the direction vertical to the grain boundary were seen opposite between the deformed matrix and the kink band.

Abstract: In this study, the authors made an experiment to observe the residual stress state in the surface of the engineered parts (for example, shot-peened steel) by X-ray stress measurement. An evaluation method was proposed for the stress gradient from the information on the X-ray Debye ring obtained with an area detector. The method utilized the fact that the X-ray penetration depth is a function of the central angle of the Debye ring α. It varies due to a section of Debye ring. It also depends on the incidence angle of X-rays and the wavelength used. Mean stress over the whole penetration depths of X-rays, which is defined as the Laplace stress, was measured by the cosα method[1, 2] by using this characteristic, and the real space stress[3-5] gradient was evaluated.

Abstract: The potential for Mg and Mg-Ni alloys to be used as hydrogen storage alloys has been known for some time. Although the maximum storage capacity in these alloys is high (7.6wt%H2 for Mg and 3.4wt%H2 for Mg2Ni), they have, until recently, been disregarded for practical applications due to their slow kinetics and high reaction temperatures. This paper discusses the recent discovery that the non-faceted/faceted hypo-eutectic Mg-Mg2Ni system can, similar to Al-Si eutectic alloys, be modified by trace additions and that this results in improved hydrogen storage properties. The hydrogen storage properties depend on the composition, including trace levels of modifying elements, and processing conditions. In alloys of optimal composition it has been shown that the reversible storage of 6.5-7wt% H2 is possible at a rate of reaction that is far better than that previously documented. In addition, the alloy can be satisfactorily processed in air, as opposed to controlled atmospheric conditions. This paper discusses the mechanism of improved hydrogen absorption/desorption kinetics when eutectic Mg-Ni hypo-eutectic alloys are modified. This discussion is based on atomic scale analysis using electron microscopy and examination with synchrotron radiation.

Abstract: Hydroxyapatite (HAP) crystalline thin-coatings have been grown using a right angle RF magnetron sputtering approach at room temperature. The surface structural information of these biocompatible coatings at nanometer scales was obtained by glancing-incidence X-ray diffraction (GIXRD) with synchrotron radiation. The GIXRD spectra were obtained by fixed incidence theta angles at 0.5 and 1 degree. Structural profile analyses were performed over these nano-coating layers with reduced substrate interference. The coating thickness was calibrated by specular X-ray reflectivity (XRR) curves. Experiments have been performed on thin-coatings of HAP sputtered on silicon wafers and acid etched titanium discs at room temperature. GIXRD analysis has shown that all the principal peaks are attributed to a crystalline HAP. Previous tests of biocompatibility with osteoblasts cells have been encouraging studies on the surface of hydroxyapatite thin coatings prepared by opposing RF magnetron sputtering approach, as a promising candidate for bioimplant materials.

Abstract: Diamond-cobalt composites are used for cutting tools. Residual stress after manufacture can reduce the lifetime of such composite cutting tools and, hence, the stress state needs to be well understood. Within this study, stress measurements on a cobalt diamond composite were made by SXRD to deduce stress states in the cobalt matrix using the (222) reflection. The application of different apertures allowed the investigation of stress in small areas of cobalt surrounding a diamond and in areas at different distances to a diamond. In the areas adjacent to the diamond increased residual stresses were found in the cobalt matrix. Furthermore, approximations for radial and tangential residual stresses have been derived which show to be different.

Abstract: The railway carbody structure for commuter and suburban train services in Japan is often made of austenitic stainless steel, which is used in the form of thin metal sheets manufactured by cold rolling. Spot welding and laser welding at lapped joints are used in the construction of such carbodies, but it is difficult to observe the strain distribution around these weld zones, which represent the critical area of the body structure’s strength. The objective of this study is to ascertain the strain distribution in the stainless steel around the weld zone of the carbody structure. To enable observation of this distribution, a strain scanning method using high-energy synchrotron radiation was applied to the strain measurement of austenitic stainless steel. The transmission method was applied in order to observe the internal weld zone. Using this method, we can measure the strain distribution from the surface to the inside of the weld zone. A lapped joint specimen, prepared by welding 2-mm-thick plates using the laser welding method, was used for measurement. Austenitic stainless steel generally poses problems in the measurement of strain due to its coarse grain and crystal texture. The gage volume in this measurement had a width of 3 mm and a height of 0.15 mm. The measurement provides the strain distribution of both residual strain and strain under loading, and the results obtained successfully show the distribution of strain in the weld zone. In addition, the differing tendency between the distribution of residual strain and that of strain under loading is clarified. The full width at half maximum (FWHM) value shows a difference between the tendency of the measured value of the weld zone and that of the base material.

Abstract: The future High Energy Materials Science Beamline HEMS at the new German high brilliance synchrotron radiation storage ring PETRA III [1] will have a main energy of 120 keV, will be fully tunable in the range of 50 to 300 keV, and will be optimized for sub-micrometer focusing with Compound Refractive Lenses and Kirkpatrick-Baez Multilayer mirrors. Design and construction is the responsibility of the Research Center Geesthacht, GKSS, with approximately 70 % of the beamtime being dedicated to Materials Research, the rest reserved for “general physics” experiments covered by DESY, Hamburg. Fundamental research will encompass metallurgy, physics and chemistry. For first experiments in investigating grain-grain-interactions a dedicated 3D-microstructure-mapper will be designed. Applied research for manufacturing process optimization will benefit from the high flux in combination with ultra-fast detector systems allowing complex and highly dynamic in-situ studies of microstructural transformations. The beamline infrastructure will allow easy accommodation of large user provided equipment. Experiments targeting the industrial user community will be based on well established techniques with standardised evaluation, allowing "full service" measurements. Environments for strain mapping [2] on large structural components up to 1 t will be provided as well as automated investigations of large numbers of samples, e.g. for tomography and texture determination. The current design for the beamline (P07 in sector 5 of the future experimental hall) consists of a nearly five meter in-vacuum undulator source (U19-5) optimized for high energies, a general optics hutch, an in-house test facility and three independent experimental hutches working alternately, plus additional set-up and storage space for long-term experiments. HEMS should be operational in spring 2009 as one of the first beamlines running at PETRA III.

Abstract: This paper presents a basic research on a measurement of strain in the bulk of materials by using high energy white X-ray from a synchrotron radiation source of SPring-8 in Japan. A high-tensile strength steel (JIS-SHY685) was used as a specimen loaded with bending. Strain distribution in it was evaluated by the energy dispersive method using diffracted X-ray transmitted through the specimen. As a result, the internal strain of high-tensile steel of 5, 10 and 15 mm thickness could be evaluated using white X-ray which range of energy from 50 keV to 150 keV. The measurement with a high degree of accuracy was accomplished using α-Fe321 diffraction in this material. The results showed that the internal strain measurement in the depth of the order of millimeter using the high energy white X-ray is practicable at SPring-8.

Abstract: At the HARWI II beamline at the GKSS outstation at DESY a new experiment for position sensitive diffractometry and tomography called DITO was built and commissioned this year. Due to the available high energy synchrotron radiation with photon energies up to 100 keV it is possible to investigate the bulk of metallic samples of a few mm thickness with both methods. The diffractometry detector allows the investigation of the phase composition as well as phase sensitive determination of residual stresses with a spatial resolution of 6 μm while the tomography detector can either measure a whole tomogram in high resolution mode with a spatial resolution of 2 μm within 3 to 4 hours or in high speed mode recording a whole tomogram within 15 seconds with a spatial resolution of 40 μm.