Papers by Keyword: Energy Dispersive X-Ray Diffraction

Abstract: In situ monitoring of structural changes, taking place upon calcium phosphate bone cements hardening process was carried out by means of the Energy Dispersive X-Ray Diffraction method. Two different cement systems were studied, one of them based on the octacalcium phosphate and another - on the dicalcium phosphate dehydrate. Both systems contained natural biopolymer chitosan and were soaked in Simulated Body Fluid. The obtained experimental results evidence that during the hardening of the cement containing octacalcium phosphate its partial transformation into hydroxyapatite takes place, whereas no significant changes were detected during the hardening process of cement containing the dicalcium phosphate dehydrate.

Abstract: The occurrence of arsenic in natural water has received significant attention during recent years. The arsenic plays an important role for its behavior and toxicity in the aqueous system. Arsenic is a toxic pollutant in water with serious health effects upon long-term intake of even low concentrations through drinking water consumption population. By means of the energy-dispersive X-ray diffraction (EDXRD) technique, confected different concentrations of sodium arsenate solution and reservoir water of Tuoketuo county in the Inner Mongolia, were analyzed. The result shows that arsenic is present within reservoir water of Tuoketuo county. But, fluorescence peak photons of arsenic in the solution are not in proportion to the concentration. So, it is difficulty to quantitatively decide the concentration of the arsenic in the water.

Abstract: Lead zirconate titanate (PZT)-Portland cement (PC) composites were produced and successfully poled at different poling field and time. The effect of polarization on the microstructure and piezoelectric properties were then investigated. It was found that, at a fixed poling field up to 2 kV/mm, the piezoelectric coefficient (d33) was found to increase with poling time. The optimum poling time was found at 45 minutes where d33 value is 42 pC/N. The optimum and most practical poling field found for the composite was at 2 kV/mm. Lower poling field would give the composite lower piezoelectricity and poling field that is too high would result to breakdown of samples. Therefore, from these results, a poling field of 2 kV/mm at 45 minutes would be the ideal polarization condition used in poling PZT-PC composites.

Abstract: Internal stresses are very important for the performance of protective hard coatings. Tensile stresses favour the formation and propagation of cracks, inducing fracture and corrosion. Medium compressive stresses hinder fatigue. But high compressive stresses, typically for hard coatings produced by PVD (physical vapour deposition) processes, support delamination in order to relax the stored elastic energy. However notwithstanding its relevance, the internal stresses are only seldom used for the optimisation and quality control of hard coatings in industry. This unsatisfying situation is caused by the deficit in efficient measuring methods. The results of thin sheets, where the stresses can be simply measured by their curvature, are not necessarily representative for the coating of thicker parts. The conventional XRD (X-ray Diffraction), based on angle-dispersive evaluation needs expensive devices and is rather time consuming. The energy-dispersive technique opens new possibilities. It is based on polychromatic radiation. The interference of the lattice plane reflections corresponding to the Bragg-equation is investigated by the diffraction intensity of the different wavelength (or photon energies), not by varying the Bragg-angle as in conventional XRD. Hence, the whole diffraction pattern can be obtained in one shoot without the use of any goniometer. This allows the construction of small and compact measuring devices and the reduction of measuring time to a few minutes. The capability of the ED-XRD (Energy Dispersive X-ray Diffraction) is demonstrated for titanium nitride and chromium nitride films deposited by cathodic vacuum arc with varying parameters. Comparisons were made with the much more time-consuming AD-XRD (Angle Dispersive X-ray Diffraction) for residual stress analysis. The results of both methods are in good agreement.

Abstract: Diffraction of penetrating radiation such as neutrons or high energy X-rays provides a powerful non-destructive method for the evaluation of residual stresses in engineering components. In particular, strain scanning using synchrotron energy-dispersive X-ray diffraction has been shown to offer a fast and highly spatially resolving measurement technique. Synchrotron beamlines provide best available instruments in terms of flux and low beam divergence, and hence spatial and measurement resolution and data collection rate. However, despite the rapidly growing number of facilities becoming available in Europe and across the world, access to synchrotron beamlines for routine industrial and research use remains regulated, comparatively slow and expensive. A laboratory high energy X-ray diffractometer for bulk residual strain evaluation (HEXameter) has been developed and built at Oxford University. It uses a twin-detector setup first proposed by one of the authors in the energy dispersive X-ray diffraction mode and allows simultaneous determination of macroscopic and microscopic strains in two mutually orthogonal directions that lie approximately within the plane normal to the incident beam. A careful procedure for detector response calibration is used in order to facilitate accurate determination of lattice parameters by pattern refinement. The results of HEXameter measurements are compared with synchrotron X-ray data for several samples e.g. made from a titanium alloy and a particulate composite with an aluminium alloy matrix. Experimental results are found to be consistent with synchrotron measurements and strain resolution close to 2×10-4 is routinely achieved by the new instrument.