http://hdl.handle.net/123456789/6 2026-07-08T17:16:11Z http://hdl.handle.net/123456789/2151386 http://hdl.handle.net/123456789/2151384 Advanced ceramic matrix composites for high energy x-ray generation High energy x-ray targets are the anodes used in high performance tubes, designed to work for long operating times and at high power. Such tubes are used in computed tomography (CT) scan machines. Usually the tubes used in CT scanners have to continuously work at high temperatures and for longer scan durations in order to get maximum information during a single scan. These anodes are composed of a refractory substrate which supports a refractory metallic coating. The present work is a review of the development of a ceramic metal composite based on aluminium nitride (AlN) and molybdenum for potential application as the substrate. This composite is surface engineered by coating with tungsten, the most popular material for high energy x-ray targets. To spray metallic coatings on the surface of ceramic matrix composites dc blown arc plasma is employed. The objective is to increase the performance and the life of an x-ray tube. Aluminium nitride-molybdenum ceramic matrix composites were produced by uniaxial hotpressing mixtures of AlN and Mo powders. These composites were characterized for their mechanical, thermal, electrical and micro-structural properties. An optimized composition was selected which contained 25 vol.% of metallic phase dispersed in the AlN matrix. These composites were produced in the actual size of an anode and coated with tungsten through dc blown arc plasma spraying. The results have shown that sintering of large size anodes is possible through uniaxial pressing, using a modified sintering cycle. http://hdl.handle.net/123456789/2151385 Ferrite-based material as a permanent magnet for components of electrical generators A permanent magnet based on ferrite for use as components of electrical generators has been fabricated by two different methods: solid–solid mixing and cooprecipitation. The conventional solid–solid mixing method uses Fe₂O₃ and BaCO₃ as starting materials with mole ratio n=BaO:Fe₂O₃=1: 6. The mixture is calcinated at 1100 °C and two crystal structures, BaOFe₂O₃ and BaFe₁₂O₁₉, were obtained with particle size of about 0.5–1.5 μm. Sintering at 1100 °C was followed by a magnetization process. Measurements give the following physical parameter values: remanence, Br=0.0792 T; magnetic saturation, Bs=1.21 T; coersivity, Hc=44.7 kA m^-1; density 3.43 g cm^-3 and porosity 9.16%. On the other hand, the cooprecipitation method uses FeCl₃ and BaCl₂ solution with mole ratio n=BaCl₂:FeCl₃=1:6. After the calcination at 900 °C and higher temperatures a single crystal structure of BaO·6Fe₂O₃ is formed with particle size of about 30–60 nm. The optimum sintering temperature for the formation of this single phase crystal structure is 1050 °C. The physical parameters of the final product have the following values: Br=0.2673 T; Bs=1.42 T; Hc=89.4 kA m^-1; density 4.34 g cm^-3 and porosity 3.36%. http://hdl.handle.net/123456789/2151383 The structure and magnetic properties of molecule-based magnet nanoparticles K_xV_y[Cr(CN)₆]_z.nH₂O We have synthesized K_xV_y[Cr(CN)₆]_z. nH₂O molecule-based magnet nanoparticles belonging to the Prussian blue (PB) family of compounds. The synthesized samples were characterized by infrared spectroscopy (IR), Raman spectroscopy, UV–Vis spectroscopy, differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The crystal structure was refined from the x-ray powder diffraction profile by the Rietveld method. The samples are cubic, Fm3m space group with lattice parameter a=1.045 nm. The magnetic properties are determined from thermal variation of the magnetization and hysteresis loop. The most interesting result is the successful preparation of K_xV_y[Cr(CN)₆]_z. nH₂O crystal Prussian blue nanomaterial which had Curie temperature (T_c) approaching room temperature.