Papers by Keyword: High Temperature Ceramic

Abstract: Abstract: The introduction of metal atoms into SiBCN network allows the development of novel high temperature ceramics and functional ceramics. In this work, cerium (Ce) containing polyborosilazane (PBSZ) is synthesized through substitution and polymerization reactions. Ce atoms are incorporated into PBSZ through the lithium replacement of H in PBSZ followed by Ce replacement of lithium. The chemical structure of the PBSZ and as-synthesized Li containing PBSZ are analyzed by Fourier transform infrared (FTIR) shows that the bands at 598 and 1183 cm-1 which can be assigned to Li-N and Si-N-Li stretching. It is suggested that lithium is incorporated into PBSZ. PBSZCe is transformed into SiBCNCe ceramic by pyrolysed in argon. Scanning electron microscope shows that the SiBCNCe ceramics are porous on the surface and corallike in the section. The chemical bondings of SiBCNCe ceramics are BN, the BN, SiC and Si3N4 characterized by X-ray photoelectron spectroscopy.

Abstract: Over the years, the self-propagating high-temperature synthesis (SHS) has become an interesting research field to prepare a large numbers of advanced materials. Recently, the demands for high temperature advanced ceramics have further intensified the research on SHS for efficient material preparation. Several reviews, large numbers of papers and patents on various aspects of material production by SHS are available in literature. These are scattered and it is desirable to have a comprehensive review of the literatures that not only helps the researchers but also guide the beginners in this area. In this paper, we have emphasized our contributions on synthesis of various advanced high temperature ceramics, the borides, carbides, oxides and their composites by SHS processes. Several advantages and disadvantages of the SHS technique for advanced high temperature (HT) materials are highlighted. The preparation of nano-sized powders and finegrained in-situ high temperature ceramic composites through SHS is specially mentioned.

Abstract: The influence of ignition parameters for energy efficient processing of high temperature non-oxide ceramics by the micropyretic synthesis route is studied numerically in this article. The simulation results show that a lower ignition power leads to longer ignition time to initiate reactions. An increase in the ignition time also increases the length of pre-heating zone before propagating, which further changes the initiate propagation velocity and oscillatory frequency of the temperature variations. Such changes in the initiate propagation velocity and temperature variations result in inhomogeneous structures at the ignition spot. The simulation also indicates that using a higher power to ignite the micropyretic reactions can lower the ignition time and further prevent the inhomogeneous structures from being formed at the ignition spot. However, more heat loss is noted to occur due to a high temperature gradient and the energy required to ignite the reaction. The numerical calculation indicates that there is a 20 % increase in the required energy and a 90% decrease in the required time to ignite the specimen when the ignition power is increased from 87.5 kJ/(g･s) to 962.5 kJ/(g ･s). In addition, the effect of the individual material property on ignition is also investigated.