Chemical precipitation techniques for the production of ceramics with controlled microstructure

The ability to control the microstructure during the sintering process is critical to the production of ceramics for advanced technological applications. In many cases, conventional ceramic processing techniques are inadequate for achieving the required level of microstructural control. In the present work, chemical precipitation techniques were investigated for the production of ceramics with controlled microstructure. The results of the research are described in three papers.; The first paper is concerned with the synthesis of nanocrystalline powders (10-15nm) of CeO{dollar}sb2{dollar} and {dollar}rm Ysb2Osb3{dollar}-doped CeO{dollar}sb2{dollar} by chemical precipitation under hydrothermal conditions and the conversion of the powder into the thin films and bulk solids. The factors controlling the stabilization of the particles in suspensions, the preparation of thin films by spin coating or dip coating and the sinterability of the films were investigated. In the second paper, microstructural control during the reaction sintering of a model ZnO-Al{dollar}rmsb2Osb3{dollar} system is considered. For powder mixtures prepared by mechanical mixing, the solid state reaction occurring during the firing process leads to a disruption of the particle packing and a significant reduction in the sintering rate. The use of coated powders (prepared by heterogenous precipitation) for alleviating the sintering difficulties was investigated. The third paper describes the application of the fabrication route based on the use of coated powders for the production, by free sintering, of SiC platelet reinforced Al{dollar}rmsb2Osb3{dollar} composites.; In addition to the work described above, the preparation of ultrafine MoSi{dollar}sb2{dollar} powders by reactive high speed milling and the sinterability of the consolidated powders were investigated. This work has been published and is included as an appendix.