Reaction Sintering Preparation Of Titaniferous Compound Ceramic Composites By Two-step Method

Structural ceramics possess such desirable properties as high melting temperatures, high hardness, and excellent wear resistance. This fact makes them outstanding as structural materials where a compromise of high hardness, good mechanical properties and high-temperature resistance is required. However, the brittleness of ceramic materials restrains its application in industry. It is possible to fabricate the nano-composite ceramics to improve their mechanical properties. Traditional preparation method of the nano-composite ceramics need to synthesize a large scale of high-quality nano-powders, but the nano-powder is expensive and difficult to prepare in quantity. During sintering process, grain growth can not be avoided, so it is difficult to prepare ceramic composites with fine microstructure.The main purpose of this paper is looking for a new method used to prepare fine grain size, high performance ceramic composites. The composites with fine microstructure were prepared by two-step in situ reaction sintering via spark plasma sintering (SPS). Compared to the one-step sintering, as-prepared samples have the finer grains and better mechanical properties. The main content of this thesis is below:The Ti and B4C micron-sized powders were selected to fabricate TiB2/TiC ceramic composites. The effects of sintering temperatures, holding time and sintering methods on properties of composites were investigated. The results show that as-sintered samples by two-step method have the fine microstructure (average grain size of 200nm) and high mechanical properties (MSP strength of 1095MPa). And the Vickers hardness and fracture toughness of TiB2/TiC composites preparation from two different methods are similar, which is 18.3GPa and 4.9MPa.m1/2.We also used Ti and SiC powders as raw materials to prepare the Ti5Si3/TiC composites. The result shows that two different kinds of method have almost no effect on the average grain size of as-sintered samples, which is 300-400nm and 200-300nm. And the MSP strength, Vickers hardness and fracture toughness of Ti5Si3/TiC composites preparation from two different methods is similar, which is 460MPa,12.3GPa and 3.7MPa.m1/2.