Effect of nitrogen pressure on combustion synthesis of Si₃N₄-SiC-TiN ceramic

The Si₃N₄-SiC-TiN multiphase ceramic was synthesized from TiSi₂ and SiC powders by self-propagating high-temperature synthesis in which SiC is acting as a diluent. The effect of nitrogen pressure on the conversion degree of the reactant was calculated in theory, and combustion synthesis was carried out under nitrogen pressures of 50, 100 and 150 MPa, respectively. The results show that the green parts of 50 vol% porosity are well nitrified under the three pressures, while those of 40 vol% porosity can not be nitrified completely in which agglomerate Si is found when they were synthesized under lower pressure. However, there is no Si detected in the final products made by 40 vol% porosity parts under 150 MPa nitrogen pressure. Accordingly, the high nitrogen pressure is of advantage to the infiltration of nitrogen and the increase of conversion degree.