Ultra-high temperature spark plasma sintering of α-SiC

Ultra High Temperature SPS (UHTSPS) was used to sinter pure α-SiC at 2450 °C. Such a high temperature and partial vacuum conditions (1200 Pa) promoted SiC sublimation and condensation reactions. In the presence of an electric field, materials with graded porosity could be produced by using UHTSPS. At high temperature, the condensation of the gaseous species was controlled by the polarity of the applied electric field. Preferential condensation of SiC occurred on the negative electrode (cooler surface) due to the Peltier effect associated with the n-type thermoelectric behaviour of SiC. In the absence of an electric field, condensation was driven by gravity and it resulted in dense SiC monoliths.