Flash Spark Plasma Sintering of SiC: Impact of Additives

Flash spark plasma sintering (FSPS) of SiC was carried out using additives (10 vol%) with different electrical conductivities: alumina (insulator), boron carbide (semiconductor), and titanium carbide metallic (conductor). The electrical conductivity of the additives plays a determinant role on the FSPS process, it controls the electrical SPS power dissipation, the development of gaseous/liquids/solid phases and time needed to complete densification. The microstructure of FSPSed SiC samples confirmed localized heating in the case of Al2O3 additive, resulting in undesired carbothermal reduction and formation of gaseous species. In the presence of TiC additive, solid state sintering led to SiC sublimation without achieving a complete densification. The presence of B4C as an additive led to a liquid phase formation, which promoted sintering contributing and the densification of the samples. The present study rationalizes the selection FSPS sintering additives based on their electrical and chemical compatibility with the SiC matrix.