Spark plasma sintering of ultrarefractory compounds

Spark plasma sintering experiments were conducted on Zr- and Hf- based borides and carbides with addition of 1, 3, and 9 Vol% MoSi2 as sintering aid. For comparison, as-received ZrC, HfC, ZrB2, HfB2 powders were also sintered. The microstructural features were investigated by means of SEM-EDS technique. Silicon carbide was detected in all the doped compositions along with significant amounts of oxide species (Hf/ZrO2, and SiO2). The effect of the MoSi2 content on densification, microstructure and mechanical properties is analysed.