SPARK PLASMA SINTERING (SPS) of BxC-TiB₂ COMPOSITES

Boron carbide displays very promising properties, such as high hardness and young modulus along with low specific density. Unfortunately, due to its covalent bonding successful sintering may be conducted only at relatively high temperature (higher than 2200°C) even external pressure is applied. Many sintered additives were suggested to decrease sintering temperature, but all of them affect mechanical properties, namely, decreasing hardness value. We suggest to examine the effect of boron carbide stoichiometry, which changes from B₄C to B₁₀C, on its sintered behavior in an SPS apparatus. To obtain boron carbide of various stoichiometry B₄C powder were mixed with an appropriate fraction of TiO₂ and annealed under vacuum for 4 hours. The resulting powder mixture consisted of boron carbide of desired stoichiometry and a novel formed TiB₂ phase. In the present study kinetic parameters of the synthesis were investigated and obtained powder mixtures were characterized. It was established that B_xC (4<x≤7)-TiB₂ mixtures may be fully densified by SPS at temperatures 200-250°C lower than that for stoichiometric boron carbide (B₄C). Mechanical properties of the sintered composites were examined and discussed.