A nanostructural approach to the interfacial phenomena in spark plasma sintered TiB2 ceramics with vanadium and graphite additives

Abstract A novel TiB2-based composite, with metallic vanadium and nano-graphite additives, was fabricated by spark plasma sintering. A comprehensive investigation was carried out to clarify the sintering behavior and interfacial phenomena. The in-situ synthesis of crystalline V3B4, V6C5, and TiC phases was proved. The formation of V6C5 was attributed to the ordering phase transformation promoted by carbon vacancies in the initially-synthesized VC. TiC was formed due to the reduction of TiO2 impurity with graphite additive. Simultaneous addition of vanadium and graphite not only resulted in the reduction of B2O3 impurity, but also the synthesis of V3B4 nano-crystals, which shows the critical role of oxide impurities on the final phase arrangement. The liquid state of B2O3 at high temperatures promoted the possibility of such reactions. The in-situ formation of such phases led to significant improvements in the mechanical properties. Compared to the monolithic TiB2 consolidated through similar conditions, 50% increase in fracture toughness and 27% enhancement in elastic modulus were observed.