Synthesis and Sintering of Nanostructured ZrB2-SiC Composite

Abstract

ZrB2 is considered a candidate material for ultra-high temperature ceramics because of its high thermal conductivity, high melting point, and low coefficient of thermal expansion. Despite these attractive properties, applications of ZrB2 are limited by its low fracture toughness below the brittle-ductile transition temperature. To improve its ductile properties, the approach universally utilized has been to add a second material to form composites and fabricate nanostructured materials. One example of this is the adding of SiC to ZrB2 to improve fracture toughness. SiC has low density, excellent resistance to oxidation in air, and a high melting point. Therefore, SiC may be a promising additive as a reinforcing material for ZrB2-based composites. A dense nanostructured ZrB2-SiC composite was rapidly synthesized and sintered by high-frequency induction heating (HFIH) within 4 min in one step, from mechanically activated powders of ZrC, 2B and Si. Simultaneous combustion synthesis and consolidation were accomplished using the combination of current and mechanical pressure. A highly dense ZrB2-SiC composite with a relative density of up to 98.4% was fabricated using the simultaneous application of 70 MPa pressure and an induced current. The mechanical properties (toughness and hardness) and the average grain size of the composite were investigated.