Novel B4C[sbnd]TiB2 composites with high electrical and low thermal conductivity by selective grain growth in reactive sintering

Abstract

High electrical conductivity and low thermal conductivity are beneficial for the electrical discharge machining performance of ceramics. In this work, B4C–TiB2 composites were prepared by spark plasma sintering of B4C–TiC–B powder mixture. The chemical reaction between TiC and B, together with subsequent selective matrix grain growth, expelled small in-situ generated TiB2 grains to form conductive interlayers around large B4C grains. The unique microstructure significantly enhances the electrical conductivity of B4C–TiB2 composites, especially at low TiB2 content, while the ultrafine in-situ formed TiB2 grains endow the composites with low thermal conductivity. The effects of TiB2 content on the microstructure, mechanical properties, thermal & electrical conductivity of the composites were investigated. B4C–20 vol% TiB2 composite exhibits excellent comprehensive performance, including a relative density, Vickers hardness, flexural strength, fracture toughness, room electrical and thermal conductivity of 98.6%, 28.15 GPa, 656 MPa, 5.46 MPa⋅m1/2, 1.08 × 105 S/m and 19.37 W/m⋅K, respectively.