Highly electro-conductive B <sub>4</sub>C–TiB <sub>2</sub> composites with three-dimensional interconnected intergranular TiB <sub>2</sub> network
Jun Zhao, Dong Wang, Xing Jin, Xiang Ding, Jianhua Zhu, Songlin Ran
Abstract
To achieve lightweight B<sub>4</sub>C-based composite ceramics with high electrical conductivities and hardness, B<sub>4</sub>C–TiB<sub>2</sub> ceramics were fabricated by reactive spark plasma sintering (SPS) using B<sub>4</sub>C, TiC, and amorphous B as raw materials. During the sintering process, fine B<sub>4</sub>C–TiB<sub>2</sub> composite particles are firstly <i>in situ</i> synthesized by the reaction between TiC and B. Then, large raw B<sub>4</sub>C particles tend to grow at the cost of small B<sub>4</sub>C particles. Finally, small TiB<sub>2</sub> grains surround large B<sub>4</sub>C grains to create a three-dimensional interconnected intergranular TiB<sub>2</sub> network, which is beneficial for an electro-conductive network and greatly improves the conductivity of the ceramics. The effect of the B<sub>4</sub>C particle size on the mechanical and electrical properties of the ceramics was investigated. When the particle size of initial B<sub>4</sub>C powders is 10.29 µm, the obtained B<sub>4</sub>C–15 vol% TiB<sub>2</sub> composite ceramics exhibit an electrical conductivity as high as 2.79×10<sup>4</sup> S/m and a density as low as 2.782 g/cm<sup>3</sup>, together with excellent mechanical properties including flexural strength, Vickers hardness (<i>HV</i>), and fracture toughness (<i>K</i><sub>IC</sub>) of 676 MPa, 28.89 GPa, and 5.28 MPa·m<sup>1/2</sup>, respectively.