Tuning mechanical and electrical performances of B4C-TiB2 ceramics in a two-step spark plasma sintering process

B4C-TiB2 is an advanced electrically conductive ceramic with excellent mechanical and electrical discharge machinable properties. It is challenging and rewarding to achieve highly conductive and hard B4C-TiB2 composites at a minimum content of conductive TiB2 that has inferior hardness but double specific gravity of the B4C matrix. A novel strategy was used to construct conductive networks in B4C-15 vol% TiB2 composite ceramics with B4C, TiC, and amorphous B as raw materials by a two-step spark plasma sintering method. The influences of particle size matching between B4C and TiC on the conducting of the strategy and the microstructure were discussed based on the selective matrix grain growth mechanism. The mechanical and electrical properties were also systematically investigated. The B4C-15 vol% TiB2 composite ceramic prepared from 10.29 pm B4C and 0.05 pm TiC powders exhibited a perfect threedimensional interconnected conductive network with a maximum electrical conductivity of 4.25x104 S/m, together with excellent mechanical properties including flexural strength, Vickers hardness, and fracture toughness of 691 +/- 58 MPa, 30.30 +/- 0.61 GPa, and 5.75 +/- 0.32 MPa<middle dot>m1/2, respectively, while the composite obtained from 3.12 pm B4C and 0.8 pm TiC powders had the best mechanical properties including flexural strength, Vickers hardness, and fracture toughness of 827 +/- 35 MPa, 32.01 +/- 0.51 GPa, and 6.45 +/- 0.22 MPa<middle dot>m1/2, together with a decent electrical conductivity of 0.65x104 S/m.