Tuning mechanical and electrical performances of B ₄C–TiB ₂ ceramics in a two-step spark plasma sintering process

Abstract

B 4 C-TiB 2 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 B 4 C-TiB 2 composites at a minimum content of conductive TiB 2 that has inferior hardness but double specific gravity of the B 4 C matrix. A novel strategy was used to construct conductive networks in B 4 C-15 vol% TiB 2 composite ceramics with B 4 C, TiC, and amorphous B as raw materials by a two-step spark plasma sintering method. The influences of particle size matching between B 4 C 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 B 4 C-15 vol% TiB 2 composite ceramic prepared from 10.29 µm B 4 C and 0.05 µm TiC powders exhibited a perfect threedimensional interconnected conductive network with a maximum electrical conductivity of 4.25×10 4 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•m 1/2 , respectively, while the composite obtained from 3.12 µm B 4 C and 0.8 µm 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•m 1/2 , together with a decent electrical conductivity of 0.65×10 4 S/m.