Graphene nanoplatelet reinforced boron carbide composites with high electrical and thermal conductivity

Monolithic B4C ceramics suffer from poor machinability, high brittleness and low thermal conductivity. Here we intend to tackle these problems by incorporating graphene nanoplatelet (GNP) into B4C matrix. Dense B4C/GNPs composites containing 0-5 vol% GNPs were fabricated by hot-pressing using Ti3AlC2 as sintering aid. The electrical conductivity increased dramatically with the incorporation of GNPs, enhancing the machinability of B4C composite remarkably by allowing electrical discharge machining. The establishment of a conducting network was revealed by conducting scanning force microscopy and a synergistic enhancement effect by conducting TiB2 particles produced by reactions between B4C and Ti3AlC2 and GNPs was responsible for the low percolation threshold. The GNPs also provided a good thermal transport channel and the thermal conductivity perpendicular to hot-pressing direction was significantly enhanced. Improvements on strength and fracture toughness by addition of GNPs were observed, and the mechanisms for the improvements include crack deflection and pull-out of GNPs.