Preparation of dense B4C ceramics by spark plasma sintering of high-purity nanoparticles

Boron carbide (B4C) is an important structural ceramic material, however, the use of this material is limited by its poor sinterability and low fracture toughness. Nano-sized powders have small particle size, high chemical activity and great sintering ability, which can promote the fabrication of the dense B4C ceramics. Herein, by spark plasma sintering (SPS) homemade high-purity nanopowders, single phase B4C ceramics with density close to the theoretical value were prepared. Results showed that the best SPS condition was holding at temperature of 1850 °C for 4 min. Under this condition the sample exhibited enhanced mechanical properties including Vickers hardness of 33.9 GPa, fracture toughness of 3.81 MPa m1/2 and flexure strength of 554.7 MPa. Transmission electron microscopy (TEM) analysis shows that non-coherent twins exist at the grain boundary instead of amorphous phase or second phase, which further confirms the high purity and high densification of the obtained B4C ceramics.