Fabrication and Mechanical Properties of Boron Nitride Nanotube Reinforced Boron Carbide Ceramics

A series of BNNTs/B 4 C composite ceramic were prepared by the spark plasma sintering (SPS) technology using boron carbide (B 4 C) powders as the matrix and boron nitride nanotubes (BNNTs) as the toughening phase. The XRD, SEM, TEM and HR-TEM were used to characterize the B 4 C samples. The influence of sintering temperature, BNNTs content and matrix particle size on the microstructures and mechanical properties of B 4 C composite ceramics, as well the toughening mechanism were investigated in detail. The experimental results showed that changing the particle size of the powder, increasing the sintering temperature and adding BNNTs could significantly improve the mechanical properties of the material. The ceramic samples obtained by adding 5wt.% BNNTs content sintered at 1750℃ displayed the best mechanical properties. Its relative density, microhardness and fracture toughness respectively were 99.41%, 32.68 GPa and 6.87 Mpa·m 1/2 , respectively. In particular, the fracture toughness value of the BNNTs/B 4 C composite ceramic was 54.59% higher than that of B 4 C ceramics without BNNTs.