Fabrication and mechanical properties of boron nitride nanotube reinforced boron carbide ceramics

A series of boron nitride nanotubes (BNNTs)/ boron carbide (B4C) composite ceramics were prepared using spark plasma sintering (SPS) technology, which uses B4C powders as the matrix and BNNTs as the toughening phase. X-ray diffraction (XRD) and scanning electron microscope (SEM) were then used to characterize the B4C ceramic samples. The effects of the sintering temperature, the BNNTs content, and the matrix particle size on the microstructure and mechanical properties of the B4C composite ceramics were investigated in detail. The experimental results showed that the ceramic samples obtained by adding a 5 wt % BNNTs content sintered at 1750 °C displayed the best mechanical properties. The relative density, microhardness, and fracture toughness were 99.41 %, 32.68 GPa, and 6.87 Mpa·m1/2, respectively. The fracture toughness was 54.59 % higher than that of the composite without the BNNTs. The toughening mechanism of the BNNTs was also studied. The pulling-out of the BNNTs, bridging, and crack branch contributed to the toughness property of the B4C-based ceramic.