Enhanced toughness of boron carbide by single-wall carbon nanotube bundles

Breaking the contradictory of hardness and toughness in B 4 C is still a challenge to fabricate robust materials. Although compositing B 4 C with carbon nanotubes (CNTs) is an effective way to improve the toughness, the toughness has the limitation about 6 MPa·m 1/2 or hardness below 30 GPa. The limitation of toughness in B 4 C-CNTs composites is caused by the weak interaction between B 4 C and CNTs, which impair the strength of composite. So, in this work, the inner compressive stress is introduced in B 4 C composite with the single-walled carbon nanotube bundles (B 4 C-SWNTb) by high pressure and high temperature (HPHT). The optimal hardness and fracture toughness are 30 GPa and 8.27 MPa·m 1/2 in B 4 C-2 vol% SWNTb composites, which is 3.3 times higher than that of pure B 4 C. The high hardness and excellent toughness of B 4 C-SWNTb composite come from grain refinement of B 4 C particles, strong combination and inner compressive stress between B 4 C and SWNTb. This work holds much significance for improving hardness and toughness simultaneously in robust matrix composites .