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

Breaking the contradictory of hardness and toughness in B4C is still a challenge to fabricate robust materials. Although compositing B4C with carbon nanotubes (CNTs) is an effective way to improve the toughness, the toughness has the limitation about 6 MPa·m1/2 or hardness below 30 GPa. The limitation of toughness in B4C-CNTs composites is caused by the weak interaction between B4C and CNTs, which impair the strength of composite. So, in this work, the inner compressive stress is introduced in B4C composite with the single-walled carbon nanotube bundles (B4C-SWNTb) by high pressure and high temperature (HPHT). The optimal hardness and fracture toughness are 30 GPa and 8.27 MPa·m1/2 in B4C-2 vol% SWNTb composites, which is 3.3 times higher than that of pure B4C. The high hardness and excellent toughness of B4C-SWNTb composite come from grain refinement of B4C particles, strong combination and inner compressive stress between B4C and SWNTb. This work holds much significance for improving hardness and toughness simultaneously in robust matrix composites.