Effect of CNT addition and its orientation on thermal shock resistance of B₄C/CNT composites fabricated by hot-pressing

This paper describes the synthesis of B4C/carbon nanotube (CNT) composite by hot-pressing and shows the details for the effectiveness of CNT addition, additive amount and its orientation on the thermal shock resistance. CNTs tend to array perpendicular to the hot-pressing direction, which caused anisotropic mechanical and thermal properties of B4C/CNT composite. We investigated the residual bending strength of thermally shocked B4C/CNT composites and determined the critical temperature ΔTC that causes precipitous strength drop. In the case of B4C/15 vol% CNT composite, the residual bending strength almost unchanged at ~450°C; ΔTC increased by 150°C or more than that of monolithic B4C. Based on the thermal stress fracture-resistance parameter R’ of the composites, it was clarified that the excellent R’ is mainly due to the higher thermal conductivity and lower elastic modulus. The numerical results showed that CNT addition has a pronounced effect on the thermal shock residual bending strength and thermal stress fracture-resistance of B4C/CNT composite.