Effects of CNTs content on microstructure and mechanical properties of Cnt/α-Al2O3 and Cnt-Csf/α-Al2O3 composites

Abstract

Abstract In this work, CNTs and short carbon fiber reinforced α-Al2O3 matrix composites (i.e., Cnt/α-Al2O3 and Cnt-Csf/α-Al2O3) were prepared by sol-gel dispersing method followed by hot pressing process. Effects of CNTs content on the mechanical properties of Cnt/α-Al2O3 and Cnt-Csf/α-Al2O3 composites were investigated and the inter- and transgranular fracture mechanisms in Cnt-Csf/α-Al2O3 composites were analyzed. The hardness and relative density of Cnt/α-Al2O3 and Cnt-Csf/α-Al2O3 composites slightly decrease as CNTs content increases. The flexural strength and fracture toughness monotonically increase with the increase in Cnt content for both Cnt/α-Al2O3 and Cnt-Csf/α-Al2O3 composites. Addition of Csf and CNTs into α-Al2O3 matrix results in a bimodal grain size microstructure of Cnt-Csf/α-Al2O3 composites, which accounts for the unique fractograph and the enhanced toughness of Cnt-Cf/α-Al2O3 composites. The flexural strength and fracture toughness of Csf5-nt06 composite are 465 MPa and 7.08 MPa/m2, 37% and 13% higher than that of Cnt06, and 42% and 34% higher than that of Csf5, respectively.