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

Abstract In this work, CNTs and short carbon fiber reinforced α-Al 2 O 3 matrix composites (i.e., C nt /α-Al 2 O 3 and C nt -C sf /α-Al 2 O 3 ) were prepared by sol-gel dispersing method followed by hot pressing process. Effects of CNTs content on the mechanical properties of C nt /α-Al 2 O 3 and C nt -C sf /α-Al 2 O 3 composites were investigated and the inter- and transgranular fracture mechanisms in C nt -C sf /α-Al 2 O 3 composites were analyzed. The hardness and relative density of C nt /α-Al 2 O 3 and C nt -C sf /α-Al 2 O 3 composites slightly decrease as CNTs content increases. The flexural strength and fracture toughness monotonically increase with the increase in C nt content for both C nt /α-Al 2 O 3 and C nt -C sf /α-Al 2 O 3 composites. Addition of C sf and CNTs into α-Al 2 O 3 matrix results in a bimodal grain size microstructure of C nt -C sf /α-Al 2 O 3 composites, which accounts for the unique fractograph and the enhanced toughness of C nt -C f /α-Al 2 O 3 composites. The flexural strength and fracture toughness of C sf 5-nt06 composite are 465 MPa and 7.08 MPa/m 2 , 37% and 13% higher than that of C nt 06, and 42% and 34% higher than that of C sf 5, respectively.