Anisotropic Fracture Toughness and Microstructure of Graphene-Reinforced TiC/Si3N4 Composite

摘要

Using the hot pressing sintering process, graphene-platelets (GPLs)-reinforced TiC/Si3N4 composite (GPLs/TiC/Si3N4) was prepared with the aim of improving its fracture toughness. Microstructure analysis shows that the pressure applied during the hot pressing sintering process leads to the orientational distribution of GPLs perpendicular to the pressing direction in the GPLs/TiC/Si3N4 composite. With the single-edge notched beam method, the fracture toughness of GPLs/TiC/Si3N4 was measured in the hot pressing direction (HPD) and perpendicular to the hot pressing direction (PHPD). The fracture toughness of the composites in HPD is higher than that in PHPD. The maximum fracture toughness of 9.6 MPa . m(1/2) in HPD was achieved for the composite containing 1 wt% GPLs, which was approximately 31.5 % higher than that of 7.3 MPa . m(1/2) in PHPD. Raman spectra showed that the defect in PHPD was larger than that in HPD. The Raman intensity of the composite in HPD is higher than that in PHPD. The toughening mechanisms include crack deflection, graphene bridging and the pull-out of GPLs, which were observed and discussed.