Microstructure and thermal/mechanical properties of short carbon fiber-reinforced natural graphite flake composites with mesophase pitch as the binder

Short carbon fiber reinforced graphite blocks (SFGs) were fabricated from a mixture of mesophase pitch, natural graphite flakes and short carbon fibers by hot-pressing at 2773 K. The effect of fiber content on the structure and thermal/mechanical properties of the SFGs was investigated. It was found that introducing the fibers lowered the densification, and also changed the pore structure and pore size distribution. Compared with the pristine block, all the SFGs earned improved in-plane thermal conductivity and mechanical strength. The formation of a heat flow network and the increase of crystalline sizes made a synergistic effect on the promotion of in-plane thermal conductivity. In-plane thermal conductivity reached the maximum when the fiber content was 6 wt.%. The increase of mechanical strength was mainly attributed to the pull-out of fibers from the matrix. The bend and compressive strength in the direction perpendicular to graphite layers reached the maximum values of 39.6 MPa and 65.5 MPa for fiber content of 8 wt.%, respectively.