Microstructure and Mechanical Properties of High-Strength Graphite Particles Coated TiO2 Film Embedded in SiC Composite

Abstract

In order to improve the fracture strength of Gp/SiC composites, the mean size (d50) 50 μm high-strength graphite particles, TiCl4used as starting materials, and the graphite particles coated TiO2film were obtained using co-precipitation method. Then the Gp/SiC composites were prepared with the “roll the snowball method” and hot-pressing sintering technology. The microstructure and phase constitution is measured by scanning electron microscopy (SEM) and electron energy spectrum (EDS). It is found that the coated graphite cores are embedded in the SiC matrix as the islands. The apparent porosity increases, density decreases, with graphite content increasing. The fracture strength and hardness decrease, fracture toughness increases with the graphite content increasing. The apparent porosity, density, fracture strength, fracture toughness, hardness of the composite are 3.8%, 2.61 g•cm-3,135 MPa, 2.82 MPa•m1/2,22.1 GPa, respectively, while the volume percent of ceramic and graphite is 6︰4 and sintered at 2000°C. The TiO2film can effectively lower the sintering temperature and impart composite better mechanical properties. The toughening mechanisms are crack deflection and branching as well as stress relaxation near the crack tip.