Papers by Author: Hong Wei Li

Abstract: SiC/C (graphite) composite ceramics with 20vol% flake graphite were fabricated by Plasma Activated Sintering (PAS) firstly; the composites treated by silicon infiltration in surface were oxidized from 800oC to 1500oC. Effect of silicon infiltration on the oxidation resistance of SiC/C (graphite) composites was characterized by TG/DTA, SEM and XRD. The results show that the graphite in surface of composites reacted with silicon to form a dense SiC film about 30μm-in-thickness. The oxidation resistance temperature was increased from 600oC to 1300oC. Below 1300oC, the surface of composites by silicon filtration was oxidized to form a dense continuous oxide film to hider the oxidation of graphite in matrix. At 1500oC, the surface oxide film was heavy damaged, and many micropores were produced; inner graphite was oxidized above 1300oC again.

Abstract: Machinable SiC/graphite composites were fabricated by Plasma Activated Sintering (PAS), which characterized by high heating rate, short time sintering and high efficiency process. The staring powder mixture included SiC, graphite power and a few sintering aids. They were sintered by PAS under 30 MPa Pressure in vacuum at 1500°C and 1550°C, respectively. The density, bending strength and hardness were measured. The phase and the microstructure of the composites were also investigated. The results indicated that the relative density of SiC/C(graphite) composite sintered at 1550°C was more than 99.5%, the bending strength was 336.6MPa, but surface Vickers hardness was 5.8GPa far lower than SiC ceramics. The machinability of SiC/Graphite sintered by PAS in 1500°C was good because the continuous weak microstructure played a crucial role in the machining process, including a lot of weak interface between the grains of SiC and graphite partials and nearly 20vol% pores in the composite ceramics.