Graphite addition for SiC formation in diamond/SiC/Si composite preparation

Abstract

Herein, graphite was used in the Si-vapor reactive infiltration of diamond/SiC/Si composites to produce composites with various SiC contents. X-ray diffraction was used to determine the phases of the composite, whereas scanning electron microscopy was used to confirm the Si–C reaction between the silicon, graphite, and diamond and to observe the SiC morphology. Various SiC contents in the composite were observed with graphite addition. Furthermore, the reaction between silicon and graphite (diamond) produced coarse (fine) SiC particles. The generation of a 10-μm-diameter Si–C area on the surface of the diamond was observed. The thermal conductivity (TC) and coefficient of thermal expansion (CTE) of the composite was investigated, where the TC varied from 317–426 W•m−1•K−1 with the increase of the SiC volume fraction from 38% to 76% and the corresponding CTE increased from 1.7 × 10-6 to 3.7 × 10−6 K−1, respectively. Furthermore, a critical point for the CTE was found to exist at approximately 250°C, where the composite was under a hydrostatic condition. Finally, the bending strength was found to range from 241 to 341 MPa.