Role of Carbon in the Sintering of Boron‐Doped Silicon Carbide

The effect of carbon on the sintering of boron‐doped SiC was studied. The free carbon present in the green compact was found to react with the SiO 2 covering the surfaces of the SiC particles; however, even if no carbon was added, the surface SiO 2 reacted with the SiC itself at a slightly higher temperature. This latter reaction was associated with the onset of substantial pore growth in the shrinking green body, which, as the pores continued to grow at higher temperatures, prevented complete densification. Therefore, the reaction of the SiC with the SiO 2 may have led to the fracture of interparticle contacts, resulting in the onset of coarsening. Thus, the role of the carbon was to prevent reaction between the SiC and the surface SiO 2 , by removing the SiO 2 at a temperature below that at which this reaction could occur.