Microstructural characterization of reaction-formed silicon carbide ceramics

Microstructural characterization of two reaction-formed silicon carbide ceramics has been carried out by interference layering, plasma etching, and microscopy. These specimens contained free silicon and niobium disilicide as minor phases with silicon carbide as the major phase. In conventionally prepared samples, the niobium disilicide cannot be distinguished from silicon in light optical micrographs. After interference layering, all phases are clearly distinguishable. Backscattered electron imaging and energy-dispersive spectrometry in the scanning electron microscope confirmed the results obtained by interference layering. Plasma etching with CF4 + 4% O2 selectively attacks silicon in these specimens. It is demonstrated that interference layering and plasma etching are very useful techniques in the phase identification and microstructural characterization of multiphase ceramic materials.