Effect Of Zro2 Impurity On Promoting Reactive Sintering Of Zrb2-Sic-Zrc Composites

ZrO2 impurity phase was examined by means of X-ray diffraction and scanning electron microscopy in reactive-sintered ZrB2-SiC-ZrC composites hot-pressed at 1 600 degrees C and 1 800 degrees C. An analytical electron microscopy study further revealed solid-solution of both Zr and O in the beta-SiC phase: Zr : Si ratios were measured to be 1.83 +/- 0.17 x 10(-2) and 1.91 +/- 0.16 x 10(-2) respectively for each sample, while O : Si ratios were in the range of 2.3 similar to 2.8 x 10(-2). Common co-existence of ZrO2 grains and SiC grains containing Zr-O solutes indicates that this oxide plays a significant role in the sintering process, which substantially modifies the reactive phase relations. Observation of an intergranular Si-Zr-C-O glassy phase suggests the presence of a similar sintering liquid as a fast or even dominant diffusion path to promote the reactive sintering.