Effect of carbon source on the synthesis of ZrB₂–SiC composite powders

This study is aimed to synthesize ZrB₂–SiC composite powders by boro-carbothermal reduction of zircon using two different carbon sources, namely expanded graphite and carbon black. The effect of carbon sources on the phase composition and microstructure of composite powders was studied using an X-ray diffractometer, a scanning electron microscope, and an energy spectrum analyzer. Pure-phase ZrB₂–SiC composite powders were prepared in 2 h at 1550 and 1500 °C 1500 °C using expanded graphite and carbon black, respectively. In the former case, anisotropic ZrB₂–SiC composite powders were synthesized. Their ZrB₂phase grains had an average diameter of 2.0 μm and regular hexagonal shape, while SiC phase grains were whisker-shaped, had an average diameter of 0.15 μm and aspect ratio exceeding 20. For carbon black, finer ZrB₂grains and shorter rod-shaped SiC grains were obtained.