Ceramics-Silikáty 68, (4) 598 - 609 (2024)

Four raw materials, namely, zirconium silicate, silica sol, boric acid, and graphite, were selected as precursor materials. Silicon carbide (SiC)-zirconium borate (ZrB₂) ceramic composite powders were prepared via carbothermal/borothermal reduction in a high-temperature tube furnace under an argon atmosphere. The effects of the boric acid dosage and calcination temperature on the phase composition and microstructure of the SiC-ZrB₂ composite powders were investigated. The results showed that when the amount of H₃BO₃ added was the theoretical amount (i.e., 0 wt.% in excess) or 10 wt.% in excess, SiC-ZrB₂ composite powders containing a certain amount of graphite could be pre-pared by holding at 1550 °C-1650 °C for 2 h. When the amount of boric acid was 20 wt.% in excess, SiC-ZrB₂ composite powders with a high purity were obtained at a calcination temperature of 1650 °C. When the amount of boric acid was 30 wt.% in excess, SiC-ZrB₂ composite powders with a high purity were successfully prepared at a calcination temperature higher than 1600 °C. In addition, when the amount of boric acid was 20 wt.% in excess, a large amount of bamboo-like whisker materials with a diameter of approximately 50-200 nm appeared in the powder samples. These materials overlapped and were wound together. When the amount of boric acid was 30 wt.% in excess, the powder samples prepared at 1600 °C-1650 °C formed a diverse microstructure consisting of flaky, spherical, and columnar particles and whisker-like substances.