Low Temperature Preparation of ZrB2-SiC Composite Powders by a Combined Molten Salt and Carbothermal/magnesium Reduction Method

Abstract:

ZrB₂-SiC composite powders were prepared in NaCl-KCl flux using zirconium, silica, boron oxide as main raw materials, magnesium powder as reducing agent by a combined molten salt and carbothermal/magnesium reduction method. The phase compositions of the resulted powders were investigated by X-ray diffraction. The influences of molar ratio of Zr/Si, content of activated carbon, silica and boron oxide on the phase composition and contents of the crystalline phase of ZrB₂-SiC composite powders were investigated. The results show that high purity ZrB₂-SiC composite powders can be synthesized with the molar ratio of n(Zr)/n(Si) is 1 and the amount of activated carbon, silica and boron oxide was respectively 120 mol%, 120 mol% and 150 mol% in NaCl-KCl flux with the molar ratio of n(NaCl)/n(KCl) is 1 at 1 200 ℃ for 2 h, and the amount of ZrB₂ and SiC was calculated as 59 wt% and 35 wt% in the prepared powders. FE-SEM results show that there exits aggregation in the final powders with the particle size of about 0.5μm. Compared with the conventional carbothermal/magnesium reduction method, the synthesis temperature of ZrB₂-SiC composite powders was reduced about 200 ℃ in the present work.