Low temperature synthesis of ZrB2-SiC powders by molten salt magnesiothermic reduction and their oxidation resistance

Abstract

Herein, we prepare phase-pure ZrB2-SiC composite powders by molten-salt-mediated reduction of ZrSiO4/B2O3/activated carbon mixtures with Mg, showing that the phase composition and morphology of the above composites is influenced by firing temperature, B:Zr and C:Si molar ratios, and the amount of excess Mg. Notably, phase-pure ZrB2-SiC powder with a ZrB2:SiC weight ratio of ~75:25 could be obtained by 3-h firing at 1200 °C, i.e., at a temperature lower than that used for conventional carbothermal reduction by at least 200 °C. As-prepared ZrB2-SiC composites exhibited grain sizes of several microns and comprised SiC nanoparticles well distributed in the ZrB2 matrix. Finally, the oxidation activation energies of the prepared ZrB2 and ZrB2-SiC powders were determined as 326 and 381 kJ/mol, respectively, which demonstrated that the introduction of SiC improved the oxidation resistance of monolithic ZrB2.