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

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.