Enhancement of the Carbothermal Reduction of Hafnium Oxide by Silicon

Mixtures of hafnia and carbon powders, containing 0.0–10 mol% of silicon, are heated and analyzed by XRD, SEM, TEM, and DTA. Furthermore, hafnia and carbon pellets, with varying degrees of silicon content, are investigated to determine the nature of the silicon influence on the reaction. The addition of up to 5.0 mol% silicon increases the yield of carbide by 400%. TEM reveal that silicon causes the formation of an amorphous layer on the hafnia particles, on which nucleation of the carbide phase take place. Taking into account that the carbide formation in Si‐free samples is only observed on the carbon surfaces, the authors conclude that the silicon‐induced layer on the hafnia surfaces increases the accessible area for carbide formation and consequently the reaction rate.