Analysis of initial stage densification kinetics of zirconium carbide (ZrC) powders

Zirconium carbide (ZrC) is a promising material for extreme environments, but the presence of oxygen (ZrOxCy or ZrO2) disproportionately influences the densification behavior. ZrOxCy consolidation was studied via spark plasma sintering (SPS) after analysis of composition, particle size, crystalline phase(s) and stoichiometry. An analytical approach to understanding the kinetics of sintering was applied to initial stage densification using two forms of constant rate heating and isothermal sintering experiments. Exponents consistent with grain boundary diffusion were identified as the dominant densification mechanism. The activation energy (Q) was determined to be 632 +/- 52 kJ/mol, consistent with independence from C/Zr stoichiometry and values of Q for Zr self-diffusion. Higher oxygen content corresponded to lower temperatures for densification and revealed a non-densifying mechanism. Critique of integral and differential approaches for analysis of SPS data are necessary to ensure discerning measurement of representative mechanisms.