Oxidation mechanisms of tantalum carbides at extreme temperatures

Abstract

This study reveals atomic-scale oxidation mechanisms in tantalum carbides (TaC and Ta₂C) under extreme thermal conditions up to 2500 K, using a high-speed electro-thermographic method enabling resistive heating rates up to 5 × 10⁵ K/s and quenching up to 5 × 10⁴ K/s. Bilayer TaC/Ta₂C coatings were synthesized on tantalum wire with tunable microstructures and subjected to controlled high-temperature oxidation in air. Real-time thermal and electrical monitoring allowed precise control of reaction, while post-quench characterization via high-resolution electron microscopy, diffraction methods, and Raman spectroscopy provided detailed insights into structural evolution. The oxidation of TaC proceeds predominantly through intergranular pathways, but for the first time, intragranular oxidation channels were observed at the nanoscale. In Ta₂C, oxidation followed both inter- and intragranular routes, with the latter dominating and involving transient formation of TaC domains. These findings establish an oxidation mechanism for tantalum carbides at nano- and atomic scales, offering insights for their application in extreme environments.