Ultra-high temperature ceramics (UHTCs)Ultra-high temperature ceramics have drawn interest for use in extreme aerodynamic environments due to their high melting points, excellent thermo-physical properties, and reasonably low densities. However, due to processing limitations, they have primarily been used as monolithic materials or coatings. Here, we introduce additional functionality (e.g., ablation resistance, transpiration cooling) by developing porous UHTC form factors. We have previously quantified the kinetic parameters of the conversion of nanoporous metals to ultra-high temperature ceramicsCeramics via carburization at elevated temperature for powders with a single feature size. However, it was observed that the phases present after carburization may not be in equilibrium, and the stability of the porous structure at high temperatures was unknown. The present work explores the phase stability and morphological evolution of nanoporous TaC, made via low temperature gas carburization, to quantify the process for creation of nanoporous ultra-high temperature ceramicsCeramics with predictable stoichiometry and stable feature sizes for a given application temperature.