Exploration of Sintering Behavior for Solid Solution Carbide Ceramics

Solid solutions of niobium carbide (NbC), tantalum carbide (TaC), and zirconium carbide ZrC), when mixed with uranium carbide (UC), emerge as promising fuel candidates for nuclear thermal propulsion (NTP) applications. Their appeal lies in high melting temperatures, stability in hot hydrogen, and low thermal neutron absorption cross-sections. Among these, the composition (Zr0.8, Nb0.1, Ta0.1)C exhibits particularly favorable properties as a surrogate fuel for NTP.

This study focuses on optimizing spark plasma sintering (SPS) conditions for achieving over 95% relative density in (Zr0.8, Nb0.1, Ta0.1)C. Various characterization techniques were employed, including grain size analysis, Archimedes’ density measurements, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), and Vickers hardness testing, to assess grain size, ideal density fraction, porosity, chemical composition, and hardness. Furthermore, the relationships among hardness, grain size, and density for samples consolidated under different sintering conditions were explored. Calculations of the activation energies for both sintering and grain growth were performed, identifying the underlying densification mechanisms through two distinct approaches.