Thermal Conductivity Characterization of Hafnium Diboride-Based Ultra-High-Temperature Ceramics

Abstract

We evaluated the thermal conductivity of HfB₂-based ultra-high-temperature ceramics from laser flash diffusivity measurements in the 25°–600°C temperature range. Commercially available powders were used to prepare HfB₂ composites containing 20 vol% SiC, some including TaSi₂ (5 vol%) and Ir (0.5 or 2 vol%) additions. Samples were consolidated via conventional hot pressing or spark plasma sintering. Processing differences were shown to lead to differences in magnitude and temperature dependence of effective thermal conductivity. We compared results with measured values from heritage materials and analyzed trends using a network model of effective thermal conductivity, incorporating the effects of porosity, grain size, Kapitza resistance, and individual constituent thermal conductivities.