Effect of additives on the thermal conductivity of zirconium diboride based composites – A review

Abstract

Abstract Re-entry space vehicle necessities sharp leading edges for better aerodynamic performance and, hence, require advanced thermal protection materials with improved safety for crew members. Material possessing high thermal conductivity and oxidation resistance are desirable at nose cap and wings leading edge of spacecraft. Consequently, the thermal shock resistance improves due to reduced thermal gradient and stresses. ZrB2 has drawn strong impetus for futuristic space vehicles as thermal protection materials under extreme thermal environments. This study reviews the effect of the incorporation of non-carbonaceous and carbon additives on the thermal conductivity of ZrB2 ceramics and based composites. Several factors such as the purity of starting powder, initial particle size, amount of sintering aids, processing route, porosity, the grain size of ZrB2 matrix, distribution of secondary phases in the matrix and sinter density of the final composite, controls the overall thermal conductivity of ZrB2 based composites.