LAUSR

Abstract UHTCs are the most suitable materials for space and hypersonic, however in service they lose their properties owing to oxidation damages. Tailoring composition and microstructure on a multiscale level may maintain structural stability in the sub-layers. Sintering of ZrB2-MoSi2 ceramics at 1900–2150 °C results in microstructures characterized by partial or complete (Zr,Mo)B2 solid solutions. This has notable impacts on the performance of the composites subjected to cyclic oxidation at 1650 °C. Coupled XRD, SEM and TEM analyses pointed out the formation of a unique interpenetrating microstructure, where ZrO2 micro-grains encase stable nano-sized MoB particles. This architecture manifested its suitability during repeated oxidation limiting the effect of oxygen attack to some microns thickness, due to diffused Mo which prevented turbulence and bursting phenomena on the outer glass. This study elucidates the processing conditions that lead to the development of prominent materials for application in new generation thermal protection systems for reusable space components.