Densification and characterization of pressureless sintered ZrB2-20 vol% MoSi2 ultra high temperature ceramic composites

Abstract

In recent times, ultra-high temperature ceramic matrix composites (UHTCMCs) comprising of ultra-high temperature ceramics (UHTCs) such as ZrB2, HfB2 etc. reinforced with additives such as SiC, MoSi2 etc. have been reported to offer tremendous potentials in applications such as Hypersonic Re-entry vehicles, solar thermal absorbers, nuclear fuel claddings etc. Porous ceramics are advantageous in the aforementioned applications areas owing to their high melting points combined with high corrosion and wear resistance. Although ZrB2-SiC UHTCMCs (synthesized using pressureless sintering technique) have been widely investigated for their densification and mechanical properties at both room and elevated temperatures (till 3000°C), there is a very limited information on the densification behaviour and mechanical properties of ZrB2-MoSi2 UHTCMCs prepared using the aforementioned sintering technique. To this end, the present study is aimed at investigating the microstructure and correlating the same with the densification behaviour and mechanical properties of porous sintered ZrB2-20 vol.% MoSi2 (ZM20) UHTCMC. To this end, the composite was ball milled for 2h followed by compaction at different pressures. The compacted samples were sintered at 1700⁰C. X-Ray Diffraction (XRD) analysis was performed for the purpose of understanding phase evolution. Subsequent, microstructural investigation was performed under different magnifications in Scanning Electron Microscope (SEM). Moreover, density measurement; hardness and indentation fracture toughness calculations were performed to investigate the room temperature mechanical properties.