Fabrication, properties and arc-jet testing of ZrB2-based composite containing short SiC fibres

Some borides-based composites are conventionally classified as ultra-high temperature ceramics (UHTCs) for their extremely high melting points. UHTCs are actively studied as key enabling technology for thermal protection structures (TPS) like wing leading edges, surface control components to be applied in the next generation of space vehicles flying at hypersonic speed or/and re-entering the Earth's atmosphere: increased performances and better maneuvrability are gained only through the design of sharp profile. For the present contribution, a fully dense ZrB2-based composite containing short SiC fibres was produced by hot pressing, and thus characterized. Nominally identical test articles with an hemispheric shape (5 mm radius of curvature) were machined and exposed to high enthalpy supersonic flows for different duration up to 19 MJ/kg using an arc-jet plasma wind tunnel. Surface temperature and optical properties were on-line monitored. Post-test microstructural changes were analyzed by SEM-EDX and correlated to test conditions through Computational Fluid Dynamics (CFD)simulations. Specific samples were also produced to evaluate the catalytic recombination of oxygen by optical emission spectroscopy and actinometry.