In-situ construction of oxidation resistant porous Mo4.8Si3C0.6/SiC(rGO) composite PDCs served as thermal insulation components of hypersonic vehicles

Abstract

Actualization of well-balanced high porosity with simultaneous increase in hardness/fracture toughness for thermal insulation composites in hypersonic aerospace vehicle components is always of great challenge. Considering significant toughening effect of unique Mo4.8Si3C0.6-SiC composites microstructure, an agile strategy is proposed to prepare porous Mo4.8Si3C0.6/SiC(rGO) polymer-derived ceramics (PDCs) via re-pyrolysis of ball-milling-induced MoSi2-SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene oxide (PVG) precursors blends with polystyrene (PS) as pore-forming agent. In-situ formed Mo4.8Si3C0.6-β-SiC nanocrystals, possessing eminent mechanical properties and good compatibility with SiOxCy/Cfree, can significantly strengthen interface bonding and increase disorder of ceramic network. Such effective hindrance to crack propagation moderates the inherent brittleness while retaining high hardness of SiC PDCs. Moreover, dense Mo4.8Si3C0.6-β-SiC/SiOxCy/Cfree(rGO) framework, with spontaneous regular pore structure, well balances loading/thermal insulation capacity. Particularly, samples with 10 wt.% PS exhibit outstanding mechanical performances (hardness: 5.10 GPa; fracture toughness: 2.24 MPa·m1/2; compressive strength: 58.15 MPa) and low thermal conductivity (0.8427 W·m-1·K-1). As demonstrated, products remain decent structural integrity after ablation of butane blowtorch flame for 1-20 min. The synergy oxidation with fast response of Mo4.8Si3C0.6 and durability of β-SiC facilitates great anti-oxidation ability, opening up manufacture of SiC-based composites for thermal protection system (TPS) of hypersonic vehicles and re-entry spacecraft with ultra-high speed.