Realizing load bearing-heat insulation integration of lightweight porosity-controlled SiC(rGO) bulk ceramics via precursor route for hypersonic vehicles

Abstract

Realizing integration of admirable load bearing and outstanding heat insulation characteristics of porosity-controlled ceramics for hypersonic vehicles is a great challenge. Herein, an ingenious strategy based on re-pyrolysis process of ball-milling-induced fillers/precursors(pore-forming agents) blends is proposed to prepare porous SiC(rGO) bulk polymer-derived ceramics (PDCs) for thermal protection. During re-pyrolysis, dense integrated β-SiC/SiOxCy/Cfree(rGO) framework, belonging to SiC(rGO)p tightly tied by SiC(rGO) from polycarbosilane-vinyltriethoxysilane-graphene oxide (PCS-VTES-GO, PVG), can be formed to maintain brilliant mechanical properties of products. Meanwhile, good interfacial compatibility of nanocomposite structure within the framework also contributes to load capacity. A uniquely uniform distribution of dentinal tubules-like pores, originated from polystyrene (PS) in SiC(rGO) region, could relax stress at crack tips and ensure good thermal insulation. Particularly, lightweight porous SiC(rGO) bulk PDCs with 10 wt% PS content possess low thermal conductivity (0.25 W·m−1·K−1), excellent fracture toughness (1.96 MPa·m1/2), outstanding hardness (3.58 GPa), optimal compressive strength (51.80 MPa) and good flexural strength (33.86 MPa). Their large-sized molding ability and good high-temperature oxidation resistance were significantly demonstrated by further exploration. Such well-balanced high load bearing and good heat insulation integration nature can be used to make thermal insulators with complex shapes in a facile and economical manner.