Graphite-assisted structural design of hierarchically porous SiC(rGO) PDCs with excellent capacity in thermal protection/insulation and load bearing for hypersonic vehicles.

High flight speed of hypersonic vehicles will push thermal insulation composites to achieve balanced enhancement of high porosity with increasing load-bearing capability. Herein, hierarchically porous SiC(rGO) polymer-derived ceramics (PDCs) with lightweight, heat-insulating, anti-ablative and tough engineered merits, are designed from polycarbosilane-vinyltriethoxysilane-graphene oxide precursors by re-pyrolysis/graphite-assisted decarburization. Graphite pore-forming agents tightly coupled with SiO x C y /C free (rGO) by C-dangling bonds, can inhibit SiO x C y decomposition, increase ceramic network disorder and expedite concurrent removal of C free. SiO 2 generated from Si-dangling oxidation bonding, efficiently densifies framework to retain mechanical performances, and meanwhile creates more interfaces to enhance phonon scattering. Such structure similar to nodular cast iron confers low thermal conductivity (0.11 W·m-1·K-1), particularly, fully preserves good compressive strength (5.4 MPa) for SiC(rGO) 40%. Under both cyclic butane flame ablation (∼1300 °C) and long-term oxidation for 7200 s, self-healing effect of SiO 2 imbues products with good structural integrity, shedding light on the opportunity to apply any thermal protection system. [Display omitted] • Hierarchically porous SiC(rGO) PDCs were ingeniously in-situ constructed. • Re-pyrolysis/graphite-assisted decarburization is a new structural design strategy. • The obtained products own well-balance between thermal insulation and load bearing. • Graphite-assisted interfacial interactions aims at strengthening ceramic framework. • Self-healing effect of SiO 2 can be promptly activated under flame scouring. [ABSTRACT FROM AUTHOR]