Design of lightweight and antioxidant SiCnws/SiC(Mox, rGO) nanocomposite from molybdenum-modified precursors for aerospace vehicle components

Abstract

Making lightweight SiC composite ceramics with good load-bearing and remarkable surficial antioxidant capacity for use in thermal protection system is challenging. In this contribution, an ingenious strategy is reported to produce SiC(Mox, rGO) nanocomposite polymer-derived ceramics (PDCs) for the first time by reactively re-pyrolyzing flexible polymolybdenumcarbosilane-vinyltriethoxysilane-graphene oxide (PMVG)/rigid SiC(Mox, rGO)p fillers blends. Highly cross-linked PMVG precursors connect up to five polycarbosilane (PCS) to optimize their formability. In-situ formed MoSi2 and Mo4.8Si3C0.6, compatible with β-SiC/SiOxCy/Cfree(rGO) matrix, can effectively strengthen interface bonding, promote nailing cracks, and even hinder β-SiC grain growth. More interestingly, using in-situ SiC nanowires (SiCnws) by Mo-containing catalyst to decorate samples is an efficient route to reinforce the ceramic network, and SiCnws/SiC(Mo0.1, rGO) nanocomposite PDCs display optimal Vickers hardness (5.19 GPa), enhanced fracture toughness (4.26 MPa·m1/2), high compressive strength (151.73 MPa), and low linear shrinkage (4.75%). Such products remain stability/integrity under flame scouring, their surface is covered by a dense SiO2 passivation layer with good self-healing capacity owing to unique non-destructive oxides of embedded MoSi2/Mo4.8Si3C0.6. This work can further provide a feasible way to overcome the critical fabrication process in lightweight porous PDCs with well-balanced high load-bearing and good thermal insulation integration for aerospace vehicle components.