Regulating graphene growth behavior through surface chemical modification of SiC fibers

The interphase in continuous SiC fiber-reinforced ceramic matrix composites is critical to their mechanical reliability, and graphene is a promising interphase material. However, the effect of substrate surface condition on graphene growth on SiC fibers remains unclear. Here, graphene grown by chemical vapor deposition on pristine SiC fibers and pre-oxidized SiO₂/SiC fibers is systematically compared. Experiments show that pristine SiC promotes early multi-point nucleation and an outward-propagating SK-like mode, whereas the pre-oxidized surface favors conformal layer-by-layer growth, leading to a smoother FM-like morphology. First-principles calculations reveal that SiC more strongly catalyzes carbon-source cracking and generates active carbon species, while SiO₂ is more favorable for carbon diffusion and conformal growth. In addition, graphene edges, steps, and curved regions tend to act as secondary nucleation sites, inducing disordered multilayer growth at later stages. These results provide guidance for tailoring graphene interphases on SiC fibers by surface pretreatment.