Sol-gel-derived SiBOC ceramics with highly graphitized free carbon

SiBOC ceramics with highly graphitized free carbon were prepared from sol–gel derived pre-ceramic gels followed by pyrolysis at 1000–1600 °C under nitrogen. The effects of boron incorporation on the precursor architecture, microstructure and crystallization of SiBOC ceramics were discussed. The experimental results showed that the incorporation of boron had little effect on the silicon bonding environment in SiBOC precursor and led to a higher ceramic yield of 89%. The crystallization of both β-SiC and free carbon was enhanced in SiBOC ceramics. Raman spectra showed that the intensity ratio of D to G band was very small for the SiBOC ceramics pyrolyzed at 1600 °C, indicating the highly ordering and graphitization of free carbon. The clear presence of D׳ band at 1610 cm⁻¹ in Raman spectra suggested the partial substitution of C with B atoms in graphite layer, which significantly promoted the graphitization of free carbon. The turbostratic graphite with 10–20 layers graphene was observed by TEM.