In-Depth Investigation of the Carbon Microstructure of Silicon Carbide-Derived Carbons by Wide-Angle X‑ray Scattering

Abstract

Polymer-based silicon carbide-derived carbons (Si-CDCs) synthesized at temperatures from 600 to 1500 °C using different templating methods were characterized by wide-angle x-ray scattering (WAXS), Raman spectroscopy, and transmission electron microscopy (TEM). A recently developed advanced algorithm for fitting the whole WAXS data curve of non-graphitic carbons, that is, carbons with a polyaromatic sp² structure, revealed fine details about the CDC microstructure on the level of the graphene layers. In particular, this approach allowed the quantification of disorder effects in the graphene stacks and the clarification of the peculiarity of CDCs. It is seen that, contrary to other types of carbons, almost no stacking of the sp² layers occurs; that is, the stack height <i>L</i>_c is rather small (8 Å) and increases only slightly with higher synthesis temperatures, whereas the graphene layer extent <i>L</i>_a grows significantly, from 16 to 29 Å. Additionally, the microstructures of various types of CDCs were investigated: a hexagonal CDC and a cubic ordered mesoporous CDC, as well as a macroporous CDC. The WAXS analysis reveals that soft-templated CDCs, featuring macroporosity with an average wall thickness of hundreds of nm, show a more uniform stacking order than mesoporous CDCs obtained by hard-templating, with an average wall thickness of a few nanometers