Fabrication of high-surface area nanoporous SiOC ceramics using pre-ceramic polymer precursors and a sacrificial template: Precursor effects

We report on the fabrication of silicon oxycarbide (SiOC) ceramics with high surface area, porosity and hierarchical pore structure, which are synthesized using pre-ceramic polymer precursors, such as hydridopolycarbosilane (HPCS), allyl-hydridopolycarbosilane (AHPCS) and their blends. Layered double hydroxides, modified by a common surfactant, namely, sodium dodecylbenzenesulfonate (SDBS), are used as the sacrificial templates, and a simple impregnation technique is employed, followed by pyrolysis and acid leaching. Characterization techniques, such as XRD, XPS, electron microscopy, elemental analysis, and nitrogen adsorption/desorption at its liquid temperature are used to verify that the SiOC materials have been successfully synthesized, and to study their chemical and structural characteristics. The emphasis is on the effects, which are shown to be significant, of the type of polymer precursor employed (AHPCS or HPCS), their weight ratio (in the case of blends), and the amount of polymer precursor used during the template impregnation. Depending on the polymer ratios and amounts utilized, SiOC particles with a variety of morphologies, ranging from plate-like to flower-like structures, have been prepared that have hierarchical structures and high surface areas, ranging from 531 m(2)/g to 1311 m(2)/g, and large pore volumes from 0.47 m(3)/g to 1.20 m(3)/g. The study provides guidance for the systematic design and fabrication of highly porous SiOC materials with potential for broad application in various fields, such as catalysis, sorption and membrane separations under harsh conditions, and biomedical device uses, among others. (C) 2017 Elsevier Inc. All rights reserved.