| Due to their promising mechanical properties, chemical durability, excellent oxidation resistance, high-temperature stability (up to 1300 °C) and other excellent properties, silicon oxycarbide (SixOy Cz) materials are being used today as catalysts, catalytic supports, gas or liquid adsorbents, lithium battery anodes, light emitters, and blood contact agents.;In this research, layered double hydroxides (MgAl-LDHs), or modified LDHs (SDBS-LDHs) are used as templates to fabricate nanoporous SixO yCz materials using precursors, such as tri-isopropylsilane (TPS) and a allyl hydridopolycarbosilane (AHPCS)/ hydridopolycarbosilane (HPCS) mixture, with synthesis methods that include chemical vapor deposition (CVD) and direct impregnation. The preparation conditions such as the pyrolysis temperature and the CVD precursor injection flow rates are investigated. We study the characteristics of the templated porous materials fabricated by different preparation routes using techniques such as small-angle X-ray diffraction (XRD), wide angle XRD, X-ray photoelectron spectroscopy (XPS), XPS elemental analysis, SEM-Energy dispersive X-ray spectroscopy (SEM-EDX), scanning and transmission electron microscopies (SEM and TEM), as well as nitrogen adsorption-desorption (BET) measurements.;The porous SixOyCz materials fabricated from the TPS precursor and the unmodified LDH template by CVD have a specific surface area as high as 541 m2/g and a total pore volume as large as 0.91 cm3/g. The materials consist of fairly uniform size hollow spheres with sizes between 10 and 30 mum and one opening, with an interior ordered layered structure and a bimodal pore size distribution, both in the mesopore and micropore regions. The template's ordered structure has been successfully reproduced by the CVD procedure. After calcination of the materials in air at 450 °C for 3 h, most of the free carbon present is eliminated and any silicon carbide present initially has been oxidized into silicon oxycarbide.;A convenient impregnation technique has also been selected to synthesize SixOyCz materials using AHPCS/HPCS polymer blends as precursors and SDBS-LDH as a sacrificial template. The produced materials demonstrate a well-aligned, slit-like pore structure, a surface area of 531 m2/g with a considerable fraction of micropores and mesopores. The key aspect of the preparation process is the stabilization of the HPCS by the AHPCS during the thermal treatment, which guarantees an interconnected porous space in the final material. Calcination in air at 450 °C for 3 h removes any free carbon from the material, while the pore structure is preserved.;The SixOyCz materials fabricated in this research, using economically-feasible templates and precursors and convenient synthesis procedures, have desirable structures, and show promise for applications such as catalyst supports, sorbents, membrane films for water filtration and gas separations, and as battery anodes, etc. |
