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Abstract

We report the fabrication of silicon oxycarbide (SiOC) ceramics with high surface area and porosity and a hierarchical pore structure. They have been synthesized using polymer blends that consist of allyl hydridopolycarbosilane (AHPCS) and hydridopolycarbosilane (HPCS) as the precursors. Layered double hydroxides (LDHs), modified by sodium dodecylbenzenesulfonate (SDBS), a common surfactant, are used as a sacrificial template, and a simple impregnation technique is employed to enable the polymer precursor to penetrate into the LDH structure. Various characterization methods, such as XRD, XPS, and SEM-EDX, are used to verify that the ceramics that are produced are SiOC materials. A key aspect of the fabrication process is the use of pre-ceramic polymer blends that are capable of producing ceramics with an interconnected porous space. Air calcination of the as-prepared SiOC ceramic removes any free carbon that is present, but preserves the pore structure of the material. The SEM images indicate that the materials' internal pore structure consists of well-aligned, slit-like pores. Nitrogen sorption measurements demonstrate that the material fabricated from polymer blend AHPCS/HPCS = 2:1 has surface areas as high as 811.7 m2/g, total pore volume as large as 0.80 cm3/g with considerable fractions of micro- and mesopores. The synthesis method that we have developed uses low-cost pre-ceramic polymer precursors and templates and generates porous SiOC ceramics with high surface area, interconnected pore space with a multi-modal pore size distribution, and high-temperature stability. As such, the technique may be considered as a convenient and cost-effective approach for the fabrication of a wide class of porous materials for such applications as catalysis, gas adsorption/separation under harsh conditions, and biomedical device uses, etc.