Silicon carbide with tunable ordered mesoporosity

• Ordered mesoporous SiC by magnesio-thermal reduction of silica and carbon composites.
• Triblock copolymers, P123 and F127, used as structuring agents.
• Low temperature reaction thanks to Mg used as reductive agent.
• Pore size and wall thickness controlled by carbon/silica ratio and copolymer nature.
• Growth mechanism governed by SiOx diffusion.

Tunable mesoporous silicon carbides (SiCs) are synthesized by magnesio-thermal reduction of homogeneous composites of silica and carbon precursors. Two triblock copolymers, P123 and F127, are used as structuring agents leading to composites showing an hexagonal mesoporous pattern which is kept by the final SiC thanks to the relatively low temperature of the magnesio-thermal reduction. Two series of mesoporous SiCs are obtained with uniform pore sizes ranging from 6.0 nm to 2.5 nm (P123 used as structuring agent) and 11.0–3.5 nm (F127) depending on the carbon/silica molar ratio in the pristine composite. In each series, SiC polytype transforms from 6H–SiC to 3C–SiC in pace of increasing the carbon content in the composite precursor. A multi step growth mechanism is proposed to account for the composite precursor to final carbide characteristics.

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