Preparation of Micro‐/Mesoporous SiOC Bulk Ceramics

Micro‐/mesoporous Si OC bulk ceramics with high surface area and bimodal pore size distribution were prepared by pyrolysis of polysiloxane in argon atmosphere at 1100°C–1400°C followed by etching in hydrofluoric acid solution. Their thermal behaviors, phase compositions, and microstructures at different nano‐SiO 2 filler contents and pyrolysis temperatures were investigated by XRD , SEM , DSC , and BET . The SiO 2 fillers and SiO 2 ‐rich clusters in the Si OC matrix act as pore‐forming sites and can be etched away by HF . At the same time, the SiO 2 filler promotes Si OC phase separation during the pyrolysis. The filler content and pyrolysis temperature have important effects on phase compositions and microstructures of porous Si OC ceramics. The resulting porous Si OC bulk ceramic has a maximum specific surface area of 822.7 m 2 /g and an average pore size of 2.61 nm, and consists of free carbon, silicon carbide, and silicon oxycarbide phases.