Polymer-derived SiOC aerogel with hierarchical porosity through HF etching

Silicon oxycarbide (SiOC) aerogels have been synthesized from preceramic polymers via pyrolysis in inert atmosphere at 1200 and 1300°C. The as synthesized materials have a typical colloidal microstructure with mesoporosity in the range 10 – 50 nm and no microporosity. HF acid attack of the SiOC aerogels dissolves preferentially the SiO2-rich phase and creates microand (small)mesopores (< 10 nm) in the aerogels microstructure finally leading to a materials with hierarchical porosity. The HF post-pyrolysis treatment is more efficient for the SiOC aerogels pyrolyzed at the maximum temperature, i.e. 1300°C, leading to a maximum value of specific surface area of 530 m2/g and total porosity of 0.649 cc/g.