Influence of supercritical drying fluids on structures and properties of low-density Cu-doped SiO2 composite aerogels

The Cu-doped SiO2 composite aerogels were successfully prepared by sol-gel process and subsequently supercritical drying with ethanol and CO2. The Cu-doped SiO2 composite aerogels had porous texture, low density (< 100 mg cm(-3)) and high specific surface area (> 800 m(2) g(-1)), which were investigated by FESEM and nitrogen adsorption desorption porosimetry. The FTIR spectra of the aerogels showed that the ethanol-dried aerogels had been modified by ethyl while the corresponding CO2-dried aerogels had more Si-OH groups. The phase structure and thermal stability were investigated by XRD and TGA, respectively. Due to the reducibility of ethanol, the copper was crystalline in ethanol-dried sample. The Cu-doped SiO2 composite aerogels dried with supercritical ethanol had larger pore diameter and better thermal stability under 400 A degrees C in comparison with CO2-dried composite aerogels. The structures and properties of Cu-doped SiO2 composite aerogels are obviously affected by supercritical drying conditions. The effect research could instruct the synthesis of different state of Cu in composite aerogels.