Structural and thermal study of highly porous nanocomposite SiO2-based aerogels

Nano-porous silica-based aerogels with additive of TiO2 were successfully synthesized by an ambient pressure drying method. After aging and washing of wet gel, surface modification with cyclohexane was followed to replace the solvent in the pores of wet gel to reduce the surface tension during ambient drying. The microstructure and thermal properties of the SiO2–TiO2 aerogels were characterized by scanning electron microscopy (SEM), transmitting electron microscopy (TEM), high resolution electron microscope (HREM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results showed that silica aerogels exhibit a sponge-like microstructure. The spherical SiO2 particles with a size of a few tens of nm form a 3-dimensional network containing homogeneous pores. Nano-TiO2 powders are physically embedded by SiO2 aerogel, and there is an obvious Ti–O–Ti and Si–O–Si bonding group based on structural analysis. The optical transmittance of the heat-treated composite aerogels was obviously decreased with increasing nano-sized TiO2 additive.