Characterization of silica nanocomposites obtained by sol-gel process using positron annihilation spectroscopy

Abstract

SiO2 matrix was prepared by a sol-gel method using tetraethoxysilane, TEOS, ethanol and water in a 1/3/10 mole ratio, with HCl and HF as catalysts. This silica gel was doped with copper with different precursors and different contents of dopant. The samples were prepared into monolithic shape, dried at 110 degreesC for 24 h and thermally treated for 2 h at 500, 900 and 1100 degreesC. The structural evolution was studied by positron annihilation lifetime spectroscopy (PALS) which has been shown to be a useful tool for pore size analysis in several materials, X-ray diffraction (XRD) and nitrogen gas adsorption. All the samples have shown, according to the positron spectroscope results, a stable pore structure up to 900 degreesC and a strong densification process at 1100 degreesC.