Spectroscopic, structural and textural properties of CaO and CaO–SiO2 materials synthesized by sol–gel with different acid catalysts

Calcium oxide and a mixed CaO(10)–SiO2(90) wt% sample were synthesized by sol–gel method, using HCl or HNO3 as hydrolysis catalysts. The powders were thermally treated at 200, 400, 600 and 800 °C. Sample characterization was carried out by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The specific surface area and pore volume were measured by the BET method. For the pure samples, it was found that the crystalline phases and structural properties depend on the catalyst used during the synthesis; whereas the surface areas were similar in both cases. On the other hand, at high temperatures, the mixed CaO–SiO2 oxide showed glass-like properties, where CaO is dispersed in an amorphous phase.