Synthesis of the ZrO2–SiO2 microspheres as a mesoporous candidate material

A series of mesoporous ZrO2–SiO2 microspheres with different amounts of silica were synthesized by a polymerization-induced colloid aggregation process, using zirconyl chloride and commercial SiO2 colloids as the raw materials. The microspheres were characterized by scanning electron microscopy (SEM), N2 adsorption–desorption isotherms, X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). According to the SEM results, the ZrO2 and ZrO2–SiO2 microspheres had spherical morphologies and the sizes of the ZrO2–SiO2 microspheres increased with increasing SiO2/ZrO2 weight ratios. The XRD spectrum of the pure ZrO2 microspheres contained characteristic peaks for a monoclinic crystalline zirconia structure. The XRD spectrum of the ZrO2–SiO2 microspheres showed a tetragonal crystalline structure. The specific surface areas of the ZrO2–SiO2 microspheres increased with increasing SiO2/ZrO2 weight ratios, and the pore volumes also increased. The average pore size of the ZrO2–SiO2 microspheres was 3–5 nm. The FT-IR spectrum of the ZrO2–SiO2 microspheres confirmed the formation of Zr-O-Si bonds. The Zr-O-Si bonds make the metastable tetragonal zirconia stable at room temperature.