Wet Chemical Synthesis of ZrO_2-SiO_2 Composite Powders

摘要

Gels of composition xZrO_2(1-x)SiO_2, with x = 10, 20, 30 and 40 vol%, have been prepared by a wet chemical method using fumed silica and zirconyl chloride as precursors. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) show that weight loss is caused by release of the absorbed water and decomposition of the Zr(OH)_4 gels. Gels were heat-treated for 2 h at 500, 700, 900, 1100 and 1350℃, and the products examined using infra-red (IR) spectroscopy. The increasing intensity of the peak at 800 cm~(-1) in the IR spectra with increasing temperature is attributed to the formation of Si-O-Si bonds among different SiO_2 particles, which means that the SiO_2 particles grow bigger with increasing temperature. The DTA exothermic peak as well as the IR results reveal that the crystallization of tetragonal zirconia (t-ZrO_2) begins at about 900℃, which is confirmed by X-ray diffraction (XRD). XRD curves also suggest that the silica matrix contributes to the thermal stability of t-ZrO_2. The stability of t-ZrO_2 is interpreted by the particle-size effect.