Improvement of Thermal Stability of ZrO_2-SiO_2 Aerogel Modified by Ca(Ⅱ) Cations

摘要

Ca(Ⅱ) modified ZrO_2-SiO_2 aerogel (CaZSA) with excellent thermal stability at 1000 °C was prepared by aging the ZrO_2-SiO_2 wet gel in calcium nitrate (Ca(NO_3)_2) ethanol solution followed with alcohol supercritical fluid drying method. The reaction between surface hydroxyl groups on the aerogel and Ca(Ⅱ) ions played an important role in reducing the high temperature activity and inhibiting the particle growth caused by the condensation of hydroxyl groups of aerogel. Moreover, tiny secondary-phase particles, Ca(Ⅱ) ions, introduced along grain boundaries serve as the pinning particles to inhibit the crystallization of ZrO_2-SiO_2 aerogel (ZSA). Thus the high-temperature stability of ZSA was significantly improved by surface modification with Ca(Ⅱ). The specific surface area of CaZSA still maintained 223 m~2·g~(-1) after 1000 °C calcination, which was 52.7% higher than that of ZSA at the same treatment condition.