Synthesis of monolithic zirconia aerogel via a nitric acid assisted epoxide addition method

Abstract

Monolithic zirconia aerogels were prepared using zirconium oxychloride (ZrOCl₂) as the precursor in the presence of the epoxide (PO) in both ethanol and mixed ethanol–water solutions, respectively. The effects of nitric acid and water contents on the gel formation behavior and the properties of the resulting aerogel were investigated. The results show that at a molar ratio of HNO₃/ZrOCl₂ of 1.0 and H₂O/ZrOCl₂ of 10, the translucent monolithic ZrO₂ aerogels were obtained and they exhibited a well-developed mesoporous structure and a high specific surface area of 454 m² g⁻¹. The as-prepared aerogels were composed of mainly amorphous phase and a spot of ZrO₂ crystal. After calcination at 750 °C for 2 h, the ZrO₂ transformed into tetragonal phase. These results suggested that this HNO₃-assisted epoxide addition method was a simple and controllable way to get translucent monolithic zirconia aerogels.