Core-shell structure ZrO2-Al2O3 aerogels prepared by one-step drying under constant pressure

Abstract

In this work, the monolithic ZrO₂-Al₂O₃ aerogels with hollow sphere structure were prepared by ambient pressure drying. In the preparation process of Al₂O₃ hollow spheres, different mole of ZrOCl₂·8H₂O was added. We explored the maximum addition of zirconium via ambient pressure drying. A series of ZrO₂-Al₂O₃ aerogels with hollow sphere structure were successfully synthesized using AlCl₃·6H₂O and ZrOCl₂·8H₂O as aluminum and zirconium precursor, and propylene oxide (PO) as the gel initiator by the sol-gel method. It was found that the gelation time was prolonged with increasing zirconium content. When the zirconium content was more than 10%, the gel can't obtain. It can only get precipitation. With the zirconium content increase, the core-shell structure can be formed, proved by SEM and TEM characterizations. The core-shell structure can be kept well under 1000 °C. When the heat treatment temperature was 1200 °C, the diffraction peaks were mainly ZrO₂ and Al₂O₃, showed by XRD. With the content of zirconium from 0 to 10%, the specific surface area of XZrO₂-Al₂O₃-aerogel increased from 170 to 582 m²/g.