High transmittance and ultra-low thermal conductivity ZrO2 aerogel via zirconium hydroxyacetate precursor

Zirconia (ZrO2) aerogels have the potential to service at temperatures exceeding 1000 degrees C, exhibiting superior insulation performance over those of silica, alumina and carbon aerogels, etc., but the zirconium chloride based salts, such as zirconium oxychloride, with overfast phase separation rate and indelible chlorine impurities, impede the development of an economic and environmentally benign synthesis. Besides, the stabilities of ZrO2 aerogels toward high temperature exposure need to be further improved. With these regards, in this work, zirconium hydroxyacetate was brought up for the first time to produce ZrO2 aerogel with the aid of a tailor-made sol-gel chemistry. Polar solvents were found to be efficient in manipulating the phase separation. After depositing silica to the gel network, ZrO2 aerogels with a maximum visible light transmittance of up to 90 %, compressive strength of 0.24 MPa (0.159 g center dot cm � 3) were successfully obtained. The thermal conductivity of the aerogel reached a recorded value of 9.67 mW center dot m � 1 center dot K-1 at room temperature. The resultant aerogels possess a uniform skeleton structure with pore distribution below 20 nm, and can retain their mesoporous structure at 1000 degrees C, keeping a specific surface area of 200 cm2 center dot g � 1. This work presents a well-established procedure for synthesizing highquality ZrO2 aerogels and promotes their utilization in optics, thermal insulation, and other related fields.