Zirconia aerogels: Effect of acid used in the sol-gel process on morphological properties

Zirconia aerogels have been prepared from butanolic zirconium(IV) tetra-n-butoxide diluted in ethanol via stoichiometric hydrolysis with water in ethanol. Nitric acid or acetic acid were used to modify the sol-gel process. After calcination in air at 573 K, the aerogel prepared with nitric acid possesses a specific surface area of 240 m² · g^–1 and a unimodal pore size distribution with a maximum at ca. 24 nm, whereas the use of acetic acid results in an aerogel with specific surface area of 228 m² · g^–1 and bimodal pore size distribution with maxima at 3 and 65 nm. The crystalline fractions of both aerogels are predominantly tetragonal with a small contribution of monoclinic ZrO₂.