Effect of cationic and non-ionic surfactants on the microstructure of ambient pressure dried zirconia aerogel

Aerogels have superior properties such as low density, large specific surface area and high thermal insulation. Zirconia aerogels have great potential applications particularly in catalysis. Synthesizing zirconia aerogels with high porosities and large specific surface areas, however, is difficult. A surfactant was introduced to the sol to prevent the collapse of the pore structure during the gelation and drying processes. Surfactant-applied zirconia aerogels were synthesized by a sol-gel method via ambient pressure drying. Hexadecyltrimethylammonium bromide (CTAB) was used as a cationic surfactant, and Brij S10 and Pluronic P-123 were used as non-ionic surfactants. All surfactants yielded positive effects in terms of preventing the collapse of the pore structures and enhancing the specific surface areas. The cationic surfactant, CTAB, improved the specific surface area by up to 89%, and this increase is explained in detail by the repulsive forces of surfactant cations. The addition of the surfactants to the zirconia aerogels also resulted in improved thermal stability by which the aerogels had relatively large specific surface areas after annealing. The incorporation of a surfactant during the sol-gel process of the zirconia aerogel prevented the collapse of the pore structure. Through a comparison of surfactant type, it was determined that the cationic surfactant was most effective at preventing pore collapse.