Mechanical Properties of Metal Oxide Aerogels

In this study we report on mechanical properties of molded, single component Al2O3, Ga2O3, Fe2O3, and ZrO2 as well as mixed aerogels, made from yttrium stabilized zirconia, yttrium aluminum garnet, and zinc aluminum spinel. Initially all aerogels were produced equally in molded bodies by a facile epoxy method and were annealed afterward at 300 °C. Then we performed uniaxial pressure tests on cylindrical aerogel monoliths to gain Young’s modulus which depends on composition, density, and post-treatment. Already pure aerogels like ZrO2 show well-promising Young’s modulus of 10.7 MPa, whereas most popular SiO2 materials display a modulus between 2 and 3 MPa at comparable densities. Moreover we focused on Al2O3 aerogels which exhibit high stability and interesting densification behavior depending on the annealing temperature. On the basis of this observation, we combined the toughness of the Al2O3 scaffold with the extraordinary hardness of ZrO2, by adding up to 20 atom % Zr, to increase the specific Young’s modulus. For the mixed material with a Zr content of 20 atom %, we reach a record value for compressible aerogels of 125 MPa mL g–1.