Hollow ordered zirconia microcage formation by spherical micelle templating with chelating triol surfactants

By appropriate selection of surfactant head group volume and binding constant of the surfactant head group moiety to Zr, the first example of spherical micelle templating in transition metal oxides was achieved. These materials consist of well-ordered arrays of spherical zirconia units as evidenced by an X-ray diffraction peak directly related to the repeat distance of the individual units which range from 15 to 30 Angstrom, depending on the surfactant chain length employed. Calcination of these materials leave an ordered cage structure of hollow zirconia spheroids which completely retain their XRD diffraction pattern. Small pores in the range of 6-8 Angstrom were revealed by argon adsorption studies. These pores are attributed to either gaps between adjacent spheres or cracks in the overall structure. This approach was also extended to make Ti, Hf, and Fe analogues of this material. These materials show promise as new sorbents, materials for separation membranes, components in sensors, new hydrocarbon isomerization catalysts, substrates for nano-encapsulation and microreactors. The hollow nature of the zirconia spheres may make them an inorganic alternative to carbon-based fullerenes. (C) 1999 Elsevier Science B.V. All rights reserved.