Hollow microspheres of ceramic material are formed by a sol-gel technique involving forming and stabilizing an emulsion of an aqueous sol of the ceramic material in an organic phase, followed by dehydration of the stabilized emulsion droplets by extraction using a water-absorbing organic liquid, to form...http://www.google.ca/patents/US5492870?utm_source=gb-gplus-sharePatent US5492870 - Hollow ceramic microspheres by sol-gel dehydration with improved control over size and morphology
