Preparation and characterization of hollow glass microsphere ceramics and silica aerogel/hollow glass microsphere ceramics having low density and low thermal conductivity

Novel thermal insulation material consisting of a frame work of hollow glass microspheres (HGMs) and embedded silica aerogel was prepared by allowing silica sol to penetrate into HGM ceramics, followed by drying under ambient pressure. HGM porous ceramics were obtained after sintering of closed packed HGMs together. Properties such as density, porosity, compressive strength, thermal conductivity (λ), and microstructure of each specimen prepared at different temperatures were systematically studied. Results showed that HGM ceramics had lower density ranging from 0.136 to 0.701 g/cm3. The density, compressive strength, and λ of HGM ceramic increased with increase in sintering temperature and true density of HGM. After filling HGM ceramic with silica aerogel, thermal conductivity was reduced by about 27%. Moreover, the introducing of aerogel changed the mode of thermal conduction of the composite by reducing heat transfer of air between HGMs. The composite showed super-hydrophobicity (contact angle >150°) due to the presence of organic methyl groups. Silica aerogel/HGM ceramics with low density and low thermal conductivity prepared by embedding of silica aerogel into HGM ceramic, not only overcame the disadvantage of large-size aerogel materials during fabrication, but also solved the problem of high water absorption of inorganic materials.