ALUMINA-COATED HOLLOW GLASS SPHERES ALUMINA COMPOSITES

Coating of alumina onto the surface of hollow glass spheres was accomp lished by controlled heterogeneous precipitation from aqueous solution s. The processing conditions were optimized to yield thin and uniform precursor coatings. After calcination, converting the precursor to alu mina, the alumina-coated hollow glass spheres formed free-flowing powd ers that were used to produce glass/alumina composites with up to 35 v ol% of controlled and well dispersed closed porosity. The dielectric c onstants and the flexural strengths of such porous composites were det ermined as a function of porosity.