High-Purity Glasses and Ceramics Prepared by Sintering Compacts of Nanosized Particles: Advantages and Perspectives

The preparation of high-purity glasses and ceramics via shaping and sintering of compacts of nanosized powders offers many perspectives for optical materials. Due to small diffusion paths inside a nanosized particle impurities can be efficiently removed in a reactive atmosphere. Of special interest are functional nanosized particles, which can be incorporated into the compact through the open pores. The starting materials used were made by flame hydrolysis. Commercially available at a low price are silica glass powders (8-40 nm in size), alumina, zirconia and titania (typically 20-30 nm in size). These powders are well suited for the preparation of advanced materials because they are non-porous and spherical. For additional applications, especially in the field of coatings, pure silica powders are not sufficient due to the small thermal expansion coefficient. Therefore, the flame hydrolysis process was modified and multicomponent (e.g. SiO2, B2O3, Na2O, Al2O3) nanosized glass powders were prepared. Compacts of these powders can be sintered to transparent coatings at temperatures down to 650 C. (Author)