Non-firing ceramics: Activation of silica powder surface for achieving high-density solidified bodies

Abstract

Sintering of most ceramic materials requires high temperatures over 1000 °C due to their high melting point. Sintering is a high-cost process, which can take several hours or days. Also, sintering at high temperatures can affect the microstructure of ceramics by causing undesired grain coarsening or changing the chemical stoichiometry of final product when volatile elements are present. In this study, a so-called “non-firing sintering” of silica particles is proposed, without using thermal energy. This method involves the chemical activation of powder surface via ball milling, where the surface of particles is rubbed against balls, and friction between particle/ball breaks the bonds of functional groups like SiOSi on the surface of particles. Results show that water adsorption increases as milling time is increased, while particle size is unchanged after ball milling according to nitrogen adsorption isotherms. Scanning electron microscopy results confirm the trans granular fracture of pellets prepared by ball milling, and transmission electron microscopy micrographs show a necking-like bonding between silica particles.