Characterization of Synthetic Amorphous Silica (SAS) Used in the Ceramics Industry

Abstract

Silica (SiO2) is one of the most important inputs for the food, pharmaceutics, polymer composite, and ink manufacturing industries. In ceramic materials, fine silica particles are widely used as a packing and sintering aid and to produce other raw materials like mullite (3Al2O3·2SiO2) and silicon carbide (SiC). As most of the silica sources found in nature have relatively low purity and nonhomogeneous properties, use of synthetic grades of silica is necessary in applications such as refractories and technical ceramics that require better control of product composition and microstructure. This paper describes a systematic comparison of four grades of synthetic amorphous silica (SAS) used in technical ceramics. The evaluated SAS materials were formulated by different methods (sodium silicate precipitation, SiCl4 pyrolysis, extraction from rice husks, and physical deposition of silicon vapour). Differences in the physicochemical and thermal and microstructural characterization of each material are related to the principles and techniques involved in their manufacture. The study verified that synthesis conditions strongly influenced the composition and physical properties of the tested SAS samples.