Flame aerosol synthesis of ceramic powders

Abstract

Flame aerosol technology is used for large-scale manufacture of ceramic commodities such as pigmentary titania, fumed silica and alumina. In addition, the introduction of this technology to the manufacture of optical fibers and its potential for cheap synthesis of ultrafine particles (e.g. nanoparticles) has renewed the research interest for better understanding of flame aerosol reactors. Here, after an overview of the history of this technology, the current state of knowledge on the role of flame process variables (additives, mixing etc.) on the characteristics of product powders is summarized in a tutorial fashion. The fundamentals of particle formation and growth are highlighted by summarizing the dynamics of spherical particles that are reasonably well understood. The latest advances on the theory of aggregate particle dynamics that are typically encountered in flame synthesis of powders are presented. Specific applications in the manufacture of fumed silica, pigmentary titania, alumina, and other oxide and non-oxide ceramic powders are reviewed. Finally, research needs are highlighted by pointing out the most promising areas for advancing the field with emphasis on instrumentation and need for detailed simulators of the process accounting for the concurrent chemistry, transport and aggregate particle dynamics. With major recent advances in diagnostics and understanding in both combustion and aerosol science and engineering, this field is ready for a new leap forward.