On Preparation of Non‐Disrupted Particles by Spray Pyrolysis

Using spray pyrolysis, solid fully‐filled zirconia particles were synthesized at relatively high reactor temperatures (～ 400 °C) by adding NaCl as impurities to zirconium hydroxychloride (ZHC) precursor that would have lead to the formation of hollow disrupted particles otherwise. FE‐SEM images show that at comparable concentration of NaCl and ZHC both cubic and spherical NaCl/ZrO₂ particles form. The particle characteristics were varied by varying solute concentration, type, and solvent content. Addition of NaCl caused the formation of both cubic and spherical particles which were non‐disrupted at even high temperatures. According to the EDS compositional analysis, the cubic particles had more Na content while the spherical ones had higher Zr content. It is concluded that growth mechanism of NaCl particles is different from that of zirconia particles. Drying of the former even at high temperatures leads to the formation of solid, fully‐filled, porous particles, whereas hollow, disrupted particles are formed using the latter.     

Preparation and Characterization of Nano-structured Ceramic Powders Synthesized by Emulsion Combustion Method

The emulsion combustion method (ECM), a novel powder production process, was originally developed to synthesize nano-structured metal-oxide powders. Metal ions in the aqueous droplets were rapidly oxidized by the combustion of the surrounding flammable liquid. The ECM achieved a small reaction field and a short reaction period to fabricate the submicron-sized hollow ceramic particles with extremely thin wall and chemically homogeneous ceramic powder. Alumina, zirconia, zirconia–ceria solid solutions and barium titanate were synthesized by the ECM process. Alumina and zirconia powders were characterized to be metastable in crystalline phase and hollow structure. The wall thickness of alumina was about 10nm. The zirconia–ceria powders were found to be single-phase solid solutions for a wide composition range. These powders were characterized as equiaxed-shape, submicron-sized chemically homogeneous materials. The powder formation mechanism was investigated through the synthesis of barium titanate powder with different metal sources.