MAHDI MOETNI - Nuclear Science and Technology R ch Insti Atomic energy organization of Iran Tehran, Iran.
SEYED JAVAD AHMADI - NFCRS, Nuclear Science and Technology Research Institute, Atomic energy organization of Iran, Tehran, Iran.
AZIMI MALEKZADEH - Chemistry Department, Damghan University, Damghan, Iran.
MORTEZA HOSSEIPOR - Department, Sharif University of Technology Tehran, Iran.

Thorium dioxide (Thoria) nano-particle was synthesized by employing supercritical water (SCW) as an excellent reaction environment for hydrothermal crystallization of metal oxide particles. This method is ideal for production of ultrafine powder having controlled stoichiometry, high quality, purity and crystallinity. The nano-crystalline thoria was synthesized in a stainless steel (31.6L) autoclave and fed with an aqueous solution of ThNO3)4.5H2O as reactant and took place under SCW condition. The products were characterized by X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM). The crystallite size of the products was calculated by Scherre equations. Some parameters which enrolled major effects like temperature, duration, initial pH and concentration of reactant were manipulated by using L9 orthogonal array (Taguchi experimental design method) to find optimization condition for synthesis of ultrafine and uniform powders. The average size of nano-particles was found to be about less than 5 nm with a particle size distribution in the 2-11 nm. range. The XRD broad peaks are attributed to presence of nano-sized thoria. The calculated yield was found to be 93%.

Thoria; Nano-Crystalline; Fine Structure; supercritical water; hydrothermal process