Synthesis of indium oxide nanoparticles by solid state chemical reaction

A three stage process consisting of mechanical milling, heat treatment, and washing has been investigated as a means of manufacturing nanoparticulate powders of In2O3. In the first stage of processing, mechanical milling was used to prepare a nanocrystalline mixture of In2(SO4)3, Na2CO3, and NaCl. Subsequent heat treatment of the milled reactant resulted in the formation of nanocrystalline In2O3 particles embedded within a matrix of Na2SO4 and NaCl. In the final stage of processing, the In2O3 powder was recovered by washing with deionised water. The duration of milling was found to determine the degree of hard agglomeration in the final washed powder. It was also found that the average particle size of the powder could be controlled between 8 and 18 nm by simply varying the temperature of the post-milling heat treatment over the range of 400 to 550°C. These results demonstrate that solid state chemical reaction can be used as a technically simple method for manufacturing nanoparticulate In2O3 powders with a controlled particle size and low levels of hard agglomeration.