Flash synthesis of titanium dioxide nanoparticles by strong exothermic reaction between solids without external energy

This paper describes the innovative flash synthesis of metal oxide nanoparticles by using only a strong exothermic reaction between solids without any external energy, such as that from an electric furnace, and its implementation for the synthesis of titanium dioxide. Flash synthesis is regarded as a type of combustion synthesis, in which the adiabatic flame temperature of the solid phase reaction is greater than the boiling point of the product. In the experiments, raw materials of different-sized titanium particles and sodium perchlorate were intensively mixed and ignited by an electrical heating foil to produce titanium dioxide through the following reaction: Ti + NaClO4 → TiO2 + NaCl. The product was obtained by removing NaCl by washing with distilled water. Evidently, all the products obtained through gasification in the heating process and nucleation and crystal growth in the cooling sublimation process were nanoparticles; the shape and crystal structure of the titanium dioxide product significantly depended on the particle size of titanium used as the raw material. That is, the smaller titanium particles (average size (AS) of 10 μm) resulted in rutile with an irregular shape, and the larger particles (AS of 25 μm) resulted in spheres of anatase with a size of 100-1000 nm. This method can be easily applied to produce other metallic oxides, thus offering many benefits such as easy mass production, energy saving, and short processing time.