Nanopowders synthesized by mechanochemical processing

The activation of chemical reactions by milling reactants in a ball mill is presented here as a novel, low cost method for the synthesis of wide range of nanopowders with mean particle sizes as small as 4 nm. The factors controlling such mechanochemical reactions are discussed with respect to their influence on particle size, size distribution, and dispersion.

Recent developments in mechanochemical nanoparticle synthesis

The results of recent investigations of the mechanochemical synthesis of CaC0₃, Cr₂0₃ and Nb₂0₅ nanopowders are reported. With all three materials studied, it is shown that the volume fraction of the matrix phase is crucial to the formation of separate, unagglomerated particles. With Cr₂0₃ and Nb₂0₅, amorphous particles were formed by mechanochemical reaction and low temperature heat treatment was required for crystallization. It is shown that, as a 'bottom up' process, mechanochemical processing enables the building up nanoparticles through solid-state chemical reaction in a microscopically uniform environment, leading to the formation of nanoparticles with narrow size distributions.

Synthesis of high surface area amorphous tin-zinc oxides by a sol-gel method

A new method to synthesize conducting oxide nanoparticles with low photocatalytic activity was investigated. Initially, the preparation of amorphous ZnO-SnO2 solid solution nanoparticles was studied using a sol-gel technique. It was found that X-ray amorphous nanopowders with low photocatalytic activity were produced when the precipitates were heat treated below 500 °C. However, FT-IR data showed that the sample may not be an oxide semiconductor. A mixture of ZnO and SnO2 crystalline nanoparticles was also produced at 800 °C and found to have much reduced photoactivity than commercial ZnO nanoparticles having a similar specific surface area.