RESUMO
Using a non-aqueous sol-gel process with a direct calcination step in air after prior drying, silver nanoparticles with average size distribution ranging from 20 to 100 nm were synthesised. Studies in reduced atmosphere were also performed with mixed results, both in phase and particle size, as the samples were found to be mixed with an amorphous phase. In oxidising atmosphere, the temperature and dwelling time were found to be critical factors with the former playing a larger role than the latter. Optimally nanoparticles of silver are best prepared by direct calcination in air of the precursor gel at 250 degrees C for 1 hour. Compared to silver particles prepared by microemulsions, the particle size is larger due to the thermal treatment, which causes a growth of the silver particles.