Fabrication of nano-sized Si powders with a narrow size distribution by two-step milling

By the combination of two successive dry milling processes (i.e., by using a multiring mill and subsequently a pin-type disintegrator), downsizing of Si powders was achieved to 30 nm crystallites and their aggregated mean volume diameter about 100 nm, with the top size less than 400 nm. Combination of the two dry milling processes proved to be effective to reduce the particle size and sharpen the size distribution of the aggregates without using any additives, tedious wet processes, or subsequent classification. Increase in the impurity due to milling was <0.1% for Fe and <0.4% for Zr, being well within a tolerable limit for most of the technological purposes.