1981 Volume 22 Issue 6 Pages 371-378
A reactor chamber was designed for the investigation on the basic physico-chemical processes of the preparation of ultrafine particles in a radio-frequency (rf) plasma. Ultratie iron particles with a statistical median size of about 10 nm (based on number) were prepared by passing pure iron powders through an rf plasma. The nature of these products was investigated by electron microscopy and X-ray diffraction analysis. Nucleation and growth mechanism were also considered. It was found that the growth process of the particles took place in a “fog” state and a Brownian collision-coalescence mechanism governed the process. The particles formed the morphology common to fcc metals, though the electron diffraction patterns showed no traces of the fcc form. This means that the particles solidified in the γ-phase and then transformed to α-phase. The particles with the size less than 60 nm could be transformed into single crystals of α-phase, but single crystals rarely existed when the particle size was larger than 100 nm.