Preparation of Fine Particles

Abstract The techniques of vapor deposition, aerosol spray pyrolysis and chemical reduction have been used to prepare fine magnetic particles. Fe particles were prepared with an average size in the range of 50-300 A by varying the gas pressure during evaporation (1–30 torr). Fe-B particles have been produced by chemical reduction with NaBH 4 . The size (100–500 A) and the boron concentration of the particles were varied by changing the reduction conditions. Amorphous and crystallized barium ferrite particles with a size of about 1000 A have been synthesized from metal salts by an aerosol technique. The magnetic and structural properties of all these particles were studied with SQUID magnetometry and transmission electron microscopy, respectively. The magnetic properties of the ultrafine metallic particles can be explained by a particle morphology consisting of an oxide shell around a metallic core.