Abstract
Ultrafine pure iron particles have been prepared by carefully controlled thermal decomposition of dilute iron pentacarbonyl vapor with hot helium. The particle size distribution of the prepared sample was extremely narrow, averaging 120 Å diameter. Particle size distribution was analyzed by electron micrography and confirmed by the B.E.T. method and x-ray line broadening. Chemical analyses and electron diffraction showed the sample to be essentially pure iron. The particles though smaller than the critical size for superparamagnetism, due to interparticle interaction, did not have this property.