Reactive Mechanical Milling Of Fe-Ni-Fe2o3 Mixtures

Fe-Ni-Fe2O3 mixture in various ratios has been milled in a high energy mill for synthesis of Ni3Fe/Fe3O4 type magnetic nanocomposite up to 10 h. The samples have been investigated in the light of X-ray diffraction, scanning electron microscopy, energy dispersive Xray spectrometry and laser particle size analysis. The formation of the composite begins after 2 h of milling. After 10 h of milling the nanocomposite with the high amount of metallic phase consists in a mixture of Ni3Fe and Fe3O4 alongside of a small amount of residual Fe2O3. Both phases are formed progressively upon increasing the milling time. Upon increasing the amount of oxide in the starting mixture at the end of the milling time the phases present in the nanocomposite material are changing. In the sample with the higher amount of oxide at the end of the milling time are present: Fe3O4, fcc Ni-based structure and unreacted Fe2O3 and Fe phases. The mean crystallite size estimated for the main phases of the nanocomposite, Ni3Fe and Fe3O4, are in the nanometric range at the end of milling time independent on starting ratio among starting materials. For both, Ni3Fe and Fe3O4, the mean crystallite size is ranging from 9 to 12 nm for all compositions. The nanocomposite particles shape is irregular. The powder consists in two types of particles: very fine particles with the size of less than 100 nm and larger particles with the size of a few micrometers. The micrometric particles are formed by fine agglomerated particles and by smaller particles that are welded together. The median diameter d(50) present a significant increase in the first stage of milling and is maintained at values close to 5 mu m, having small variations on each milling time.