محمد مالکی شهرکی

The effect of mechanochemichally synthesized nanoceramics Ni0.5Co0.5Fe2O4 (NCF) on the sintering process was studied. After 60 h of mechanochemichal treatment, the amount of formed ferrite phase reaches to about 70 vol%. From 60–100 h 10% increase in volume fraction of synthesized magnetic phase can be observed. Further increment in process time had no remarkable effect on the NCF phase formation. After 60 h, ceramic nanoparticle formation is directly reflected by TEM image and specific surface area (28 m2/g equivalent to 40 nm in diameter). The coercivity (Hc) shows a drastic diminution from 1996 to about 159 Oe by 60 h process time. Further milling treatment has no observable effect on the values of Hc. Additionally, the magnetization saturation (Ms) increases up to ~13 emu/g by 60 h mechanical milling of powders mixture. Thereafter from 60 h to 100 h, the Ms rapidly increased from 13 to 32 Oe. Finally, with continuing mechanochemichal process up to 130 h the Ms slightly diminished (~29 emu/g). Additionally, compared to synthesized powders the higher values of MS (65 emu/g) and lower values of HC (140 Oe) for sintered ceramic were detected. The low sintering temperature (1300 °C) for magnetic NCF sample prepared from nanoparticles may be caused by the high activity of nanoceramics.