Effect of External Magnetic Field on Formation of Co-Ferrite by Aging Co-Fe Hydroxide Gel

Abstract

The crystallization of CoFe₂O₄ by aging Co-Fe hydroxide gels prepared by the addition of mixed FeCl₃ and CoCl₂ solution into caustic alkaline solution has been investigated. During the procedure of crystallization, the Co-Fe hydroxide gels were kept in the magnetic filed of 10000 gauss for several hours at 98°C. The substance aged up to 98°C in the magnetic field containtheedw ateorf 9 w t/0. T lies pecisfiucr facaere aw as133m2/gsp, ecifgirca vity. 4.32, and crystallite size 12.2 nm, while the sample prepared without the application of magnetic field, showed the values 21wt%, 147.3m2/g, 3.36 and 4.1 nm, respectively. On the other hand, the substance aged for 5 h in the magnetic field contained the water of 6 wt%, specific surface area 82.1 m2/g, specific gravity 4.33, and crystallite size 14.8 nm, while the sample produced without the magnetic field, had the values 7 wt%, 80.0 m2/g, 3.94 and 13.5 nm, respectively.
The samples aged in the magnetic field thus resulted more favourable for the crystallization than the one aged withou' t the magnetic field at the earlier aging stage. However the surface area, specific gravity, and of crystallite size for the aged sample in the magnetic field were still inferior to those prepared by the ignition of the gels at 1200°C for 5 h.