Synthesis of Barium Hexaferrite Magnet from the Oxides of Cold Rolling Mill Wastes

Efendi Mabruri


SUMMARY

Barium hexaferrite or BaFe12O19 is the most widely used ceramic magnet for many application and still place the top of global permanent magnet market in term of monetary value and product weight because of inexpensive raw material availability and the simplicity of the process. Research on the synthesis of barium hexaferrite magnet was conducted for getting useful of the oxides of cold rolling mill wastes. The oxides of cold rolling mill wastes were ground in ball mill to decrease the particles size down to -400 meshes. XRD analysis of the oxide powders showed all intensity peaks corresponded with those of Fe2O3. Then the oxides were mixed with BaCO3 at certain composition in ball mill and subsequent calcined to get barium hexaferrite compounds and XRD analysis on powders resulted from mixing and calcining at 1200oC for 3 hours showed all intensity peaks corresponded with those of BaFe12O19. After reground in ball mill to decrease the particles size down to the average of 1,5mm, the barium hexaferrite powders were then pressed and sintered at a range of temperature of 1000, 1100, 1200, 1225, 1250 and 1300oC in air and the influence of sintering temperature and time on magnetic properties and microstructures were studied. The magnetic properties measurement by permagraph showed that Br, Hc and (BH)max of barium hexaferrite increased as sintering temperature raised from 1000oC to 1200oC and decreased at higher temperature of sintering. The increasing of these magnetic properties is related to the increasing of magnet densities as sintering temperature raised up to 1200oC. The grain growth developed after sintering at the temperature over 1200oC to 1300oC characterized by SEM caused the magnetic properties slightly decreased. In the range of experimental parameter used, the higher magnetic properties achieved by magnet sintered at temperature of 1200oC and time of 2 hours.

(Makalah lengkap diterbitkan di Jurnal Elektronika dan Telekomunikasi No.2, Vol.III, Agustus-September 2003)