SURFACTANT-ASSISTED BALL-MILLING OF BAFE12O19 FERRITE DISPERSION

A systematic study of the influence during mechanical processing of electrostatic interactions involving cationic and anionic surfactants on the surface and bulk properties of the complex oxide system barium ferrite is reported. Morphological examination by scanning electron microscopy shows a rapid decrease in powder particle size and homogenisation with milling time. In addition, from X-ray diffraction experiments changes in the crystal structure of the oxide were found. Barium ferrite decomposition (oxide phases separation) was linked with surfactant molecule type (ion and counterion) and oxide surface electrostatic potential. During room-temperature ball milling in aqueous dispersions a process of fast decomposition can be observed. For a cationic surfactant at pH 10 the milling terminates in BaCO3 and magnetite Fe3O4 as main phases and the material remains magnetic. In the case of anionic surfactant type and the same pH value, the barium ferrite structure remains as the main phase, because surfactants do not absorb onto the oxide surface. On the basis;of adsorption driven by electrostatic interactions it was possible to explain the effects of different surfactants on the milling product in dispersions with a low pH value.