The dispersion of single-domain BaFe12O19 particles in water

We have studied the dispersion of single-domain BaFe12O19 particles in water and calculated the interparticle interaction energies due to the van der Waals and magnetic dipole-dipole forces. The magnitudes of the attraction energies varied significantly with the particles' sizes and the separation distances between the particles. The contribution of the van der Waals potential was important only for the closest separation distances (up to 3 nm). The thermal energy exceeded the magnetic dipole-dipole attraction between the particles with radii larger than 20 nm at separation distances of several 100 nm. The electrosteric stabilization of the BaFe12O19 particles was possible only for particles with radii up to 15 nm and thicknesses up to 6 nm. The studied BaFe12O19 powder was a combination of several fractions, with respect to the particles' sizes. The particles were treated with a surfactant, dodecylbenzylsulfonic acid, using a combination of milling and high-power ultrasound. The zeta-potential of the surfaces of these particles increased in comparison to the raw particles. We analyzed the dispersed particles using thermogravimetry, mass spectrometry, and transmission electron microscopy, and we determined the parameters for the stabilization of the BaFe12O19 powder.