Effect of acid-base interaction on magnetic dispersion containing α-Fe metal particles

The importance of Lewis acid-based interaction in magnetic dispersions was investigated to understand how it plays a role in determining the dispersion stability and dispersibility of α-Fe metal particles used for high density recording media. To prevent aggregation of metal particles, surface treatment on the passivated oxide surface layer with organic dispersants or metallo-organic coupling agents was carried out to render the metal particle surface more compatible for binders. Being used as binder resins in tape formulation, polyurethanes were found to be predominantly basic, while viny alcohol copolymers were predominantly acidic. It was also found that if basic polymers are chosen as binders, they allow good dispersion of ferromagnetic particles with predominantly acidic surface only, as evidenced by the enhanced absorption of polyurethane onto the surface of α-Fe particles with acidic surfactant treatments