Deposition of Sn hydrosols on Co- gamma -Fe/sub 2/O/sub 3/ magnetic particles

An improved colloidal solution of tin hydrous oxide has been developed. This solution was found to readily deposit onto the low-wettability surface of Co- gamma -Fe/sub 2/O/sub 3/ particles to form a uniform layer of irremovable coating. Based upon the chemical characterization of the tin-sol-treated surface, the effectiveness of such treatments on magnetic oxide particles is described in terms of dispersion stability, dispersibility, rheological behavior, and other magnetic tape performance. A significant improvement in wetting, dispersion and flow behavior was observed for the 1% Sn coated magnetic particles upon dispersion in a polyurethane-based formulation. Additional magnetic tape data also revealed that surface treatments on magnetic particles facilitate the particle orientation by exposure to a 2000-Oe external magnetic field before dying, as evidenced by the high values of hysteresis squareness up to 0.8, indicating good dispersion of magnetic particles.<
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