The prevention of diffusional growth of cobalt particles in mercury

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Abstract
A suspension in mercury of cobalt particles of median diameter 45 AA was prepared by electrolytic deposition at room temperature from a saturated solution of cobalt sulphate. The effect of a number of metal additives on the diffusional growth (Ostwald ripening) of the particles was examined and it was concluded that both gallium and tin were successful in inhibiting growth providing that the quantity of additive was approximately equal to that necessary to form a monolayer coating on the particles. The earlier work of Luborsky (1957-63) indicated that an excess of tin led to the destruction of the magnetic moment of the cobalt particles. The present work has shown that an excess of gallium produces a similar result to that of tin. Resistivity and X-ray fluorescence measurements indicate that the gallium adheres to the surface of the particles, either to form a coating or to form an intermetallic compound with the surface cobalt atoms.