Instability of the Fine Particle Structure of Certain Electrodeposits

Abstract

The effect of cold-working and annealing on fine particle Co–P and Co–N–P electrodeposits is described. It is shown that the rod-type structure is sensitive to both cold-working and annealing while the platelet structure is sensitive only to annealing. Quantitative differences in response to annealing are discussed. It is suggested that both rod and platelet particles are coated with a thin layer of nonmagnetic cobalt-cobalt phosphide or nickel-nickel phosphide. This nonmagnetic coating explains both the high coercivity of the samples and the effect of annealing.

Magnetic Properties and Corrosion Behavior of Thin Electroless Co-P Deposits

“…The magnetic moment density of the deposits was found to be 111 emu/g for samples prepared in the sulfate bath, and 116 emu/g for samples prepared in the chloride bath, and independent of the thickness of the deposit. The calculated magnetic moment densities, assuming the phosphorus to exist in the films as the nonferromagnetic Co2P, were 120 emu/g and 125 emu/g for the films from the sulfate and chloride baths, respectively 9 The discrepancy between the measured and calculated values of the magnetic moment of the deposits may be attributed to the presence of some cobalt oxide or an amorphous cobalt phase (6).…”

“…11. This result indicates the formation of a corrosion layer of greater specific volume than the metal, again indicative of a protective product (6).…”