Effects of annealing temperatures on the physicochemical properties of nickel-phosphorus deposits

The dependence of physicochemical properties, including microhardness, magnetism, morphology, crystalline information, roughness factor and hydrogen evolution ability, on the phosphorus content, varying from 0 to 28 atomic percentage (at.%), of Ni-P deposits with annealing in air at eight temperatures (i.e., 100, 200, 300, 400, 500, 600, 700 and 800'Q were systematically compared. The microhardness reached a maximum at 400degreesC due to the crystallization of Ni and Ni3P at 400 degreesC and the significant diffusion of Cu into the Ni-P deposit at temperatures greater than or equal to500degreesC, confirmed by the depth profiles of Ni, P, Cu and 0 elements. The paramagnetism of Ni-P deposit was gradually transformed into ferromagnetism at 400 degreesC, attributable to the phase separation of Ni and Ni3P. The roughness factor, R-a, of the deposits with P contents less than or equal to12 at.% were increased with increasing the annealing temperature at temperatures <400 degreesC but R-a of the deposits with 17-28 at.% of P is approximately independent of the annealing temperature. The rate of hydrogen evolution decreased with increasing the annealing temperature because the specific activity (ilR(a)) of the Ni-P deposits was decreased with increasing the annealing temperature. (C) 2002 Elsevier Science B.V. All rights reserved.