Effect of polarization type on properties of Ni–W nanocrystalline electrodeposits

Abstract

Nickel-tungsten nanocrystalline coatings were electrodeposited from a Watts type bath onto a copper substrate, at different current densities selected from activation, mixed and diffusion controlled regions in the cathodic scan plot at room temperature. The results confirm that tungsten codeposition proceeds via the adsorption and reduction of complexes produced in the bulk of solution. The coatings obtained were single phase solid solutions and their grain sizes increased with current density. A cauliflower-type surface morphology with highest hardness was obtained when the current density was in the activation controlled region. The surface morphology obtained in the mixed controlled region was distorted, and then converted to a nodular morphology in the diffusion controlled region. In the mixed control region, coatings with the highest corrosion resistance were obtained due to the lowest exchange current density for water reduction.

Effect of current density on deposition process and properties of nanocrystalline Ni–Co–W alloy coatings

“…The first time constant, which appears as a small capacitive loop at very high frequencies, belongs to the formation and adsorption of a surface oxide film. This loop is also observed in Ni-W electrodeposition according to the results obtained by Kabi et al [12]. The second time constant, which appears as a large capacitive loop at medium frequencies, results from double layer capacitance parallel to charge transfer resistance.…”

“…Regarding the mechanism of tungsten deposition proposed by Imanaga et al [13], the high-frequency capacitive loop observed on the Nyquist plots can be an evidence for intermediate tungsten oxide formation [12]. On the other hand, the capacitive loop which appears at low frequencies should be due to the slow bulk diffusion of electrochemical active species, which participate in electrodeposition process [12].…”

Effect of current density and bath composition on crystalline structure and magnetic properties of electrodeposited FeCoW alloy

“…This indicates complete dissolution of elements in the cobalt matrix and a single phase solid solution would occur. Similar results were also reported by other researchers [16,[24][25][26]. By increasing current density the amount of iron content increased.…”

Application of Electroforming Process to Bulk Amorphous Ni-W Alloy

“…At first, we decided the composition of bulk amorphous Ni-W alloy from the reported data 9,[12][13][14][15][16][17][18][19] with our present results. Figure 1 shows the relationship between grain size and W-concentration in electrodeposited Ni-W alloys.…”

“…[9] T. J. Rupert et al [12] K.R. Sriraman et al [13] S. Kabi et al [14] A. Giga et al [15] H. Cesiulis et al [16] C.A. Schuh et al [17] T. Yamasaki [18] H. Somekawa et al [19] 0.035 at%/mm in the bulk specimen.…”