Electrodeposition of Co-W Alloys with P and Ni

Abstract

The aim of the present study is to explore the electrolyte composition in order to obtain Co-W, Co-Ni-W, Co-P-W, Co-Ni-P-W alloys with smooth morphology, high reaction rate, and underscoring the interactive reduction behavior of the codepositing elements. The recommended electrolyte formulation: 0.2 M MeSO4, 0.4 M Na2WO4, 0.5 M citric acid, and 1.5 M ammonia (“Me” represents the iron group metal); provides an optimal pH buffer capacity in the range of 7.5 to 8.5 at 70 °C. Smooth and crack free films of Co-W, Co-P-W, Co-Ni-W, and Co-Ni-P-W alloys were electrodeposited. Nanowires and nanotubes of the alloys were realized in alumina templates with constant potential and pulsed potential, respectively. The amount of W in the alloys, deposited on a rotating cylinder electrode galvanostatically, decreased with an increase in P incorporation (from 30 at.% to 15 at.% in alloys Co-P-W, and up to 30 at.% to 1.3 at.% in Co-Ni-P-W at the content of P up to 11 at.%) and also with the amount of Ni (from 30 at.% to 14 at.% in Co-Ni-W) . The partial current densities were determined from WDS chemical analyses and weight of the deposits. The Co partial current density was reduced when codeposited with W, and the W partial current density was reduced when P was incorporated into the deposit. The ratio of Ni to Co in the deposited ternary alloys differs from that of the electrolytes, characteristic of the anomalous co-deposition behavior. The anomalous co-deposition of Co with Ni is eliminated when phosphorous is incorporated into the alloys. These interacting reduction observations can be explained by a competing adsorption mechanism. The described baths can be used both for thin film and nanostructures electrodeposition.