Electrodeposition of Tungsten Alloys

The concentration of citrate ions also affects the FE and W-content of the deposit. The effect was found to depend on current density and on the concentration of nickel ions in the bath. In general, the FE was found to decrease as the concentration of Ci was increased. At a low current density (5 mA cm i, the tungsten content increased from 10 to 33 at.% as the concentration of Ci was increased from 0.25 M to 0.60 M. At a higher current density (15 mA cm i, however, the trend reversed and the tungsten content increased from 31 to 60 at.% as the concentration of Ci was decreased. The effects of the citrate ion concentration on the FE and on the tungsten content in the deposit were studied in solutions of very low concentration of N + ions, and the FE was also found to decrease with increasing Ci concentration. 

The effect of nickel sulfamate, saccharin and sodium chloride as additives was studied by Eliaz et The effect of adding 

Several studies were published in recent years on electrodeposition of W-Co alloys. Donten and Stojek used pulse electrodeposition to increase the tungsten content in amorphous Co-W alloys. These alloys contained, in addition, small amounts of boron or phosphorous. They showed that, if a symmetrical current pulse was used, the tungsten content in the alloys reached a maximum value of 41.4 at.%, which is higher than in the case of direct current deposition. However, when using any asymmetrical 

With respect to the last type of mechanism, Gileadi and coworkers recently studied the induced codeposition of W-Ni from moderately alkaline baths containing citrate as a complexing agent, with or without ammonia. The range of bath compositions and operating conditions is shown in Appendix A. The working hypotheses in these studies were that  

A tungstate-citrate complex reacts with a nickel-citrate complex, to form a mixed-metal complex, of the type [(Ni)(HWO4)(Cit)]2-. 

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