| Tungsten-cobalt alloy has been widely used due to its excellent performance, the simple process and low investment cost are becoming a hot research. At present, The main methods for preparing tungsten-cobalt alloy are high-temperature melting, powder metallurgy and co-deposition, and the production process can be greatly shortened by co-deposition method which has a mature technology, reduce the production cost. Control parameters co-deposition process tungsten-cobalt alloy does not have reliable data, This paper to study the co-deposition of tungsten-cobalt electrochemical mechanism.The electrochemical reduction process of Co2+ on silver, gold and platinum electrode was studied in 0.05 mol·L-1 Co SO4 aqueous solution at 298 K. The electrochemical reduction process of Co2+on silver, gold and platinum electrodes are irreversible electrode processes analyzed by cyclic voltammetry curve. The exchange coefficient of cobalt ions on silver, gold and platinum electrodes were 0.254, 0.808 and 0.28 respectively, that calculated through the reduction peak potential and logarithm of scanning speed diagram. the cathodic reduction process of cobalt ions is controlled by diffusion step through the analyzation of reductive peak and square root of the scan rate diagram and the diffusion coefficient on silver, gold and platinum electrodes were 0.016×10-7cm2·s-1, 0.006×10-7cm2·s-1and 0.032×10-7cm2·s-1respectively. The reduction process of cobalt ions on silver, gold and platinum electrodes are irreversible through the test of Tafel curve. The analysis indicates that the cathodic reduction process of cobalt ions is controlled by diffusion step by the use of the current intensity relation schema and chronopotentiometric curves. The diffusion coefficient of cobalt ions on silver, gold and platinum electrodes are 2.2×10-7 cm2·s-1, 1.974×10-7 cm2·s-1 and 3.07×10-7cm2·s-1respectively. Through the test of chronoamperometry curve, it is proved that cathode reduction process of cobalt ions is controlled by diffusion step while the the deposition process of cobalt metal on silver, gold and platinum electrodes are instantaneous nucleation, the diffusion coefficient of cobalt ions on silver, gold and platinum electrodes are calculated to be 1.468×10-6 cm2·s-1, 1.4×10-6 cm2·s-1 and 5.5×10-6 cm2·s-1 respectively.The electrochemical reduction process of W6+ on silver, gold and platinum electrodes were studied in 0.05 mol·L-1Na2WO4 aqueous solution at 298 K. The cathode reduction process of W6+ in silver, gold and platinum electrodes were irreversible through testing cyclicvoltammetry curves, Tafel curves and potential time curves. The electron transfer number correspond to the reduction peaks were analyzed using the linear slope of E-lg[(Ip–I)/I]diagram. The first number on silver electrode is two and the electrochemical reaction is WO42-+2e→WO32-+O, while the second is one and the reaction is WO32-+e→WO2-+O; The first electron transfer number on gold electrode is two and the electrochemical reaction is WO42-+2e→WO32-+O, while the second number is two and the reaction is WO32-+2e→WO22-+O; the number on the platinum electrode is one and the electrochemical reaction is WO42-+e→WO3-+O. The relationship of reduction peak potential and the half peak potential is |Ep-Ep/2|=1.857RT/(αn F), the charge transfer coefficient which indicate the change of ion state were calculated. The first transfer coefficient on silver electrode is 0.257 and the second is 0.47, the first charge transfer coefficient on gold electrode is 0.096 and the second is0.263, the coefficient on platinum electrode is 0.483. Analysis chronoamperometry curves, it is obvious that cathode electrochemical reduction process of tungsten ions is controlled by diffusion step.The electrochemical reduction process of cobalt and tungsten ions codeposited on silver,gold and platinum electrodes were studied in 0.05 mol·L-1 Co SO4 and 0.05 mol·L-1 Na2WO4 mixed aqueous solution at 298 K. The analysis indicates that the electrodeposition reduction process of tungsten and cobalt ions on silver, gold and platinum electrodes were irreversible through cyclic voltammetry curve testing. The deposition potential of tungsten-cobalt alloy were about-0.95 V,-0.90 V and-0.95 V respectively. Analysis chronopotentiometric curves, the deposition reduction process of tungsten and cobalt is affected by diffusion step. Analysis chronoamperometry curves, the tungsten-cobalt alloy is finally achieved after the deposition of cobalt and tungsten ions and the nucleation process of which is instantaneously. |
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