Electro-crystallization Mechanism of Nickel-tungsten-phosphorus Alloy and Its Coating Structure and Microhardness

Mechanism of electrocrystallization of nickel-tungsten-phosphorus alloy and its coating structure and microhardness Yang Fangzu Niu Zhenjiang Cao Gangmin Xu Shujun Zhou Shaomin (Department of Chemistry, Xiamen University, State Key Laboratory of Physical Chemistry of Solid Surfaces, Institute of Physical Chemistry, Xiamen 3G1005, China) With microhardness. As a result, in the solution containing ammonium citrate as a ligand, the boundary alloy deposit has lower electrochemical activity than the alloy. According to the curve of the potential step, the curve analysis shows that on the glassy carbon electrode, the process of evaluating the electrical conductivity of the alloy is performed in accordance with the mode of diffusion nucleation and nucleation, and the number of crystal nuclei on the electrode surface increases with the increase of the overpotential. .

Another test result shows that the boundary alloy coating exhibits a distinct amorphous character. The obtained 1 alloy electrodeposited layer code B030607 chromium coating has a wide range of uses. The chromic acid used in the traditional chrome plating process has a high toxicity and is a harmful component that causes environmental pollution and harms human health. The urgent need to solve the alloy electrodeposition mortar is to look for new types of decorative and functional chromium-based coatings that meet the quality requirements. At present, in addition to research chromium plating chromium solution, the studied chromium plating layer has 88163, boundary, 21 and other alloys, and electroless plating alloy and composite plating, 8 and other plating 1. Kashi alloy coating corrosion resistance Both wear resistance and thermal stability are significantly higher than those of 4 alloy coatings.

The properties of the electrodeposited layer of the alloy are closely related to its electrocrystallization process and structure. The properties of the electrode alloy electrodeposited layer and its composite coating have been reported to be 1.13. We have conducted a research on nickel-tungsten alloy electrodeposition 1416. During the deposition process, the tungstate is reduced to an intermediate valence oxide; only when the Si+ is present in the bath, the boundary is 0! Can be induced to reduce the formation of metal alloys in order to form a step alloy. Inhibitory alloy electrocrystallization process follows the diffusion control transient nucleation dimension growth mode. In this paper, sodium phosphite was added to the citrate neutral alloy plating solution to explore the electrodeposition voltammetry characteristics and electrical crystallization behavior of the alloy 1. The increase of the overpotential of the research electrode during the electrocrystallization process The effects; and the effect of different current densities on the structure crystallite size and microhardness of the electrodeposited layer of the contempt alloy.

1 Experimental methods Cyclic voltammetry and potentiostatic step tests were performed using a U.S. 0 pay company, 3660 electrochemical comprehensive test system. The experiment was conducted in a glass cell electrolytic cell. A glassy carbon electrode with a diameter of 0.5,1 embedded in a polyvinyl fluoride rod is used as a research electrode, a Pt wire is an auxiliary electrode, and a saturated calomel electrode SCE is a reference electrode. Before each experiment, the mortar electrode was polished with 06 metallographic sandpaper and cleaned with distilled water.

10. Prepare the solution with a chemically pure reagent and deionized water, adjust with pH 7.07.5 molybdenum ammonia or citric acid. The deposition condition temperature is 55, the anode is a graphite plate, the cathode is a red copper piece, and the working area is 2., 13. The plating solution is stirred at a medium speed with a magnetic heating stirrer. The deposition current densities 2 were 2.04.0 and 8.0, respectively, and the deposition time was 90 min.

The structure and crystallite size of the coating were measured using Japan Science and Technology Co., Ltd. Ogawa 3 polycrystalline target, ray diffraction, target, A=0.15406 nm, tube flow 30 mA, tube pressure 40 kV, slit system DSSS 0.15 mm RS, graphite monochromator Filtering, scanning speed 6, min 1. Determination of the coating structure, and calculate the crystallite size z, Hfc, as the crystal surface index by the following formula.

The microhardness of the coating was measured with a type 1 microhardness tester from Shanghai Optics Instrument Factory. The load was 50 and the contact time was 158. The hardness value was calculated according to the following formula: where ffv is the microhardness value, kg, mm2; IP is the load weight ,g;i is the diagonal length of the indentation, mm.

Results and Discussion Cyclic Voltammetric Behavior of Glassy Carbon Electrode in Bound 1 Solution The sodium phosphate in the solution of nickel sulfate and sodium tungstate was called the evaluated boundary + solution, respectively, and the cyclic voltammetry behavior at the glassy carbon electrode was scanned. For 50mV, the s1 curve is bright, and the potential scans to 1. in the negative direction. When the left and right sides, the boundary alloy induced co-deposition begins to occur, the cathode current increases rapidly; at the time of reverse scanning, the anodic dissolution peak of the bounded alloy at 15 points . From curve 2, it can be seen that in the boundary solution, when the potential on the glassy carbon electrode is scanned to the negative direction of about 1.0, the co-deposition of the alloy along the boundary 1 occurs gradually, and in the reverse scan, there is an anode of the alloy deposit at 0.13. Oxidation peak. Similar to the boundary alloy, the electrode process on the glassy carbon electrode is irreversible, and a deposition layer with a metallic luster can be observed in the cathode process with a relatively intense hydrogen evolution. The anodic stripping peak potential of the boundary alloy deposit is more positive than that of the state boundary alloy, indicating that the alloy has a lower electrochemical activity. In addition, the glassy carbon electrode has a sensitive current loop in the cyclic voltammetry in the boundary + solution, which is similar to the previous 1416 result. It shows that it has experienced the mechanism of your alloy electrocrystallization process. The common method of mechanism. 2 is the current time transient curve of the electrode 1 of the upper boundary of the glassy carbon electrode at 0.95, 1.00, and 1.05, respectively. It can be seen that both of them have a rising current at the beginning and then gradually decrease, and the current appears. The great phenomenon again shows that the electrodepositing of the boundary alloy has undergone a nucleation process. According to hemispherical nuclei diffusion, the instantaneous nucleation and the continuous nucleation mechanism of electrocrystallization are controlled by the sub-family wide relationship, large value, and time. Data processing of 2 can be obtained 3102,1 curve, wherein curve 1 instantaneous nucleation theory curve, curve 2 continuous nucleation theory curve. From 3, it can be seen that at different potentials, the 2 experimental curves are all closer to the non-dimensional curve of the instantaneous nucleation, the bright and the guilty alloy electrocrystallization method is performed in 1819. At the deposition potential of 0.95, the 2 curve is very close to the theoretical curve, which shows that the alloy crystal of the B1 alloy follows the theoretical mechanism very well; whereas at the deposition potential of 1.05, the experimental curve gradually deviates from the theoretical curve. With the progress of electrodeposition, the electrodeposition mechanism of the boundary alloys has changed gradually because the hydrogen evolution on the electrode surface and the glassy carbon surface are more easily replaced by the deposition layer. In the initial stage of instantaneous nucleation of electrocrystallization, 1 has approximate formula 18, which is 87 kwh, 312, the current density is 2, the Faraday constant is 0 claws, the charge number, the diffusion coefficient, coffee crystal core density, 2, the molar mass is 8, Density 8,3, Molar Concentration 2 Increases the initial phase value for the relationship of Strict 2 4. Can exhibit a good linear relationship with 2, 2 0.25. From Formula 1, it is assumed that the diffusion coefficient does not change significantly with respect to the potential, then the crystal The condition of the nuclear density is proportional to the slope of the straight line 2 and the larger the slope, the greater the number of nucleated nuclei. From 4 calculations, the constant potential is 0.95, 1.00 and the bit shifts from 0.95 to 1.00, that is, the overpotential increases, the number of crystal nuclei on the electrode surface is significantly increased, the deposition potential progresses from 1.00 to 1.05, and the electrode surface The increase in the number of nuclear crystal densities is not much.

The crystallite size and microhardness of the electrodeposited layer structure of the 1-bearing alloy were changed under the conditions of the composition and deposition conditions of the nickel-tungsten-phosphorus alloy plating bath, and the deposition current density was changed to 12.0%, 4.0, and 8.0, respectively. , ray diffraction, ruler 0 results were 5 curves 12 and 3. Experimental results show that the ruler, the middle of the 4 in the vicinity of 44.9455.1 electrodeposited layer diffraction peaks, diffraction peak diffraction intensity is small, relatively short and fat, half The broadening of the peak width is also large, and it clearly shows the amorphous structure characteristics. The crystallite size of the electrodeposited layer of the boundary alloy increases with the deposition current density from 2.02 to 4.0 and 8.0 dm2, and decreases from 2.1 nm to 1.7 nm and then to 2.3 nm, as calculated.

With the increase, the microhardness of the electrodeposited layer obtained by the alloy is improved, but the increase is not significant, and the microhardness value is about 450 kg, mm2. Therefore, the alloy with a pronounced amorphous structure characteristic is regarded as a conforming part. The quality-required generation of chrome plating can be used in corrosion-resistant and wear-resistant environments.

3 Conclusions The electro-crystallization process of the glass carbon electrode in the upper order is in accordance with the diffusion-controlled instantaneous nucleation-dimensional growth mode. With the increase of the overpotential, the number of crystal nuclei on the electrode surface increases.

Under the composition and deposition conditions of the alloy plating solution, the electrodeposited layer of NiWP alloy has a good bond with the copper matrix and is bright and smooth. The alloy exhibits obvious amorphous characteristics. It has lower electrochemical activity than the boundary alloy, and the microhardness value is about 450 kg, mm2. It can be applied in environments with corrosion resistance and constant wear resistance.

5 Guo Zhongcheng, Liu Hongkang, Wang Zhiyang and others. Forging and environmental protection to the imperial office so 30,1995,1515 230 Li Zhenliang, Yang Fangzu, Yao Shibing and so on. Journal of Xiamen University Shi, Pan 61 Nu, 1999, 382230 Huang Ling, Dong Yuxiu, Yang Fang, et al. Plating and finishing, eg; 7 cuts, 1999, 18