Compositionl Control and Characterization of Fe-Ni Deposits Prepared by Pulse-Reverse Plating

• Main Authors: Penny Tsay, 蔡品儀
• Other Authors: Chi-Chang Hu
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/25520465868390252966

碩士 === 國立中正大學 === 化學工程研究所 === 91 === The deposition of Fe-Ni deposits in the pulse-reverse electroplating mode from simple chloride solutions without any additives or surfactants was proposed in this work. The optimal plating settings were approached by using experimental strategies. The compositional effects on the physicochemical properties, including crystalline information, morphology, roughness factor, and magnetic property, of Fe-Ni deposits were systematically examined. The electrochemical properties of various Fe-Ni deposits were systematically investigated in this work. The purpose of the first part in this work is to identify the optimal electroplating conditions to produce Fe-Ni deposits with the same compositions of the plating solutions (i.e., non-anomalous codeposition) since the composition of plating baths is easily controlled. To efficiently find the key variables affecting the composition of Ni (and/or Fe) in the Fe-Ni deposits, the fractional factorial design (FFD) was first employed. These variables were subjected to the steepest ascent investigation to approach the optimal conditions for the equilibrium deposition of Fe-Ni deposits. The central composite design (CCD) coupled with the response surface methodology (RSM) was used to examine the relationship between the composition of Fe-Ni alloys and the plating variables around the optimal conditions of the equilibrium plating of Fe-Ni deposits. The composition of various Fe-Ni deposits was measured through means of an energy-dispersive X-ray (EDX) spectroscope. The Fe-Ni deposits prepared by the pulse-reverse plating method were examined by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), atomic force microscopy (AFM) and superconducting quantum interference device (SQUID) magnetometer. From the above analysis, we found that the Fe-Ni deposits have good crystal structure; the surface morphology of pure nickel deposit gradually changed with adding Fe metals; and the Fe-Ni deposits exhibit normal saturation magnetization. The roughness of Fe-Ni deposits with the Fe content ≧50 at% is proportional to the Fe content of deposits. The hydrogen and oxygen evolution activities were investigated through means of Tafel polarization. From the Tafel behavior, the hydrogen evolution activity was proportional to roughness factor of deposits. However, there is no systematic relationship between roughness factor and the oxygen evolving activity. This phenomenon was also found for the electrochemical active surface area. The electrochemical active surface area (EASA) of Fe-Ni deposits and the capacitive characteristics were investigated in NaOH and in Na2SO3, respectively, through means of cyclic voltammetry (CV). The effects of annealing in N2 and Ar atmospheres on the corrosion behavior of Fe-Ni deposits were also investigated though means of open circuit potential-time measurement, linear sweep voltammetry (LSV), and Tafel polarization. From the linear sweep voltammetry behavior, we found that annealing enlarged corrosion resistance. From the polarization curves, annealing render the positive shiftin corrosion potential (Ecorr) and the decrease in current (icorr). In both annealing atmospheres, annealing at 400℃ foe 1hr was the optimal setting for the Fe-Ni deposits with the highest corrosion resistance. In addition, deposit annealed in Ar should the better corrosion behavior than that annealed in N2.