Electrodeposition Of Pd-fe Alloy Plating Process And Mechanism

In the thesis, the development of application and electroplating technology for Pd alloys are reviewed briefly. Then, both theory of alloys codeposition and principles of Cylic Voltammetry(CV) technique, TAFEL technique and Rotating Disk Electrode(RDE) are introduced in detail. Basing on many former researchful works, the technology and mechanism of electrodeposition on Pd-Fe alloy film are investigated in our experiments, including the following several main aspects:Firstly, potential-pH plots of Fe-H2O , Pd-H2O and Fe-NH4+-H2O systems are drawn, and the correlative thermomechanical analysis was made. From above plots, it can be seen that the balance potential of palladium is greatly different from that of iron. In order to achieve a codeposition of palladium and iron, some complexible agent must be added into electroplating solution.Secondly, Pd-Fe alloy is electrodeposited by pulse electroplating with agitating . The electrolyte solution is made up of FeSO4.7H2O, Pd(NH3)2Cl2, Sulfosalicylic Acid with crystal water and Ammonium Sulfate. The technological parameters of electrodepositing Pd-Fe alloy film is obtained from these experiments.Thirdly, the electrodepositing experiment shows that alloy film with different Pd/Fe atom ratio can be obtained by means of controlling technological parameters. The increment of concentration of Fe2+ ion can help to increase the content of iron in the film; the conductance salt has minor effect on the content of iron in the film; the increment of pH can decrease the content of iron ; temperature of the solution has a complicated effect on the content of iron, with the increasing of temperature of the solution , the content of iron in the film decreases in the beginning and increases afterwards, and there is the lowest value at about 60 C ; the content of iron in the film obtained from the solution by Ethylene diamine anhydrous adjusting pH is much more than that by NH3-H2O; the prolong of pulse toff can decrease the content of iron; the content of iron in the film increases with elevating the pulse voltage; the prolong of electroplating time can reduce the content of iron in the film.Fourthly, using the RDE and electrochemical workstation as the main equipments, the mechanism of Pd-Fe alloy codeposition is researched by CV, TAFEL andChronoamperometry(CA) technique. First, the potential value of Pd-Fe alloy codeposition is ascertained by comparing CV curves of Fe +, Pd + and Pd-Fe, and several factors of affecting peak value of current and deposition potential are analyzed. Second, current density of exchange and transferring coefficient are calculated by attributing the TAFEL curves of Fe2+, Pd2+ and Pd-Fe. Third, the course of nucleating of Pd-Fe alloy is researched by adopting CA technique.Fifthly, experimental results on the electrochemical mechanism show:First, the codeposition potential of Pd-Fe alloy locates between that of Fe2+ ion and that of Pd2+ ion. When the concentration of Fe2+ ion in the solution is increasing, the peak of Pd-Fe codeposition potential seldom moves, but peak value of anodic current is increasing gradually; The conductance salt makes peak of potential move toward positive and makes peak value of current increase. The increment of the solution's pH makes peak of voltage move toward positive. When pH is less than 4, the peak of codeposition nearly disappears. When pH of the solution is adjusted by Ethylene diamine anhydrous, the peak of codeposition moves toward more negative. The increment of the electrode rotate rate or scan rate all make peak of potential move toward negative and make peak value of current increase.Second, by attributing and calculating the data of TAFEL curves, it shows that the transferring coefficient of the mixture system making up of Pd2+ and Fe2+ in the cathode is bigger than that of Fe2+ ion or Pd2+ ion. It also shows that the electrode potential of Pd-Fe codeposition affects activation energy in the cathodic reaction more obviously than that of Fe2+ or Pd2+ .Third, it also shows that the course of nucleating...