On the Formulations and Electrodeposition Conditions for the Pd –Ag Alloy Films
Date Issued
2004
Date
2004
Author(s)
Lin, Yi-Hang
DOI
zh-TW
Abstract
This study is about the preparation and chracteriaztion of Pd-Ag alloy films based on various electrodeposition methods. The objective of the work is to produce the alloy thin films composed of Pd 77wt% - Ag 23wt%. The electrodeposition experiments was carried out by the methods of the chronopotentiometry, chronoamperometry, and pulse plating, with the change on the compositions of the electrodeposited bath. The substrates to be used in this study are SS-316 stainless steel, copper and palladium. The surface structure of the films was examined by SEM. The compositions of the electrodeposited films was analyzed by ICP. Also, the formation of the alloy phase was verified by XRD.
Firstly, Pd(NH3)4Cl2, AgNO3 and ammonia bath were used during the chronopotentiometric electroplating. The Pd-Ag alloy was electrodeposited on the stainless steel (ss-316) with current densities varied between -0.1mA/cm2 and -5mA/cm2. The surface structure is dendritic at high current densities with the composition of Ag in the range 46wt% ~ 97wt%. When the applied potential lies between -0.4V~-1.2V(vs. Ag/AgCl/sat’d KCl) on the Cu substrate, the Pd composition varies between 11~73wt% within the electrodeposited film, and the surface structure is dendritic. The XRD analysis results show that the Pd-Ag alloys are non-uniform within the electrodeposited film.
In the electrolyte bath composed of Pd(NH3)4Cl2, AgNO3 and Na2S2O3, the Pd-Ag alloy was electrodeposited both on the SS-316 stainless steel and the Cu substrates by the chronoamperometry method. When the operating potential of the eletrodeposition is controlled between -1.0V ~-1.2V, the Pd composition is between the 78% and 80% according to ICP analysis. The composition of Pd ranging between 21% ~ 38%, corresponding to the operating potentials in the range of -0.4V~1.2V. The electrodeposited films are continuous, as judged by the SEM analysis.
In electrolytic bath composed of Pd(NH3)4Cl2, AgNO3, enthylenediamine, 2-mercaptopropanoic acid, different electrolytic concentrations (enthylenediamine and 2-mercaptopropanoic acid) were used, together with the addition of the palladium ion and the silver ion for the chronoamperometric electrodeposition. The palladium compositions are below 15% in the electrodeposited film when increasing the ratio of 2-mercaptopropanoic acid to ethylenediamine, as analyzed by the ICP analysis. The ratio of palladium to silver within the electrodeposited film changed, when the ratio of palladium ions to silver ions was varied in the bath. The palladium compositions within the films varied between 68% ~87% at -0.8V~-1.2V, when 0.1M Pd(NH3)4Cl2, 0.03M AgNO3, 0.1M ethylenediamine, and 0.15M 2-mercaptopropanoic acid. It has been verified, by the XRD, that the Pd-Ag alloy phase has been formed for the electrodeposited films.
After performing the chronopotentiometric experiments, a pulse plating method for electrodeposition with an electrolytic bath composed of Pd(NH3)4Cl2, AgNO3, ethylenediamine, 2-mercaptopropanoic acid bath was tried. The pulse plating parameters, including the period of the pulse plating, P value (pause time / pulse time), and the average current density were varied in the experiments. In this electrolytic bath, the Pd-Ag alloy ratio wasn’t affected by changing both the period of the pulse plating and the P value. The Pd composition within the film increased with the increase of the average current density during the pulsing plating.
In this study, the best electrodeposited film was obtained by using the chronopotentiometric electroplating with the use of the Pd(NH3)4Cl2, AgNO3, ethylenediamine, 2-mercaptopropanoic acid electrolytic bath. The adhesion of the electrodeposited film is good and it can achieve the desired Pd 77wt%-Ag 23wt% electrodeposited films.
Subjects
合金電鍍
銀
脈衝電鍍
鈀
定電位電鍍
chronoamperometric electroplating
alloy electrodeposition
palladium
pulse plating
silver
Type
thesis
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