الفهرس 
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Abstract
Electrodeposition of Cu-Zn alloy is usually carried out in industry from cyanide baths, which give deposits of good quality and with high mechanical properties. However, cyanide ions are toxic and non-environmentally friendly. Therefore, this thesis was focused on the development of a new environmentally friendly bath based on amino acids. To achieve this purpose, it was important to study the electrodeposition of Cu and Zn individually and Cu-Zn alloy from amino acid complex baths under similar operating conditions. This thesis consists of four chapters.
The first chapter is the introduction, which includes some of the fundamentals of metal and alloy electrodeposition and a general introduction to the electrodeposition of Cu, Zn and Cu-Zn alloy applications in industry. Literature surveys of up-to-date research concerning the electrodeposition of Cu, Zn and Cu-Zn alloy electrodeposition are given.
Chapter two includes the experimental details. The cells and the electric circuits used in electrodeposition as well as in throwing power, throwing index and Wagner number measurements, in addition to the electric circuit used in measurements of all the voltammetric techniques. Detailed calculations of cathodic current efficiency as well as of the compositions of the alloy were given.
Chapter three includes the results and discussions of zinc, copper, and copper-zinc alloy electrodeposition. This chapter is divided into three parts:
Part 1: presented the study of zinc deposition from the Cysteine complex bath onto steel substrates. Detailed investigations were carried out such as the influence of Cys concentration, pH, temperatures and current density on the cathodic current efficiency, throwing power, voltammetric studies (including the i - E curves, ALSV and CV) and the characterization of zinc deposits (SEM and EDX).
It was found that the cathodic current efficiency was decreased with either increasing Cys concentration or raising the bath temperature and increasing current density, while it increased slightly with increasing the pH.
The addition of Cys to the electrolytic bath significantly enhances the deposit shape and becomes whitish than that produced without Cys.
Increasing the concentration of Cys decreased the polarization and increased the current density. Moreover, increasing the pH decreases the polarization and increases the current density. Finally, increasing the temperature decreased the polarization and decreased the current density.
Tafel kinetic parameters were discussed, and it confirmed the fact that the addition of Cys to the zinc plating bath accelerated the rate of deposition.
The cyclic voltammetry study was carried out onto GCE in the potential range of -0.5 V to -1.5 V vs. Ag/AgCl. The addition of Cys shifted the cathodic peak toward more negative potential values while the height and area of the anodic were decreased. Increasing the pH value shifted the cathodic peak toward less negative potential values while the height and area of the anodic peak were increased. Which improves the effect of the substrate.
The anodic linear stripping voltammetry of zinc deposited onto GCE exhibited one dissolution peak. The addition of Arg decreases the height and the area under the peak. Increasing the applied potential leads to increased height and area under the peak.
The current time transients revealed that the growth of zinc metal is a diffusion-controlled process. As the cathodic step potential is made more negative or the pH is increased, the values of the instantaneous and steady-state current are increased. On the other hand, the addition of Cys decreased the throwing power, throwing index as well as the Wa.
The scanning electron microscopy (SEM) examination showed that the zinc deposited on steel from the bath without Cys is compact, non-porous and composed of typical grains structure of zinc crystals. The addition of Cys changed the morphology of the zinc crystals. It becomes more homogeneous with zinc crystal oriented parallel to the cathode.
Energy dispersive X-ray showed that the intensity KCnt of zinc at 1.0, 8.5, and 9.5 keV is decreased with increasing Cys addition.
Part 2: presented the study of copper deposition from the complex with Arg onto steel substrates. Detailed investigations were carried out such as the influence of Arg concentration, pH, temperatures, and current density on the cathodic current efficiency, throwing power, voltammetric studies (polarization curves, ALSV and CV) and the characterization of copper deposits (SEM and EDX).
It was found that the addition of Arg ions to the copper plating bath improved the appearance of the copper deposits. It was found also that the cathodic current efficiency of copper deposition decreased with increasing the Arg concentration, pH value and temperature while it increased with increasing current density till 0.013 Acm-2 after that started to be darker and burned.
The cathodic polarization curves were characterized by the concentration of Arg decreasing the polarization by shifting the potential to a less negative direction with increasing the concentration on steel substrate while onto GCE has the opposite effect. This means Arg ions increased the rate of copper deposition on steel substrate and retard it on GCE and this conclusion was supported by the data of Tafel kinetic parameters. Moreover, increasing the pH values increases the polarization and shifts the potential to a slightly more negative potential. Finally, increasing the temperature decreased the polarization and shifted the potential to more positive.
The cyclic voltammetry study was carried out on GCE in the potential range of 0.6 V to -0.6 V. The addition of Arg while the height and area of the anodic peak are decreased.
The anodic linear stripping voltammetry of copper deposited onto GCE exhibited one dissolution peak. The addition of Arg sharply decreased the height and the area of the anodic peak. Also, increasing the applied potential decreased the height and area of the peak while the height and area of the peak increased with increasing time.
The current-time transients revealed that the addition of Arg to the plating solution has no significant effect on the mechanism of nucleation and growth.
On the other hand, the addition of Arg, pH values and elevation of bath temperature decreased the T.P., T.I. and Wa.
The scanning electron microscopy (SEM) examination revealed that the addition of Arg increased the rate of copper crystallite nucleation.
EXD analysis showed that the copper deposited from the Arg bath showed that the intensity KCnt of copper at 1.0, and 8.0 keV increased up to 0.1 M after increasing to 0.15 M and started to decrease the intensity with increasing Arg addition.
Part 3: presented the codeposition of Cu-Zn alloy onto a steel substrate from the Arg complex bath. Detailed investigations were carried out such as the Arg concentration, pH, temperatures, and current density on the cathodic current efficiency of Cu-Zn alloys. The throwing power was investigated. Voltammetric studies and the microstructure investigations of the Cu-Zn alloy were studied in detail.
It was found that the cathodic current efficiency of the alloy was decreased with increasing Arg concentration. The current efficiency of the alloy increased with increasing current density up to 0.012 Acm-2 after that started to decrease as the substrate started to detach with burn. The data revealed that the cathodic current efficiency of the alloy decreased gradually with an increase in the pH values. Elevation of bath temperature has a slightly decreasing effect on the current efficiency of the alloy deposition.
The data revealed that the curves are shifted towards more negative potentials and the limiting current density decreased with increasing the concentration of Arg. Moreover, the cathodic polarization curves of the alloy deposition were found to be pH-dependent, and the curves were shifted to more negative potential values as the pH of the bath increased. In addition, the limiting current was decreased.
The anodic linear stripping voltammetry of Cu-Zn alloy deposited onto GCE exhibited two dissolution peaks. The stripping charge was enhanced by increasing the concentration, inhibiting the stripping charge and decreasing the height of the anodic peak of the alloy. Also decreasing the pH value leads to enhance the stripping charge. The stripping charge increased as the deposition potentials were made more negative.
The current time transients recorded during the electrodeposition of Cu-Zn alloy showed that changing either the concentration of Arg or cathodic step potentials has no significant effect on the i -t transient.
The addition of Arg decreased T.P., T.I. and Wa and also increasing the pH values decreased them as well.
The SEM study showed that the morphology of the Cu-Zn alloy deposited on steel from the bath without Arg was deposited in a cubic-like structure covering the surface. However, the addition of a very low concentration of Arg increased the formation of the grains and some small circular grains stimulated on the cathode surface. At the concentration of Arg (0.1M), the surface became completely covered with circular grains of different sizes and at 0.15M the agglomeration and more organized grains were observed. On the other hand, the photomicrographs showed that at low current density, the deposit obtained was homogeneous and consisted of fine grains which completely covered the substrate surface. Increasing the current density to 0.012 A cm-2 exhibits organized grains with cover all the substrate and in 0.09 A.cm-2 seems that organized grains start to decrease which is in agreement with the CCE% results.
The microstructure of the as-deposited Cu-Zn alloy was examined by X-ray diffraction analysis and the results showed that the Cu-Zn alloy deposited from the Arg complex bath consisted mainly of one phase a Cu- Zn alloy with preferential orientation of (210) or (111, 110). The data showed also that the preferential orientation was found to be strongly dependent on the plating conditions, the increasing of Arg concentrations tended to decrease (110) with increasing(111,210).
EXD analysis showed that the zinc and copper deposited from the Arg bath showed the intensity KCnt of copper at 9.0, and 8.0 keV, zinc 1.0, and 8.5 keV is increased with increasing Arg. However, the effect of current density shows that increasing the current up to 0.012 Acm-2 shows the decrease of the overall intensity.