Copper, tin and their alloy deposits are popular for its various applications in industrial aspects like enhance corrosion resistance and provide decorative finish. This work concentrated on the fabrication of these coatings, accomplished by electrodeposition technique which allows the control of thickness and microstructure of the films. Previously these metals and alloy were electrodeposited from different aqueous electrolytes. However these baths suffer from various environmental issues and deposits suffers from H evolution and metal oxide formation. As a result solution 2 ionic liquid (IL) was proposed as an alternative. ILs are categorized as salts liquid at room temperature and consist only of cations and anions. Presently Choline chloride based IL was used due to its advantages of low cost, low melting point, low toxicity, low viscosity and high conductivity than other ILs. Physical properties of the ILs like density, viscosity and conductivity were measured with variation of temperature and concentration of added metallic salts. To determine the electrochemical properties of individual metals and alloy, voltammetry scans were carried out using various scan rates and agitation rates. For all these measurements the concentration of Cu and Sn were varied in a range of 0.01 to 0.2 M and 0.01 to 0.1 M respectively at temperature range of 25 to 55 °C using a platinum rotating disk electrode (RDE). Deposition experiments were then carried out under potentiostatic and galvanostatic conditions using a stainless steel RDE. Material properties of the deposits like crystalline structure, grain size, strain, deposit morphology and chemical composition were analyzed using x-ray diffraction (XRD), optical microscope and scanning electron microscopy (SEM). The measurement showed that density and viscosity decreases and conductivity increases with rise in operation temperature for the electrolyte with and without metal ions. The reduction of both the metal was found to be mass transfer control and limiting current for metal deposition was found. The diffusion co-efficient -7 2 -7 2 obtained for Cu and Sn in the IL system was 1.22x10 cm /s and 1.96x10 cm /s -3 respectively. For individual metal Cu and Sn, best deposits were obtained at 4.7x10 2 -3 2 A/cm and 1.6x10 A/cm respectively using RDE speed of 700 rpm at 25 °C. The Cu deposit showed face centered cubic structure of 66±10 nm grain size and that of Sn was 62±10 nm with tetragonal crystalline structure. The smooth and bright Cu-Sn alloy deposit was obtained by applying potential in the range of 0.35 to 0.36 V vs. Ag wire or -3 2 0.8 to 0.9x10 A/cm of RDE speed is 220 rpm at 25 °C. The obtained deposits showed orthorhombic CuSn structure with a grain size of 21±10 nm. On annealing the 3 crystalline structure changed to hexagonal CuSn structure and the crystalline size 103 was obtained as 77±50 nm.
|University of Newcastle upon Tyne
|Electronic Thesis or Dissertation
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