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No description available.

No description available.

No description available.

No description available.

No description available.

The use of friction energy to deposit metals in the solid phase on a substrate, called Friction Surfacing, is typically used to provide hardfacing and corrosion resistant coatings. The process involves rotating a rod under pressure onto a moving substrate and a coating is generated from the rod material at the rubbing interface. The complex events occurring during the process have so far been studied only on flat surfaces with constant geometry. The introduction of standard machine tools in the friction surfacing process has allowed applications using complex shapes. This work aimed at developing new thermal models in order to control the parameters of the friction surfacing process for new applications. It was postulated in this work that the thermal events in the process have to be modelled in order to control the temperature of the bond between the coating and the substrate. Consequently the development of a three dimensional transient thermal model was undertaken. It was identified that the thermal response of the process is directly linked to the shape of the substrate below the rod. As the considered applications for the process involved non-uniform shapes of substrates, the finite volume method was chosen to build this model, which was integrated into a control algorithm. In order to simplify the model, new studies of the rod were undertaken. Analytical and finite volume methods were used and important results linking the dimension of the rod to the process parameters were established. These models were evaluated against experimental data. New ways of representing the rod that simplified the modelling of the friction surfacing process were established. Using the results from these studies, a new transient thermal model of the friction surfacing process was created, based on the finite volume method. Experimental runs were simulated and, by comparison with experimental data, the accuracy of the model was established. The different assumptions that were made during the design of this model were also discussed. Using the model, an iterative calculator was designed to predict the machine parameters for new shapes allowing a constant bonding temperature to be maintained and producing a trajectory for the rod. The error in this prediction was calculated, and it was shown that great accuracy is required in the measurement of the real bond temperature in order to minimise prediction errors.

Thin films of copper alloys are of interest for electronic applications. These are routinely produced by electrodeposition using aqueous solutions. The solvent strongly affects composition and morphology of the deposit which consequently affects the electrical and mechanical properties. The novelty of this thesis is that copper alloys are deposited from Deep Eutectic Solvents, DESs, which are forms of ionic liquids. The work shows that novel morphologies and compositions can be obtained using this approach. The electrodeposition of copper alloys is described from a solution of the metal salts in choline chloride based ionic liquids using urea and ethylene glycol as hydrogen bond donors. The thesis is split into three sections focussing on Cu alloys with Ag, Sn and P. These were chosen for their different phase behaviour. It is shown that the composition and morphology can be varied by altering the deposition potential and copper ion concentration of the plating bath. A variety of analytical techniques have been used to probe the deposition of these alloys. Although many of these are relatively standard for such studies this project uses an electrochemical quartz crystal microbalance (EQCM) for the first time to determine alloy composition in real time. From this data, the two systems Cu-Ag and Cu-Sn are shown to be close to 100% current efficiency, but the Cu-P does not fellow this trend. Analysis of the chronoamperometric transient behaviour during electrodeposition suggests that pure copper electrodeposition proceeds via three-dimensional instantaneous nucleation with diffusion-controlled growth. However, the deposition of most alloys does not fit either progressive or instantaneous nucleation models well. The alloy phases formed during deposition were analysed using X-ray diffraction and the surface morphologies and the compositions of the electrodeposited Cu alloys were analysed using SEM/EDAX. Thin films of Cu and Cu-P were electroformed onto Ti substrates and then peeled off. The mechanical properties of these films were tested and it was found that the incorporation of phosphorous was found to have a significant effect on the stress-strain curves. The final part of this study involved the dissolution of copper using cyclic voltammetry and EQCM and it was shown that diffusion of the chloride ligand to the electrode limits the rate of the anodic process.

It is well known that, depending on deposition conditions, the structure of titania coatings may be amorphous, brookite, anatase or rutile, or a mixture of phases, and that the anatase phase is the most promising photocatalyst for the degradation of organic pollutants. The formation of anatase depends on the energy delivered to the growing film, which in turn depends on the operating parameters chosen. In this study, coatings have been deposited onto glass substrates by pulsed magnetron sputtering (100 - 350 kHz) both from metallic targets in reactive mode and directly from oxide powder targets. In the former case, initially FFE (full face erosion) magnetrons were used. The FFE magnetrons have the capability to oscillate the central pole in the magnetic array. This is designed to increase the area of the target that is sputtered, which improves target utilisation and, by keeping the central region of the target clean, also improves process stability by reducing the tendency for arcing. In this particular study; a model (that complies with Lobi's) was presented in which new influential factors in pulse magnetron sputtering (such as pulse frequency, duty cycle and FFE oscillation speed) have been considered. Further sets of coatings have been produced both from metallic and powder targets in which the titania is doped with tungsten, niobium or zinc ferrite. The powder sputtering technique used here was an economic way of testing dopant materials before going to the expense of purchasing a full size sputtering target. The as-deposited coatings were analysed by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and micro Raman spectroscopy. Selected coatings have been annealed at temperatures in the range of 100 - 700°C and re- analysed. The photocatalytic activity of the coatings has been investigated through measurements of the degradation of organic dies, such as resazurin and methyl orange, under the influence of UV and fluorescent light sources. The resazurin test provided a quick indication of whether the surfaces were active or not. However, the level of photocatalytic activity was quantitatively assessed by the methyl orange tests performed on the coatings annealed at optimum temperature of 700°C. In this study for both sets of experiments; reactively and directly sputtered titanial titania doped coatings; the influence of deposition parameters (such as pulse frequency and duty) and its relation to the structures/ properties of the as-deposited/ post-annealed coatings has been investigated.

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