Plasma electrolytic oxidation, or PEO, is a surface modification process for the production of ceramic oxide coatings upon substrates of metals such as aluminium, magnesium and titanium. Two methodologies for the quantitative study of electrical breakdown (discharge) events observed during plasma electrolytic oxidation processes were developed and are described in this work. One method presented involves direct measurement of electrical breakdowns during production of an oxide coating within an industrial scale PEO processing arrangement. The second methodology involves the generation and measurement of electrical breakdown events through coatings pre-deposited using full scale PEO processing equipment. The power supply used in the second technique is generally of much lower power output than the system used to initially generate the sample coatings. The application of these techniques was demonstrated with regard to PEO coating generation on aluminium substrates. Measurements of the probability distributions of discharge event characteristics are presented for the discharge initiation voltage; discharge peak current; event total duration; peak instantaneous power; charge transferred by the event and the energy dissipated by the discharge. Discharge events are shown to increase in scale with the voltage applied during the breakdown, and correlations between discharge characteristics such as peak discharge current and event duration are also detailed. Evidence was obtained which indicated a probabilistic dependence of the voltage required to initiate discharge events. Through the scaling behaviour observed for the discharge events, correspondence between the two measurement techniques is demonstrated. The complementary nature of the datasets obtainable from different techniques for measurement of PEO discharge event electrical characteristics is discussed with regards to the effects of interactions between concurrently active discharge events during large scale PEO processing.

Nanoindentation has emerged as a leading technique for the investigation of mechanical properties on small volumes of material. Extensive progress has been made in the last 20 years in refining the nstrumentation of nanoindentation systems and in analysis of the resulting data. Recent development has enabled investigation of materials under several dynamic conditions. The palladium-hydrogen system has a large miscibility gap, where the palladium lattice rapidly expands to form a hydrogen-rich β phase upon hydrogenation. Nanoindentation was used to investigate the mechanical effects of these transformations on foils of palladium. Study of palladium foils, which had been cycled through hydrogenation and dehydrogenation, allowed the extent of the transformed region to be determined. Unstable palladium foils, which had been hydrogenated and were subject to dynamic hydrogen loss, displayed significant hardening in the regions which were not expected to have transformed. The reason for this remains unclear. Impact indentation, where the indenter encounters the sample at relatively high speeds, can be used to probe the strain rate dependence of materials. By combining impact indentation and elevated temperature indentation, the strain rate dependence of the superelasticity of nickel-titanium was probed over a range of temperatures. Similar trends in elastic energy ratios with temperature were observed with the largest elastic proportions occurring at the Austenite finish transformation temperature. Multiple impact and scratch indentation are two modes of indentation which are thought to approximate erosive and abrasive wear mechanisms, respectively. These were utilised to investigate the wear resistance of several novel coatings formed by plasma electrolytic oxidation (PEO) of Ti-6Al4-V. Multiple impact indentation results appear to subjectively rank the erosive wear performance of both ductile and brittle materials. Comparison of normalised performance of coating systems on aluminium in abrasive wear to scratch hardness showed similar degrees of resistance.

Tartrate stabilization is the process that removes components that contribute to the crystallization of potassium hydrogen tartrate (KHT) and calcium tartrate (CaT) which is an undesirable outcome for wine quality. There are a variety of current tartrate stabilization techniques such as cold stabilization, chemical additives, ion exchange resins, and electrodialysis that stabilize wine, but the most popular being cold stabilization. Cold stabilization requires high amounts of energy and resources to stabilize wine. With the ever increasing demand for more efficient processing, an alternative tartrate stabilization technology based on an electrolytic method was developed and its viability to stabilize wine was determined. Twelve treatments involving different combinations of time and current were replicated three times each on different batches of Chardonnay wine. Several different variables were analyzed for stability and quality purposes. Tartaric acid, potassium, calcium, and conductivity differences were the most important factors for tartrate stability. Temperature, titratable acidity, pH, color (hue and intensity), and chemical oxygen demand (COD) were indicators of sensory quality characteristics of the wine. The concentrations of potassium, calcium, and tartaric acid were reduced by the electrolytic method at satisfactory process parameters, inherently making the wine more stable. The temperature and hue were significantly affected by the electrolytic method and accelerated the oxidative browning process. Electrolytic treatment of Chardonnay is a viable alternative stabilization technology. The technology can be further developed to become a great option in terms of water and energy consumption, process time, and price.

The primary goal of this research was to investigate the effects associated with the application of magnetic fields to single electrodes.

This is a study involving some of the chemistry of osmium tetroxide in perchloric acid solution. The research was originally instigated from a seminar report on the ruthenium III thiocyanate complex ion which was studied in perchloric acid solution. The seminar report given by Craig Townsend discussed how a spectrophotometric study by Yaffe and Voight (1951) was made of the ruthenium III thiocyanate complex ion, Similar possibilities were recognized as being possible in attacking the problem of an osmium thiocyanate complex or complexed. Some of the chemistry involved in the study of the ruthenium III thiocyanate complex will be discussed later. It will now suffice to say that the complex was studied by reacting ruthenium IV perchlorate and sodium thiocyanate to produce the complex ion. Townsend (1953), following the general procedure of Yaffe and Voight, took osmium tetroxide and sodium thiocyanate in a perchloric acid solution and reacted them to produce a rose colored osmium thiocyanate complex ion. He then determined a general formula and a value for the dissociation constant for the complex. Many problems were encountered in the Townsend study; and, therefore, there was reason for further study along these same lines. Some of the general characteristics of osmium and its related elements will be noted first.

A comparative study of the electro-oxidation of ethanol and methanol was carried out on a Pt/ceria composite electrode prepared by electro-deposition. Modification of the Pt electrode was realized by co-deposition from a 1.0 mM K₂PtCl₆ solution that also contained a 20 mM suspension of ceria. The electro-catalytic activities and stabilities of the Pt/ceria catalyst towards ethanol electro-oxidation reactions (EOR) and methanol electro-oxidation reactions (MOR) were investigated by potentiodynamic and potentiostatic methods in 0.5 M sulfuric acid and 1.0 M sodium hydroxide solutions at various concentrations of ethanol and methanol. The kinetics of ethanol and methanol on a Pt/ceria composite electrode were measured in 0.5 M sulfuric acid and 1.0 M sodium hydroxide solutions using a rotating disk electrode (RDE). Cyclic voltammetry was employed in temperatures ranging from 15 to 55°C to provide quantitative and qualitative information on the kinetics of alcohol oxidation. The temperature dependence of the electro-catalytic activities afforded the determination of apparent activation energies for ethanol and methanol oxidation.

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No description available.

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