In order to clarify the role that water plays in the photocatalytic process, changes in the IR and Raman spectra of P25 TiO₂ thin films were observed upon exposure to liquid water. Further investigation of these spectral changes via dehydration of thin films under nitrogen and oxygen of different humidities led to the observation of spectroscopic features that have been assigned to localised surface phonon modes. When the effect of UV irradiation on these features was investigated, a broad IR absorption due to transitions of electrons in shallow traps was detected under dry nitrogen but not under dry oxygen. Further investigation of the photocatalytic properties of P25 TiO₂ showed a complete removal of a stearic acid film. The final products have been tentatively assigned to a mixture of short chain carbonyl species and adsorbed carbonates as well as carbon dioxide and water. The IR spectrum of the fuel cell membrane material Nafion is complex and literature data varies in some of the assignments. The compound perfluoro(2-ethoxyethane)sulfonic acid was used as a model compound for the Nafion side chain resulting in a clearer assignment of the Nafion IR spectrum. In light of these new assignments changes induced in the region 1100-1300 cm⁻� by variation in humidity and ion exchange have been shown to be mainly the result of changes in the sulfonate asymmetric stretching modes. By flowing a series of solutions containing tetramethylammonium ions and perchlorate ions the surface charge characteristics of a Pt black film were determined in the pH range 2-12. There proved to be a weak positive charge below pH 4 and a weak negative charge above pH 9. Between these points there appeared to be no overall charge on the surface. When perfluoro(2-ethoxyethane)sulfonic acid was adsorbed to a Pt black film changes in its IR spectrum indicated a strong binding via interactions between the sulfonate groups and the Pt surface. The nature of the adsorption of Nafion was less clear cut and, whilst adsorption is strong, it seems possible that hydrophobic interactions between the Nafion backbone and the surface are involved.

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (M.Eng)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 96-106.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Marder, Seth; Committee Member: Bredas, Jean-Luc; Committee Member: Kroger, Nils; Committee Member: Perry, Joe; Committee Member: Sandhage, Ken. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph.D.)--University of Wyoming, 2009. / Title from PDF title page (viewed on July 2, 2010). Includes bibliographical references.

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Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018. / Electrochemical and non-enzymatic fructose detection has evoked keen interest in the scientific literature. Several authors have reported on different methods of electrode preparation for fructose sensors. However, little systematic study has been conducted to design a cheap, efficient method of depositing metal oxides to detect fructose. To address the challenge, a Co3O4 thin film was fabricated using a simple solution step deposition on Fluorine doped Tin oxide (FTO) glass electrode. In this study, a report on the selective oxidation of fructose on Co3O4 thin film electrode surface is presented. Electrode characterization was done using X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscope (SEM), Atomic Fluorescence Microscopy (AFM), and Electrochemical Impedance Spectroscopy (EIS). All cyclic voltammetry (CVs) and chronoamperometry tests were carried out by the use of an AUTOLAB POTENTIOSTAT 302 N, controlled by Nova 2.0 software instrumentation using a customized 50 cm3 electrochemical cell. The cell consisted of a graphite rod as the counter electrode (CE), 3 M Ag/AgCl reference electrode (RE) and the fabricated Co3O4/FTO as the working electrode (WE). All experiments were carried out at 25±2 ⁰C. From the results, the constructed sensor exhibited two distinctive linear ranges in the ranges of 0.021 – 1.74 mM and from 1.74 - ~15 mM, covering a wide linear range of up to ~15 mM at an applied potential of +0.6V vs. Ag/AgCl in 0.1M NaOH solution. The sensor demonstrated a high, reproducible and repeatable sensitivity of 495 (lower concentration range) & 53 (higher concentration range) μA cm-2 mM-1 for a low R.S.D of 5 %. The Co3O4 thin film produced a low detection limit of ~1.7 μM for a signal to noise ratio of 3 (S/N = 3); a fast response time of 6s and long term stability. The repeatability and stability of the electrode resulted from the chemical stability of Co3O4 thin film. The study showed that the sensor was highly selective towards fructose compared to the presence of other key interferences i.e. AA, AC, and UA. Because of such a favourable electrocatalysis of the Co3O4 sensor towards fructose, the ease of the electrode fabrication and reproducibility makes it a future candidate for commercial applications in the food and beverages sector.

An investigation was conducted on the interaction between nickel metal and single crystals of magnesium oxide. The nickel was cleaned with purified hydrogen gas at 800°C and melted under vacuum (5 x 10⁻⁵ mm. Hg) in contact with the magnesium oxide. The interface was examined metallographic-ally. The formation of compounds at the interface was examined by X-ray diffraction techniques. The magnesium oxide was plastically deformed by thermal stresses which occurred on cooling. Slip occurred on four slip planes only. The slip sources were present in the surface at a depth not exceeding ten microns. They were in the form of dislocation half-loops introduced in the surface during cleavage. The introduction of these half-loops was due to the formation of cleavage steps. Rows of dislocation half-loops were due to the multiplication of a half-loop on a slip plane oriented in the direction of propagation of the cleavage crack. Bond formation consisted of the formation of a magnesium-nickel compound (Mg₂Ni). The bond strength exceeded the stress for brittle fracture of magnesium oxide. Attack of the magnesium oxide occurred preferentially at the perimeter of the interface. This led to groove-formation, which resulted in a large hysteresis of wetting. The diffusion of nickel into magnesium oxide seemed to take place mainly by diffusion along dislocations. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A research report submitted in fulfilment of the requirements for the degree of Master of Science in Engineering (50/50) to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, 2018 / Metal dusting (MD) is a severe form of corrosion in which iron, steels, and nickel (Ni) and cobalt (Co) based alloys disintegrate into a metal or carbide powder with a coke deposit when exposed to strongly carburising gases (carbon activity, ac>1) at elevated temperatures (400800°C). Temperature affects both the driving force and rate of the reaction, represented by gas phase supersaturation with carbon, and the rates of the various processes involved in converting that energy difference into the dusting process. Therefore, process streams such as reformer gas can be benign when hot, but becomes aggressive below critical temperatures. There are different views in literature about the effect of temperature on metal dusting of different materials and alloys. Alloy 800 experiences metal dusting (MD) at 525°C, which is the temperature of the tube sheet of reformers in petrochemical industry. This alloy is specifically used for tube ferrules in the reformers. The reformer trains can reach a critical (highest) internal temperature of 650°C. Therefore, these two temperatures were compared. The effect of temperature and exposure time on the metal dusting of Alloy 800 were investigated in terms of the form of attack and the degradation mechanism. From the results obtained, it was observed that the longer exposure periods result in more carbon deposition and the carbon filaments in the coke become finer as compared to the nanotubes obtained after shorter exposure periods. The alloy suffered metal dusting attack after a relatively short exposure period of three days (72 hours) at both temperatures of 525°C and 650°C, with very little coking. / TL2019