Theses and Dissertations

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Browsing Theses and Dissertations by Author "Akanni, M.S."

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    Preparation and Characterisation of Pyrolytically-Deposited Thin Oxide Films from Metal-Organic Compounds
    (Obafemi Awolowo University, 1987) Lambi, John Ngolui; Ajayi, O.B.; Akanni, M.S.
    A simple and versatile pyrolytic method of preparing thin metal oxide films that is based on the Metal Organic Chemical Vapour Deposition (MOCVD) technique and that is operative at relatively low temperatures (420°C) has been utilised to prepare the thin metal oxide films of indium, zinc, aluminium and copper from the appropriate metal acetylacetonate or carboxylate. To fully understand the pyrolytic route leading to film formation, the thermal decomposition of some of the starting materials was investigated in detail at 420°C in air and N,, using separately, a Muffle furnace and a flow system. The identities of the products as determined by a combination of techniques are Cu, CO2, a carboxylic acid and an odd chain-length alkene, in the case of the copper(II) soaps; ZnO, CO2 and a ketone for the zinc soaps; and a mixture of Cu, Cu20 and CuO in the case of the copper(II) acetylacetonate. While mechanisms have been proposed to account for the degradative routes of the soaps, which of the metal acetylacetonates is still inconclusive. A combination of Ion Beam, X-ray and optical absorption studies have shown that the oxide films of indium, zinc and aluminium are, of the expected stoichiometry, while that of copper is of mixed composition (CuO/Cu2O/Cu). It is not immediately clear why carbon and alkali metal contamination was observed for the Al2O3 and CuO/Cu2O/Cu films but not for the In2O 3 film. Scanning Electron Microscopy (SEM) has shown the films to be polycrystalline. The observed optical characteristics (high transmittances, T = 75-90%; moderate reflectances, R < 21%; low absorbances, A < 8%; high refractive indices, nf > 1.5 and low extinction coefficients, k < 0.4) are as expected for these thin films. Potential uses of these thin layers based on their observed properties are also discussed.
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    Preparation and Conductivity Measurements of some Metal 9, 10- Dihydroxyoctadecanoates
    (Obafemi Awolowo University, 1986) Mbaneme, Prince Chukwulozie; Akanni, M.S.
    The preparation of 9,10-dihydroxyoctadecanoic acid is carried out using oleic and elaidic acids as reported by Swern and Co-workers. Characterization of the acids is done by taking the melting points and the infrared spectra. The 9,10-dihydroxyoctadecanoic acid obtained from Oleic acid is used in preparing lead(II), Zinc(II), Mercury(II) and Cadmium(II) 9,10-dihydroxyoctadecanoates. The identity of lead(II) and Zinc(II) 9,10-dihydroxyoctadecanoates is established by the results of the melting points, elemental analysis, IR and NMR spectra. The electrical conductances of the pure soap and some binary mixtures with the corresponding metal Octadecanoates are measured. It is found that while the plots of logarithm of conductivity against inverse temperature of the lead(II) 9,10-•dihydroxyoctadecanoate (Pb(OH)2A2) show a maximum, that of Zinc(II)9,10-dihydroxyoctadecanoate(Zn(OH)2A2 and its binary mixtures Zinc(II)octadecanoate/Zinc(II)9,10-dihydroxyoctadecanoate (ZnA2/Zn(OH)2A2) are linear. However, for the binary mixtures of lead(II)octadecanoate/lead(II)9,10-dihydroxyoctadecanoate (pbA2/Pb(OH)2A2) at low mole fractions (XPb(OH)2A2 <0.02) non-linear graph characteristics of the behaviour of lead(II) carboxylate systems are observed while for high mole fractions (XPb(OH)2A2 > 0.03) the shape of the curves resemble that of pure Pb(OH)2A2,the observance of a maximum in the system is interpreted in terms of the interaction of lead ions with the hydroxyl groups. Plots of molar volume against temperature for PbA2 /Pb(OH)2A2 show curvature in support of such interactions, suggesting deviations from ideal behaviour of the liquid systems. The activation energies for conduction and dissociation (ΔHKµ +ΔH/3) for the pure lead(II) and Zinc(II)9,10-dihydroxyoctadecanoates and their mixtures are obtained. For lead(II) octadecanoate/ lead(II)9,10-dihydroxyoctadecanoate at low mole fraction the enthalpy decreases steadily up to a point with increase in mole fraction and then increases. However, for the zinc soaps and its mixtures the enthalpy terms are found to be fairly constant with increasing mole fraction even when the actual conductivity falls.