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  • Polymer and Materials Science  (2)
  • Bemisia argentifolii
  • 1990-1994  (2)
  • 1
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Surface oxidation reactions of cobalt, molybdenum and mixed cobalt-molybdenum metals have been investigated using x-ray photoelectron spectroscopy (XPS). The oxide stoichiometries have been determined from XPS intensity measurements. Such quantification has been important in identifying oxide compositions with characteristic XPS spectra. A number of discrete binary molybdenum oxides have been characterized after reactions at 200°C and pressures ranging from 1 atm to 10-6 Pa. At the lowest pressure, the Mo 3d spectra and O/Mo ratios suggest the formation of a molybdenum-oxygen structure with a stoichiometry near unity. By contrast, at higher pressures, oxides that are predominantly MoO2 and MoO3 appear, but other intermediate oxide structures are also identified. Well-defined binary oxides of cobalt can be prepared from cobalt metal after heating in oxygen at different pressures. New binary oxides of cobalt and molybdenum have been generated by the reaction on MoO3 or Co3O4 substrates. Oxidation of a thin film of molybdenum on a Co3O4 substrate has been shown to produce a nearly stoichiometric surface layer of CoMoO4. The procedure could be useful for the production of other ternary oxides of possible interest for use as XPS reference materials.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Extended chain polyethylene fibres have been treated in ammonia and oxygen lo-pressure gas discharges (plasmas) in order to enhance adhesion to epoxy and unsaturated polyester resins, respectively, and thus significantly improve fibre/resin interfacial properties in fibre-reinforced polymer composites. Ammonia plasma treatment results in the incorporation of amine functional groups onto the fibre suface. The treated fibre surface has been analysed using XPS and spectrophotometric techniques. Extended chain polyethylene/epoxy composites made from ammonia, plasma-treated fibres show a marked increase in interlaminar shear strength over composites made from untreated, corona-treated or oxygen plasma-treated fibres. The increase in fibre/resin adhesion after ammonia plasma treatment is confirmed by SEM observations of fracture surfaces, which show clean interfacial fracture surfaces in composites made from treated fibres. Fibres modified by oxygen plasma treatment contain a significant concentration of carbon-oxygen functionalities, which contribute to the polarity of the surface and hence increase wet-out by unsaturated polyester resins. The concentration and nature of carbon-oxygen species on the fibre surface have been determined by XPS. Pull-out tests on multifilament yarns embedded in a polyester resin confirm the high fibre/matrix adhesion achieved with the oxygen plasma-treated fibres compared to corona-treated or untreated fibres. Tensile properties of the fibres are reduced significantly after prolonged treatment in an oxygen plasma, while in an ammonia plasma the fibre strength is unaffected.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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