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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 675-681 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Since the prediction of Liu and Cohen [Science 245, 841 (1989)] of the potential extraordinary mechanical properties of crystalline β-C3N4, many authors have attempted its synthesis. However, in most cases, the obtained materials are amorphous phases with a complex bonding structure. Their characterization is complicated due to the absence of a reference compound, the lack of long-range order, and the poor knowledge about their bonding structure. In this article, we present 1H, 13C, and 15N solid-state nuclear magnetic resonance (NMR) measurements for the determination of the bonding types in amorphous CNx films. NMR measurements do not require long-range order and are able to clearly identify the signals from the sp2- and sp3-bonded phases. The analysis of the data obtained by other characterization techniques, such as infrared spectroscopy, x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, and x-ray absorption near-edge spectroscopy on the same sample, based on the information acquired by NMR, enables the description of a structure model for the studied amorphous-CNx phase prepared by dc-magnetron sputtering and to revise the interpretation found in the literature. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 1016-1026 
    ISSN: 0142-2421
    Keywords: XPS analysis ; nanoparticles ; XAS ; EELS ; quantitative characterization of powders ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: For the present study we have considered powders made up of small particles (〈1 μm) coated with a uniform overlayer. Different models have been developed to predict the elemental compositions in this kind of sample by x-ray photoelectron spectroscopy (XPS) and absorption spectroscopies: electron energy-loss spectroscopy (EELS) and x-ray absorption spectroscopy (XAS). Isolated spherical or cubic particles, aggregated spherical particles and continuously layered models have been considered to take different possible textures of the samples into account. Theoretical curves have been compared to experimental data obtained for Al2O3/Al ultrafine powders made up of Al metal cores coated with an Al2O3 overlayer. The dependence of both photoelectron and absorption spectroscopy analysis on overlayer thickness and sample texture as a function of particle size is discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0142-2421
    Keywords: x-ray absorption spectroscopy ; total electron yield ; oxides ; EXAFS probing depth ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Calibration of the probing depth by x-ray absorption spectroscopy (XAS) in oxide materials is intended by measurement of the total electron yield (TEY) of electrons ejected by absorption of the radiation. Measurements have been carried out for three series of electrolytic metal oxide overlayers with different thickness. The experiments have been conducted at the Ti K, Ta LIII and Zr K edges. Analysis of the XAS spectra is carried out by factor analysis and conventional Fourier transformation and fitting analysis. The data showed that the information depth by XAS follows the order ZrO2〉TiO2〉Ta2O5 at the Ti K, Ta LIII and Zr K edges.As an alternative, the absorption spectra of the same samples were measured in the conversion electron yield (CEY) mode: i.e. by measuring the current of He+ ions produced by the ejected electrons in an atmosphere of He in contact with the sample. Here, the information depth is slightly different from that obtained by TEY. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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