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  • 1995-1999  (4)
  • 1
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Under fuel cell conditions, using a protonic conductor Nafion® electrolyte, active cobalt porphyrins (TpOCH3PPCo or CoTMPP and derivatives) and cobalt tetraazaannulene (CoTAA) supported on an active charcoal were investigated towards oxygen reduction to test their activity and stability. Over a 200 h period, performances were found almost constant with CoTAA after an 800°C heat treatment (HT 800), whereas performances with different substituted phenyl porphyrins declined. XPS analyses were also carried out on these electrodes. On all samples they displayed a complete loss of cobalt within the measurement accuracy. Heat treatment temperature effects were visible on the Nls spectra for the CoTAA samples, the most stable and active samples presenting the lowest oxidation state after current drain application.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 48 (1997), S. 229-238 
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract For the catalytic synthesis of carbon nanotubes having fullerene- like diameters, a detailed description of the catalyst preparation is given. Silica-supported catalyst samples (prepared from Co-acetate solution of different pH) were tested in the decomposition of acetylene. Catalysts with various pretreatments (different calcination temperature, time and atmosphere) were compared in the carbon nanotubes production and characterized by X-ray photoelectron spectroscopy (XPS). The quality and the quantity of the bucky tubes were studied by transmission electron microscopy (TEM). As a final conclusion, it is possible that changing the pH of the solution during catalyst preparation allows control of the quality of the carbon nanotubes, namely the amount of turbostratic straight and helical tubes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 1569-1584 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Three monomers with different degrees of unsaturation, 1-propanol, allyl alcohol, and propargyl alcohol, are plasma-deposited to obtain alcohol functions containing polymers. To obtain information on the behaviors of these monomers in the plasma, the polymers deposited in the reactor and in the postdischarge region are characterized by high-energy resolution XPS, IR, HREELS, elemental analysis, and chemical derivatization. XPS results show that oxygen-rich polymers can be obtained from the unsaturated monomers at low power for both regions or at high power in the postdischarge region. In the reactor at high power, fragmentation of the monomer leads to the elimination of oxygen fragments and ablation reactions during the polymerization process. Detailed structural information on the chemical structure and content of functional groups are obtained by simulation of the XPS C1s core levels of the polymers before and after derivatization with trifluoroacetic anhydride. In soft conditions, allyl alcohol leads to the formation of polymers with a relatively low degree of crosslinking and a high hydroxyl content (53-72%). However, the high resolution of the XPS spectrometer allows one to detect the presence of secondary or tertiary alcohol functions resulting from chain branching reactions in this polymer. Results from this multitechnique characterization indicate also that the hydroxyl conversion and crosslinking reactions are more pronounced for poly(1-propanol) and poly(propargyl alcohol). Alcohol, ether, and carbonyl functions are present in equivalent quantities in poly(propargyl alcohol) while poly(1-propanol) contains mainly ether functions (50%). The presence or absence of alcohol functions at the extreme surface of the polymers in relation to the chain mobility and the tendency of hydrogen bonding between hydroxyl groups was studied by HREELS. © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 597-614 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The surface chemistry of plasma-deposited films created from amine-functionalized saturated (propylamine) and unsaturated (allylamine and propargylamine) precursors has been investigated by high-energy resolution XPS, chemical derivatization, elemental analysis, and HREELS.XPS results show that nitrogen-rich deposits are obtained from unsaturated precursors at low power or at high power in the postdischarge region. Quantitative information on the chemical groups in the polymers is obtained by simulating the XPS C1s and N1s core levels and by performing derivatization reactions. The proportion of primary amine functions deduced from tagging reactions with pentafluorobenzaldehyde in the liquid phase and with 4-trifluoromethylbenzaldehyde in the vapor phase varies between 10 and 33%. These groups are converted into imine (more than 50%) in polypropylamine and polyallylamine, while imine and nitrile functions were found in polypropargylamine. HREELS has allowed us to distinguish between different nitrogen-containing functionalities present at the extreme surface of the polymers. The comparison of the HREELS and TIR spectra shows that the chemical composition at the extreme surface of the samples is representative of that of the bulk. To explain the conversion of the chemical groups in the plasma, polymerization mechanisms are proposed for each of the monomers. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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