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  • Chemistry  (2)
  • LEIS  (2)
  • 1990-1994  (4)
  • 1
    Electronic Resource
    Electronic Resource
    The growth mechanism of nickel in the preparation of Ni/Al2O3 catalysts studied by LEIS, XPS and catalytic activity (1994)
    Springer
    Catalysis letters 25 (1994), S. 315-324 
    Details
    ISSN: 1572-879X
    Keywords: Ni/Al2O3 catalysts ; growth mechanism ; hydrogenation of toluene ; surface characterization ; ALE ; LEIS ; ISS ; XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of Ni/Al2O3 catalysts prepared from vapor phase by the atomic layer epitaxy (ALE) technique have been studied. A model is proposed for the growth mechanism of nickel in its oxidic form on alumina, from sequences of treatments with Ni(acac)2 and air. In the study activity measurements were combined with surface analysis by LEIS and XPS. During the first preparation sequence (〈 5 wt% Ni) atomically dispersed nickel is obtained on the alumina support. The nickel atoms are catalytically inactive, but act as nuclei for the growth of the catalytically active Ni-species during the subsequent preparation sequences. The highest utilization of nickel atoms in the hydrogenation of toluene was obtained when the nickel nuclei were covered with one layer of active nickel species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00816311
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of a Pt-Pd combustion catalyst on an alumina washcoat, with and without prior hydrothermal treatment of the washcoat (1992)
    Springer
    Catalysis letters 13 (1992), S. 27-37 
    Details
    ISSN: 1572-879X
    Keywords: Pt-Pd/alumina ; combustion catalyst ; hydrothermal treatment ; xylene oxidation ; light-off temperature ; TEM/STEM/EDS ; LEIS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two Pt/Pd catalysts on cordierite monoliths were prepared by impregnating two differently treated alumina washcoats with 10 μmol [Pt+Pd] per gram catalyst in the atomic ratio Pt/Pd=4.0. Both washcoats were first thermally treated, calcined, for 2 h at 550 °C in air and one of them was additionally treated, hydrothermally, in 100% steam for 2 h at 814 °C. The hydrothermally treated catalyst was more active for complete oxidation of xylene in air: its light-off temperature was 232 °C, compared to 259 °C for the sample calcined only. To explain this higher activity, both catalysts were characterized by BET surface area, pore-size distribution, hydrogen chemisorption, X-ray diffraction, TEM/STEM/EDS and low-energy ion scattering spectroscopy (LEIS). The catalyst with a hydrothermally treated washcoat had 30% lower surface area, larger alumina crystal size, higher degree of crystallization of alumina and larger average catalyst pore size (11 nm vs. 6 nm), than the one with the washcoat, treated only thermally. The LEIS results indicated a surface enrichment of Pd on both catalysts. The Pt signal in LEIS was higher for the hydrothermally treated sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770944
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  • 3
    Electronic Resource
    Electronic Resource
    Analytical and electrochemical study of passive films formed on nickel - chromium alloys: Influence of the chromium bulk concentration (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 22 (1994), S. 462-466 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Depth composition and chemical states of elements constituting the overlayers of Ni—xCr alloys (x = 0-30 at.%) passivated in borate buffer solutions (pH = 9.2) were determined as a function of the chromium bulk content of the alloy. Depth sputter profiling was performed using both Auger electron spectroscopy (AES) and low energy ion scattering spectroscopy (LEIS). Chemical bonding and (oxy-hydroxy) structures of alloying elements in the passive films were investigated by x-ray photoelectron spectroscopy (XPS). The electrochemical study mainly consists in establishing the cathodic reduction kinetics of the passive layers to characterize the resistance of the internal Cr2O3 barrier to reduction.Very thin films (less than 2.5 nm) were obtained in those conditions showing duplex structures where minor external nickel oxy-hydroxide layers are depicted covering an inner protective barrier mainly composed of chromium oxide Cr2O3. Only at high bulk chromium contents (〉 15 at.%) are complete Cr2O3 layers built at the interface with the metallic alloy. Beneath the film, in the underlying matrix, a metallic nickel enrichment combined with a chromium depletion is observed, which seems to confirm, as for Fe—Cr alloys, a mechanism by which Cr oxidizes preferentially in this medium during the first steps of the film growth.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740220198
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and properties of sulfur cyanide trifluoride, SF3CN, sulfur dicyanide difluoride, SF2(CN)2, and sulfinyl cyanide fluoride, FS(O)CNDedicated to Professor Dietrich Mootz on his 60th Birthday. (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 1221-1226 
    Details
    ISSN: 0044-2313
    Keywords: sulfur cyanides ; sulfur cyanide trifluoride ; sulfur dicyanide difluoride ; sulfinyl cyanide fluoride ; infrared ; Raman ; NMR ; uv ; mass spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Eigenschaften von Schwefelcyanidtrifluorid, SF3CN, Schwefeldicyaniddifluorid, SF2(CN)2, und Sulfinylcyanidfluorid, FS(O)CN.Schwefelcyanidtrifluorid, SF3CN, und Schwefeldicyaniddifluorid, SF2(CN)2, wurden hergestellt durch Methathese zwischen Schwefeltetrafluorid, SF4, und Trimethylsilylcyanid, (CH3)3SiCN, bei - 30°C. Die Umsetzung von SF3CN mit frisch sublimiertem Selendioxid, SeO2, führte zu Sulfinylcyanidfluorid. IR-, Raman, 19F-NMR-, UV und Massenspektren sowie einige physikalische und chemische Eigenschaften dieser neuen Verbindungen werden mitgeteilt.
    Notes: Sulfur cyanide trifluoride, SF3CN, and sulfur dicyanide difluoride, SF2(CN)2, have been prepared by metathesis between sulfur tetrafluoride, SF4, and trimethyl silyl cyanide, (CH3)3SiCN, at - 30°C. Treatment of SF3CN with freshly sublimed selenium dioxide, SeO2, lead to sulfinyl cyanide fluoride, FS(O)CN. IR, Raman, 19F-NMR, uv and mass spectra of the novel compounds are presented as well as some physical and chemical properties.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190712
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