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  • EXAFS  (2)
  • Analytical Chemistry and Spectroscopy  (1)
  • Glass transition  (1)
  • 1
    Electronic Resource
    Electronic Resource
    An EXAFS study of Cu/ZnO and Cu/ZnO-Al2O3 methanol synthesis catalysts (1993)
    Springer
    Catalysis letters 20 (1993), S. 259-268 
    Details
    ISSN: 1572-879X
    Keywords: EXAFS ; XANES ; methanol synthesis catalysts ; Cu/ZnO ; Cu/ZnO-Al2O3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cu K-absorption edge and EXAFS measurements on binary Cu/ZnO and ternary Cu/ ZnO-Al2O3 catalysts of varying compositions on reduction with hydrogen at 523 K, show the presence of Cu microclusters and a species of Cu1+ dissolved in ZnO apart from metallic Cu and Cu2O. The proportions of different phases critically depend on the heating rate especially for catalysts of higher Cu content. Accordingly, hydrogen reduction with a heating rate of 10 K/min predominantly yields the metal species (〉50%), while a slower heating rate of 0.8 K/min enhances the proportion of the Cu1+ species (∼ 60%). Reduced Cu/ZnO-Al2O3 catalysts show the presence of metallic Cu (upto 20%) mostly in the form of microclusters and Cu1+ in ZnO as the major phase (∼ 60%). The addition of alumina to the Cu/ZnO catalyst seems to favour the formation of Cu1+/ZnO species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769298
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  • 2
    Electronic Resource
    Electronic Resource
    Exafs investigations of Fe-, Ni-, Co- and Cu- MoS2/γ-Al2O3 hydrodesulphurization catalyst systems (1991)
    Springer
    Catalysis letters 9 (1991), S. 427-440 
    Details
    ISSN: 1572-879X
    Keywords: EXAFS ; Sulphided Ni- and Co-Mo catalysts ; Fe-MoS2 catalyst ; Cu-MoS2 HDS catalysts supported on Al2O3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In-situ EXAFS studies have been carried out on several transition metal (T)-MoS2 (T = Fe, Co, Ni or Cu) catalysts supported on γ-Al2O3. While Mo is present in small crystallites of MoS2 in all the systems studied, the local sulphidic environment around the transition metal atom varies significantly with the catalytic activity. Short T-S distances (compared to the bulk sulphides) are found in the case of the Ni and Co catalysts due to the formation of the active ‘Ni(Co)-Mo-S’ state. In the case of Fe, which is not a good promoter, the Fe-S distance in the catalyst is only slightly shorter than in the bulk sulphides. No such short distance is found in the Cu-MoS2/Al2O3 system since Cu acts as a poison; instead only bulk sulphides are formed. Effects of the method of preparation, order of impregnation, metal loading and other factors have been examined to arrive at the conditions favourable for the formation of the active Ni(Co)-Mo-S state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764835
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The Chemistry of the Noncrystalline State (1986)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 25 (1986), S. 31-46 
    Details
    ISSN: 0570-0833
    Keywords: Noncrystalline state ; Amorphous materials ; Disorder ; Solids ; Glass transition ; Glasses ; Materials science ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article sets out to describe and account for the chemical and physical consequences of the presence of gross disorder in solids. Knowledge of the structure of such disordered materials is an obvious prerequisite to a further understanding of other properties and behavior, and our current knowledge of the structure of various noncrystalline systems is discussed together with the experimental techniques which need to be employed in order to obtain such information. The so-called glass transition, which takes place as a liquid is supercooled below the crystallization temperature, is discussed in terms of the various models which have been proposed to account for this phenomenon. The effect of noncrystallinity on electronic properties is also discussed, and we highlight new developments in the understanding of electron localization and transport processes. Finally, two applications of amorphous solids are considered in some detail: optical fibers for use in communication networks and “superionic” glasses for possible use in solid-state batteries.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198600311
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  • 4
    Electronic Resource
    Electronic Resource
    Raman study of the high-temperature phase transition of malonic acid (1984)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 15 (1984), S. 41-46 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman spectra of the high-temperature (α) phase of crystalline malonic acid, CH2(COOH)2, and its deuteriated derivative, CD2(COOD)2, have been investigated at 370 K in the wavenumber shift range 0-4000 cm-1. An assignment of the internal and external vibrations is given. Comparison of the infrared and Raman spectra of the α and β phases shows that the high-temperature phase (α) consists of quivalent centrosymmetric dimer rings and that the corresponding space group is C2h6—C2/c with molecules occupyging C2 sites. The temperature dependence of various Raman lines, in particular those due to lattice modes, indicates that the phase transition is of first order and that during the transition, reorientation of the molecules about the c axis is strongly coupled with the low-frequency torsional (γOH…O) and librational modes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250150110
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