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  • 1
    Electronic Resource
    Electronic Resource
    Influence of Viscoelastic Characteristics of the Colloidal Suspension on the Formation of SnO〈sub〉2〈/sub〉 Supported Membranes (1997)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 132-136 (Apr. 1997), p. 1738-1741 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/44/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.132-136.1738.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Study of Hybrid Silica-Polyethyleneglycol Xerogels by Eu3+ Luminescence Spectroscopy (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 427-432 
    Details
    ISSN: 1573-4846
    Keywords: hybrid gels ; Eu3+ spectroscopy ; polymer electrolytes ; optical probes ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Good optical quality Eu3+-doped silica-polyethyleneglycol hybrids were prepared by the sol-gel process. Thermomechanical analysis showed an increase of the glass transition temperature, due to the stiffness of the polymeric network, as the amount of Eu3+ increased. Europium luminescent properties were used to study structural evolution during the sol-gel transition. For lower doping concentrations dried gels present statistical distributions of Eu3+, typical of an amorphous environment, while for higher concentrations a crystalline-like environment of Eu3+ was observed. A broad emission band was observed in the visible part of the electromagnetic spectrum and assigned to the intrinsic emission from the hybrid polymeric network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008673211834
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  • 3
    Electronic Resource
    Electronic Resource
    Short Range Order Evolution in the Preparation of SnO2 Based Materials (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 261-268 
    Details
    ISSN: 1573-4846
    Keywords: SnO2 xerogel ; sintering ; Eu3+ spectroscopy ; XRD ; EXAFS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The evolution of Eu3+ doped SnO2 xerogels to the cassiterite structure observed during sintering was studied by means of Eu3+ spectroscopy, XRD and EXAFS at the Sn K-edge. Eu3+ ions adsorbed at the surface of colloidal particles present a broad distribution of sites, typical of oxide glasses. With sintering at 300°C, this distribution is still broadened. Crystallization is clearly observed by the three techniques with increasing sintering temperature. It is found that the addition of Eu3+ limits the crystallite growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026458212142
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  • 4
    Electronic Resource
    Electronic Resource
    EXAFS and XRD Study of the Structural Evolution during Isothermal Sintering of SnO2 Xerogels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 269-274 
    Details
    ISSN: 1573-4846
    Keywords: SnO2 xerogels ; sintering ; EXAFS ; XRD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation of an ordered (crystalline) phase during isothermal sintering of SnO2 monolithic xerogels, at 200, 250, 300, 400, 500, 600 and 700°C, has been analyzed by the combined use of EXAFS and XRD techniques. For the desiccated gel (110°C), EXAFS results show the formation of small microcrystallites with the incipient cassiterite structure. Between 110 and 250°C, the dehydratation reaction leads to an amorphization evidenced by a decrease of the long and short range crystallographic order. It is due to fissure formation in the xerogel network. For higher temperatures, a continuous coagulation of the crystallites occurs, leading to grain growth. Grain and pore growth obeys the same kinetic relation, so that the microstructure grows by simple enlargement while its morphology is static.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026410313051
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  • 5
    Electronic Resource
    Electronic Resource
    Formation of SnO2 Supported Porous Membranes (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 477-481 
    Details
    ISSN: 1573-4846
    Keywords: supported membrane ; SnO2 coating ; pore size distribution ; sintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this work, the effect of the substrate microstructure on the formation of SnO2 membranes and of the sintering conditions on their porosity have been analysed. Samples have been prepared by colloidal suspensions cast on alumina or kaolin substrates. Supported membranes have been characterized by Hg porosimetry, MEV, XRD and N2 adsorption-desorption isotherms. The results show that the narrower pore size distribution of alumina substrate allowed to prepare membranes more homogeneous and free of cracks than that supported on kaolin. The crystallite and pore sizes of the membranes could be controlled by adjusting the temperature of sintering, allowing materials with adequate microstructure with application for ultrafiltration process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018337908450
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  • 6
    Electronic Resource
    Electronic Resource
    Study of the Selectivity of SnO2 Supported Membranes Prepared by a Sol-Gel Route (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 805-811 
    Details
    ISSN: 1573-4846
    Keywords: SnO2 membranes ; ultrafiltration ; selectivity ; rejection capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this work the sol-gel process was used to prepare SnO2 supported membranes with an average pore size of 2.5 nm. The effects of salt concentration (NaCl or CaCl2) and of the pH of the aqueous solutions used on the flux and selectivity through the SnO2 membrane were analyzed by permeation experiments and the results interpreted taking account of the zeta potential values determined from the electrophoretic mobility of the SnO2 powder aqueous dispersion. The results show that the ion flux (Na+, Ca2+ and Cl−) throughout the membrane is determined by the electrostatic repulsion among these species and the surface charge at the tin oxide-solution interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008638332190
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  • 7
    Electronic Resource
    Electronic Resource
    Improved Conductivity Induced by Photodesorption in SnO2 Thin Films Grown by a Sol-Gel Dip Coating Technique (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 793-798 
    Details
    ISSN: 1573-4846
    Keywords: thin films ; impurities in semiconductors ; electronic transport ; recombination and trapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thin films of undoped and Sb-doped SnO2 have been prepared by a sol-gel dip-coating technique. For the high doping level (2–3 mol% Sb) n-type degenerate conduction is expected, however, measurements of resistance as a function of temperature show that doped samples exhibit strong electron trapping, with capture levels at 39 and 81 meV. Heating in a vacuum and irradiation with UV monochromatic light (305 nm) improves the electrical characteristics, decreasing the carrier capture at low temperature. This suggests an oxygen related level, which can be eliminated by a photodesorption process. Absorption spectral dependence indicates an indirect bandgap transition with Eg ≅ 3.5 eV. Current-voltage characteristics indicate a thermionic emission mechanism through interfacial states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008634131282
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  • 8
    Electronic Resource
    Electronic Resource
    Investigation of New Ion Conducting Ormolytes Silica-Polypropyleneglycol (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 909-913 
    Details
    ISSN: 1573-4846
    Keywords: hybrid material ; ionic conductor ; solid electrolyte ; silica-polypropyleneglycol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two groups of hybrid organic-inorganic composites exhibiting ionic conduction properties, so called ORMOLYTES (organically modified electrolytes), have been prepared by the sol-gel process. The first group has been prepared from mixture of a lithium salt and 3-isocyanatopropyltriethoxysilane(IsoTrEOS),O,O′-bis(2-aminopropyl)polypropyleneglycol. These materials produce chemical bonds between the organic (polymer) and the inorganic (silica) phases. The second group has been prepared by an ultrasonic method from a mixture of tetraethoxysilane (TEOS), polypropyleneglycol and a lithium salt. The organic and inorganic phases are not chemically bonded in these samples. The Li+ ionic conductivity, σ, of all these materials has been studied by AC impedance spectroscopy up to 100°C. Values of σ up to 10−6 Ω−1 · cm−1 have been found at room temperature. A systematic study of the effects of lithium concentration, polymer chain length and the polymer to silica weight ratio on σ shows that there is a strong dependence of σ on the preparation conditions. The dynamic properties of the Li+ ion and the polymer chains as a function of temperature between −100 and 120°C were studied using 7Li solid-state NMR measurements. The ionic conductivity of both families are compared and particular attention is paid to the nature of the bonds between the organic and inorganic components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008627424438
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