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  • Articles  (259)
  • sol-gel  (259)
  • Springer  (259)
  • Chemistry and Pharmacology  (259)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 8 (1998), S. 205-214 
    ISSN: 1572-8870
    Keywords: Phosphazenes ; sol-gel ; urethane ; surface functionalization ; heparin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A sol-gel precursor was prepared by the reaction of poly[bis(2-(2-hydroxyethoxy)ethoxy)phosphazene] (1) with 3-isocyanatopropyltriethoxysilane. It was then sol-gel polymerized to produce a covalently interconnected phosphazene-silicate network with urethane functionalities. Isocyanato groups were introduced on the surface of the network through coupling by allophanate formation between hexamethylene diisocyanate and urethane functionalities on the gel surface. Heparin was immobilized on the surface of the network by reacting hydroxyl or amino groups of heparin with the surface isocyanato groups. The activity of the immobilized heparin was 4.0% that of free heparin.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solution chemistry 20 (1991), S. 1149-1157 
    ISSN: 1572-8927
    Keywords: Tetraethyl orthosilicate ; ethanol ; 1-propanol ; 1-butanol ; sol-gel ; dielectric spectroscopy ; dielectric relaxation ; ceramics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dielectric properties of mixtures of 1-alcohols (ethanol, 1-butanol and 1-hexanol) and tetraethyl orthosilicate (TEOS) were determined by means of the time domain method (TDS). To all spectra were fitted a model function containing a sum of three debye relaxation terms with fixed τ2 and τ3. Initially, to 2–3 mole%, TEOS did not influence static permittivity nor main relaxation time of the alcohol. For higher concentrations there is a linear decrease in both these parameters. Qualitatively the effects of TEOS are comparable with those of a nonpolar hydrocarbon on the alcohol structure.
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  • 3
    ISSN: 1572-879X
    Keywords: alumina ; carbon monoxide oxidation ; ethylene oxidation ; platinum ; cerium ; sol-gel ; thermostability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Various alumina-based supports were prepared by adding metal elements such as alkaline and rare earths to sol-gel alumina synthesized from aluminium isopropoxide using 2-methylpentane-2,4-diol as a solvent and the influence of the additives on the thermostability of the supports was investigated. It was found that Ba and Sr are the most effective in improving the thermostability of the alumina, La is moderately effective while Zr, Mg and Ca are ineffective. The influence of the additives on the catalytic activities of Pt/CeO x /MO y -Al2O3 (M=Ba, Sr, La) after the calculation at 1273 K was also investigated. Pt/CeO x /BaO-Al2O3 and Pt/ CeO x /La2O3-Al2O3 showed higher catalytic activity than Pt/CeO x /Al2O3, while Pt/CeO x / SrO-Al2O3 showed lower catalytic activity. The activity order was Ba 〉 La = none 〉 Sr in terms of CO and C2H4 oxidation.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 36 (1996), S. 41-49 
    ISSN: 1572-879X
    Keywords: sol-gel ; Ru/Al2O3 ; ethylene glycol ; characterization ; chelating agent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ru/Al2O3 catalysts were prepared by sol-gel method with an organic additive (ethylene glycol). The effect of the addition of ethylene glycol on the properties of Ru/Al2O3 was characterized by BET, XRD, EXAFS, and TGA/DTA. Ethylene glycol was effective to promote the phase transition of α-Al2O3 even at 800°C calcination with high surface area. This finding is ascribed to the modified structure of aluminum alkoxide by ethylene glycol addition in the solution state. Ethylene glycol is also effective to get small particles of ruthenium after the reduction at 500°C. The EXAFS and UV-Vis spectra of Ru complex revealed that the coordination structure of Ru depended on the additive used. The ethylene glycol sol prefers to form octahedral Ru complex. This Ru complex in alumina matrix is stable up to 200°C and forms small Ru oxide particles even at 300°C calcination. This suggests that ethylene glycol coordinates to the Ru complex as well as to aluminum ion in the initial state, which is important to control the final properties of the Ru/Al2O3 catalyst.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 28 (1998), S. 1051-1059 
    ISSN: 1572-8838
    Keywords: Carbon-Ceramic electrodes ; Li ion batteries ; intercalation ; Li salt solutions ; EIS ; sol-gel ; Ormosil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Graphite electrodes comprising silica binder were tested in ethylene carbonate–dimethyl carbonate (EC–DMC), propylene carbonate and tetrahydrofuran solutions. The electrochemical behavior of these electrodes was analyzed using chronopotentiometry, slow-scan rate cyclic voltammetry (SSCV), impedance spectroscopy and potentiostatic intermittent titration technique (PITT). The electrode morphology and integrity were studied by scanning electron microscopy (SEM). Using silica binder, graphite particles are usually embedded in the current collector in an unoriented form. Thus, the electroanalytical study of these electrodes and the comparison of their response with that of highly oriented PVDF based graphite electrodes, provided insight into the effect of particle orientation on the general electrochemical behavior of lithiated graphite anodes. In general, the higher the particle orientation and compact packing in the electrodes' active mass, the better the performance o f the Li–graphite electrodes, as the surface films developed are better passivating and the interparticle electronic contact is also better. The silica binder may have advantages over other binders such as PVDF in its ability to better retain the electrode integrity upon cycling. However, the practical use of such electrodes requires further optimization, especially in connection with particle orientation and compact packing.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 6 (1996), S. 221-236 
    ISSN: 1572-8870
    Keywords: Hybrid materials ; metal oxides ; polytorganophosphazenes ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this paper the sol-gel preparation of hybrid materials made of metal oxide and polytorganophosphazenel components is described. The main problem focused on during this research was to avoid phase separation in order to get homogeneous materials. This problem was pursued looking at the formation of genuine chemical bonds between the exploited polyphosphazenes and the inorganic composite networks. Investigations on the thermal, mechanical, and electroconductive properties of the synthesized, phosphazene-containing composite materials showed that these matrices presented improved mechanical and thermal features with respect to those of the original phosphazene macromolecule, while the ionic conductivities of the prepared molecular hybrids doped with lithium or silver trillate are of the same order of magnitude as those measured for the neat, original phosphazene substrate.
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  • 7
    ISSN: 1572-9028
    Keywords: titania-silica ; mixed oxide ; sol-gel ; aerogel ; epoxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The paper provides a short overview on the various Ti- and Si-containing epoxidation catalysts, with a focus on the development and characterisation of titania-silica mixed oxides prepared by the sol-gel-aerogel method. Titania-silica aerogels, dried by semicontinuous extraction of the solvent with supercritical CO2 at low temperature, possess high surface area, an amorphous mesoporous structure, and a rather even distribution of Ti in the silica matrix. The catalytic activities of mixed oxides, silica-supported titania and Ti-substituted molecular sieves (TS-1, Ti-Β and Ti-MCM-41) are compared in the epoxidation of 1-hexene, 1-octene, cyclohexene, cyclododecene and norbornene, based on literature data. The activities (i.e. the amount of converted olefin per unit time and catalyst weight) vary in a broad range of several orders of magnitude. It is shown that the low temperature aerogel containing 20 wt% TiO2 is superior to any other Ti- and Si-containing catalyst for the epoxidation of cyclic olefins. In the epoxidation of linear alkenes TS-1 has outstanding activity. Ti-substituted large and ultra-large pore molecular sieves require further development concerning their catalytic performance.
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  • 8
    ISSN: 1572-879X
    Keywords: molybdenum oxide ; silica support ; sol-gel ; impregnation ; partial oxidation ; methane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two kinds of MoO3/SiO2 catalysts, MoO3-I and MoO3-S, were prepared by impregnation and sol-gel method, respectively. When MoO3 loading was increased, formation of MoO3 crystals was observed to begin at a MoO3 loading of 8 and 16 wt% with MoO3-I and MoO3-S, respectively. The highest yield of formaldehyde from methane oxidation was attained also at those critical values of MoO3 loading of 8 and 16 wt% over MoO3-I and MoO3-S, respectively. It is suggested that the active species for formaldehyde formation is well dispersed molybdenum oxide clusters on SiO2 support: the optimum dispersion of the clusters affords the highest activity for formaldehyde formation.
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  • 9
    ISSN: 1572-879X
    Keywords: hydrogenation ; ruthenium/tin/alumina ; combination ; sol-gel ; impregnation ; ethyl phenylacetate ; 2-phenylethanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A ruthenium-tin-alumina catalyst, prepared by a combination of kneading and impregnation methods, which we have named the combination method, was able to selectively hydrogenate ethyl phenylacetate to 2-phenylethanol; tin oxide was used as a chloride-free tin source. For this combination catalyst, the optimum atomic ratio for Ru: Sn was found to be 1 ∶ 4. X-ray diffraction measurements showed the presence of tin particles. It appeared that the number of the tin particles had a large effect on the hydrogenation of C=O groups. However, the catalyst prepared with ruthenium oxide had a low activity, possibly owing to the ruthenium metal or ruthenium-tin alloy, which was formed and which obstructed the reaction.
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  • 10
    ISSN: 1572-879X
    Keywords: support ; cerium ; alumina ; sol-gel ; thermostability ; platinum ; three-way catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Various CeOx-Al2O3 powders were prepared and the influence of the method of support preparation on the thermostability of the mixed alumina-supported Pt catalysts and on their oxidation of CO was investigated. It was found that the complexing agent-assisted sol-gel method is effective in improving the thermostability of the mixed alumina-supported Pt catalysts. Monolith Pt-Rh three-way catalysts were prepared using these aluminas and other thermostable alumina including Ba. Activity of the catalysts was also investigated after conducting accelerated thermal engine aging in order to test their durability. Under normal operating conditions of the automobile engine, the activity of the Pt-Rh three-way catalyst using the CeOx-Al2O3 support prepared by the complexing agent-assisted sol-gel method is nearly equal to that of the catalyst using the CeOx impregnated onto BaO-Al2O3 powder prepared by the same sol-gel method.
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