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  • 1
    Electronic Resource
    Electronic Resource
    Phase Separation Process of Polymer—Incorporated Silica-Zirconia Sol-Gel System (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 71-76 
    Details
    ISSN: 1573-4846
    Keywords: silica-zirconia ; poly(ethylene oxide) ; spinodal decomposition ; light scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gels with interconnected domain morphologies in the micrometer-range have been prepared in the silica-zirconia system. The domain formation kinetics in the gelling solution have been examined. Growth of an ordered structure on the length scale of micrometers, for which the kinetics are interpreted as spinodal decomposition, was observed by time-resolved light scattering measurements. The remarkable feature of the silica-zirconia system was that a time-dependent decrease of the wavelength of compositional fluctuations was observed. This occurred in the early stage, probably because the fast condensation reaction which was induced by the addition of zirconia, lead to a substantial change in quench depth on a timescale similar to that of the growth of concentration fluctuations. In the following stage, the coarsened domain structure was frozen-in by the sol-gel transition as the permanent morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026451122195
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  • 2
    Electronic Resource
    Electronic Resource
    Phase separation process of polymer—Incorporated silica-zirconia sol-gel system (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 71-76 
    Details
    ISSN: 1573-4846
    Keywords: silica-zirconia ; poly(ethylene oxide) ; spinodal decomposition ; light scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gels with interconnected domain morphologies in the micrometer-range have been prepared in the silica-zirconia system. The domain formation kinetics in the gelling solution have been examined. Growth of an ordered structure on the length scale of micrometers, for which the kinetics are interpreted as spinodal decomposition, was observed by time-resolved light scattering measurements. The remarkable feature of the silica-zirconia system was that a time-dependent decrease of the wavelength of compositional fluctuations was observed. This occurred in the early stage, probably because the fast condensation reaction which was induced by the addition of zirconia, lead to a substantial change in quench depth on a timescale similar to that of the growth of concentration fluctuations. In the following stage, the coarsened domain structure was frozen-in by the sol-gel transition as the permanent morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436820
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  • 3
    Electronic Resource
    Electronic Resource
    Designing Double Pore Structure in Alkoxy-Derived Silica Incorporated with Nonionic Surfactant (1998)
    Springer
    Journal of porous materials 5 (1998), S. 103-110 
    Details
    ISSN: 1573-4854
    Keywords: silica ; sol-gel ; phase separation ; solvent exchange ; surfactant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The principle of designing double-pore structure in alkoxy-derived silica is described with the experimental system containing polyoxyethylene nonylphenylether. The formation of macropores is consistently explained in terms of the concurrence of a phase separation and a sol-gel transition in the polymerizing silica-surfactant-solvent system. The composition-morphology relationship exhibited a substantial variation depending on the length of oxyethylene units in the surfactant molecule. The mesopore volume obtained after basic solvent exchange and a heat-treatment suggested that the surfactant with shorter oxyethylene chain tends to be incorporated more in the gel phase to give higher mesopore volume. The small-angle X-ray scattering measurement of the gelling and aging system supported this hypothesis indicating micelle formation in the system containing a surfactant with shorter oxyethylene chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009633102016
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  • 4
    Electronic Resource
    Electronic Resource
    Pore Structure Control of Silica Gels Based on Phase Separation (1997)
    Springer
    Journal of porous materials 4 (1997), S. 67-112 
    Details
    ISSN: 1573-4854
    Keywords: pore structure control ; silica gels ; phase separation ; spinodal decomposition ; chromatography ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In the alkoxy-derived sol-gel system, various macroporous morphologies can be obtained by inducing the phase separation parallel to the sol-gel transition. This principle of macroporous morphology control can be best applied to pure silica and silica-based multicomponent oxide systems. The earlier the phase separation takes place than the sol-gel transition, the larger the characteristic sizes of pores and gel skeletons become. The time resolved light scattering measurements revealed that the morphology formation process exhibits the features of spinodal decomposition and that the final gel morphology is determined by the competitive kinetics between the domain coarsening and the structure freezing by sol-gel transition. The mesopore structure of such macroporous gel skeletons could be easily tailored by the solvent exchange procedures. Silica gels with controlled macropores and mesopores were successfully applied as a material for the continuous rod type column for high performance liquid chromatography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009627216939
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