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  • Polymer and Materials Science  (3)
  • chromatography  (2)
  • microporous crystals  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 19 (2000), S. 65-70 
    ISSN: 1573-4846
    Keywords: porous material ; phase separation ; microporous crystals ; chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Recent progress in the sol-gel science concerning the porous gels made by phase separation has been reviewed. Based on the principle and technique explored for monoliths, the material shape has been extended to a macroporous thick film and a macroporous gel in a confined space such as capillary, both of which are expected to find useful applications in the chromatography. The modifiable size range of the additional porosity within the micrometer-sized gel skeleton has been broadened from micropores by zeolite, mesopores by surfactant templates to macropores by intensive hydrothermal treatments. A detailed investigation of 3D interfacial structure in real space has been performed using the laser scanning confocal microscope, which enabled quantitative comparison of the structure with those of other phase-separating systems.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 19 (2000), S. 769-773 
    ISSN: 1573-4846
    Keywords: silica ; macropores ; deposition ; silicalite-1 ; microporous crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Microcrystalline silicalite-1 was formed on the inner surface of macroporus silica glasses prepared by the sol-gel process. By heating a homogeneous precursor solution at 100°C under a hydrothermal condition, 2–5 μm of plate-like particles of silicalite-1 were deposited. With an increase of mixing time of the precursor solution, the number of silicalite-1 particles increased, accompanied by the relative decrease of the particle size. Depending on the temperature and the duration of the heat-treatment of the macroporous silica, the amount of deposited silicalite-1 varied. Below 1000°C, the amount increased with the heat-treatment temperature, as a result of the competition between the precipitation of silicalite-1 and the dissolution of silica from the macroporous silica glass under a strongly basic condition. On the other hand, above 1000°C the amount of deposited silicalite-1 decreased in accordance with the decrease of the macropore diameter by the heat-treatment, because of the limited transport of the dissolved silicate species through the smaller macropores.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of porous materials 4 (1997), S. 67-112 
    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.
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  • 4
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: It has been shown that the prerequisite for glasses and glass-ceramics to bond to living bone is the formation of a layer of biologically active bonelike apatite on their surfaces. The hydrated silica formed on the surfaces of glasses and glass-ceramics plays an important role in nucleating the apatite. In the present study, the structure of the hydrated silica responsible for the apatite nucleation was investigated in an accellular simulated body fluid with ion concentrations nearly equal to those of human blood plasma. Three kinds of porous silica gels were prepared by hydrolysis and polycondensation of tetraethoxysilane in pure water or in aqueous solution containing polyethylene glycol or polyacrylic acid. The silica gels prepared in aqueous solution containing polyethylene glycol or polyacrylic acid had micron-size interconnected pores, whereas the gel prepared in pure water did not. All the gels contained a large volume of nanometer-size pores, almost the same amounts of silanol groups and D2 defect, and showed a high dissolution rate of the silica. Despite this, only the gel prepared in the solution containing polyethylene glycol formed the apatite on its surface in the simulated body fluid. This indicates that only a certain type of structural unit of the silanol group is responsible for the apatite nucleation. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 375-381 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: It is known that the prerequisite for glasses and glass-ceramics to bond to living bone is the formation of biologically active bonelike apatite on their surfaces, and a certain type of hydrated silica developed on their surfaces plays an important role in nucleating the apatite. In the present study, the apatite-forming ability of silicate ion dissolved from different silica materials into a simulated body fluid was examined as follows. Polyether sulfone substrates pretreated with O2 plasma were placed in parallel to plates of three kinds of silica gels prepared in different media and silica glass, with a distance of 0.5 mm between them in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma for 4 days, and then soaked in a solution with ion concentrations 1.5 times those of the simulated body fluid for 6 days. After the first soaking, silicon combined with oxygen was detected on the surfaces of the substrates faced to all the silica gels, whereas it was not detected on that faced to the silica glass. After the second soaking, the former formed a bonelike apatite layer on their surfaces, but the latter did not. These results indicate that silicate ion which is dissolved from the silica gels and adsorbed on the substrates has an apatite-forming ability, irrespective of the microstructure of the original silica gels. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 7-15 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Pure soluble silica prepared by a sol-gel method induced bone-like hydroxyapatite formation onto its surface when the silica was immersed in a simulated body fluid (SBF), whereas silica glass and quartz did not. This finding directly supports the hypothesis that hydrated silica plays an important role in biologically active hydroxyapatite formation on the surfaces of bioactive glasses and glass-ceramics, which leads to bone-bonding. Gel-derived titania is also a hydroxyapatite inducer because of its abundant TiOH groups. These results provide further insight into the unique osseointegration of titanium and its alloys. It is suspected that gel-derived titania develops an apatite layer by taking calcium and phosphate from the body fluid, thus producing bonebonding. Although sufficient AlOH groups may remain in the alumina gel, they do not serve to initiate apatite generation when immersed in SBF. This phenomenon explains the fact that an intermediate fibrous tissue is usually found to separate the alumina implant from bone. One may infer that both abundant OH groups and negatively charged surfaces of gel-derived silica and titania are important for hydroxyapatite induction. Material which possesses and / or develops both a negatively charged surface and abundant OH groups in a physiologically-related fluid is most likely to be an efficient apatite inducer. Such materials are suitable candidates to serve as bone-bonding biomaterials. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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