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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 12 (1998), S. 15-20 
    ISSN: 1573-4846
    Keywords: sodium silicate ; silica xerogel ; washing solvent ; ethanol ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This study deals with the use of ethanol as washing solvent in the preparation of the silica gels from sodium silicate in order to enhance the textural properties, especially surface area. We here examined the effect of ethanol-washing on surface area, micro- and mesopore volume, and average pore size. The silica xerogels prepared from sodium silicate solution exhibited an extremely high surface area of 1139 m2/g by washing their hydrogels with ethanol. Compared to water-washed xerogels, ethanol-washed xerogels showed higher surface areas, total pore volumes, and larger average pore sizes. Unlike the surface area of water-washed xerogel, that of the ethanol-washed xerogel was not affected by the silica concentration of initial solution. This study indicates that the textural properties of sodium silicate-derived xerogels are further enhanced by using ethanol as washing solvent.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 18 (2000), S. 191-198 
    ISSN: 1573-4846
    Keywords: sodium silicate ; silica gel ; microporosity ; hydrophobicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Microporous silica gels were prepared in the pH range of 3–4 using sodium silicate as a silica source. Surface polarity of these gels was modified by grafting hydrophobic groups into the silica gel matrix with the help of hydrophilic solvents (acetone, acetonitrile, ethanol and methanol) and alkoxysilane compounds containing nonhydrolyzable alkyl groups. The porous framework and hydrophobicity of the silica gels were evaluated using nitrogen adsorption/desorption and water adsorption measurement techniques. All the measured isotherms were found to be type I which is indicative of microporosity. The surface area and microporosity of these samples were estimated by analyzing the measured nitrogen adsorption/desorption data using BET, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The micropore size distribution was determined from their nitrogen adsorption isotherms using the slit-pore model of the Horvath-Kawazoe equation. Silica gels with high surface area (over 500 m2/g) as well as high microporosity (over 0.2 cc/g) were obtained at gelation pH of 3.50 from the water-solvent system.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of electroceramics 1 (1997), S. 105-111 
    ISSN: 1573-8663
    Keywords: photostriction ; photovoltaic effect ; sol–gel ; PLZT, doping effect ; tungsten, niobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Lanthanum-modified lead zirconate titanate (PLZT) ceramic materials have gained considerable attention due to their photostriction, which is the superposition of photovoltaic and piezoelectric effects. However, the photovoltaic effect and the induced strain response are also influenced by the fabrication and processing conditions. The PLZT ceramics produced by conventional oxide mixing process exhibit moderate photostrictive properties due to the inhomogeneous distribution of impurities. In this study, ceramics of PLZT (3/52/48) doped with WO3 and Nb2O5 were prepared by sol–gel technique using lead(II) acetate trihydrate, lanthanum(III) acetylacetonate hydrate, Zr, Ti, Nb, and W alkoxides. It was found that WO3 and Nb2O5 were effective in suppressing the grain growth of PLZT, which lead to the enhancement of photovoltaic and photostrictive properties. Photovoltaic and photostrictive responses show ed a maximum for samples with 0.5 at% WO3 doped sol–gel PLZT. It has been shown that the sol–gel derived PLZT ceramics with proper density possess the possibility of enhancing the photostriction over ceramics produced by conventional oxide mixing process.
    Type of Medium: Electronic Resource
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