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Masanori Hirano - One of the best experts on this subject based on the ideXlab platform.

  • direct formation of anatase tio2 Silica Sio2 composite nanoparticles with high phase stability of 1300 c from acidic solution by hydrolysis under hydrothermal condition
    Chemistry of Materials, 2004
    Co-Authors: Masanori Hirano, Hiroyuki Iwata
    Abstract:

    Anatase (TiO2)/Silica (Sio2) composite nanoparticles that were directly synthesized from solutions of TiOSO4 and tetraethyl orthoSilicate by hydrolysis under hydrothermal conditions at 200 °C showed far more enhanced phase stability than pure anatase-type TiO2. By the presence of 48.2 mol % Sio2 as mostly amorphous phase, the crystallite growth of anatase was completely suppressed to maintain the crystallite size (14−16 nm) of the as-prepared condition after heating at 1000 °C, and the anatase-to-rutile phase transformation was retarded to maintain the anatase-type structure up to 1300 °C with no trace of rutile phase. The critical crystallite size of anatase in the composite samples for the anatase-to-rutile phase transformation was suggested to be around 70−100 nm. The Silica, which contained -OTi groups around tetrahedrally coordinated Si and was regarded to exist mostly as amorphous phase, was considered to play an important role in suppressing diffusion between anatase crystallites, which led to the ...

  • Direct Formation and Photocatalytic Performance of Anatase (TiO2)/Silica (Sio2) Composite Nanoparticles
    Journal of the American Ceramic Society, 2004
    Co-Authors: Masanori Hirano
    Abstract:

    Anatase (TiO2)/Silica (Sio2: 23.9–27.7 mol%) composite nanoparticles were directly synthesized from (i) the reaction of titanyl sulfate (TiOSO4) and sodium metaSilicate (Na2SiO3) under mild hydrothermal conditions, (ii) the acidic precursor solutions of TiOSO4 and tetraethylorthoSilicate (TEOS) by thermal hydrolysis, and (iii) the metal alkoxides, i.e., tetraisopropoxide (TTIP) and TEOS, by the sol–gel method. Their photocatalytic activities were evaluated by measurements of the relative concentration of methylene blue after UV irradiation. The as-prepared TiO2/Sio2 composite nanoparticles showed far more improved photocatalytic activity than the pure anatase-type TiO2. The composite nanoparticles formed from (i) TiOSO4 and Na2SiO3 as well as those from (ii) TiOSO4 and TEOS showed fairly good photocatalytic activity, and it was better than that of those synthesized from (iii) the metal alkoxides, which was suggested to be due to the difference in crystallinity of the anatase.

Hiroyuki Iwata - One of the best experts on this subject based on the ideXlab platform.

  • direct formation of anatase tio2 Silica Sio2 composite nanoparticles with high phase stability of 1300 c from acidic solution by hydrolysis under hydrothermal condition
    Chemistry of Materials, 2004
    Co-Authors: Masanori Hirano, Hiroyuki Iwata
    Abstract:

    Anatase (TiO2)/Silica (Sio2) composite nanoparticles that were directly synthesized from solutions of TiOSO4 and tetraethyl orthoSilicate by hydrolysis under hydrothermal conditions at 200 °C showed far more enhanced phase stability than pure anatase-type TiO2. By the presence of 48.2 mol % Sio2 as mostly amorphous phase, the crystallite growth of anatase was completely suppressed to maintain the crystallite size (14−16 nm) of the as-prepared condition after heating at 1000 °C, and the anatase-to-rutile phase transformation was retarded to maintain the anatase-type structure up to 1300 °C with no trace of rutile phase. The critical crystallite size of anatase in the composite samples for the anatase-to-rutile phase transformation was suggested to be around 70−100 nm. The Silica, which contained -OTi groups around tetrahedrally coordinated Si and was regarded to exist mostly as amorphous phase, was considered to play an important role in suppressing diffusion between anatase crystallites, which led to the ...

G. Ghosh - One of the best experts on this subject based on the ideXlab platform.

  • Temperature dispersion of refractive indexes in some Silicate fiber glasses
    IEEE Photonics Technology Letters, 1994
    Co-Authors: G. Ghosh
    Abstract:

    Temperature coefficients of refractive indexes dn/dT determine the temperature characteristics of an optical fiber transmission system. These coefficients are analyzed critically for the first time to find refractive indexes at different temperatures for three optical fiber glasses fused Silica (Sio2), aluminoSilicate and Vycor, and to predict therefrom the optical design parameters such as chromatic dispersion and zero-dispersion wavelength from the UV to the 1.7 μm region.

Norihisa Fukaya - One of the best experts on this subject based on the ideXlab platform.

Asadi Shima - One of the best experts on this subject based on the ideXlab platform.

  • Green synthesis of bis(indolyl)methanes in water using sulfonic acid functionalized Silica (Sio2-Pr-SO3H)
    iranian journal of catalysis, 2015
    Co-Authors: Mohammadi Ziarani Ghodsi, Aslani Zeinab, Asadi Shima
    Abstract:

    Bis(indolyl)methanes are important group of bioactive metabolites of terrestrial and marine regions. They were synthesized by different methods. Herein, a clean, one-pot synthesis of bis(indolyl)methane derivatives by cyclo-condensation reaction of indole and various aldehydes using Sulfonic acid functionalized Silica (Sio2-Pr-SO3H) in aqueous media is reported. The advantages of this new method were simple operation, good yields, short reaction times and easy work-up. Sulfonic acid functionalized Silica as an efficient heterogeneous solid acid catalyst could be prepared by simple operation from commercially available cheap starting materials such as Silica. It catalyzes various organic reactions and could be easily removed, recovered and reused without significant loss of activity.