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1.
Atsunori Matsuda Tatsuo Matoda Yoshinori Kotani Toshihiro Kogure Masahiro Tatsumisago Tsutomu Minami 《Journal of Sol-Gel Science and Technology》2003,26(1-3):517-521
Anatase nanocrystals were precipitated mainly at the surface of the silica-titania gel films with hot water treatment, whereas the addition of poly(ethylene glycol) (PEG) in the films led to the dispersion of anatase nanocrystals in the whole of the films after the treatment. Both films with and without PEG showed high photocatalytic activities for acetaldehyde, NO
x
and stearic acid in the gas-solid system, and for methylene blue and potassium iodide in the liquid-solid system. The addition of PEG improved the photocatalytic activities of the resultant films due to the smaller anatase crystallites and the porous film structure. The residual silica under-layer of the superficially anatase-precipitated films is expected to act as a protective one for an organic polymer substrate against the photocatalytic degradation. 相似文献
2.
I. M. Miranda Salvado F. M. A. Margaça J. Teixeira 《Journal of Sol-Gel Science and Technology》1994,2(1-3):289-294
Silica-titania gels, prepared in acidic conditions, with contents of TiO2 up to 6 mol%, have been studied by small angle neutron scattering (SANS) as wet gel with increasing aging times. In all samples, small primary particles have been found with a diameter of about 3 nm. At the gel point, cylindrical clusters, ca. 10 nm long, were observed as well. These grow with aging time, becoming branched. The cluster-cluster diffusion limited aggregation model is found to be consistent with the SANS results. The growth process is independent of the TiO2 content. It is mainly influenced by the ratio of the aging time to the gelation time. 相似文献
3.
Spectroscopy and Structure of Sol-Gel Systems 总被引:1,自引:0,他引:1
Sol-gel derived glasses may differ from conventional melt-quenched glasses owing to the peculiar microstructures existing at the gel state, such that, even after gel densification, some differences may remain in their composition and molecular structure.This paper discusses structural characteristics of thin film oxide gels and glasses, with a special emphasis on SiO2-TiO2 based systems, which are of particular interest for sol-gel integrated optics applications. Short range structure aspects are discussed based on infrared, X-ray photoemission and X-ray photoabsorption spectroscopies. The chemical homogeneity of sol-gel materials is evaluated, based on X-ray photoemission and nuclear magnetic resonance spectroscopies, dealing in particular with the issue of homo- vs. heterocondensation. Finally, some microstructural features of sol-gel derived films are analyzed, namely the relationship between infrared absorption and porosity and the structure of nanocrystalline sol-gel films, based on grazing incidence X-ray diffraction and micro-Raman spectroscopy. The types of structural information obtainable by each different technique are compared in detail. 相似文献
4.
Balek V. Málek Z. Šubrt J. Guglielmi M. Innozenzi P. Rigato V. Della Mea G. 《Journal of Thermal Analysis and Calorimetry》2004,76(1):43-48
Emanation Thermal Analysis (ETA) was demonstrated as a tool for the characterization of microstructure changes of a sol-gel
precursor for silica-titania layers deposited on the glass plate to be used as planar waveguides. Temperature ranges of 280-330
and 380-500°C, respectively, in which the densification of the layers took place, were determined by ETA under in situ conditions
of the sample heating. Results of thermogravimetry were compared with the ETA data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Milagrosa Ramirez del Solar Luis Esquivias 《Journal of Sol-Gel Science and Technology》1994,3(1):41-46
A first approach to the ultrastructural evolution during the sintering process of TiO2-SiO2 aerogels has been done on the basis of the gelation kinetics and dried gel previous analysis, in order to tailor the mixed glass sol-gel processing.Small Angle X-Ray Scattering (SAXS) technique was used to study the evolution of the ultrastructure of porous aerogels partially densified at several temperatures. The analysis of the scattering intensity profiles on the basis of the Porod's Two Phase Media Model gives valuable information about pore-solid matrix interface evolution on sintering. 相似文献
6.
7.
M. Montagna E. Moser F. Visintain M. Ferrari L. Zampedri A. Martucci M. Guglielmi M. Ivanda 《Journal of Sol-Gel Science and Technology》2003,26(1-3):241-244
SiO2(1 – x)-TiO2(x) monomode waveguides at 632.8 nm, with x in the range 0.07–0.2 and thickness of about 0.4 m, were deposited on silica substrates by a dip-coating technique. Nucleation of TiO2 nanocrystals and the growth of their size by thermal annealing up to 1300°C were studied by waveguided Raman scattering in the SiO2(0.8)-TiO2(0.2) composition. In the low frequency region (5–50 cm–1) of the VV and HV polarized Raman spectra the symmetric and quadrupolar acoustic vibrations are observed. The mean size of the titania particles are obtained from the frequencies of the Raman peaks. The results are compared with those obtained from the measure of the linewidths in the X-ray diffraction spectra. Nanocrystals with a mean size in the range 4–20 nm are obtained by thermal annealing in a corresponding range of 700–1300°C. 相似文献
8.
Del Monte F. Cheben P. Grover C.P. Mackenzie J.D. 《Journal of Sol-Gel Science and Technology》1999,15(1):73-85
Crack-free films with thicknesses of up to 30 m were prepared by the sol-gel process using the dip-coating technique. Thick films were obtained from various starting solutions based on two, three or four components, with particular emphasis on ternary systems. The ternary systems were composed of two tetraalkoxy precursors (a silicon tetraalkoxide and a zirconium or a titanium tetralkoxide ) and a trialkoxysilane with a non-hydrolyzable group. By using these trialkoxysilanes, the tendency of the films to crack during the drying process is reduced because of the stress absorption by the network structure. The use of zirconia or titania allows for control of the refractive index of the films. Optical parameters of the films including refractive index, thickness, surface roughness and UV-Vis and IR transmission spectra were determined for each composition and the structural characteristics of the films were inferred from the IR spectra. UV cut-off and antireflective properties were also studied for some compositions. 相似文献
9.
Atsunori Matsuda Yoshinori Kotani Toshihiro Kogure Masahiro Tatsumisago Tsutomu Minami 《Journal of Sol-Gel Science and Technology》2001,22(1-2):41-46
Anatase nanocrystals of 5 to 10 nm in diameter were formed in the silica-titania films by treatment with hot water. The formation of nanocrystals with hot water treatment was a unique phenomenon to the silica-titania system and the addition of organic polymers such as PEG was indispensable for the high dispersion of anatase nanocrystals in the films. The hydrolysis of Si—O—Ti bonds with hot water was considered to play an important role for the formation of anatase nanocrystals. The resultant films were transparent even after the formation of anatase nanocrystals. Acetaldehyde was photocatalytically decomposed into CO2 on the films which were subjected to a hot water treatment. The amounts of generated CO2 were twice of that of introduced acetaldehyde, indicating that the total acetaldehyde was completely decomposed to CO2. Anatase nanocrystals-dispersed films can be formed on various kinds of substrates including those with poor heat resistance such as organic polymers and organisms by this process, so that the substrates coated with the films are expected to be widely used for photocatalytic applications. 相似文献
10.
In a program on the development of metal (e.g. Au, Ag, Cu and their alloy) nanoparticles in sol-gel derived films, attempts
were made to synthesize different coloured coatings on glasses and plastics. The absorption position of surface plasmon resonance
(SPR) band arising from the embedded metal nanoparticles was tailored by controlling the refractive index of the matrix for
the development of different colours. Thus different coloured (pink to blue) coatings on ordinary sheet glasses were prepared
by generating Au nanoparticles in mixed SiO2-TiO2 matrices having refractive index values ranging from about 1.41 to 1.93. In another development,in situ generation of Ag nanoparticles in the inorganic-organic hybrid host leads to the formation of different abrasion resistant
coloured coatings (yellow to pink) on polycarbonate substrates after curing. As expected, the SPR peak of Ag or Au is gradually
red-shifted due to the increase of refractive index of the coating matrices causing a systematic change of colour 相似文献