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  • 1
    Electronic Resource
    Electronic Resource
    Influence of temperature and time on the stability of silver in silica sol-gel glasses (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 917-921 
    Details
    ISSN: 1573-4846
    Keywords: silver doped glasses ; silver stability ; colloidal silver ; thermochromic glasses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The darkening of silica sol-gel glasses doped with 0.05 mol% silver was studied. Six sols were prepared from TEOS and silver nitrate. Different additives were used, to influence the chemical and physical states of silver: oxidizing or reducing agents (H2O2, As2O5), colloid stabilizer (sodium citrate) and network modifiers (Li2O, CaO). Sols were gelified at 60°C and densified at 600°C. The samples without additives and those prepared with H2O2 at room temperature even if they were protected from light. With increased temperature, the darkening became samples were heated above, 400°C, reversible bleaching took place. This darkening-bleaching is of thermal nature (“thermochromic effect”) and seems to be determined by a reversible aggregation-disaggregation of tiny silver particles. The presence of sodium citrate, as an additive delayed the darkening effect and the presence of CaO delayed it even further. Lithium oxide inhibited it totally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436960
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  • 2
    Electronic Resource
    Electronic Resource
    Microhardness and toughness of Na2O-B2O3-SiO2 materials prepared by the sol-gel procedure (1988)
    Springer
    Journal of materials science 7 (1988), S. 791-792 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00722103
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation and characterization of silicate gel glasses containing Cr2O3 (1994)
    Springer
    Journal of sol gel science and technology 2 (1994), S. 895-901 
    Details
    ISSN: 1573-4846
    Keywords: color ; silica glass ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of thermal treatment on the structural incorporation of Cr2O3 in xCr2O3·(100 − x)SiO2 and 5R n O·xCr2O3·(95 − x)SiO2 (where x=0.01−1 mol.% and R=Li, Na and Ca) gel glasses was studied by optical absorption spectrophotometry, DTA-TG, XRD and electron microscopy. Samples heat treated at 60°C have green color due to the presence of Cr3+ in octahedral coordination. The optical transmission, and color (yellow, orange or ambar), of the samples heat treated between 200 and 700°C prove that Cr3+ (octahedrally coordinated) and Cr6+ (tetrahedrally coordinated) are both present. Segregation of Cr2O3 take place at temperatures above 800°C. In reducing conditions the gel glasses were green due to the presence of a high content of Cr3+ ions. Samples containing Li or Na show crystalline phases at temperatures below 850°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486372
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  • 4
    Electronic Resource
    Electronic Resource
    Coloration mechanism in silicate gels and gel-glasses containing iron (1996)
    Springer
    Journal of sol gel science and technology 6 (1996), S. 169-177 
    Details
    ISSN: 1573-4846
    Keywords: iron oxide ; colloidal particles ; color mechanism ; spectrophotometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The present investigation was carried out in order to study the incorporation of iron oxide in several samples with a general composition xFeO-(100-x)SiO2 (x between 0.1 and 9.5) and 5RnO-xFeO-(95-x)SiO2 (R=Li, Na or Ca) prepared by the sol-gel method. Samples were gelated and dried at 60°C and thermally treated between 200 and 1000°C in oxidizing and reducing atmospheres. The color change and structural evolution were studied by VIS and NIR spectrophotometry, TEM and X-ray diffraction. When the temperature increases, the color changes from yellow to brown-reddishness, going through a bright ruby-red, at the same time the absorption edge shifts to higher wavelengths and at elevated temperatures to smaller wavelengths newly. A part of iron oxide is incorporated into the glass network and the remaining as colloidal particles, producing a double mechanism of coloration by optical absorption and dispersion. In the samples heat-treated in oxidizing conditions all iron is present in the ferric state. When the heat-treatment is carried out in reducing conditions the presence of iron (II) was detected at temperatures of nearly 1000°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425974
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  • 5
    Electronic Resource
    Electronic Resource
    Photoluminescence of a silver-doped glass (1996)
    Springer
    Applied physics 63 (1996), S. 431-434 
    Details
    ISSN: 1432-0630
    Keywords: 78.55 ; 78.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The absorption, emission and excitation spectra of Ag+ ions in a soda lime glass doped with two different concentration of silver are investigated. Absorption spectra exhibit a main broad band peaked at about 260 nm (4.77 eV) with a shoulder at about 227 nm (5.46 eV). The relative height of the shoulder depends on silver concentration in the glass. Emission spectra of Ag+ are dominated by an ultraviolet broad band at about 330 nm (3.76 eV). The excitation spectra for this emission show a preponderant broad band peaked at about 227 nm (5.46 eV) which coincides with peak position of the shoulder displayed in the optical absorption spectra. A weak broad featureless emission band centred at about 550 nm (2.25 eV) with an excitation peak at about 242 nm (5.12 eV) is tentatively related to an impurity from the host silica glass rather than originated in silver-type centres. Comparison of the luminescence decay curves for both emissions show substantial differences between them. Consequently, the emissions in the time-resolved spectra can easily be discriminated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571669
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization and study of Na2O-B2O3-SiO2 glasses prepared by the sol-gel method (1988)
    Springer
    Journal of materials science 23 (1988), S. 2142-2152 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The sol-gel procedure has been used to prepare vitreous materials whose compositions are situated in the liquid-liquid immiscibility area of the Na2O-B2O3 SiO2 phase equilibrium diagram. Gels were prepared from different precursors and under different experimental conditions. After determining optimum conditions for gelling and heat-treatment, the gels were characterized with the aid of thermal analysis, X-ray diffraction, density and specific surface area measurements, as well as infrared and near-infrared spectroscopy. The textures of the samples and their microstructures were studied by means of scanning electron microscopy and transmission electron microscopy, respectively. The phase separation in the gels was compared to the same phenomenon in one of the glasses of identical composition, but prepared by conventional melting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01115781
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  • 7
    Electronic Resource
    Electronic Resource
    Dielectric properties of R2O−SiO2 glasses prepared via sol-gel (1989)
    Springer
    Journal of materials science 24 (1989), S. 2884-2890 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Gels from R2O−SiO2 (R=potassium, sodium and lithium) systems with a maximum alkaline content of 5 mol % were prepared. The conductivity and the alkaline ion incorporation degree as a function of temperature were studied by a.c. impedance spectroscopy and dielectric relaxation measurements. At low temperature (20 to 200°C) the major contribution to the total electric conductivity is due to water conducting species (mainly protons) which are adsorbed inside the gels. From 450°C gels start to behave as conventional glasses. The total electric conductivity and activation energy values for conduction at those high temperatures are of the same order as those for glasses prepared by direct melting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02385642
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  • 8
    Electronic Resource
    Electronic Resource
    Study of the colouring process in copper ruby glasses by optical and EPR spectroscopy (1984)
    Springer
    Journal of materials science 19 (1984), S. 1468-1475 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The mechanism responsible for the development of the ruby colour in silica glasses containing copper have been investigated by means of optical and EPR spectroscopy. During the striking treatment, the evolution of the concentration of Cu+ and Sn2+ has been followed through their luminescence bands, whereas the Cu2+ concentration has been monitored by the EPR spectra. To account for the data, a model for the colouring which involves two simultaneous redox reactions: (i)2Cu+→Cu2++Cu0 (ii)2Cu2++Sn2+→2Cu++Sn4+ has been proposed. According to it, the role of tin is to act as a redox buffer to regenerate Cu+, therefore favouring the coalescence of Cu2O colloids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00563041
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  • 9
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    Nonlinear optical susceptibility of multicomponent tellurite thin film glasses (2008)
    American Institute of Physics
    Details
    Publication Date: 2008-12-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Dielectric properties of R2O−SiO2 glasses prepared via sol-gel (1989)
    Springer
    Details
    Publication Date: 1989-08-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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