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  • grafting reactions  (1)
  • self-diffusion  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 263 (1985), S. 1025-1030 
    ISSN: 1435-1536
    Keywords: Layer silicic acids ; organosilanes ; grafting reactions ; interlamellar compounds
    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 The grafting of organosilyl groups in the interlamellar space of certain crystalline silicic acids, such as H-magadiite, occurs when the interlayer spaces have been expanded previously by intercalation of some polar organic substances. The interlamellar Si-OH groups are then accessible to silylating reagents and Si-O-Si bridges form between the silicic acid surface and the organic groups. The grafting reaction is controlled by a diffusion mechanism: desorption of the polar organic guest molecules has to occur simultaneously with the diffusion of the reacting molecules into the interlayer space. The resulting materials are organosilicic compounds which retain the lamellar structure of the starting crystalline silicic acids. Their surface properties are determined by the grafted groups.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 26 (1999), S. 658-667 
    ISSN: 1432-2021
    Keywords: Key words Albite ; aluminosilicate ; thermoluminescence ; self-diffusion ; ionic-diffusion ; interfaces ; ultraviolet emission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Laboratory driven ionic thermal exchange of alkali feldspars from K to Na produces samples which are strongly luminescent in the ultraviolet region near 320 nm. The sites providing this luminescence are suggested as being correlated with the motion of Na atoms along interface-interphases of the material (i.e. with Na-O bond fracture). The thermoluminescence peaks show multi-order kinetics. Thermal preheatings of low albite sensitize the feldspar lattice with respect to thermoluminescence generated by exposure to UV irradiation and heating produces a strong blue luminescence spread over the range 350 nm to 500 nm band in feldspars. The upper temperature for thermoluminescence in feldspars is ∼300 °C, which is also the point where ionic conductivity of albite (010) begins, but the 300 °C region is also the starting point of a large second glow peak in adularia. Whilst it seems appropriate to link the Na motion to the 350–500 nm emission, it is unclear whether these changes are the result of the large anisotropic thermal vibration of Na atoms or the massive Na jumps that occur when the lattice reaches 300 °C. A speculative model is considered in which the UV TL emissions of natural minerals are linked to different interface-interphases (grain boundaries, exsolution limits, twinning planes, antiphase domains). Increased interface coherency energies are related to the kinetic order and the spectral position of luminescence emission peaks.
    Type of Medium: Electronic Resource
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