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  • 1
    Electronic Resource
    Electronic Resource
    Aero-sol-gel Reactor for Nano-powder Synthesis (1999)
    Springer
    Journal of nanoparticle research 1 (1999), S. 379-392 
    Details
    ISSN: 1572-896X
    Keywords: nanoparticles ; aero-sol-gel ; aerosol ; sol-gel ; hydrolysis/condensation ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract This paper discusses a new approach to the synthesis of nano-structured oxides where sol-gel reactions are carried out in aerosol droplets. This aero-sol-gel (ASG) reactor allows for manipulation of the structure, chemical composition and surface area of silica powders through variation of process parameters. ASG powders differ in nanostructure from other continuous process powders such as pyrolytic and solution-route powders. ASG powders contain mesopores (〉2-nm) and micropores (〈2-nm), the mesopores being responsible for high surface areas measured by nitrogen adsorption using BET theory. Primary particles of close to molecular scale are believed to lead to exceedingly large specific surface areas on the order of 600-m2/g. These primary particles aggregate into nanometer scale mass-fractal aggregates that cluster in micron scale agglomerates. Under controlled reaction conditions the powder structure is reproducible as measured by small-angle X-ray scattering, SAXS, analysis. The ASG reactor displays transport effects similar to those previously seen in laminar flame reactors as evidenced by the effect of reactor geometry and reactant concentration on product structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010066622968
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Interpenetrating and pseudo-interpenetrating polymer networks of polyethylacrylate and zeolite 13X (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 673-677 
    Details
    ISSN: 0887-624X
    Keywords: polyethylacrylate ; interpenetrating polymer networks ; zeolite 13X ; pseudo IPN ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Free radical polymerization of liquid ethylacrylate in the presence of zeolite 13X yielded PIPNs without crosslinker and IPNs if the crosslinker ethylene glycol dimethacrylate was present. We studied these materials both unextracted as well as partially extracted with a variety of solvents using DSC, SEM as well as Small Angle X-ray Scattering (SAXS). These studies suggest that in the composites polyethylacrylate chains entered the internal pores of the zeolite. These chains had an extended state and did not exhibit a bulk glass transition, a similar behavior to that previously reported for polystyrene/zeolite 13X composite. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Ellipsometric study of the glass transition and thermal expansion coefficients of thin polymer films (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 319-326 
    Details
    ISSN: 0887-6266
    Keywords: thermal expansion ; thin films ; ellipsometer ; glass transition ; refractive index ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The glass transition (Tg) of thin polystyrene films (ca. 3000 A˚) cast on silicon wafers was determined by a new technique. An ellipsometer was used to determine the refractive index and thickness of the polystyrene films. Tg was determined by measuring the temperature dependence of the refractive index. The change in thickness with temperature was used to calculate the linear and bulk thermal expansion coefficients of the material. A significant shift in Tg, possibly due to strains induced in the cooled films, was observed between heating and cooling for polystyrene films. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310310
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Nano-structured, semicrystalline polymer foams (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 3063-3072 
    Details
    ISSN: 0887-6266
    Keywords: nano-structured foams ; semicrystalline polymers ; small-angle scattering ; platelet model ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Semicrystalline polymers gelled from thermally quenched semidilute solutions can, in some cases, be supercritically dried to produce nano-structured foams of exceedingly high specific surface area. This article investigates the nano-morphology of these semicrystalline foams. The common morphological feature that these systems display in small-angle scattering can be described by uncorrelated lamellar platelets. The morphological details, which can be obtained using microscopy and small-angle scattering, indicate that these low-density systems occupy a morphological niche between polymeric crystallites from dilute solutions, and spherulitic crystals derived from concentrated solutions and melts. Because these crystalline morphologies occur in concentration ranges between dilute and concentrated, they may offer simple insight into the mechanisms available for distortion of ideal, dilute-solution-derived crystallites as polymer concentration is increased. Several mechanisms for the observed distortions are proposed. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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