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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nanoparticle research 1 (1999), S. 379-392 
    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
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  • 2
    ISSN: 1572-896X
    Keywords: particle population ; fluid mechanics ; flame synthesized aerosols ; CFD ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The interaction of fluid mechanics and particle dynamics at the very early stages of flame synthesis largely affects the characteristics of the product powder. Detailed simulations provide a better understanding of these processes, which take place in a few milliseconds, and offer the possibility to influence the product characteristics by intelligent selection of the process parameters. The present paper reports on the simulation of titania powder formation by TiCl4 oxidation in an aerosol flow reactor. A commercially available fluid mechanics code is used for the detailed calculation of the fluid flow and the chemical reaction at non-isothermal conditions. This code is then interfaced with a model for aggregate particle dynamics neglecting the spread of the particle size distribution. The simulation shows the onset of the particle formation in the reactor and calculates the dynamic evolution of the aggregate particle size, number of primary particles per aggregate and the specific surface area throughout the reactor. The presented, newly developed calculation technique allows for the first time the simulation of particle formation processes under the authentic, complex conditions as found in actual aerosol reactors.
    Type of Medium: Electronic Resource
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