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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 7657-7667 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Smoluchowski's equation is widely applied to describe the time evolution of the cluster-size distribution during aggregation processes. Analytical solutions for this equation, however, are known only for a very limited number of kernels. Therefore, numerical methods have to be used for describing the time evolution of the cluster-size distribution. In this work, we present a novel self-consistent method for solving Smoluchowski's equation for any homogeneous kernel. The method considers dynamic scaling to be valid but does not need to assume a given form for the scaling distribution Φ(x). Moreover, the scaling distribution Φ(x) is obtained as a natural result of the algorithm. Due to the implementation of dynamic scaling concepts, the algorithm converges almost immediately with a minimal calculation effort. Comparing calculated size distributions with the corresponding analytical solutions shows the validity of the method. The method is then used to fit experimental data for diffusion limited aggregation. For this purpose, a fitting procedure is developed which allows us to fit the corresponding parameters for any given homogeneous kernel. As an application, a full comparison between the experimental data and the numerically obtained cluster-size distributions for the constant and the Brownian kernel was carried out. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 6025-6031 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: This paper is concerned with the microstructure observed in colloidal dispersions of charged polymeric particles and their interaction potential at very low ionic strength. Both aspects are probed with the aid of new experimental data for nonaqueous media. The structure factor of ordered dispersions (with methanol–water and ethanol–water solvent mixtures) was determined using static light scattering. A different behavior (in the studied range of molar fraction) depending on the alcohol type is found. These results are analyzed assuming a Yukawa potential and applying integral equation theories (the Ornstein–Zernike equation and the HNC closure). The obtained effective charge is almost constant for methanol–water mixtures, whereas a decrease with the alcohol molar fraction is observed for ethanol–water. In order to account for these effects, a charge renormalization procedure is applied and discussed. The surface charge turns out to be an unsuitable input parameter for such an approach. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    ISSN: 0167-2738
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 104 (1997), S. 104-106 
    ISSN: 1435-1536
    Schlagwort(e): Structure factors ; colloidal stability ; polymer colloids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The structure factorS(q) was measured for a colloidal dispersion of latex microspheres (40 nm of diameter) by both static and dynamic light scattering (using a Malvern Instruments spectrometer, λ=488 nm). The structure was formed for a sample of particle number density 2×1013 ml−1. The interaction potential was determined from the experimentalS(q) by means of the straightforward use of three different closures (Percus-Yevick, hipernetted chain, mean spherical approximation). Some difficulties found with this procedure (such as the cut-off effect) are discussed. However, these closures lead to very similar results. Furthermore, the results are tested and compared with the simulations based on a Yukawa potential.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 104 (1997), S. 138-140 
    ISSN: 1435-1536
    Schlagwort(e): Colloidal aggregation ; fractal structure ; static light ; scattering ; dynamic scaling ; dynamic light scattering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The aggregation kinetics and cluster morphology of polystyrene particles in rapid colloidal aggregation are studied. Experimental results for three aggregating systems with different amount of surfactant adsorbed on the particles are presented. The homogeneity parameterλ of the Van Dongen model was determined from the time evolution of the mean hydrodynamic radius, measured by dynamic light scattering. This parameter allowed the aggregation mechanism to be identified. The cluster fractal dimension was measured by static light scattering.
    Materialart: Digitale Medien
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