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  • 1
    Electronic Resource
    Electronic Resource
    The influence of particle size on the magnetorheological properties of an inverse ferrofluid (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 2032-2042 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dependence of magnetorheological properties on particle size is studied, using a model magnetorheological fluid consisting of nonmagnetic silica particles suspended in a ferrofluid. For small particles a strong increase of magnetorheological properties with particle size was found. At a certain particle size and field strength a crossover occurs to a regime where there is only a very limited size dependence. This can be understood in terms of the length of the chains in relation to the gap size of the geometry. Crossover occurs when the average chain length becomes comparable to the gap size. The remaining size dependence may be explained by polydispersity, variations in the morphology, variations in the sterically stabilizing layer of the particles and surface roughness of the geometry. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.482011
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  • 2
    Electronic Resource
    Electronic Resource
    Reactive scattering with a state selected beam: the influence of the internal state and orientation of no upon the chemilum1nescent reactivity with O"3
    Amsterdam : Elsevier
    Chemical Physics Letters 76 (1980), S. 13-15 
    Details
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0009-2614(80)80594-X
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  • 3
    Electronic Resource
    Electronic Resource
    Microrheological modeling of weakly aggregated dispersions (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5845-5853 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A microrheological model of aggregating dispersions is proposed in which the shear stress is estimated as the sum of hydrodynamic and structural parts. The former is attributed to the hydrodynamic cores of fractal aggregates, which behave as a suspension of impermeable spheres. The latter accounts for the forces transmitted by chains of particles linking neighboring aggregates into a transient network. To calculate the structural part the concept of fractal aggregation is incorporated into a transient network theory, to account for the creation and breakup of chains of colloidal particles connecting the aggregates. Rigid and soft chains are distinguished. The former have multiply connected backbones which deform as contorted elastic rods, while the latter have at least one soft junction and deform without elastic resistance until fully loaded. The contribution of the soft chains to the stress tensor is neglected. The calculations treat two different mechanisms for the evolution of rigid chains: a purely mechanical one, which corresponds to a shear-controlled structure built up in flow, and a thermal mechanism, which pertains to a quasiequilibrium structure undisturbed by shear. We calculate steady-shear viscosities in the former case and viscoelastic functions in the latter. The model can be fitted satisfactorily to the experimental results for a well-characterized polystyrene latex dispersion with physically acceptable parameters. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469317
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  • 4
    Electronic Resource
    Electronic Resource
    Transient shear viscosity of weakly aggregating polystyrene latex dispersions (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 5353-5360 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The transient behavior of the viscosity (stress growth) of a weakly aggregating polystyrene latex dispersion after a step from a high shear rate to a lower shear rate has been measured and modeled. Single particles cluster together into spherical fractal aggregates. The steady state size of these aggregates is determined by the shear stresses exerted on the latter by the flow field. The restructuring process taking place when going from a starting situation with monodisperse spherical aggregates to larger monodisperse spherical aggregates is described by the capture of primary fractal aggregates by growing aggregates until a new steady state is reached. It is assumed that the aggregation mechanism is diffusion limited. The model is valid if the radii of primary aggregates Rprim are much smaller than the radii of the growing aggregates. Fitting the model to experimental data at two volume fractions and a number of step sizes in shear rate yielded physically reasonable values of Rprim at fractal dimensions 2.1≤df≤2.2. The latter range is in good agreement with the range 2.0≤df≤2.3 obtained from steady shear results. The experimental data have also been fitted to a numerical solution of the diffusion equation for primary aggregates for a cell model with moving boundary, also yielding 2.1≤df≤2.2. The range for df found from both approaches agrees well with the range df≈2.1–2.2 determined from computer simulations on diffusion-limited aggregation including restructuring or thermal breakup after formation of bonds. Thus a simple model has been put forward which may capture the basic features of the aggregating model dispersion on a microstructural level and leads to physically acceptable parameter values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467199
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  • 5
    Electronic Resource
    Electronic Resource
    Steady shear viscosity of weakly aggregating polystyrene latex dispersions (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 9213-9223 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In order to describe the steady shear behavior of weakly aggregating dispersions a microrheological model is developed. This model combines the concept of fractal aggregation in shear flow with the transient network modeling originally developed for polymer dynamics. The former accounts for the hydrodynamic stress in the aggregates, while the latter is employed to calculate the stress component arising from the forces transmitted by chains of particles combining the neighboring aggregates into a network. The contribution of this network is shown to be significant for steady shear behavior at low volume fractions of solid and low shear rates. The validity of the model is tested by fitting it to experimental data on a well characterized weakly aggregating polystyrene latex dispersion. In this way a number of relevant parameters, among which the fractal dimension df of the aggregates and the capture efficiency of particle chains belonging to neighboring aggregates, are determined. The best agreement of the calculations with the experiments is found at small capture efficiencies and rather high fractal dimensions, i.e., 2.0≤df≤2.3. Hence, combining the steady-shear viscosity measurements with the microrheological interpretation one obtains a tool for probing the structure of weakly aggregating dispersions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465537
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  • 6
    Electronic Resource
    Electronic Resource
    A counter-rotating Couette apparatus to study deformation of a sub-millimeter sized particle in shear flow (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1391-1397 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a new counter-rotating Couette apparatus that has been developed for deformation studies of single sub-millimeter sized particles in shear flow. New features are the adaption to the low viscosities of water-based systems and temperature control of the device. The inner to outer radius ratio of the cylinders used is 0.9785 and the height to width aspect ratio of the gap is 4.0, while the inner radius is 100 mm. Because of the limited particle size a high mechanical accuracy of the Couette geometry is necessary. The swing of the inner cylinder is less than 2 μm and that of the outer cylinder less than 4 μm. We achieved this by carefully choosing the design parameters of the aerostatic bearing and the coupling between cylinder and motor unit. Furthermore, special drive units give a shear rate resolution of 0.018 s−1, while the maximum shear rate is 100 s−1. For a liquid viscosity on the order of 1 mPas the effective maximum shear rate is 30 s−1. We have shown that deformations as small as (L−B)/(L+B)(approximate)0.01 of giant bilayer vesicles (typical radius 10 μm) with length L and width B can be observed with our device. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148771
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of chromate-phosphate conversion layers on Al-alloys by electrochemical impedance spectroscopy (EIS) and optical measurements
    Amsterdam : Elsevier
    Electrochimica Acta 38 (1993), S. 2577-2580 
    Details
    ISSN: 0013-4686
    Keywords: aluminum ; conversion coating ; corrosion ; impedance spectroscopy. ; luminescence
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0013-4686(93)80155-S
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  • 8
    Electronic Resource
    Electronic Resource
    The influence of the internal state and translational energy of the molecular reactant upon the chemiluminescent reaction Ba + N"2O -〉 BaO^* + N"2
    Amsterdam : Elsevier
    Chemical Physics 108 (1986), S. 391-402 
    Details
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-0104(86)80107-0
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  • 9
    Electronic Resource
    Electronic Resource
    The influence of the orientation of the NO molecule upon the chemiluminescent reaction NO+O"3-〉NO"2^*+O"2
    Amsterdam : Elsevier
    Chemical Physics 89 (1984), S. 121-139 
    Details
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-0104(84)85303-3
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of translational and internal energy upon the chemiluminiscent part of the exothermic reaction NO + O"3 -〉 NO^*"2 + O"2 -〉 NO"2 + hν + O"2
    Amsterdam : Elsevier
    Chemical Physics 45 (1980), S. 55-64 
    Details
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-0104(80)85168-8
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