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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 3992-3999 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A microscopic expression for the divergence of the stress tensor is derived for inhomogeneous suspensions of rigid colloidal particles of arbitrary shape. This expression is valid for arbitrary large gradients in the shear rate, concentration, and orientational order parameters. The corresponding Navier–Stokes equation is a necessary ingredient to describe phenomena like shear-banding, phase separation kinetics, and phase coexistence under shear flow conditions. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 3431-3436 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the development of the structure of crystals of colloidal hard spheres in time when gravity effects are minimal and polydispersity is small (<3%). The initial stacking of the close-packed hexagonal layers that make up the crystals is varied by applying various types of shear stress during nucleation of the crystals. The experimental powder diffraction patterns are consistent with a fraction of a faulted-twinned face-centered cubic (fcc) structure that grows at the expense of randomly stacked crystallites. If a faulted-twinned fcc structure is generated initially, no change is found over a considerable time. The present observations rule out the possibility that a randomly stacked structure is the equilibrium structure of colloidal crystals of (nearly) hard spheres, and point to the thermodynamic or kinetic stability of faulted-twinned fcc crystals in these systems. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 5112-5125 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Spinodal decomposition of colloids in the initial and intermediate stages is described on the basis of the Smoluchowski equation. Hydrodynamic interaction is treated in an approximate way. In the intermediate stage, where a dominant length scale exists, the static structure factor is found to exhibit universal scaling behavior. The corresponding dynamic scaling function is derived from the nonlinear equation of motion for the static structure factor. This scaling function is a much more sharply peaked function of the wave vector than the well-known empirical Furukawa scaling function, which applies to the transition stage where sharp interfaces contribute considerably, giving rise to a Porod tail at larger wave vectors. The wave vector where the static structure factor exhibits a maximum is found to vary with time—in the intermediate stage—like ∼t−α, where the exponent α varies between 0.2 and 1.1, depending on the relative importance of hydrodynamic interaction. Experiments on a microemulsion and binary polymer melt confirm the predicted scaling behavior. © 1996 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6193-6205 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: On the basis of the Smoluchowski equation, "the Liouville equation for colloidal systems,'' shear flow distortion effects on the structure factor for temperatures and densities close to the spinodal, c.q. the critical point, are considered. The results are valid in the classical region where the equilibrium structure factor attains the Ornstein–Zernike form. From the structure factor distortion we derive scaling relations for the shear-rate dependent turbidity and flow dichroism for various flow geometries. The dimensionless group which expresses the effect of the shear flow is essentially λ=Pe0(γ(overdot))/(ξRV)4, with Pe0(γ(overdot))=γ(overdot)R2V/2D0 (γ(overdot) is the shear rate, RV the range of the pair-interaction potential, ξ−1 the correlation length, D0 is the Stokes–Einstein diffusion coefficient). As a consequence, very small shear rates (small values of Pe0) have very large effects close to the spinodal, c.q. the critical point, since then ξRV is a small number. Flow dichroism can be many decades larger than for systems far into the stable region of the phase diagram. Relaxation of turbidity and flow dichroism as a shear flow is turned off is also considered. The temperature, density, shear rate, and time dependence of the relaxation is described by scaling functions depending on the two dimensionless groups λ and γ(overdot)t (t is the time lapse after switching off the shear flow).
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  • 6
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 7072-7080 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The anomalous behavior of the (zero frequency) shear viscosity of colloidal systems on approach of the gas–liquid critical point is analyzed. As a result of hydrodynamic interactions, the anomalous behavior is found to be qualitatively different from that of molecular systems. On the basis of the asymptotic solution of the Smoluchowski equation for the shear rate dependent pair-correlation function, an expression for the non-Newtonian zero frequency viscosity of a near-critical suspension is derived. The viscosity depends on two dimensionless groups: on ξ−1d via a cutoff function and on λ∝γ(overdot)ξ4 via the structurefactor (ξ is the correlation length in the equilibrium system, d is the core diameter, and γ(overdot) is the shear rate). The transition from weak to strong shear occurs at λ≈1. The anomalous behavior of both the zero shear viscosity and the non-Newtonian characteristics is formally due to the fact that close to the critical point, where ξ is large, a very small shear rate γ(overdot) is sufficient to make λ a large number. The critical exponent for the zero shear viscosity is found to be equal to that of the correlation length. This exponent is much larger than for molecular systems, which is known to be very small (≈0.03). The exponential behavior sets in at ξ/d≈3. © 1995 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 6941-6949 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An amorphous sediment of charged colloidal particles in a nonaqueous solvent was prepared by centrifugation. The evolution of sediment height and volume fraction profile to equilibrium were studied with light scattering. A simple sedimentation–diffusion equation allows the experimental data to be modeled quantitatively. The top of the sediment crystallizes within a week, whereas the lower part of the sediment does not show any sign of crystallization after several months, indicating a strong concentration dependence of crystallization rate.
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5983-5990 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A calculation of the static structure factor for a system of fully aligned rod-like charged macromolecules, based on the Ornstein–Zernike equation in MSA approximation is presented. The hard core of the molecules is modeled by an ellipsoid. For very long rods this should be a good model. To obtain explicit results, for the long-ranged interaction potential a superposition of screened Coulomb potentials is chosen, although the theory is applicable for any long-ranged interaction potential. The full Ornstein–Zernike equation is reduced to a set of one-dimensional Ornstein–Zernike equations, which are coupled through their closure relations. This feature makes it necessary to obtain the structure factor by a numerical procedure.
    Type of Medium: Electronic Resource
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