Phonons in suspensions of hard sphere colloids: Volume fraction dependence

2004 ◽  
Vol 121 (16) ◽  
pp. 7849 ◽  
Author(s):  
H. Kriegs ◽  
G. Petekidis ◽  
G. Fytas ◽  
R. S. Penciu ◽  
E. N. Economou ◽  
...  
Keyword(s):  
Hard Sphere ◽  
Volume Fraction

Static lengths in glass-forming monodisperse hard-sphere fluids from periodic array pinning

Soft Matter ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 402-407 ◽  
Author(s):  
Yuxing Zhou ◽  
Scott T. Milner
Keyword(s):  
Structural Relaxation ◽  
Hard Sphere ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Relaxation Times ◽  
Periodic Array ◽  
Length Scale ◽  
Master Curves ◽  
Particle Volume ◽  
Glass Forming

In glassy hard-sphere fluids, with varying particle volume fraction and distance between pinned particles, particle diffusivities and structural relaxation times both collapse to master curves, revealing a growing static length scale.

scholarly journals Slowing down of dynamics and orientational order preceding crystallization in hard-sphere systems

2020 ◽  
Vol 6 (43) ◽  
pp. eabc5916
Author(s):  
Felix Lehmkühler ◽  
Birgit Hankiewicz ◽  
Martin A. Schroer ◽  
Leonard Müller ◽  
Beatrice Ruta ◽  
...  
Keyword(s):  
Hard Sphere ◽  
Soft Matter ◽  
Volume Fraction ◽  
Orientational Order ◽  
Strong Increase ◽  
Quasi Equilibrium ◽  
Slowing Down ◽  
X Ray Scattering ◽  
Matter System ◽  
Scattering Study

Despite intensive studies in the past decades, the local structure of disordered matter remains widely unknown. We show the results of a coherent x-ray scattering study revealing higher-order correlations in dense colloidal hard-sphere systems in the vicinity of their crystallization and glass transition. With increasing volume fraction, we observe a strong increase in correlations at both medium-range and next-neighbor distances in the supercooled state, both invisible to conventional scattering techniques. Next-neighbor correlations are indicative of ordered precursor clusters preceding crystallization. Furthermore, the increase in such correlations is accompanied by a marked slowing down of the dynamics, proving experimentally a direct relation between orientational order and sample dynamics in a soft matter system. In contrast, correlations continuously increase for nonequilibrated, glassy samples, suggesting that orientational order is reached before the sample slows down to reach (quasi-)equilibrium.

An improved small-angle X-ray scattering analysis of δ′ precipitation in an Al–Li alloy for growth kinetic studies

1999 ◽  
Vol 32 (3) ◽  
pp. 426-435 ◽  
Author(s):  
Cheng-Si Tsao ◽  
Tsang-Lang Lin
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Hard Sphere ◽  
Volume Fraction ◽  
The Other ◽  
Improved Method ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Two Parameters

An improved method for small-angle X-ray scattering (SAXS) data analysis is developed to reconstruct the free-form particle size distribution of δ′ precipitation in an Al–Li alloy. This improved method consists of four iterative steps; the interparticle interference is also included. The indirect transform method (ITM) plus a hard-sphere (HS) model which considers the depleted zones are used in the analysis of δ′ precipitation in an Al–Li alloy. Two parameters, namely the hard-sphere volume fraction, ηHS, and the ratio of hard-sphere radius to the particle radius,RHS/R, which determine the structure factor of the interparticle effect, are iteratively calculated using the monodisperse assumption and Gaussian size distribution. These two parameters are finally used in reconstructing the particle size distribution by the ITM + HS method. This method is tested by analysing simulated SAXS data and shows a better agreement than found in similar studies. This improved method is applied to analyse a set of experimental SAXS intensities from δ′ (Al3Li particles) precipitation in an Al–9.7 at.% Li alloy. The monodisperse results are compared with the polydisperse ITM + HS results. The current ITM + HS method fits the SAXS data better than the other methods. The variations of average radii with aging time were found to follow the kinetic power law. The SAXS results are used to investigate the theoretical kinetic model of the volume-fraction effect on late-stage coarsening (Ostwald ripening). By comparing both experimentally obtained asymptotic size distributions of δ′ particles as well as coarsening rate constants with those predicted by the various kinetic models, the modified Lifshitz–Slyozov–Wagner (MLSW) theory is found to be in better agreement with the experimental results than the other theories.

Flow of Dispersions Near Close Packing

1989 ◽  
Vol 155 ◽  
Author(s):  
L. Marshall ◽  
C. F. Zukoski
Keyword(s):  
Hard Sphere ◽  
Creep Compliance ◽  
Volume Fraction ◽  
Shear Thickening ◽  
Time Spectrum ◽  
Close Packing ◽  
Shear Rates ◽  
Volume Fractions ◽  
Exponential Relaxation ◽  
Hard Sphere Liquids

ABSTRACTThe flow of hard sphere-like suspensions near close packing is explored. The change in viscosity with stress and volume fraction shows that at volume fractions above 0.5 shear thickening occurs and that the characteristic shear rates for shear thinning and shear thickening decrease rapidly above this volume fraction. The creep compliance is well characterized by a stretched exponential relaxation time spectrum above volume fractions of 0.52. These results suggest that the limiting volume fraction where the zero shear rate viscosity diverges is determined by a liquid/glass phase transition very similar to that predicted for hard sphere liquids.

Phonon Dispersion in Suspensions of Hard Sphere Colloids*

1990 ◽  
Vol 195 ◽  
Author(s):  
D.A. Weitz ◽  
J. Liu ◽  
L. Ye ◽  
Ping Sheng
Keyword(s):  
Hard Sphere ◽  
Volume Fraction ◽  
Phonon Dispersion ◽  
Brillouin Scattering ◽  
Compressional Wave ◽  
Frequency Mode ◽  
Pure Liquid ◽  
Sphere Diameter ◽  
Longitudinal Modes ◽  
Lower Frequency Mode

ABSTRACTWe use Brillouin scattering to measure the dispersion of the propagating acoustic modes in a suspension of hard sphere colloids. We find two distinct longitudinal modes when the sound wavelength becomes comparable to the sphere diameter. The higher frequency mode has a velocity intermediate between those of the pure solid and the pure liquid phases, and its velocity increases with increasing volume fraction, ø. The lower frequency mode has a velocity less than the velocities in either the pure fluid or pure solid phases, and its velocity decreases with increasing ø. We interpret the higher frequency mode as a compressional wave which propagates through both the solid and the fluid, as expected for a composite medium. The lower frequency mode has not been observed before, and is interpreted as a surface acoustic mode, which propagates between adjacent spheres through a decaying portion of the excitation in the fluid.

scholarly journals Homogeneous melting near the superheat limit of hard-sphere crystals

Soft Matter ◽  
2018 ◽  
Vol 14 (13) ◽  
pp. 2447-2453 ◽  
Author(s):  
Feng Wang ◽  
Ziren Wang ◽  
Yi Peng ◽  
Zhongyu Zheng ◽  
Yilong Han
Keyword(s):  
Bulk Modulus ◽  
Hard Sphere ◽  
Volume Fraction ◽  
Superheat Limit

We find the superheat limit of hard-sphere fcc crystals at volume fraction 0.494 due to the vanishing bulk modulus.

Shear Thinning Properties of Dense Suspensions: Rheology and Flow Dichroism

1992 ◽  
Vol 289 ◽  
Author(s):  
Jonathan W. Bender ◽  
Norman J. Wagner
Keyword(s):  
Hard Sphere ◽  
Volume Fraction ◽  
Equilibrium Structure ◽  
Total Stress ◽  
Colloidal Forces ◽  
Dense Suspensions ◽  
Theory Comparison ◽  
Sphere Suspensions ◽  
The Relationship ◽  
Optical Dichroism

AbstractAn expression relating dichroism to the non-equilibrium structure was derived through Rayleigh-Gans light scattering theory. Comparison of this expression to a micromechanical expression for the thermodynamic contribution to the total stress demonstrates a stress-optical relationship. Optical dichroism and viscosity measurements on monodisperse, near hard-sphere suspensions as a function of shear rate, volume fraction, and particle size demonstrated the relationship experimentally. This work provides a rheo-optical method for determining the various contributions of the colloidal forces to the overall stress.

Theory of tracer diffusion in concentrated hard-sphere suspensions

2019 ◽  
Vol 870 ◽  
pp. 1105-1126 ◽  
Author(s):  
S. S. L. Peppin
Keyword(s):  
Glass Transition ◽  
Hard Sphere ◽  
Volume Fraction ◽  
Pore Space ◽  
Particle Volume Fraction ◽  
Tracer Diffusion ◽  
Tracer Diffusivity ◽  
Particle Volume ◽  
Cross Diffusion ◽  
Sphere Suspensions

A phenomenological theory of diffusion and cross-diffusion of tracer particles in concentrated hard-sphere suspensions is developed. Expressions for the diffusion coefficients as functions of the host particle volume fraction are obtained up to the close-packing limit. In concentrated systems the tracer diffusivity decreases because of the reduced pore space available for diffusion. The tracer diffusivity can be modelled by a Stokes–Einstein equation with an effective viscosity that depends on the pore size. Tracer diffusion and segregation during sedimentation cease at a critical trapping volume fraction corresponding to a tracer glass transition. The tracer cross-diffusion coefficient, however, increases near the glass transition and diverges in the close-packed limit.

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