The effects of interparticle interactions and particle size on reversible shear thickening: Hard-sphere colloidal dispersions

2001 ◽  
Vol 45 (5) ◽  
pp. 1205-1222 ◽  
Author(s):  
Brent J. Maranzano ◽  
Norman J. Wagner
Keyword(s):  
Particle Size ◽  
Hard Sphere ◽  
Shear Thickening ◽  
Colloidal Dispersions ◽  
Interparticle Interactions

Stability of a Binary Colloidal Suspension and its effect on Colloidal Processing

1989 ◽  
Vol 155 ◽  
Author(s):  
Wan V. Shih ◽  
Wei-Heng Shih ◽  
Jun Liu ◽  
Ilhan A. Aksay
Keyword(s):  
Particle Size ◽  
Hard Sphere ◽  
Colloidal Particles ◽  
Colloidal Suspension ◽  
Fluid Phase ◽  
Ceramic Processing ◽  
Colloidal Processing ◽  
Interparticle Interactions ◽  
The Stability ◽  
Binary Suspension

The stability of a colloidal suspension plays an important role in colloidal processing of materials. The stability of the colloidal fluid phase is especially vital in achieving high green densities. By colloidal fluid phase, we refer to a phase in which colloidal particles are well separated and free to move about by Brownian motion, By controlling parameters such as pH, salt concentration, and surfactants, one can achieve high packing (green) densities in the repulsive regime where the suspension is well dispersed as a colloidal fluid, and low green densities in the attractive regime where the suspensions are flocculated [1,2]. While there is increasing interest in using bimodal suspensions to improve green densities, neither the stability of a binary suspension as a colloidal fluid nor the stability effects on the green densities have been studied in depth as yet. Traditionally, the effect of using bimodal-particle-size distribution has only been considered in terms of geometrical packing developed by Furnas and others [3,4]. This model is a simple packing concept and is used and useful for hard sphere-like repulsive interparticle interactions. With the advances in powder technology, smaller and smaller particles are available for ceramic processing. Thus, the traditional consideration of geometrial packing for the green densities of bimodal suspensions may not be enough. The interaction between particles must be taken into account.

STRUCTURAL PARAMETERS OF AQUEOUS COLLOIDAL DISPERSIONS OF FULLERENE C60

2019 ◽  
pp. 31-37
Author(s):  
V.Yu. Fokina ◽  
E.А. Kizima ◽  
I.V. Miheev ◽  
A.I. Ivankov ◽  
V.M. Garamus
Keyword(s):  
Particle Size ◽  
Fractal Dimension ◽  
Particle Size Distribution ◽  
Structural Parameters ◽  
Colloidal Dispersions ◽  
Fullerene C60 ◽  
Solvent Exchange ◽  
X Ray ◽  
Dense Nucleus ◽  
Exchange Technique

Two types of fullerene C60 water dispersions were investigated by a small-angle X-ray and neutron scattering. As a result, structural parameters of fullerene aggregates were obtained. The water dispersions were obtained by the solvent-exchange technique and by huge dilution of initial C60/Nmethylpyrrolidone solution. The structure organization of water dispersions is considered in respect to their technique preparation. It was shown that fullerene aggregates were characterized by highly polydispersity in size for all dispersions. In the case of son/nC60 dispersion it was found that fullerenes formed aggregates with a dense nucleus (namely a surface fractal) with a radius of 58 ± 1 nm and a fractal dimension of 2.3. In turn, the nmp/nC60 system was characterized by the branched aggregates with fractal dimension 1.5 and bimodal particle size distribution.

Rheology of colloids

Surfactants ◽  
2019 ◽  
pp. 400-424
Author(s):  
Bob Aveyard
Keyword(s):  
Strain Rate ◽  
Shear Strain ◽  
Shear Thickening ◽  
Rheological Behaviour ◽  
Maxwell Model ◽  
Colloidal Dispersions ◽  
Shear Strain Rate ◽  
Plastic Behaviour ◽  
Shear Thickening Fluids ◽  
External Forces

Lyophobic colloidal dispersions, aggregated surfactant systems, and polymer solutions, as well as foams and emulsions, can all be deformed by weak external forces; rheology is the study of deformation and flow of materials. Various rheological quantities arising from the response of a material to shear are defined. For liquids the stress, τ‎, applied is related to the rate of deformation, that is, the shear strain rate, γ̇. For Newtonian fluids τ‎ and γ̇ are linearly related and τ‎ / γ̇ is the viscosity, η‎. Other nonlinear relationships correspond to shear thinning and shear thickening fluids and to plastic behaviour in which there is a yield stress. Viscoelastic systems exhibit both viscous and elastic properties; such behaviour is often treated using the simple Maxwell model. Some illustrative experimentally observed rheological behaviour is presented.

New bounds on the sedimentation velocity for hard, charged and adhesive hard-sphere colloids

2011 ◽  
Vol 667 ◽  
pp. 403-425 ◽  
Author(s):  
W. TODD GILLELAND ◽  
SALVATORE TORQUATO ◽  
WILLIAM B. RUSSEL
Keyword(s):  
Brownian Motion ◽  
Upper Bound ◽  
Hard Sphere ◽  
Large Scale ◽  
Hard Spheres ◽  
Colloidal Dispersions ◽  
Sedimentation Velocity ◽  
Close Packing ◽  
Interparticle Potential ◽  
Equilibrium Microstructure

The sedimentation velocity of colloidal dispersions is known from experiment and theory at dilute concentrations to be quite sensitive to the interparticle potential with attractions/repulsions increasing/decreasing the rate significantly at intermediate volume fractions. Since the differences necessarily disappear at close packing, this implies a substantial maximum in the rate for attractions. This paper describes the derivation of a robust upper bound on the velocity that reflects these trends quantitatively and motivates wider application of a simple theory formulated for hard spheres. The treatment pertains to sedimentation velocities slow enough that Brownian motion sustains an equilibrium microstructure without large-scale inhomogeneities in density.

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