Abstract
We present experimental and theoretical results on the electrorheological response and microstructure of colloidal suspensions composed of silica nanoparticles dispersed in a silicon oil, as a function of electric field strength and silica water content. Using small-angle neutrons scattering experiments, we determined the evolution of the static structure factor of the suspensions when an electric field is applied. Experimental data were fitted with model calculations using the Percus-Yevick solution for Baxter's hard-sphere adhesive potential. The obtained stickiness parameter is directly related to the polarization interactions that depend on the water content of silica particles. The influence of the polarization interparticle potential on the rheology of the silica dispersions was investigated in a second time. A microscopic theory for the shear viscosity of adhesive hard-sphere suspensions was successfully used which describes the steady shear viscosity of suspension in terms of the fractal concept.
Highlights
Electrorheological (ER) fluids, which consist of polarizable particles suspended in an insulating liquid, have recently stimulated considerable interest within the scientific and engineering communities
We examine the rheology of the fluid in the presence of an applied electrical field and we report its influence on the structure of the fluid by small-angle neutron scattering (SANS)
The rheological behavior of the composite is described as a Bingham plastic where the shear stress plotted against the shear rate beyond a critical shear rate is described by τ = τB + ηplγ
Summary
Electrorheological (ER) fluids, which consist of polarizable particles suspended in an insulating liquid, have recently stimulated considerable interest within the scientific and engineering communities. They are materials that find potential application in a wide variety of systems especially in the realm of smart structures and intelligent systems. If the field exceeds a certain threshold, these dipoles attract each other and assemble into chains that are aligned along the field direction. These chains extend across the whole fluid and block its flow, giving rise to the electrorheological effect [4].
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