PHASE SEPARATION AND TURBIDITY OF ELECTRORHEOLOGICAL FLUIDS

The turbidity of a suspension of silica particles in a silicone oil is studied in the presence of an electric field. We present experimental results which show a very strong attenuation of a laser beam when the electric field is switched on. We give a theoretical interpretation of these results with the help of a Rayleigh Gans Debye theory applied to cylinders. This model allows us to obtain the average length of the aggregates as a function of the coupling parameter λ, which is me ratio of the electrostatic energy to kT. These results agree with a theoretical prediction and also with the results of Monte-Carlo simulations. The kinetics of the beginning of field induced aggregation can be obtained from the change of the turbidity with time after the application of a voltage step.

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ELECTROSTATIC INTERACTIONS FOR PARTICLE ARRAYS IN ELECTRORHEOLOGICAL FLUIDS II: MEASUREMENTS

International Journal of Modern Physics B ◽

10.1142/s0217979294001196 ◽

1994 ◽

Vol 08 (20n21) ◽

pp. 2895-2902 ◽

Cited By ~ 8

Author(s):

YING CHEN ◽

H. CONRAD

Keyword(s):

Shear Modulus ◽

Electric Field ◽

Shear Strain ◽

Enhancement Factor ◽

Shear Force ◽

Electrostatic Interactions ◽

Silicone Oil ◽

Electrorheological Fluids ◽

Proportionality Constant ◽

Er Fluids

The force required to shear one-, two- and three-chain clusters of 230 µm dia. glass beads in silicone oil was measured. In each case the shear force was proportional to the shear strain, the proportionality constant increasing with electric field and number n of chains in the cluster. The derived shear modulus G also increased with n. An extrapolation of the present results suggests that a cluster of 4–5 chains would give the stress enhancement factor of 10–20 observed for real ER fluids.

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Investigation of Thermal Conductivity of Alumina/Silicone Oil Electrorheological Fluids

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.129-131.421 ◽

2010 ◽

Vol 129-131 ◽

pp. 421-425 ◽

Cited By ~ 1

Author(s):

Yi Chun Wang ◽

Xiao Xia Sun ◽

Xiao Rong Tang ◽

Fa Cheng Wang

Keyword(s):

Thermal Conductivity ◽

Field Strength ◽

Electric Field ◽

Electric Field Strength ◽

Silicone Oil ◽

Conductivity Measurement ◽

Electrorheological Fluids ◽

High Voltage Power Supply ◽

Heating Device ◽

Er Fluids

Electrorheological (ER) fluids are new materials with good properties such as dielectric constant, dielectric loss or conductivity, which display remarkable rheological behavior, being able to convert rapidly and repeatedly from a liquid to solid when an electric field is applied or removed. In this study, suspensions of alumina (A) were prepared in silicone oil (SO). The effects of electric field strength and temperature of the suspensions on thermal conductivity were determined. Thermal conductivity measurement in different conditions was carried out via experimental instrument with high-voltage power supply and water heating device to investigate the effects of electric field strength and temperature on ER performance and thermal conductivity. The results show that the thermal conductivity is in accordance with ER properties enhanced by increasing the field strength and decreasing the temperature.

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Characteristic Times of Microsturcture Formation in Electrorheological Fluids, Determined by Viscosity and Speckle Activity Measurements

Applied Rheology ◽

10.1515/arh-2005-0003 ◽

2005 ◽

Vol 15 (1) ◽

pp. 38-45 ◽

Cited By ~ 2

Author(s):

Elvio Alanis ◽

Graciela Romero ◽

Carlos Martinez ◽

Liliana Alvarez ◽

Magdalena Mechetti

Keyword(s):

Electric Field ◽

Structure Formation ◽

Apparent Viscosity ◽

Light Transmission ◽

Silicone Oil ◽

Speckle Pattern ◽

Electrorheological Fluids ◽

Microstructure Formation ◽

Electrical Field ◽

Activity Measurements

AbstractViscosity measurements of a suspension of cornstarch in silicone oil, at several concentrations and subject to different electrical field strengths, were conducted. An increase in the apparent viscosity, in correlation with the field strength, which is characteristic of the so-called electrorheological fluids (ERF), was observed. For a given field intensity, the value of the viscosity increases rapidly in the first seconds after the application of the electric field, and then it increases slowly until it finally approaches a saturation value. This behaviour of the apparent viscosity has been related to the microstructure formation due to interactions between dipoles induced by the electric field. Characteristic times, related to structure formation after application of an electric field, are investigated by means of diffuse light transmission and speckle-pattern activity measurements. Two characteristic times were found that should be related to the state of aggregation of the suspended particles: orientation of the non-isotropic particles and later chain formation. These results agree reasonably with that obtained from electrorheological measurements. Microscopic observations of structure formation are also reported.

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TERNARY ELECTRORHEOLOGICAL FLUIDS WITH COMPOSITE PARTICLES DISPERSED IN LIQUID BLENDS

International Journal of Modern Physics B ◽

10.1142/s0217979206040738 ◽

2006 ◽

Vol 20 (25n27) ◽

pp. 3987-3992 ◽

Cited By ~ 1

Author(s):

KEIJI MINAGAWA ◽

YASUNORI AOKI ◽

TAKESHI MORI ◽

MASAMI TANAKA

Keyword(s):

Electric Field ◽

Composite Particle ◽

Silicone Oil ◽

Ternary Mixtures ◽

Electrorheological Fluids ◽

Ternary Blend ◽

Diphenylmethane Diisocyanate ◽

Binary And Ternary Mixtures ◽

Poly Propylene ◽

Binary Suspension

The electrorheological (ER) properties were studied with ternary suspensions containing solid and liquid dispersoids in silicone oil (DMS). The solid dispersoid used was polyether/montmorillonite nanocomposite particles in which polyether molecules were intercalated between the layers of montmorillonite. The liquid dispersoid was urethane-modified polyether prepared from 4,4′-diphenylmethane diisocyanate (MDI) and poly(propylene glycol) (PPG). The steady shear viscosity and dynamic viscoelasticity were measured with a rotating parallel disc rheometer equipped with ER measurement system. The binary and ternary mixtures of these solid and liquid dispersoids with DMS, i.e. composite particle/DMS suspension, polyether/DMS liquid blend, and ternary blend containing both dispersoids, showed an increase of viscosity in response to an electric field (positive ER effect). The ER effect of a ternary suspension containing the particles and polyether liquids was larger than those of binary suspension or blend with one of these dispersoids. The ER effect was found to be improved by combination of the solid and liquid dispersoids, although the recovery time of viscosity after removing the electric field became rather longer, which would be due to the partly irreversible macroscopic aggregation of the dispersoids.

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Effects of conductivity in electric-field-induced aggregation in electrorheological fluids

Physical Review E ◽

10.1103/physreve.52.1669 ◽

1995 ◽

Vol 52 (2) ◽

pp. 1669-1693 ◽

Cited By ~ 60

Author(s):

Boris Khusid ◽

Andreas Acrivos

Keyword(s):

Electric Field ◽

Electrorheological Fluids ◽

Induced Aggregation

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Effect of external magnetic field on lane formation in driven pair-ion plasmas

Journal of Plasma Physics ◽

10.1017/s0022377821000027 ◽

2021 ◽

Vol 87 (2) ◽

Author(s):

Swati Baruah ◽

U. Sarma ◽

R. Ganesh

Keyword(s):

Magnetic Field ◽

External Magnetic Field ◽

Field Strength ◽

Electric Field ◽

Electric Field Strength ◽

Coupling Parameter ◽

Critical Parameters ◽

Coulomb Coupling ◽

Lane Formation ◽

Parameter Values

Lane formation dynamics in externally driven pair-ion plasma (PIP) particles is studied in the presence of external magnetic field using Langevin dynamics (LD) simulation. The phase diagram obtained distinguishing the no-lane and lane states is systematically determined from a study of various Coulomb coupling parameter values. A peculiar lane formation-disintegration parameter space is identified; lane formation area extended to a wide range of Coulomb coupling parameter values is observed before disappearing to a mixed phase. The different phases are identified by calculating the order parameter. This and the critical parameters are calculated directly from LD simulation. The critical electric field strength value above which the lanes are formed distinctly is obtained, and it is observed that in the presence of the external magnetic field, the PIP system requires a higher value of the electric field strength to enter into the lane formation state than that in the absence of the magnetic field. We further find out the critical value of electric field frequency beyond which the system exhibits a transition back to the disordered state and this critical frequency is found as an increasing function of the electric field strength in the presence of an external magnetic field. The movement of the lanes is also observed in a direction perpendicular to that of the applied electric and magnetic field directions, which reveals the existence of the electric field drift in the system under study. We also use an oblique force field as the external driving force, both in the presence and absence of the external magnetic field. The application of this oblique force changes the orientation of the lane structures for different applied oblique angle values.

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