Modeling and Simulation of Microscale Bipolar Particle Dynamics in an Applied Electric Field

2013 ◽  
Author(s):  
Mohammad Robiul Hossan ◽  
Robert Dillon ◽  
Prashanta Dutta
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Applied Electric Field ◽  
Numerical Study ◽  
Particle Dynamics ◽  
Opposite Polarity ◽  
Surface Charges ◽  
Ellipsoidal Particles ◽  
Polar Moment ◽  
String Formation

The colloidal dynamics of bipolar microparticles is of growing theoretical interest in understanding and advancement of electrorheology and ferroelectric research. In this paper we present an interface resolved numerical study to analyze dynamics of ellipsoidal bipolar microparticles for various initial configurations. The bipolarity is imposed by providing surface charges of opposite polarity at the two ends of ellipsoidal particles. The numerical simulations show that in the absence of an external electric field, ellipsoidal particles form a head-to-tail chain or stay apart from each other depending on the inter-particle distance, as well as the magnitude and direction of the inherent polar moment. On the other hand, in presence of an external electric field, the assembly or clustering mechanism primarily depends on the magnitude and direction of the applied electric field. Simulation results also show that the electrorotation process is a function of initial configuration. This comprehensive numerical study will help to better understand the mechanisms of clustering, string formation, and the disaggregation of bipolar microparticles.

Activation of CO2 on Copper Surfaces: The Synergy Between Electric Field, Surface Morphology and Excess Electrons

2020 ◽  
Author(s):  
Amin Jafarzadeh ◽  
Kristof M. Bal ◽  
Annemie Bogaerts ◽  
Erik C. Neyts
Keyword(s):  
Surface Morphology ◽  
Electric Field ◽  
Surface Charge ◽  
External Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Marginal Effect ◽  
Electric Field Effect ◽  
Surface Charges ◽  
Copper Surfaces

<p>In this work we use DFT calculations to study the combined effect of external electric fields, surface morphology and surface charge on CO<sub>2</sub> activation over Cu (111), Cu (211), Cu (110) and Cu (001) surfaces. We observe that the binding energy of the CO<sub>2</sub> molecule on Cu surfaces rises significantly upon increasing the applied electric field strength. In addition, rougher surfaces respond more effectively to the presence of the external electric field towards facilitating the formation of a carbonate-like CO<sub>2</sub> structure and the transformation of the most stable adsorption mode from physisorption to chemisorption. The presence of surface charges further strengthens the electric field effect and consequently gives rise to an improved bending of the CO<sub>2</sub> molecule and C-O bond length elongation. On the other hand, a net charge in the absence of externally applied electric field shows only a marginal effect on CO<sub>2</sub> binding. The chemisorbed CO<sub>2</sub> is more stable and further activated when the effects of an external electric field, rough surface and surface charge are combined. These results can help to elucidate the underlying factors that control CO<sub>2</sub> activation in heterogeneous and plasma catalysis, as well as in electrochemical processes.</p>

Activation of CO2 on Copper Surfaces: The Synergy Between Electric Field, Surface Morphology and Excess Electrons

2020 ◽  
Author(s):  
Amin Jafarzadeh ◽  
Kristof M. Bal ◽  
Annemie Bogaerts ◽  
Erik C. Neyts
Keyword(s):  
Surface Morphology ◽  
Electric Field ◽  
Surface Charge ◽  
External Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Marginal Effect ◽  
Electric Field Effect ◽  
Surface Charges ◽  
Copper Surfaces

<p>In this work we use DFT calculations to study the combined effect of external electric fields, surface morphology and surface charge on CO<sub>2</sub> activation over Cu (111), Cu (211), Cu (110) and Cu (001) surfaces. We observe that the binding energy of the CO<sub>2</sub> molecule on Cu surfaces rises significantly upon increasing the applied electric field strength. In addition, rougher surfaces respond more effectively to the presence of the external electric field towards facilitating the formation of a carbonate-like CO<sub>2</sub> structure and the transformation of the most stable adsorption mode from physisorption to chemisorption. The presence of surface charges further strengthens the electric field effect and consequently gives rise to an improved bending of the CO<sub>2</sub> molecule and C-O bond length elongation. On the other hand, a net charge in the absence of externally applied electric field shows only a marginal effect on CO<sub>2</sub> binding. The chemisorbed CO<sub>2</sub> is more stable and further activated when the effects of an external electric field, rough surface and surface charge are combined. These results can help to elucidate the underlying factors that control CO<sub>2</sub> activation in heterogeneous and plasma catalysis, as well as in electrochemical processes.</p>

Electric-Field Induced Formation of Superconducting Granular Balls

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2529-2535
Author(s):  
R. Tao ◽  
X. Xu ◽  
Y. C. Lan
Keyword(s):  
Surface Energy ◽  
Electric Field ◽  
Liquid Nitrogen ◽  
Applied Electric Field ◽  
Strong Electric Field ◽  
Particle Surface ◽  
Cooper Pairs ◽  
Surface Charges

When a strong electric field is applied to a suspension of micron-sized high T c superconducting particles in liquid nitrogen, the particles quickly aggregate together to form millimeter-size balls. The balls are sturdy, surviving constant heavy collisions with the electrodes, while they hold over 106 particles each. The phenomenon is a result of interaction between Cooper pairs and the strong electric field. The strong electric field induces surface charges on the particle surface. When the applied electric field is strong enough, Cooper pairs near the surface are depleted, leading to a positive surface energy. The minimization of this surface energy leads to the aggregation of particles to form balls.

Electrohydrodynamic Kelvin-Helmholtz Instability of Two Rotating Dielectric Fluids

1998 ◽  
Vol 53 (1-2) ◽  
pp. 17-26
Author(s):  
Mohamed Fahmy El-Sayed
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Rotation Frequency ◽  
Short Wave ◽  
Surface Charges ◽  
Rotation Surface ◽  
Dielectric Fluids ◽  
Fluid Velocities ◽  
Conditions Of Stability

Abstract A linear stability analysis of a novel electrohydrodynamic Kelvin-Helmholtz system consisting of the superposition of two uniformly rotating dielectric media is presented. The characteristic equation for such an arrangement is derived, which in turn yields a stability criterion for velocity differences of disturbances at a given rotation frequency. The conditions of stability for long and short wave perturbations are obtained, and their dependence on rotation, surface tension and applied electric field is discussed. Limiting cases for vanishing fluid velocities, rotation frequency, and applied electric field are also discussed. Under suitable limits, results of previous works are recovered. A detailed analysis for tangential and normal applied electric fields, in the presence and absence of surface charges, is carried out.

RAPIDLY ROTATING BOSE–EINSTEIN CONDENSATES IN AN APPLIED ELECTRIC FIELD

2008 ◽  
Vol 22 (17) ◽  
pp. 2691-2699
Author(s):  
LI-HUA LU ◽  
YOU-QUAN LI
Keyword(s):  
Electric Field ◽  
Density Distribution ◽  
External Electric Field ◽  
Applied Electric Field ◽  
Vortex Lattice ◽  
Particle Density ◽  
Einstein Condensate ◽  
Bose Einstein Condensate ◽  
Particle Density Distribution ◽  
Bose Einstein

The rapidly rotating Bose–Einstein condensate in the presence of an external electric field is studied. The vortex lattice formed in the condensate will shift after the electric field is applied. The electric field changes the particle density distribution and makes the system more stable. A method to detect this shift is also suggested.

Structures and Properties of Carbon Nanotubes/Thermosets Nanocomposites Subjected to External Electric Field during Cure Stage

2013 ◽  
Vol 743-744 ◽  
pp. 126-137 ◽  
Author(s):  
Jian Ping Yang ◽  
Jing Kuan Duan ◽  
Chang Xiu Fan ◽  
Pei De Han ◽  
Shuang Xi Shao ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electric Field ◽  
External Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Polymer Networks ◽  
Interpenetrating Polymer Networks ◽  
Host Matrix ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

In this investigation, the multi-walled carbon nanotubes (MWCNTs) were dispersed in an interpenetrating polymer networks (IPNs) based on acrylate and cycloaliphatic epoxy resin (CER). The influences of the external electric field on the MWCNTs dispersion and the microstructure of host matrix were evaluated by means of optical microscopy, scanning electric microscopy (SEM) and atomic force microscopy (AFM), respectively. The microscopy measurements showed that the distribution of the MWCNTs depended strongly on the properties of the applied electric field. Applying AC electric field to the liquid MWCNTs/thermoset systems during curing stage could redistribute the MWCNTs, which arranged them in chain-like structures and oriented fibrous inclusions parallel to the applied electric field. However, the similar phenomenon was not observed in DC electric field. From the observations of AFM measurement, it was found that the utilization of the external electric field resulted in the nanostructured twophase structures in the resulting MWCNTs/thermoset nanocomposites. These novel electric-field-induced morphology transformations were mainly attributed to the curing process under the applied electric fields. The relationships between the microstructures and various physical properties of nanocomposites were also presented in this paper. The resulting nanocomposites displayed the interesting dielectric properties and the thermal stability properties, which significantly depended on their special microstructures of inclusions and the host matrix.

Two-Fluid Electroosmotic Flow in Microchannels

2008 ◽  
Author(s):  
T. N. Wong ◽  
Y. Gao ◽  
C. Wang ◽  
C. Yang ◽  
N. T. Nguyen ◽  
...  
Keyword(s):  
Electric Field ◽  
Applied Electric Field ◽  
Electroosmotic Flow ◽  
Viscosity Ratio ◽  
Experimental Investigations ◽  
Fluid Interface ◽  
Surface Charges ◽  
Interface Position ◽  
Proposed Model ◽  
Two Fluid

This paper presents theoretical and experimental investigations of the pressure-driven two-liquid flow in microchannels with the electroosmosis effect. For a fully developed, steady state, laminar flow of two liquids combined the pressure gradient, electroosmosis and surface charges at the liquid-liquid interface, we have derived analytical solutions that relate the velocity profiles and flow rates to the liquid holdup, the aspect ratio of the microchannel, the viscosity ratio of the two liquids and the externally applied electric field. It was shown that adjusting the externally applied electric field could control the fluid interface position precisely. The prediction from the proposed model compares very well with measured data.

Dielectrophoretic Interactions and Chaining of Ellipsoidal Particles in a Microchannel

2016 ◽  
Author(s):  
Mohammad Robiul Hossan ◽  
Partha P. Gopmandal ◽  
Prashanta Dutta ◽  
Robert Dillon
Keyword(s):  
Electric Field ◽  
Stress Tensor ◽  
Applied Electric Field ◽  
Immersed Boundary ◽  
Immersed Interface Method ◽  
Immersed Interface ◽  
Ellipsoidal Particles ◽  
Clockwise Direction ◽  
A Chain ◽  
Final Orientation

Recent experimental studies report that the understanding of dielectrophoretic (DEP) interactions and chaining of irregularly shaped particles, particularly ellipsoidal shaped particle, are critical for development of smart materials, engineered biological cellular structure and tissue formation. This paper presents a comprehensive numerical investigation of direct current (DC) dielectrophoretic (DEP) chaining and interactions of ellipsoidal particles in a microchannel. A hybrid immersed boundary-immersed interface method is employed to explain the fundamental mechanism of DEP interactions and chaining of ellipsoidal particles. Electric field equations are solved by the immersed interface method while the immersed boundary method is employed to solve fluid equations. The DEP force was estimated by using Maxwell’s stress tensor (MST) and the Cauchy stress tensor (CST) was employed to evaluate hydrodynamic force. The results show that the electrical properties of fluid and particles are the main deciding factor on the final orientation of ellipsoidal particles. However the size, shapes and initial positions and orientations have significant impact on interaction time spans. Results also show that if the interacting particles are electrically similar i.e. having same electrical conductivity then they always form a chain parallel to the applied electric field, otherwise they form a chain which is orthogonal to the applied electric field. In parallel chaining, particles rotate in a clockwise direction, while in orthogonal (to the applied electric field) chaining, particles rotate in counter-clockwise direction to reach to the final orientation. Results also indicate that the ellipsoidal particles go through an electro-orientation process if initially the major axis of the ellipsoidal particles is not in perfect alignment with the applied electric field. The electro-orientation and DEP interaction take place simultaneously to reach to final stable orientation. This study provides critical insight on the mechanism of DEP interactions and chaining of ellipsoidal shaped particles.

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