Simulation of charge transport and steady state in non-polar media between planar electrodes with insulating layers

Neyts, Kristiaan; Karvar, Masoumeh; Drobchak, Oksana; Brans, Toon; Strubbe, Filip; Beunis, Filip

doi:10.1016/j.colsurfa.2012.10.022

Cited by 9 publications

(22 citation statements)

References 9 publications

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“…When the voltage V 1 is not sufficiently high, the space-charge due to the generated charged inverse micelles can lead to a steady-state bulk field that is lower than E ≅ V 1 /d and spatially inhomogeneous. 30 As a result of E < V 1 /d, the concentration of generated charges in steady-state can be higher than expected from eq 10 and nonlinearly increasing. This case is illustrated in Figure 1d, where the curve for t = 0 corresponds to the steady-state distribution at voltage V 1 .…”

Section: Theorymentioning

confidence: 91%

“…n ̅ /ε 0 ε r kT, but in all cases where φ 1 ≫ 1 the initially present charged inverse micelles eventually get separated 27,28,30 corresponding to a total transported charge Q = zen ̅ dS. During this transient the concentration of newly generated inverse micelles gradually increases according to eq 3 until quasi steady-state is reached.…”

Section: Theorymentioning

confidence: 99%

“…Since the formation of a charged inverse micelle comes at a large free energy cost, we can restrict to the case that β ≪ α and therefore that n ̅ ≪ n ̅ 0 . 10 When a voltage difference is applied across the electrodes, the transient current I (t) can be modeled with 27,30 …”

Section: Theorymentioning

confidence: 99%

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Characterizing Generated Charged Inverse Micelles with Transient Current Measurements

2015

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ABSTRACT:We investigate the generation of charged inverse micelles in nonpolar surfactant solutions relevant for applications such as electronic ink displays and liquid toners. When a voltage is applied across a thin layer of a nonpolar surfactant solution between planar electrodes, the generation of charged inverse micelles leads to a generation current. From current measurements it appears that such charged inverse micelles generated in the presence of an electric field behave differently compared to those present in equilibrium in the absence of a field. To examine the origin of this difference, transient current measurements in which the applied voltage is suddenly increased are used to measure the mobility and the amount of generated charged inverse micelles. The mobility and the corresponding hydrodynamic size are found to be similar to those of charged inverse micelles present in equilibrium, which indicates that other properties determine their different behavior. The amplitude and shape of the transient currents measured as a function of the surfactant concentration confirm that the charged inverse micelles are generated by bulk disproportionation. A theoretical model based on bulk disproportionation with simulations and analytical approximations is developed to analyze the experimental transient currents.

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Section: Theorymentioning

confidence: 91%

Section: Theorymentioning

confidence: 99%

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Characterizing Generated Charged Inverse Micelles with Transient Current Measurements

2015

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“…The application of high DC voltage causes the generation and transport of charge inside the polyethylene-based insulation materials. This results in an inevitable accumulation of space charge inside the insulation material [5,6]. This space charge accumulation not only distorts the electric field distribution under DC stress, but also causes the deterioration of insulating materials in the long term.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Electric Field and Space Charge Dynamics in Dielectric under DC Voltage with Superimposed Switching Impulse

et al. 2019

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The influx of a switching impulse during DC steady-state operations causes severe electrical stress on the insulation of HVDC cables. Thus, the insulation should be designed to withstand a superimposed switching impulse. All major manufacturers of DC cables perform superimposed switching impulse breakdown tests for prequalification. However, an experimental approach to study space charge dynamics in dielectrics under a switching impulse superposed on DC voltage has not been reported yet. This is because, unlike the DC stress, it is not possible to study the charge dynamics experimentally under complex stresses, such as switching impulse superposition. Hence, in order to predict and investigate the breakdown characteristics, it is necessary to obtain accurate electric field distribution considering space charge dynamics using a numerical approach. Therefore, in this paper, a numerical study on the switching impulse superposition was carried out. The space charge dynamics and its distribution within the dielectric under DC stress were compared with those under a superimposed switching impulse using a bipolar charge transport (BCT) model. In addition, we estimated the effect of a superimposed switching impulse on a DC electric field distribution. It was concluded that the temperature conditions of dielectrics have a significant influence on electric field and space charge dynamics.

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“…Both findings saw stronger electrostatic screening of the electric field and a faster decay of transient current in their devices. In a later study, at high voltage, the approximated analytical solution still showed effective electrostatic screening by the high charge density [57]. Their simulation model is based on a previous 1-D numerical model that includes drift, diffusion, generation, recombination, and voltage drop of the electric double layers (EDL) within the planar electrode [58].…”

Section: Determination Of the Zeta Potential Of Porous Substrates By mentioning

confidence: 99%

Effect of nanodroplet ink concentration on image contrast for reverse-emulsion electrophoretic displays

Wang¹

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Reverse-emulsion electrophoretic display technology is based on an electro-responsive ink comprised of self-assembled nanodroplets dispersed in a non-polar liquid. The dye-containing nanodroplets are selectively driven toward or away from the viewing plane of a display by electric fields. The hypothesis of this study is that image contrast in a nanodroplet electrophoretic display is governed by concentration and steric effects that limit the intensity of the dark state. Simultaneously, steric effects as well as electrostatic screening can diminish whiteness in the light state. This hypothesis has been tested by multiphysics simulation of dilute species in electrostatic fields and experimental measurements of relative luminance in test displays. Concentration level was varied in a range of dilutions from full concentration (100%) to one-eighth (12.5%) and the highest contrast ratio was achieved at 25%. The test devices exhibited behavior that was similar to the saturation effects predicted by simulation, accounting for steric effects. Ink concentration showed little effect on switching time, reaching steady-state within approximately 2 seconds for all concentration levels. The hypothesis was further tested by experimentally observing the effect of driving voltage between 1 V to 8 V. The results showed no significant improvement of contrast even at higher voltage, further suggesting that concentration and steric effects dictate maximum contrast. me the opportunity to conduct research within his group but also taught me the meaning of professionalism. This thesis would not be possible without his encouragement and direction. I would also like to thank Dr. Bryning for his friendly nature, immense knowledge, and valuable discussions. He was the Ironman that provided me with the tools to make data acquisition possible. Our constant laughter was what kept my dreams and spirits high. Next, I would like to thank Dr. Maryam Mobed-Miremadi. She is one of the kindest professors. She constantly provided new ideas, guidance, and encouragement to pursue a higher education degree. To my loving friends, it has been a great journey. I enjoyed our laughter, joy, and overnight projects with less than healthy food. A very special thanks to Will Schulkins for his invaluable assistance with dynamic light scattering measurements. I offer my sincere appreciation to Remy Cromer for giving me the opportunity to work with his nanodroplet ink. Finally, I would like to dedicate this work to my parents, Danny and Viola. This thesis is tangible evidence of my appreciation for my friends and family. Thank you for never doubting my ability, for your constant support, and for your unconditional love. It has provided me strength and willpower to complete this challenge and has helped me become a better person. v

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Simulation of charge transport and steady state in non-polar media between planar electrodes with insulating layers

Cited by 9 publications

References 9 publications

Characterizing Generated Charged Inverse Micelles with Transient Current Measurements

Characterizing Generated Charged Inverse Micelles with Transient Current Measurements

Evaluation of Electric Field and Space Charge Dynamics in Dielectric under DC Voltage with Superimposed Switching Impulse

Effect of nanodroplet ink concentration on image contrast for reverse-emulsion electrophoretic displays

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