Dc Electric Field Research Articles

Simple microfluidic device for simultaneous extraction and detection of microplastics in water using DC electrical signal

DC electric field between two microwires in a straight microchannel was employed to electrophoretically accumulate and detect microplastics in water.

An Analysis of DC Electric Field Generated by Electric Railway Considering Constructions

An Analysis of DC Electric Field Generated by Electric Railway Considering Constructions

Effect of Combined Dc Electric Field and Pulsed Magnetic Field on the Transient Melt Pool in Laser Additive Manufacturing Process

Effect of Combined Dc Electric Field and Pulsed Magnetic Field on the Transient Melt Pool in Laser Additive Manufacturing Process

On the absence of collective motion in a bulk suspension of spontaneously rotating dielectric particles.

A suspension of dielectric particles rotating spontaneously when subjected to a DC electric field in two dimensions next to a no-slip electrode has proven to be an ideal model for active matter [Bricard et al., Nature, 2013, 503, 95-98]. In this system, an electrohydrodynamic (EHD) instability called Quincke rotation was exploited to create self-propelling particles which aligned with each other due to EHD interactions, giving rise to collective motion on large length scales. It is natural to question whether a suspension of such particles in three dimensions will also display collective motion and spontaneously flow like bacterial suspensions do. Using molecular dynamics type simulations, we show that dielectrophoretic forces responsible for chaining in the direction of the applied electric field in conventional electrorheological fluids and the counter-rotation of neighboring particles in these chains prevent collective motion in suspensions undergoing spontaneous particle rotations. Our simulations discover that the fundamental microstructural unit of a suspension under Quincke rotation is a pair of counter-rotating spheres aligned in the direction of the electric field. We perform a linear stability analysis that explains this observation.

Electric field regulation of polypropylene insulation for high voltage DC cables

High voltage cable is the key factor to determine the quality and capacity of power transmission. Polypropylene has widely attracted more attention because of its excellent heat resistance, insulation and green environmental protection, and it is used as cable material. Polypropylene insulation material for high voltage cable needs to bear pulsed voltage and the DC rated voltage, which can easily cause electric field to be distorted and lead the space charge to be accumulated. Meanwhile, the change of cable temperature will also affect the conductivity of insulating material and promote the accumulation of space charge, resulting in the distortion of internal electric field of insulating material and the initiation and growth of electric tree. Therefore, it is necessary to regulate the electric field of high voltage cable so as to suppress the deterioration phenomena such as electric field distortion, partial discharge and electrical demoralization. In this work, the theory and method of regulating DC electric field of polypropylene insulation of high voltage cable is first introduced. Then the main direction of electric field regulation is presented. Finally, the application prospect of polypropylene cable insulation is also put forward.

Influence of surface viscosities on the electrodeformation of a prolate viscous drop.

Contaminants and other agents are often present at the interface between two fluids, giving rise to rheological properties such as surface shear and dilatational viscosities. The dynamics of viscous drops with interfacial viscosities has attracted greater interest in recent years, due to the influence of surface rheology on deformation and the surrounding flows. We investigate the effects of shear and dilatational viscosities on the electro-deformation of a viscous drop using the Taylor-Melcher leaky dielectric model. We use a large deformation analysis to derive an ordinary differential equation for the drop shape. Our model elucidates the contributions of each force to the overall deformation of the drop and reveals a rich range of dynamic behaviors that show the effects of surface viscosities and their dependence on rheological and electrical properties of the system. We also examine the physical mechanisms underlying the observed behaviors by analyzing the surface dilatation and surface deformation.

Polarization characteristics of polymer dispersed liquid crystal films and their effects on electro-optical properties

The electro-optical properties of polymer dispersed liquid crystal film vary with liquid crystal content and externally applied electric field, but the analysis of the film morphology cannot directly reflect the mechanism of electro-optical properties. Therefore, the polymer dispersed liquid crystal film prepared by blending liquid crystal material E7 and photopolymer NOA65 is used. Herein, the dielectric polarization regulated electro-optical properties and their related mechanisms under different liquid crystal content and electric fields are revealed. The results show that in a frequency range of 10<sup>–1</sup>–10<sup>6</sup> Hz, the film exhibits three relaxation processes respectively at low frequency, medium frequency and high frequency, which are generated by thermionic polarization, interfacial polarization and orientation polarization. According to the Arrhenius equation, the activation energy values of such polarization processes are calculated. It is found that with the increase of liquid crystal content, the activation energy of orientation polarization decreases from 0.88 eV to 0.83 eV, leading the threshold field strength and the saturation field strength of the diversion of liquid crystal molecule to decrease. Thermionic polarization under DC electric field forms an internal electric field, which causes the threshold field strength and saturation field strength to increase greatly, as compared with the scenarios under AC electric field. Such a thermionic polarization also leads the polarization relaxation time to increase, resulting in the extension of response time. This study is of guiding significance in further analyzing and improving the electro-optical properties of polymer dispersed liquid crystal films.

Atomization and combustion characteristics of a biodiesel–ethanol fuel droplet in a uniform DC electric field

Electric field has the potential to influence the combustion characteristics of hydrocarbon fuel. In this paper, the atomization and combustion characteristics of the droplets of biodiesel and biodiesel–ethanol blend in a uniform direct-current electric field were investigated using photography. It was revealed that a certain electric field strength could induce droplet deformations and cone jets. For the droplet blended with 10 vol. % ethanol, the sizes of the secondary droplets from bubble breakups decreased with the increase in electric field strength, possibly due to the Coulomb repulsion in the ligament. The high breakup intensity of the droplet blended with 30 vol. % and 50 vol. % ethanol covered up the effect of electric field on the sizes of secondary droplets from bubble breakups. During the entire range of electric field strength, cone jets generated smaller secondary droplets in comparison with bubble breakups. Moreover, the electric field distorted the flame morphology, especially the flame width increased at the electric field strength of 50 kV/m. The maximum droplet temperature decreased with the electric field strength, in addition to the biodiesel droplet. Overall, the electric field ameliorates fuel droplets' atomization and combustion characteristics.

500kV급 HVDC 폴리머 애자의 전계 완화에 관한 연구

An HVDC(high voltage direct current) is economical owing to its excellent power transmission efficiency and a low insulation class compared with HVAC(high voltage alternative current). In addition, HVDC is known as a high efficiency green technology because power systems with different frequencies can be connected asynchronously. Therefore, research on the HVDC is being actively conducted. In order to develop HVDC transmission lines, it is necessary to secure insulation design technology for DC insulators. DC has different properties from AC due to the presence of space charge and the temperature dependence of conductivity. However, until now, there is no standard for the insulation design of DC insulators. In this study, the difference in insulation design was verified through AC electric field and DC electric field analysis, and a corona ring design was derived to improve the electrical stability of the 500kV DC insulator.

Influence of positive DC electric field on rime icing on the insulator and its experimental verification in the natural environment

AbstractThe electric field imposes a significant effect on ice accretion on the insulator. The impact of an AC electric field on insulator icing in an artificial climate chamber has been addressed. Compared with AC, DC electric field exerts an attraction on supercooled water droplets, which is more detrimental to the power system. Moreover, the icing on energised insulators is rarely studied in the natural environment. In the present research, an electrical, fluid coupled‐field simulation was carried out on the insulator. The force characteristics and motion deviation features of water droplets at different positive DC electric field strengths were studied. On this basis, rime icing on the insulator energised with different positive DC voltages was investigated in the field. Results show that the charged droplet shifts along the electric field line under a positive DC voltage. The deviation degree of the droplet increases with the increment of the voltage and droplet size and decreases with an increase in wind speed. As the voltage rises, the surface roughness, icing amount and icing length of rime ice‐covered insulator increase. Consequently, compared with that without energisation, the local collision coefficient, icing amount and icing length increase by 17.6%, 46.4% and 63.9%, respectively, under a 40 kV DC voltage.

Incidence of Electric Field and Sulfuric Acid Concentration in Electrokinetic Remediation of Cobalt, Copper, and Nickel in Fresh Copper Mine Tailings

In the present study, the assessment of heavy metal contaminant migration from fresh mine tailings was conducted using the electrokinetic remediation technique (EKR). In this sense, a pilot EKR cell was designed to evaluate the recovery potential of copper, nickel, and cobalt species. In particular, the focus was on the impacts of electric field intensity and pH in initial mixture and testing their interaction in copper, nickel, and cobalt migration. Experiments were made using a 22 factorial experimental design with a central point, using DC electric fields from 1.0 to 2.0 V cm−1 and H2SO4 pretreatment solutions from 1.0 to 2.0 mol L−1, along with an ANOVA test with error reduction. The metal removal rates were approximately 7% for cobalt, neglectable for copper, and 6% for nickel. In the best cases, the highest concentrations by migration at the cathodic zone were 11%, 31%, and 30%, respectively. According to ANOVA tests, factor interaction was proven for each metal in the half cell near the cathode and the closest zone from the cathode specifically. Both factors affected metal concentrations, which indicates that when the goal aims for species accumulation in a narrower section, each factor has a significant effect, and their interaction makes a proven enhancement. Thus, using 2.0 V cm−1 and 2.0 mol L−1 showed a high improvement in metal concentration in the cathodic zone.

Electric field gradient focusing with electro-osmotic flow to reduce analyte dispersion: Concept and numerical investigation

In proteomics, the need to precisely examine the protein compounds of small samples, requires sensitive analytical methods which can separate and enrich compounds with high precision. Current techniques require a minimal analysis time to obtain satisfactory compound separation where longer analysis time means better separation of compounds. But, molecular diffusion will create broadening of the separated compound bands over time, increasing the peak width, and thus reducing the resolution and the enrichment.Electric field gradient focusing (EFGF) is a separation technique, in which proteins are simultaneously separated and enriched by balancing a gradient electrostatic force with a constant hydrodynamic drag force. Because of this balance, analytes are continuously pushed back to their focusing point, limiting the time-dependent peak broadening due to molecular diffusion. Current EFGF techniques are however still suffering from peak broadening because of flow-profile inhomogeneities.In this paper, we propose to use AC electro-osmotic flow (AC EOF) to create a homogeneous flow in EFGF. The interference between the electric field gradient and the AC EOF was thoroughly analysed and the concept was validated using numerical simulations. The results show that a plug flow is obtained on top of a small, distorted boundary layer. While applying different DC electric fields in the electrolyte, a constant flow velocity can be obtained by including a DC offset to the electrodes generating the AC EOF. The plug flow is then maintained over the whole separation channel length, while an electric field gradient is applied. This way, the flow-induced contribution to peak broadening can be minimized in EFGF devices. By modelling the separation of green fluorescent protein (GFP) and R-Phycoerythrin (R-PE), it was shown that the peak width of separated compounds can be reduced and that the separation resolution can be improved, compared to current EFGF methods.

Planar acoustomagnetoelectric effect in three-dimensional Dirac materials

Using the Boltzmann equation techniques, we develop a theory of the planar acoustomagnetoelectric (AME) effect in three-dimensional (3D) gapless Dirac materials with a linear (massless) dispersion law of conduction electrons. The effect arises if the magnetic field H applied to the sample makes an angle Φ≠0, π/2 with the wavevector q of the acoustic wave and consists in the appearance of a dc electric field Eac directed perpendicular to the wavevector q, with all three vectors q, H, and Eac lying in the same plane. We study this effect in the quantum regime (the electron mean free path l0 is large compared to the wavelength 2π/q), where it occurs as a result of the momentum transfer from an excited acoustic wave, considered a flow of individual acoustic quanta, to conduction electrons subjected to the magnetic field. Our theory predicts that for the 3D Dirac material Cd3As2 exposed to a strong, but non-quantizing magnetic field H=10 kOe and an acoustic wave with a frequency of 10 GHz and an intensity of 2 kW/cm2, the AME field Eac with its specific angular dependence (Eac∝sin⁡2Φ) can reach values of the order of 0.01 V/cm at room temperature, which can be readily measured in the experiment.

Improved Wide-Temperature-Range Insulation Properties of Block Polypropylene by UV-Irradiated Cografting of Maleic Anhydride and 4-tert-Butylstyrene

Polypropylene (PP), as a recyclable thermoplastic polymer, is a promising insulating material for application as an environmentally friendly insulation layer in high-voltage-direct-current (HVDC) cables. However, the lack of toughness and the poor wide-temperature-range electrical properties under a DC electric field seriously restrict its development and application. Herein, a block polypropylene with a low elastic modulus is selected and grafted with organic molecules of maleic anhydride (MAH) and 4-tert-butylstyrene (St*) as a masterbatch (PP-g-(St*-co-MAH)) by an ultraviolet-irradiated radical reaction. The modified b-PP with different grafting contents was prepared by diluting the masterbatch through melt blending, and their DC electrical properties at a wide temperature range of 40–100 °C were tested. The results indicate that the introduction of a comonomer St* significantly improves the grafting rate of MAH and suppresses the degradation of PP chains during the grafting reaction; thus, the PP-g-(St*-co-MAH) possesses improved thermogravimetric performance and maintains the original mechanical properties and workability. The grafted functional groups introduce deep charge traps into the matrix and thus effectively suppress the space charge injection and accumulation, significantly reduce the conductivity, and enhance the breakdown strength of PP at wide temperature ranges. Among the tested materials, the PP grafted with 0.57 wt % St*-co-MAH exhibits the best electrical properties, while inadequate or excessive grafting content of St*-co-MAH relatively weakens the positive effects of grafting modification. The mechanism is analyzed based on calculation of the trap level and the three-dimensional (3D) electric potential.

The effect of electrically pre-stressing of high DC electric field on performance of SDBD thruster in near space

The space charge on the surface of solid dielectric has great influence on the surface dielectric barrier discharge (SDBD). In this paper, the surface space charge of SDBD is effectively regulated by the effect of electrically pre-stressing of high DC electric field to improve the dynamic performance of ion wind thruster. The conduction current, surface charges, thrust and thrust-to-power ratio are measured respectively for the ion wind thruster with and without the effect of electrically pre-stressing. The experimental results show that compared with the ion wind thruster without the effect of electrically pre-stressing, the instantaneous polarization current of the SDBD ion wind thruster with the effect of electrically pre-stressing is reduced by 42.7%, and the attenuation constant of the relaxation polarization current is reduced by about 28.8%, which effectively reduces the relaxation polarization loss of the thruster under the alternating electric field. In addition, the discharge time of anode and cathode increases respectively by about 20.0% and 43.3%, and the variation of surface space charge increases by about 50.6% in one voltage cycle. The saturation thrust of the thruster is increased from 1070 μN/m to 1660 μN/m by about 55.1%. The maximum thrust-to-power ratio of the thruster is increased from 993 μN/kW to 2125 μN/kW by about 114.0%.

Structural Integrity Assessment of Aligned and Non-aligned Single Walled Carbon Nanotubes in Epoxy Resin

Carbon nanotubes have gained popularity due its unique electrical and thermal properties and high strength, widely finding it application in medical and electrical field. In the presented study the single walled carbon nanotubes (SWCNT) are assumed to be aligned using a DC electric field, taking into account transportation phenomena like the rotation of tube and its polarization to form chain like structure. Authors have examined and compared the structural properties under tensile loading of aligned and non-aligned single walled carbon nanotubes SWCNT in epoxy matrix using finite element analysis. COMSOL Multiphysics has been used to model the specimens and investigate its properties. The result lays out trends and relation between various parameters and the strength of the epoxy based SWCNT composite. The study draws out result on how changes in parameters of epoxy based SWCNT composite changes its physical properties.

Oscillatory Motion of Water Droplets Both in Oil and on Superhydrophobic Surface under Corona Discharge.

Charged droplets driven by Coulomb force are an important part of a droplet-based micro reactor. In this study, we realized the rapid oscillatory motion of droplets both in oil and on superhydrophobic surface by injecting charges through corona discharge. Distinct from the oscillatory motion of water droplets under a DC electric field, charge injection can make the motion of water droplets more flexible. A droplet in the oil layer can move up and down regularly under the action of corona discharge, and the discharge voltage can control the movement period and height of the droplet. In addition, the left-right translation of droplets on a superhydrophobic surface can be achieved by injecting charges into the hydrophobic film surface through corona discharge. Two kinds of droplet motion behaviors are systematically analyzed, and the mechanism of droplet motion is explained. The present results could help establish new approaches to designing efficient machines in microfluidics and micromechanical equipment.

Interaction of spatial-Gaussian lasers with the magnetized CNTs in the presence of DC electric field and enhanced THz emission

The interaction of spatial-Gaussian lasers with magnetized carbon nanotubes (CNTs) in the presence of a DC electric field is shown to broaden the surface plasmon resonance effectively. The prime feature of the interaction of lasers with magnetized CNTs is that when the electron cylinder of CNT is shifted with respect to the ion cylinder, the space charge electric field is developed in the overlapped region and results in the restoration force of the electrons. The restoration force along with the ponderomotive and magnetic forces assist to increase the nonlinear current which is further enhanced by the drift velocity acquired by the electrons of CNTs due to the applied static electric field. This action is also responsible for the enhanced THz yield at surface plasmon resonance condition where is the polarization coefficient, is the relative permittivity of the dielectric substrate, is the cyclotron frequency of CNT electrons and is the plasma frequency. The study reveals that THz generation from the magnetized CNTs may be a promising source for the detection of dangerous chemicals like royal demolition explosive (RDX), pentaerythritol tetra-nitrate (PETN), trinitrotoluene (TNT), etc.

The evolution characteristics of surface charge on the gas–solid interface under the long-time co-action of DC-temperature gradient

The charge accumulation phenomenon at the gas–solid interface under the co-action of DC electric field and temperature gradient is of great significance, but its long-time evolution characteristics are still unclear. In this work, the accumulation and dissipation characteristics of the surface charge on the epoxy-SF6 interface within 216 h were obtained, indicating that, (a) the normal surface electric field is increased by the temperature gradient along the gas–solid interface, which results in a prominent increase in the surface charge density; (b) there are different evolution processes of surface charge in high and low temperature regions under the co-action of DC-temperature gradient, and the increase of the charge trap density caused by the degradation of solid material is considered to be an important reason for the charge evolution; (c) the total charge dissipation ratio within 600 s decreases with the increase of charging time in DC electric field, and the surface charge dissipates mainly to the gas side of the interface; (d) the large amount of charge accumulated at the interface distorts the surface electric field at the triple junction points. The total electric field strength at the low-temperature tri-junction point increases by 35.5%, while the direction of the tangential field at the high-temperature tri-junction point reverses during the long-time co-action of the DC-temperature gradient. The results of this work may be helpful to understand the long-time charge evolution characteristics of the gas–solid interface under the DC-temperature gradient and to reveal the failure mechanism of the gas–solid interface.

Simultaneous enhancement of the electrocaloric effect and electrostrain via exploiting the reversible polarization rotation

Self-actuating ferroelectric cooling technology have drawn increasing attention for its extensive application prospect, where simultaneous enhancement of electrocaloric effects (ECE) and electrostrain (ES) in ferroelectric materials is necessary prerequisites for the efficient operation of the cooling system. In this work, we proposed a self-actuating dual cooling cycle system combining the positive and negative ECE/ES effect, and further confirmed its feasibility in 0.7 Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-30PT) single crystal via bipolar electric field regulation. A suitable reverse electric field can generate negative ECE and ES simultaneously due to the reversible polarization rotation, whereas a high reverse electric field will lead to a serious perform loss as a result of emergent irreversible polarization jumping. The optimal reverse electric field (-Eop) can enhance the total ECE and ES by 31% and 17% respectively, whose effective combination can significantly improve the cooling capacity of the self-actuating cooling system. Moreover, compared to traditional P-E and/or I-E measurements, we proposed a more applicable and precise method to determine the -Eop under square-wave DC electric field, i.e. capacitance-voltage measurement. Our work not only provides new ideas for improving the ECE and ES of the ferroelectric materials, but also promotes the design of ferroelectric cooling systems.