Applied DC Electric Field Research Articles

Preparation of CaWO4-based glass-ceramics with uniform crystal distribution and enhanced luminous property by thermoelectric coupling treatment

To address the issue of crystal aggregation in CaWO4-based glass-ceramics under high temperature or prolonged durations, while also aiming to enhance the luminescent properties, a thermoelectric coupling treatment is introduced during the preparation process of glass-ceramics. In this study, the influence of applying an external DC electric field on the nucleation and crystallization was examined. Techniques such as DSC, XRD, and SEM are utilized to investigate the crystal types and microstructure of the glass-ceramics. Furthermore, the luminescent performance under ultraviolet and X-ray is characterized, with PL, PLE, and XEL spectra being measured. The findings reveal that thermoelectric coupling treatment augments the crystallization content, refines crystal distribution, and enhances luminescent properties. The applied DC electric field provides energy for thermodynamic reactions, reduces activation energy for bond breaking, accelerates ion migration, and facilitates crystal nucleation precipitation. Crucially, it induces polarization of Ti and Zr ions within crystal nuclei, generating electrostatic repulsion between nuclei. These effects mitigate crystal aggregation, refine distribution, and amplify crystal count. This underscores the potential of thermoelectric coupling treatment in synthesizing optical materials utilizing glass-ceramics as luminescent base materials, offering insights for similar researches endeavors.

Self-Propulsion by Directed Explosive Emulsification.

An active droplet system, programmed to repeatedly move autonomously at a specific velocity in a well-defined direction, is demonstrated. Coulombic energy is stored in oversaturated interfacial assemblies of charged nanoparticle-surfactants by an applied DC electric field and can be released on demand. Spontaneous emulsification is suppressed by an increase in the stiffness of the oversaturated assemblies. Rapidly removing the field releases the stored energy in an explosive event that propels the droplet, where thousands of charged microdroplets are ballistically ejected from the surface of the parent droplet. The ejection is made directional by a symmetry breaking of the interfacial assembly, and the combined interaction force of the microdroplet plume on one side of the droplet propels the droplet distances tens of times its size, making the droplet active. The propulsion is autonomous, repeatable, and agnostic to the chemical composition of the nanoparticles. The symmetry-breaking in the nanoparticle assembly controls the microdroplet velocity and direction of propulsion. This mechanism of droplet propulsion will advance soft micro-robotics, establishes a new type of active matter, and introduces new vehicles for compartmentalized delivery.

CPA-induced Hz to THz broadband absorber with switchable perfect absorption between radio-microwave and THz frequency spectrum

The coherent perfect absorption (CPA) occurring in the graphene sheet suspended in air can be utilized to develop an ultrathin, ultra-broadband absorber working in the frequency range from a few hertz (Hz) to terahertz (THz) with perfect absorption. A graphene sheet is studied to induce the CPA to cover radio, microwave and lower THz frequency ranges. A graphene resonator able to provide the surface plasmon resonance (SPR) is combined with the graphene sheet to provide CPA at either side of a thin dielectric layer forms metamaterial structure with the cavity and enhances the absorption bandwidth in the THz region by creating a resonance near quasi-CPA frequency. A dielectric silicon resonator is embedded in the structure, which creates dipolar resonances between the resonances obtained by the formed cavity between the graphene sheet and resonator. This enhances the absorption level in the THz region. The absorption bandwidth is further enhanced to 7 THz by including a graphene disc at the top of the silicon resonator. Thus, the multiple multi-order resonances occurring in the silicon dielectric and SPR of graphene resonators are merged with the phenomena of CPA occurring in the graphene sheets to extend the CPA bandwidth in the THz regime. The doping level of graphene or its tunable Fermi energy based on the applied DC electric field provides the tunability in the total obtained absorption bandwidth. The symmetric structure provides polarization-insensitive behavior with an allowed incident angle of more than 45° with more than 90% absorption.

Electrohydrodynamics of diffuse porous colloids.

The present article deals with the electrohydrodynamic motion of diffuse porous particles governed by an applied DC electric field. The spatial distribution of monomers as well as the charge distribution across the particle are considered to follow sigmoidal distribution involving decay length. Such a parameter measures the degree of inhomogeneity of the monomer distribution across the particle. The diffuse porous particles resemble several colloidal entities which are often seen in the environment as well as in biological and pharmaceutical industries. Considering the impact of bulk pH and ion steric effects, we modelled the electrohydrodynamics of such porous particulates based on the modified Boltzmann distribution for the spatial distribution of electrolyte ions and the Poisson equation for electric potential as well as the conservation of mass and momentum principles. We adopt regular perturbation analysis with weak field assumption and the perturbed equations are solved numerically to calculate the electrophoretic mobility and neutralization fraction of the particle charge during its motion as well as fluid collection efficiency. We further deduced the closed form relation between the drag force experienced by the charged porous particle and the fluid collection efficiency. In addition to the numerical results, we further derived the closed form analytical results for all the intrinsic parameters indicated above derived within the Debye-Hückel electrostatic framework and homogeneous distribution of monomers within the particle for which the decay length vanishes. The deduced mathematical results as indicated above will be useful to analyze several electrostatic and hydrodynamic features of a wide class of porous particulate and environmental entities.

Study on behavior and emission of methane/hydrogen diffusion flame with applied DC electric field

Study on behavior and emission of methane/hydrogen diffusion flame with applied DC electric field

Control and promotion of probiotic cells' aggregation and viability using DC electric field and standing acoustic waves

Bacterial cells' long-term stability can be induced through cell aggregation. This study aimed to stimulate probiotic cells' aggregation, suspended in 10 mM KH2PO4 at 18 ± 2 °C, utilizing DC electric fields (10–100 mA) and combined electric field (40 mA) with standing acoustic waves (at a frequency range of 26 kHz to 296 kHz). It was demonstrated that the sole application of acoustic waves on the rod-shaped Bifidobacterium animalis subsp. lactis (BIFIDO) did not trigger cell aggregation. However, the application of DC electric field to BIFIDO, induced polarization and aggregation of the BIFIDO cells, as indicated by spectrophotometric measurements (OD600) and visualized by fluorescence microscopy. The aggregation of BIFIDO cells was accelerated (∼6 times) when applying simultaneously DC electric field and standing acoustic waves, due to the accumulation of the cells at the acoustic pressure nodes, and due to the polarization of the cells by dielectrophoresis (DEP) phenomenon. The synergistic effect of DC electric field and standing acoustic waves not only facilitated the aggregation of the cells, but also considerably enhanced the hydrophobicity of BIFIDO cells, without compromising their viability or altering their surface charges. Enhanced viability and stability of the aggregated probiotic cells, in comparison to the non-aggregated, was also observed. Industrial relevanceThe present study points out the application of DC electric field and Standing Acoustic waves to aggregate probiotic cells. An important attribute of aggregated cells is their greater tolerance to environmental stresses. This technology could be applied for large-scale manipulation and aggregation of cells, as for instance during fermentation, prior to drying or encapsulation of cells, or during other industrial cell treatment technologies.

Dielectrophoresis-assisted removal of Cd and Cu heavy metal ions by using Chlorella microalgae

A novel dielectrophoresis (DEP)-assisted device for the bioremediation of heavy metal ions by using Chlorella microalgae is presented in this paper. To generate the DEP forces, pairs of electrode mesh were inserted in the DEP-assisted device. By applying DC electric field via the electrodes, the inhomogeneous electric field gradient is induced and the strongest non-uniform electric field exists near the mesh cross-corner. After the adsorption of Cd and Cu heavy metal ions by Chlorella, the Chlorella chain were trapped along the vicinity of the electrode mesh. Then, the effects of Chlorella concentration on the adsorption of heavy metal ions, and the applied voltage and electrode mesh size on the removal of Chlorella are conducted. In the co-existing Cd and Cu solutions, the individual adsorption ratio of Cd and Cu reaches as high as approximately 96% and 98%, respectively, showing excellent bioremediation capability of multiple heavy metal ions in wastewater. By adjusting the applied electric voltage and the mesh size, the Chlorella adsorbed with Cd and Cu are captured by negative DC-DEP effects and the removal ratio of Chlorella reach an average of 97%, providing a method for the removal of multiple heavy metal ions in wastewater by using Chlorella microalgae.

Heat transfer enhancement in fatty acid layer at the interface of two metallic bodies by applying DC electric field

By applying an electric field, the enhancement of the heat transfer ability in a thin fatty-acid layer between two metallic bodies with different initial temperatures was observed. The interfacial (with a lauric-acid layer) heat transfer improved remarkably. Such improvement was not observed with a saturated hydrocarbon, whose molecule comprises nonpolar groups. It is considered that the improvement of heat transfer in the fatty-acid layer is induced by the flow of the charged molecules generated in adsorption and desorption on the metal surface as an electrode, it greatly depends on the electrochemical properties of the surface.

Electric field driven self-assembly of dissolved graphene foam particles in a capillary

The ability to self-organize particles under the influence of an external excitation (magnetic field, electric field, temperature, light or crossed effect) is one of the most fundamental aspects of science, which can be directly transferred to practical applications. Magneto- or electro- rheological fluids are an example of using such phenomena. The most important challenge is to reduce the energy required to induce self-assembly in larger structures from fractured parts. In this paper the self-construction ability of graphene microparticles is presented. The main observation regarding the self-assembly of graphene foam in a thin glass capillary into a single chain in methanol upon applied DC electric field is reported. The mechanism of self-ordering of molecules is discussed in terms of charge separation in semi-conducting graphene particles upon an applied DC electric field.Additionally, in order to prepare thin coatings with fixed self-assembled graphene structures inside, silica hydrolysate was applied.

Structures and velocities of noisy ferroelectric domain walls

Ferroelectric domain wall motion is fundamental to the switching properties of ferroelectric devices and is influenced by a wide range of factors including spatial disorder within the material and thermal noise. We build a Landau-Ginzburg-Devonshire (LGD) model of ${180}^{\ensuremath{\circ}}$ ferroelectric domain wall motion that explicitly takes into account the presence of both spatial disorder and thermal noise. We demonstrate both creep flow and linear flow regimes of the domain wall dynamics by solving the LGD equations in a Galilean frame moving with the wall velocity $v$. Thermal noise plays a key role in the wall depinning process at small fields $E$. We study the scaling of the velocity $v$ with the applied DC electric field $E$ and show that noise and spatial disorder strongly affect domain wall velocities. We also show that domain walls develop a local, metastable paraelectric region and widen significantly in the presence of thermal noise in materials with ``multiwell'' potentials, representative of ferroelectrics at temperatures $T$ just below a first-order phase transition (Curie) temperature ${T}_{c}$. These calculations point to the potential of noise and disorder to become control factors for the switching properties of ferroelectric materials, for example for advancement of microelectronic applications.

Generation of electric-field-induced anti-Stokes Raman scattering in the visible region (E-CARSv) from nitrogen in air

Electric-field-induced anti-Stokes Raman scattering in the visible region (E-CARSv) is a third-order nonlinear optical effect used for measuring electric field sensitively, especially at atmospheric or higher pressure. This study demonstrated E-CARSv generation from nitrogen molecules using a visible laser at 532 nm, a tunable infrared laser at approximately 4.3 μm, and an applied DC electric field. The results revealed that the square root of the signal intensity was proportional to the external electric field strength, which corresponded with the theoretical prediction. E-CARSv can be applied to a wide range of mediums containing nitrogen molecules, including plasmas generated in an open-air environment.

The effects of electric field on physical properties of LLZO made by flash sintering method

Li7La3Zr2O12 (LLZO) is one of the promising electrolytes for all-solid-state lithium-ion batteries. Since in conventional sintering, lithium retention is hard to control in LLZO, flash sintering, characterized by shorter sintering time and lower sintering temperature, can be beneficial. In this study, Al-doped LLZO (LALZO)powder was successfully synthesized by the combustion sol-gel method. The product was characterized by thermal analysis (TG/DTA) to evaluate its thermal behavior. Afterward, the effect of an electrical field in an isothermal approach on the relative density and phase composition of LALZO has been investigated. The obtained LALZO powder was uniaxially pressed into a dog-bone shape at 100 MPa. The samples were held in a tube furnace at 850 °C with an applied DC electrical field ranging from 40 V.cm−1 to 100 V.cm-1, while the current density was limited to 200 mA.mm−2. The phase composition was analyzed with X-ray diffraction (XRD), and the ionic conductivity was investigated using an AC impedance spectroscopy. Dense LALZO was flash sintered successfully, and the sample sintered with an electric field of 60 V.cm−1 showed a pure cubic LALZO with 92.4% relative density and a total ionic conductivity of 0.31 mS and activation energy of 0.37 eV. Moreover, it was revealed that the change in the electric field does not significantly affect the relative density. Also, increasing the electric field causes the incubation time to become shorter. This behavior is thought to be due to electric field strength as a driving force for nucleation mechanisms.

Reactive Flash Sintering of High-Entropy Oxide (Mg, Co, Ni, Cu, Zn)1-xLixO at Room Temperature.

(Mg, Co, Ni, Cu, Zn)1−xLixO is a type of high-entropy oxide that has high ionic conductivity at room temperature and is used as a solid electrolyte. (Mg, Co, Ni, Cu, Zn)1−xLixO was successfully synthesized from precursor powder by applying reactive flash sintering for less than 4 min at room temperature (25 °C). AC and DC electric fields were independently applied to sinter ceramic samples; consequently, AC and DC electric field application resulted in relative densities that exceeded 90% and 80%, respectively. X-ray diffraction spectra of samples revealed the existence of a clear halite structure with an insignificant impurity phase, proving that (Mg, Co, Ni, Cu, Zn)1−xLixO crystals were successfully produced.

Ultra–low loss tangent and giant dielectric permittivity with excellent temperature stability of TiO2 co-doped with isovalent-Zr4+/pentavalent-Ta5+ ions

The excellent giant dielectric properties (ExGDPs) are represented in the isovalent–Zr4+/pentavalent–Ta5+ ions co–doped TiO2 with different co–doping percentages (x%ZrTTO). The dopants were dispersed homogeneously in a highly compact–grained ZrTTO microstructure. The mean grain size and cell parameters with bond lengths slightly enlarged as x% increased. The (1%–5%) ZrTTO oxides exhibited ultra–low tanδ values of 0.004–0.016 with the giant dielectric permittivity (ε′∼2.7–3.7 × 104); while the ε′ of the 5%ZrTTO was slightly dependent on the temperature ranging from −60 to 200 °C, following the temperature dependence requirement for application in the X7/8/9R capacitors. Impedance spectroscopy showed a very large resistance of the grain boundaries. The dielectric properties of the 1%ZrTTO were strongly dependent on the applied DC electric field, indicating the dominant internal barrier layer capacitor (IBLC) effect. However, the dielectric properties of the 5%ZrTTO were nearly independent on the applied DC electric field up to 30 V/mm, which was primarily resulted from electron localization in defect dipoles. Therefore, the ExGDPs of the x%ZrTTO were attributed to the combined effects of the IBLC and localized–electron defect–dipoles related to oxygen vacancies (Ti4+⋅e−−VO••−e−⋅Ti4+ and 3Ti4+⋅e−−VO••−TaTi•) and Ti4+⋅e−−TaTi•.

Investigation on effect of semiconducting screen on space charge behaviour of polypropylene‐based polymers for HVDC cables

High voltage direct current (HVDC) power transmission cable is critical for realising sustainability through renewable energy revolution. Eco-friendly thermoplastic polypropylene (PP)-based polymers/nanocomposites are regarded as promising candidates for replacing current thermoset crosslinked polyethylene (XLPE) cables. As an essential component of the extruded HVDC cable for improving conductor/insulation interface and suppressing charge injection to insulation at high DC electrical stresses, developing semiconducting (SC) screens that are compatible with PP-based insulation is of similar importance but has not been well studied yet. This work aims at designing PP-based semiconducting screens and investigating space charge behaviours of SC/PP/SC sandwich specimen to unfold the effect of semiconducting materials, bonding methods, applied DC electric field, and temperature on charge injection, accumulation, transportation, and dissipation in PP-based insulation. Although conventional thermal, mechanical, and low field electrical characterisations demonstrated that all of the developed semiconducting materials meet the performance criteria of commercial semiconducting materials, their space charge and local electric field distribution varied significantly at high DC fields. Compared with the traditional non-bonded configuration used at lab-scale, charge injection was enhanced in hot-pressed SC/PP/SC samples with tightly bonded interfaces, which better reflects the real situation in extruded cables. High temperature further intensified charge injections. Besides, our results also revealed that high temperature and electric field strongly influence charge mobilities and consequently their distribution and local electric field in PP-based insulations.

Electric-field-induced second harmonic generation in silicon dioxide.

Electric-field-induced second harmonic generation (EFISH) as a third order nonlinear process is of high practical interest for the realization of functional nonlinear structures. EFISH in materials with vanishing χ(2) and non-zero χ(3) offers huge potential, e.g., for background-free nonlinear electro-optical sampling. In this work, we have investigated SiO2 as a potential EFISH material for such applications using DC-electric fields. We were able to observe significant second harmonic generation (SHG) in comparison to the background SHG signal. The fundamental excitation at 800 nm results in a SHG signal at 400 nm for high applied DC electric fields, which is a clear indication for EFISH. Additionally, we were are able to precisely model the EFISH signal using time-domain simulations. This numerical approach will be of great importance for efficiency enhancement and prove as a valuable tool for future device design.

Dipole–dipole interactions effects on mobility and conductivity of ionic and bonded defects in hydrogen-bonded chains

Defect formation and transport in a hydrogen-bonded system is studied via a two-sublattice soliton-bearing one-dimensional model. Our two component model completes and extends our previous study (Tchakoutio Nguetcho and Kofane, 2007; Tchakoutio Nguetcho et al., 2008; Li et al., 2015) made on the dynamics of defects in a quasi-one-dimensional nonlinear model of complex hydrogen bond systems. The inclusion of dipole–dipole interactions provides a new class of differential equations possessing several key parameters and many singular straight lines. In order to evaluate and measure the variations effects on each interaction parameter, we use dynamic system methods to first say what are really the key parameters of the system, and then discuss on phase portraits bifurcations to derive a variety of exotic solutions corresponding to phase trajectories under different parameter conditions. Among the rich variety of soliton patterns obtained, we focus our attention to kink (antikink) solutions. The response of these solitonic defects to an externally applied DC electric field makes this system an excellent model to describe the protonic conductivity in complex hydrogen-bonded networks. Therefore, we evaluate analytically the effect of dipole–dipole interactions on the mobility of the kink–antikink pair and the specific electrical-conductivity of the protons transfer.

Laser induced visible and infrared emission of a tungsten filament.

The measurements of laser induced emission (LIE) of a tungsten filament upon irradiation with the focused beam of a CW IR laser diode are reported. It was found that the emission occurred in visible and infrared range. The influence of the applied DC electric field significantly affected the intensity of LIE of the tungsten filament. The origin of LIE is discussed in terms of multiphoton ionization of tungsten W+ atoms assisted by light emission due to the intervalence charge transfer in the tungsten hybrid domain (W, W+).

Effect of Ionic Wind Induced by DC Electric Field on Biogas/Air Turbulent Premixed Flame Structure

ABSTRACT Effect of DC electric field on lean premixed biogas turbulent flame structure at low and medium turbulence intensity was studied experimentally using OH-PLIF. OH signal distribution, turbulent burning velocity and flame structure geometric parameters were derived. Results show that downward electric field could broaden the downstream burned gas and push the flame tip down. The flame base is closer to the burner rim in downward electric field for the modification of thermal diffusion and flow modification caused by ionic wind. The effect on flame tip height reduction is more obvious for biogas flame with a higher CO2 ratio. According to the flame structure analysis, the turbulent burning velocity of biogas is increased slightly due to the modification of flow field by ionic wind generated by downward electric field, and the increment decreases with the increase of turbulence intensity. In addition, there’s a decrease in mean flame surface density and an increase in centerline flame brush thickness. The flame surface curvature PDF distribution is nearly not affected by the application of DC electric field. For turbulent flames, the effect of electric field is non-uniform and inconstant, which induces extra flow perturbation. This perturbation is different from turbulence, and the combined effects lead to the variation of flame structure.

Dielectric elastomer actuator behavior of silicone/cyanoethylsucrose composite films: Morphology and space‐charge distribution

AbstractThe composite films of polydimethylsiloxane (PDMS) and cyanoethylsucrose (CR‐U) were prepared and investigated as an electroactive silicone actuator in the air. CR‐U is highly viscose and soluble in tetrahydrofuran (THF) and acetone (ACT). The composites showed a phase‐separation structure, in which the spherical CR‐U dispersed in the PDMS domain. The films from THF had an asymmetric cross‐sectional view, in which CR‐U large sphere dispersed with a thin skin layer of PDMS on one side. On the other hand, the films from ACT had a symmetric cross‐sectional structure, in which CR‐U small sphere dispersed uniformly without a PDMS thin skin layer. By applying DC electric field, the films from THF deformed by expanding the thin skin layer regardless of the electric field polarity. The films from ACT showed almost no deformation. The space‐charge distribution explained deformation behavior.