Action Of Electric Field Research Articles

Influence of the filter grain morphology on separation efficiency in dielectrophoretic filtration.

Recovery of noble materials from waste is essential for industries around the globe. Dielectrophoretic (DEP) filtration, an electrically switchable particle separation technique, can be applied to tackle this challenge. It is highly selective regarding particle size, material or shape. Expanding the scope of DEP towards high throughput and improving the trapping efficiency are vital to make DEP a viable robust alternative to conventional separation methods. DEP filtration works by selective immobilisation of particles in a porous medium by the action of an inhomogeneous electric field. The field inhomogeneity comes from scattering an electric field at the phase boundary between the particle suspension and the filter surface. In this article, we show how the filter structure affects the DEP separation. We study fixed bed filters of three different grain types and find that the morphology of the grains highly influences the DEP filter efficiency. Specifically, grains with irregular surface structure and high perceived angularity show high separation efficiency. We believe these insights into the design of DEP filtration will pave the way towards its application in, for example, the recovery of valuable materials from electronic waste dust.

Electric field effect of sliding graphene/hexagonal boron nitride heterobilayer

The first-principles computer-aided design of atomistic heterostructures can discover the physical properties of new materials and help them widely find applications in frontier scientific fields. Here, we report an investigation on the heterobilayer composed of one sheet of two-dimensional (2D) graphene on the surface of one-layer hexagonal boron nitride (h-BN). We calculate and simulate the binding energies, electric dipoles related to interlayer sliding, and twisting angles of three stacking orders in graphene/hBN heterobilayer. The relative energies of these three heterobilayers are obtained by using first-principles calculations method and the AB stacking structure exhibits the lowest energy. We have also found that the electric field perpendicular to the 2D plane can control the dipole magnitude of the bilayer system, and even change the polarization direction. We studied the kinetic stability of graphene-hBN bilayer heterostructures under the action of external electric fields using Ab initio molecular dynamics (AIMD), as well as the thermodynamic stability. Finally, we propose that the graphene/h-BN heterobilayer might play an important role in the field of information electronics as a 2D material with interesting physical properties.

Dynamics of coupled rotors in external fields

Coupled hindered rotor model is crucial for exploring the rotational dynamics of complex molecules under different external environments. When coupled hindered rotor molecules are subjected to the combined action of static electric and laser fields, their rotational dynamics get significantly modified, leading to interesting physics. In this study, we solve the time-independent Schrödinger equation for the coupled pair of rotors in the combined action of static electric and laser fields using the nine-point finite difference method and obtain rotational energy spectra and eigenvectors. We then use the partition function approach to understand thermal behaviour by studying thermal properties like heat capacity and entropy. We also explore the impact of temperature, coupling strength, and external fields strength parameters on these properties. The orientation of the coupled rotor is strongly dependent on the coupling strength between the coupled rotors as well as the hindrance. We analyse this directional parameter under a broad range of barrier height, coupling strength, and external fields strength parameters. Our analysis may provide insight into the rich and interesting physics, which may pave the way for future experimental and theoretical studies in this area.

780 nm near-infrared photorefractive holograms recorded in undoped Bi12TiO20 crystal under the action of external electric field

In this paper, we studied recording and erasure of photorefractive holographic gratings recorded at 780 nm in an undoped Bi12TiO20 (BTO) crystal sample under the action of an externally applied electric field. The diffraction efficiency was measured by directly chopping the diffracted beams by the gratings recorded in a two-wave mixing setup without using of any phase-modulation technique of the recording beams or feedback mechanism. An enhancement of 3.5-fold in the diffraction efficiency was observed when the applied electric field increased from 0 to 6 kV/cm. The theoretical dependence of the diffraction efficiency on the external electric field considering the effect of screening of charges near the electrodes was investigated, and the result is supported by good fit to the experimental data, allowing us to compute characteristic parameters of the material, including the values of photoactive donor concentrations (ND1)eff ≈ 0.12 × 1016 cm−3 and (ND2)eff ≈ 0.8 × 1015 cm−3, respectively, for the levels placed at 1.6 eV and 1.3 eV below the conduction band responsible for photorefractive recording in the BTO sample.

Facile design of surface electric field driven tourmaline/g-C3N4 layered stacked photocatalysts with enhanced photocatalytic activity for antibiotic removal

In the field of photocatalysis, Graphitic carbon nitride (g-C3N4) has received a lot of attention for its superior functionality and benefits. However, it suffers from the fatal defect of low charge separation efficiency, which is well addressed by tourmaline's self-contained surface electric field. In this work, tourmaline/g-C3N4 (T/CN) composites were successfully synthesized. Due to its surface electric field effect, tourmaline and g-C3N4 are stacked on top of each other. It makes its specific surface area increase greatly and more active sites are exposed. Additionally, the rapid separation of photogenerated electron holes under the action of electric field promotes the photocatalytic reaction. T/CN exhibited excellent photocatalytic performance under visible light, with 99.9% Tetracycline (TC 50 mg L−1) removal after 30 min. Compared to tourmaline (0.0160 min−1) and g-C3N4 (0.0230 min−1), the T/CN composite's reaction rate constant (0.1754 min−1) was 11.0 and 7.6 times higher. A series of characterizations also determined the structural properties and catalytic performance of the T/CN composites, which were found to have a larger specific surface area, narrower band gap, and higher charge separation efficiency compared to the monomer. In addition, the toxicity of tetracycline intermediates and their degradative pathways were investigated, and the toxicity of the intermediates was found to be reduced. Given the quenching experiments and active substance determination, it was also found that h+ and ·O2− play a major role. This work provides more inspiration for photocatalytic material performance research as well as green innovation for environmental management.

ИСПОЛЬЗОВАНИЕ ОРТОГОНАЛЬНЫХ СИЛЬНЫХ ЭЛЕКТРИЧЕСКИХ И МАГНИТНЫХ ПОЛЕЙ ДЛЯ СОЗДАНИЯ ЧАСТОТНО-ПРЕОБРАЗОВАТЕЛЬНЫХ УСТРОЙСТВ АВТОДИННОГО ТИПА

In the framework of the drift-diffusion model of carrier transport in the bulk of III–V typesemiconductors, under external action of strong constant electric and magnetic fields orthogonallyoriented relative to each other, a new principle for applying the discovered effects is proposed, whichtake into account the nonlinearities of the output parameters of the working chip, which leads to thepossibility creation of new semiconductor structures controlled by a magnetic field (SSCMF). Previously,the diffusion component of the output current density was not taken into account as a separateeffect arising under the orthogonal action of strong electric and magnetic components, which was atfirst time considered in this paper. It is shown that this component is a part of the inductive transverseoutput current and can be considered as an independent effect. The proposed practical applicationis based on the classical relations that describe the component spatial representation of the effectivemass energy dependence and the parameters of the kinetic equations for the carriers drift andheating in the bulk of highly mobile III–V type semiconductors structures. (The energy dependence ofthe reciprocal effective mass value was obtained under the assumption that this parameter becomesheavier in the framework of the two-valley representation. However, the mechanism of such increasingis not considered in detail, but is taken into account as a result of expansion in a Taylor series.)At the same time, some new phenomena were also hypothetically discovered: a diffusion detectoreffect and a transverse induction effect controlled by a magnetic field, similar in its manifestation tothe Gunn effect observed in this direction. The results obtained open the prospect for creating fundamentallynew frequency-converting devices based on the above SSCMF, such as autodyne-type converters(mixers), one of the designs of which is also proposed in this work in a waveguide version. Inthe case of experimental confirmation of the discovered effects, which can be investigated using theblock diagram of the measuring setup proposed in the work, we can conclude that there are promisingnew applications of magnetically controlled semiconductor structures. In addition, equipmentdevelopers will be interested in the possibility of using the magnetic field orientation angle to controlthe output parameters of such structures as part of converters

Electroacoustic Effect and Electrical Superconductivity of Metals

The paper discusses the conditions under which superconductivity of metals would be detected at atmospheric pressure and at room temperature. One of the possible directions of research to achieve these conditions is to change the phonon spectrum of metals in order to increase the Debye temperature, and therefore to increase the temperature of the superconducting transition Tc. According to the idea of the work and to the estimates made in it, the maximum frequency of phonons nmax in metals can be increased by the short-term action of an external constant electric field (electric pulse). The duration of the pulse should be (10–5–10–7) s. The voltage of the constant electric field source is U » 1V. A decrease in the crystal lattice parameter should be accompanied by an increase in the maximum phonon frequency nmax and, accordingly, by an increase in the Debye temperature. The characteristic size of the sample, in which the change in electron concentration can be realized, should not exceed the length of electron shielding in metals, i. e. ≈ 10–8 m. The sequential action of a certain number of electric field pulses can maintain a superconducting state in a metal sample for some finite time.

Boundary layer effect of light transmission through ionic liquid under electric field

The field strength distribution in the ionic liquid boundary layer under the action of an external electric field is non-uniform. Whether its transmittance (absorption coefficient) spatially varies arouses our interest in exploring the underlying laws. In this paper, with the help of an infrared microscope, a special experimental device was designed and established. The transmittance in the ionic liquid (methyl propyl imidazole iodide, C3MImI) at different distances from the electrodes (cathode, anode) was measured under electric voltages from 0 V to 0.5 V. Results showed that transmittances of ionic liquid at the boundary layer present nonlinear change with the nonlinear electronic strength under the different applied voltage, and there is a critical threshold (0.2 V) distinguishes the sensitive and non-sensitive responses to the electric field. Our study provides a physical basis for microscale electro-optic regulation and is significant, especially for precise regulation of light field transmittance in micro-nano channels/structures.

Study on the dissociation properties and spectra of chlorodifluoromethane under an external electric field

Chlorodifluoromethane (HCFC-22) is a kind of greenhouse gas, the study of its properties and dissociation methods is of great value to reduce its pollution. Based on the density functional theory (DFT), the structure, spectra and dissociation characteristics of HCFC-22 gas molecules under applied electric field (0 V·nm−1–12.856 V·nm−1) are discussed at the 6–311 G++ (d, p) level. The results all show that HCFC-22 molecule is more easily dissociated under an external electric field. The dissociation characteristic of the molecule is as follow: the dissociation barrier decreases gradually with the increase of external electric field. In addition, the UV–Vis spectrum of HCFC-22 is redshifted and the excitation energy decreases gradually under the action of external electric field. The results of this study provide theoretical support for the application of electric field to degrade HCFC-22 molecules, which can help solve the problem of air pollution.

0D/1D CuFeO2/CuO nanowire heterojunction arrays for improved photoelectrocatalytic reduction of CO2 to ethanol

CuO material with a bandgap of 1.2–1.9 eV and suitable energy level is a promissing material for photoelectrocatalytic reduction of CO2. However, the serious photocorrosion limits its performance improvement. Herein, an in-situ synthesis route is designed to fabricate 0D/1D CuFeO2/CuO nanowire heterojunction arrays with large specific surface. The nanowire heterojunction arrays presented excellent activity for photoelectrochemical reduction of CO2 to ethanol with an optimal faradaic efficiency of 66.73% at - 0.6 V (vs. Ag/AgCl). A heterojunction is formed between CuFeO2 and CuO, and the enhanced charge transfer mechanism is proposed based on the measurement of energy band structures. Under the action of interfacial built-in electric field of heterojunction, photogenerated holes are transferred from the valence band of CuO to CuFeO2, and photogenerated electrons are transferred from the conduction band of CuFeO2 to CuO with high selective reduction of CO2 to ethanol.

Charge Relaxation in Chalcogenide Films under Electron Beam Irradiation

We studied processes of charge relaxation after point irradiation of AsxSe100-x and GexSe100-x chalcogenide films with an electron beam. Two relaxation processes were found in the dose range from 2,05 * 102 μCcm−2 to 9,3 * 107 μCcm−2. The relaxation times of these processes differ by more than 103 times. It is shown that the first relaxation process is associated with the relaxation of the positive charge in the near-surface region of irradiated film. The second, slower relaxation process is due to the process of the formation of a negative charge layer inside the film and electron-induced mass transport under the action of an internal electric field.

High-efficient capture and degradation of formaldehyde based on the electric-field-enhanced catalytic effect

Enhancing the generation of active groups is of great significance for alleviating the catalyst deactivation of formaldehyde (HCHO) by accelerating the decomposition of intermediate products. Herein, an electric-field-enhanced catalytic effect was proposed for the efficient capture and degradation of HCHO base on carbon cloth loaded manganese oxide catalyst (MnOx-CC). Under the action of electric field, MnOx can generate more hydroxyl radicals (•OH) and superoxide radicals (•O2-), thus accelerating the degradation of HCHO and intermediates at room temperature. After the introduction electric field (∼1 ×104 V/m), •O2- and •OH radical on the surface of MnOx-CC catalyst can be increased by 8 times and 23 times, respectively. At weight hourly space velocity of 300,000 mL/(gcat h) for ∼15 ppm HCHO, MnOx-CC-Electric Field catalyst reached the removal efficiency of 99.4%, and the CO2 conversion efficiency of 81.2%, without decrease significantly within 80 h. Theoretical calculation shows that the electric field can increase the electron state density of Mn atom at the Fermi level and reduce the adsorption energy of HCHO, O2 and H2O, thus promoting the generation of active groups and degradation of intermediate products. The electric-field-enhancement catalytic effect provides a new approach for the degradation of Volatile Organic Compounds.

The Electrodegradation Process in PZT Ceramics under Exposure to Cosmic Environmental Conditions.

Long-time electric field action on perovskite piezoelectric ceramic leads to chemical degradation. A new way to accelerate the degradation is the exposure of the ceramic to DC electric fields under a vacuum. A high-quality commercial piezoelectric material based on PbZr1-xTixO3 is used to study such impacts. To avoid the influence of ferroelectric properties and possible removal of oxygen and lead oxides during the degradation process, the experiments are in the temperature interval of 500 °C > T > TC. Changes in resistance during the electrodegradation process is an electrically-induced deoxidation, transforming the ceramic into a metallic-like material. This occurs with an extremely low concentration of effused oxygen of 1016 oxygen atoms per 1 cm3. Due to this concentration not obeying the Mott criterion for an isolator-metal transition, it is stated that the removal of oxygen mostly occurs along the grain boundaries. It agrees with the first-principle calculations regarding dislocations with oxygen vacancies. The decrease in resistivity during electrodegradation follows a power law and is associated with a decrease in the dislocation dimension. The observed reoxidation process is a lifeline for the reconstructing (self-healing) properties of electro-degraded ceramics in harsh cosmic conditions. Based on all of these investigations, a macroscopic and nanoscopic model of the electrodegradation is presented.

Charge carrier transport and polarization in M/PZT/M structures

A model of non-stationary charge carrier transport in M/PZT/M ferroelectric structures has been developed. It is assumed that, at room temperature, electrons generated by oxygen vacancies are captured by Ti+3 levels and move between them under the action of electric fields caused by the external bias and polarization. The polarization distribution in a PZT film is described with varying degrees of complexity, from a constant value outside the defect layers to one determined by the equation following from the Landau–Ginzburg theory. The numerical simulation performed made it possible to explain the reasons and conditions for the appearance of current–voltage characteristics with unusual current peaks, to show the existence of several solutions in the Landau–Ginzburg model for a film with Schottky barriers, and to reveal the response of charged domain walls to an applied voltage.

Photoelectret effect in polymer-AIIBVI (CdS, ZnS) composites of photosensitive semiconductors

The photoelectret effect in composite heterostructures consisting of polar (fluorinecontaining) and non-polar (polyolefins) polymers - high density polyethylene (HDPE), low density polyethylene (LDPE), F42, F2-ME and the inorganic phase AııBvı (CdS, ZnS) has been studied. It has been established that the difference in photoelectret potentials in a given volume share of the inorganic phase mainly depends on the polarity of the polymer matrix. A possible mechanism of the photoelectret effect formed under the combined action of a strong electric field and light in these composites. It has been experimentally established that the potential barrier formed at the polymer- AııBvı semiconductor interface separates the electric charge carriers formed as a result of the internal photoelectric effect and ensures the formation of an electret potential difference. The electret charge state of polymer- AııBvı composites was studied using the spectrum of thermally stimulated current.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

Polarization and built-in electric field improve the photocatalytic overall water splitting efficiency of C2N/ZnSe heterostructures

The type-II van der Waals heterostructure photocatalytic system is an ideal band alignment structure for photocatalysis, which the high separation efficiency of photo-induced carriers. By using density functional theory, we predicted two van der Waals (vdW) heterostructures, namely, C2N/ZnSe-ML (monolayer) and C2N/ZnSe-BL (bilayer), respectively. For the C2N/ZnSe-BL heterostructure, it has an intrinsic type-II band alignment, in which the built-in electric field formed at the interface accelerates the separation of photogenerated electrons-holes in heterostructure. The photogenerated electrons-holes have been accumulated near the conduction band minimum of C2N and the valence band maximum of ZnSe-BL, respectively, which the C2N/ZnSe-BL heterostructure is a type-II photocatalytic heterostructure. However, the C2N/ZnSe-ML heterostructure has a strong built-in electric field from C2N to ZnSe-ML because the ZnSe-ML is a polarized material with a polarized electric field inside, which form a type-Ⅱ heterostructure and realizes the effective separation of photogenerated electron-holes under the action of built-in electric field. The C2N/ZnSe-X (ML, BL) heterostructures are both direct band-gap semiconductors and they can harvest sunlight efficiently almost in the range of the solar spectrum. These distinguishing features confirm that the C2N/ZnSe-X (ML, BL) heterostructures have promising prospects in the sphere of photocatalysis for the separation of photogenerated electron-holes.

Correlation between multi-factor phase diagrams and complex electrocaloric behaviors in PNZST antiferroelectric ceramic system

Ferroelectric (FE) phase transition with a large polarization change benefits to generate large electrocaloric (EC) effect for solid-sate and zero-carbon cooling application. However, most EC studies only focus on the single-physical factor associated phase transition. Herein, we initiated a comprehensive discussion on phase transition in Pb_0.99Nb_0.02[(Zr_0.6Sn_0.4)_1−<i>x</i>Ti_<i>x</i>]_0.98O₃ (PNZST100<i>x</i>) antiferroelectric (AFE) ceramic system under the joint action of multi-physical factors, including composition, temperature, and electric field. Due to low energy barrier and enhanced zero-field entropy, the multi-phase coexistence point (<i>x</i> = 0.12) in the composition–temperature phase diagram yields a large positive EC peak of maximum temperature change (Δ<i>T</i>_max) = 2.44 K (at 40 kV/cm). Moreover, the electric field–temperature phase diagrams for four representative ceramics provide a more explicit guidance for EC evolution behavior. Besides the positive EC peaks near various phase transition temperatures, giant positive EC effects are also brought out by the electric field-induced phase transition from tetragonal AFE (AFE_T) to low-temperature rhombohedral FE (FE_R), which is reflected by a positive-slope boundary in the electric field–temperature phase diagram, while significant negative EC responses are generated by the phase transition from AFE_T to high-temperature multi-cell cubic paraelectric (PE_MCC) with a negative-slope phase boundary. This work emphasizes the importance of phase diagram covering multi-physical factors for high-performance EC material design.

Graphene nanoplatelets/polydimethylsiloxane electromagnetic shielding composites based on bipolar pulsed electric field-induced alignment

Conductive polymer composites require high conductive filler loadings to achieve relatively ideal electromagnetic interference (EMI) shielding performance, which brings problems such as heavy weight and poor processability and ultimately limits their application in the aerospace field. To solve the above problems and realize the preparation of excellent EMI shielding composites with low filler loadings, a bipolar pulsed electric field-induced graphene nanoplatelets (GNPs) alignment method is proposed in this paper to improve the electrical conductivity and EMI shielding performance. The orientation and alignment of GNPs in the matrix were characterized by x-ray diffraction and scanning electron microscopy, and the results showed that GNPs formed a conductive network. The electrical conductivity of the composite material in the X-band was measured, and the results showed that the bipolar pulsed electric field could significantly improve the electrical conductivity of the composite material; the improvement percentage reached 100%–300% under the five filler loadings. In addition, the EMI shielding effectiveness of the composite material in the X-band was tested. The results showed that the EMI shielding effectiveness of the composite material with a mass fraction of 14% increased from 16.48–15.86 dB to 21.37–20.99 dB with the action of the bipolar pulsed electric field, and the improvement percentage was 32%. This is the first study on improving the EMI shielding performance of composite materials by applying a bipolar pulsed electric field, and it provides an effective method to prepare EMI shielding composites with low filler loadings.

Synthesis and characterization of Al2O3‐TiC‐ZrO2 ceramics with intragranular nanostructure by spark plasma sintering

AbstractIn this paper, Al2O3‐TiC ceramic composites with intragranular nano‐ZrO2 were prepared in vacuum by spark plasma sintering (SPS). The effect of ZrO2 particles with different nano‐sizes on the microstructure and mechanical properties of ceramics was studied. The results show that SPS can achieve relative densification of materials without generating new impurity phases. At the same time, the sintering densification temperature of ceramic materials can be reduced by adding ZrO2 (20 nm) particles. Under the action of SPS strong electric field, the nano‐ZrO2 adsorbed on the surface of the matrix particles can enter the interior of matrix grains, and form intragranular nanostructures when the grain boundaries move and the particles merge. The microstructure and mechanical properties of ceramic materials can be improved through the intragranular structure formed by nanoparticles. The main reasons for the increased strength and toughness of ceramic materials are crack deflection, crack bridging and transgranular fracture.