Arc Appearance Research Articles

Synthesis, Structural characterization and complex impedance analysis of a novel organic-inorganic hybrid compound based on Mercury (II) chloride

The organic-inorganic hybrid compounds are promising materials due to their electro-optical and semiconducting properties. In this study, a single crystal of (C6H16N)2[HgCl4] has been synthesized and characterized using single-crystal X-ray diffraction at room temperature, SEM/EDS and complex impedance spectroscopy. The crystal structure is centrosymmetric with the monoclinic system (P21/c space group). It consists of isolated tetrahedral anions [HgCl4]2− and protonated amines (C6H16N) +. SEM/EDS analyses proved the composition of the title compound. The frequency-dependent electrical and dielectric properties were analyses using complex impedance spectroscopy in the frequency range of 10−1 Hz – 1 MHz. The Nyquist plots (-Z’’ vs Z’) was characterized by the appearance of a single semicircle arc, indicating a non-Debye type relaxation process in the (C6H16N)2[HgCl4] material. The AC conductivity followed Jonscher law, and the variation of frequency exponent s with temperature suggested that non-overlapping small polaron tunneling (NSPT) is the dominant electrical transport mechanism. So, this work will be very beneficial to the further development of the (C6H16N)2[HgCl4] compound and its potential electrical applications.

Analysis of the Electric Arc in Low Voltage Circuit Breakers

Low Voltage Circuit Breakers (LVCBs) play an important role in electric power systems as they are responsible for switching on and off electric currents, as well as for safety of equipment and human beings. Their working base is the electric arc that appears between their contacts when establishing or interrupting the electric current in the circuit. This electric arc is a complex phenomenon where lots of physic interactions take place in a very short time. Therefore, the optimization of the operation of LVCBs makes necessary a deep understanding of the phenomena involved in the appearance of the electric arc. This knowledge can be achieved by means of modelization and simulation tools. This option allows us to obtain the evolution of physical magnitudes which would be difficult to measure in laboratory tests. The aim of this paper is to describe the phenomena of the electric arc in LVCBs, as well as the specification of the mathematical, physical and software needs for its modelization and simulation.

Influence of geomagnetic disturbances on scintillations of GLONASS and GPS signals as observed on the Kola Peninsula

We have compared effects of geomagnetic disturbances during magnetic storms of various types (CME and CIR) and during an isolated substorm on scintillations of GLONASS and GPS signals, using a Septentrio PolaRx5 receiver installed in Apatity (Murmansk Region, Russia). We analyze observational data for 2021. The magnetic storms of November 3–4, 2021 and October 11–12, 2021 are examined in detail. The November 3–4, 2021 magnetic storm was one of the most powerful in recent years. The analysis shows that the scintillation phase index reaches its highest values during nighttime and evening substorms (σϕ≈1.5–1.8), accompanied by a negative bay in the magnetic field. During magnetic storms, positive bays in the magnetic field, associated with an increase in the eastward electrojet, lead, however, to quite comparable values of the phase scintillation index.
 An increase in phase scintillations during nighttime and evening disturbances correlates with an increase in the intensity of ULF waves (Pi3/Pc5 pulsations) and with the appearance of aurora arcs. This confirms the important role of ULF waves in forming the auroral arc and in developing ionospheric irregularities. The predominance of the green line in the spectrum of auroras indicates the contribution of disturbances in the ionospheric E layer to the scintillation increase. Pulsating auroras, associated with ionospheric disturbances in the D layer, do not lead to a noticeable increase in phase scintillations. Analysis of ionospheric critical frequencies according to ionosonde data from the Lovozero Hydrometeorological Station indicates the contribution of the sporadic Es layer of the ionosphere to jumps in phase scintillations.
 The difference between phase scintillation values on GLONASS and GPS satellites during individual disturbances can be as great as 1.5 times, which may be due to different orbits of the satellites. At the same time, the level of GLONASS/GPS scintillations at the L2 frequency is higher than at the L1 frequency. We did not find an increase in the amplitude index of scintillations during the events considered.

Влияние геомагнитных возмущений на сцинтилляции сигналов ГЛОНАСС и GPS спутников по данным наблюдений на Кольском полуострове

We have compared effects of geomagnetic disturbances during magnetic storms of various types (CME and CIR) and during an isolated substorm on scintillations of GLONASS and GPS signals, using a Septentrio PolaRx5 receiver installed in Apatity (Murmansk Region, Russia). We analyze observational data for 2021. The magnetic storms of November 3–4, 2021 and October 11–12, 2021 are examined in detail. The November 3–4, 2021 magnetic storm was one of the most powerful in recent years. The analysis shows that the scintillation phase index reaches its highest values during nighttime and evening substorms (σϕ≈1.5–1.8), accompanied by a negative bay in the magnetic field. During magnetic storms, positive bays in the magnetic field, associated with an increase in the eastward electrojet, lead, however, to quite comparable values of the phase scintillation index.
 An increase in phase scintillations during nighttime and evening disturbances correlates with an increase in the intensity of ULF waves (Pi3/Pc5 pulsations) and with the appearance of aurora arcs. This confirms the important role of ULF waves in forming the auroral arc and in developing ionospheric irregularities. The predominance of the green line in the spectrum of auroras indicates the contribution of disturbances in the ionospheric E layer to the scintillation increase. Pulsating auroras, associated with ionospheric disturbances in the D layer, do not lead to a noticeable increase in phase scintillations. Analysis of ionospheric critical frequencies according to ionosonde data from the Lovozero Hydrometeorological Station indicates the contribution of the sporadic Es layer of the ionosphere to jumps in phase scintillations.
 The difference between phase scintillation values on GLONASS and GPS satellites during individual disturbances can be as great as 1.5 times, which may be due to different orbits of the satellites. At the same time, the level of GLONASS/GPS scintillations at the L2 frequency is higher than at the L1 frequency. We did not find an increase in the amplitude index of scintillations during the events considered.

Numerical analysis of low-current arc characteristics in micro-TIG welding

A semi-empirical two-temperature (2-T) arc model is developed to study the near-electrode regions and thermal non-equilibrium characteristics of low-current arcs that employ pin-to-pin electrodes in micro‑tungsten inert gas (TIG) welding. Special emphasis is given to accurately depict the electrodes-arc attachment area and the spatial distributions of plasma temperature in 1–4 A argon arcs. The conditions of thermal non-equilibrium, as well as the coupling of the arc plasma and the cathode, are considered. The simulated electron temperature distributions are in good agreement with the arc appearances captured by the high-speed camera, and the predicted arc voltage is only 1.8 V lower than the experimental data. In contrast to TIG welding arcs that operate at higher currents, the temperature contours of the low-current arc column are parallel but slightly expanded in the vicinity of the electrodes. As the arc current decreases, the near-cathode voltage drop increases substantially. The electron temperature in the center of the arc column is almost constant, while the heavy particle temperature drops significantly, causing the arc column to contract. The heat flux at the center of the anode surface does not change as the arc current increases, but it increases significantly outside the 0.25 mm radius.

Study of the effect of the substitution of Fe by Ti on the microstructure and the physical properties of the perovskite system La0.67Ca0.2Ba0.13Fe1-xTixO3 with x = 0 and 0.03 at low temperatures.

La0.67Ca0.2Ba0.13Fe1-xTixO3 samples (x = 0 and 0.03) were synthesized by the auto-combustion method. Analysis of XRD diffractograms revealed that these compounds crystallize in the cubic system with the space group Pm3̄m. The dielectric properties have been studied in the 102-106 frequency range and the 120-280 K temperature range. Analysis of AC conductivity shows that the conduction mechanisms are of polaronic origin and that they are co-dominated by the NSPT and OLPT models. The monotonic increase in conductivity with increasing temperature results from the reduction of defect centers and the increase in charge carrier mobility. Such variation is consistent with impedance variation at different frequencies and temperatures indicating semiconductor behavior. Nyquist diagrams are characterized by the appearance of semi-circular arcs. These spectra are modeled in terms of equivalent electrical circuits confirming the contribution of grains (Rg//CPEg) and grain boundaries (Rgb//CPEgb). The dielectric analysis showed an evolution of the dielectric constant in accordance with Koop's theory and the phenomenological model of Maxwell-Wagner. The low conductivity and the high values of the real permittivity at low frequency make our compounds potential candidates for energy storage and applications for electronic devices and microwaves.

Determination of the critical contact separation length for DC interruption in a vacuum subject to an external transverse magnetic field

The objective of this work is to experimentally determine the critical contact separation length Lcritical for DC interruption in vacuum under an external transverse magnetic field (TMF), according the interruption behaviors and vacuum arc characteristics. L is defined as the separation length at the instant of TMF application. Lcritical is the critical and the minimal necessary separation length of the contacts for a successful DC interruption in vacuum. A pair of Helmholtz coils was used to generate the external TMF. A high-speed camera was used to record the vacuum arc appearance. The experimental results quantitatively determine Lcritical for DC vacuum interruption under a certain DC and the external TMF. When the DC ranged from 100 to 500 A under an external TMF of 30 mT, Lcritical ranged from 2.1 to 3.7 mm and did not show linear variation. Second, the extinguishing time of DC vacuum interruption te at various currents significantly increased in a similar pattern under decreasing L in the range of 0.3–1.6 ms. The decrease in L mainly increased the duration of the stable stage and had little apparent influence on the duration of the unstable stage of the DC vacuum arc. Third, the physical mechanism determining Lcritical in DC vacuum interruption under a TMF could be explained from two aspects: the expansion of the vacuum arc column and the diffusion of the metal plasma. In successful DC vacuum interruption, Lcritical should be large enough for the formation and expansion of the “C”-shaped arc column, and enough space should be available for the diffusion of the metal plasma.

Вклад ионосферных возмущений, регистрируемых радаром EISCAT, в сцинтилляции GPS-сигналов

It is performed an analysis of the influence of ionosphere disturbances on GPS scintillations at the auroral oval using receiver at Skibotn station (SKN, CGM — 66.28N, 103.41E). The ionosphere parameters were determined using EISCAT UHF radar data. We analyze the events for the years 2015-2022 when the GPS and EISCAT data were available. In this paper we present typical events. The optical aurora observations at Skibotn stations in 557.7 and 630.0nm spectrum lines were used as well. It is shown that the strongest GPS phase scintillations (σΦ > 1) were produced by the ionosphere disturbances in the E-region (100–120 km), these disturbances were accompanied by the appearance of the auroral arcs. Ionosphere disturbances in the F-region (> 200 km) do not produce any significant phase scintillations. The night-time and evening substorms accompanied by the negative magnetic bay produce strongest GPS phase scintillations. At the same time, positive magnetic bays, associated with the growth of the eastern electrojet, during magnetic storm produce comparable phase scintillation as night-time substorms. We did not find a clear growth of the amplitude scintillations during considered events.

Observation of Source Plasma and Field Variations of a Substorm Brightening Aurora at L ∼ 6 by a Ground‐Based Camera and the Arase Satellite on 12 October 2017

AbstractAuroral brightening is one of the most common phenomena that occur during substorm onset and is usually recognized as a projection of the substorm‐associated magnetospheric plasma dynamics to the ionosphere. However, electromagnetic fields and plasma features associated with the substorm brightening arc have not been well understood. In this study, we present a comprehensive observation of the source plasma and field variations of a substorm brightening aurora in the inner magnetosphere. We performed a unique conjugate observation of a substorm brightening auroral arc observed by a ground‐based camera and by the Arase satellite in the magnetospheric source region at L ∼ 6. The event was observed at Tromsø (69.6°N, 19.2°E), Norway, on 12 October 2017. The brightening arc indicates east‐west structures with longitudinal scales of ∼0.5°–2.0°. Field‐aligned bi‐directional electrons with an energy range between 66 and 1,800 eV were detected by the satellite, simultaneously with the appearance of the brightening arc in the camera. These electrons were probably supplied from the auroral brightening region in the ionosphere, indicating that the satellite was on the same field line of the brightening aurora. The magnetic and electric field data show characteristic fluctuations and earthward Poynting flux around the time that the satellite crossed the aurora. Anti‐phase oscillations between the thermal pressure and the magnetic pressure are also reported. Based on these observations, we suggest the possibility that a ballooning instability occurred in the source region of the substorm brightening arc in the inner magnetosphere at L ∼ 6.

Influence of heat input on the appearance, microstructure and microhardness of pulsed gas metal arc welded Al alloy weldment

In order to achieve high-quality welding of aluminum alloys, reasonable control of welding heat input is critical. Different combinations of welding parameters can achieve the same heat input, however, the relevant research results has not been reported. In this paper, the pulsed-gas metal arc welding (P-GMAW) of 4047 Al–Si alloy was used as the research object. Combining design of welding current, welding voltage and welding speed, three sets of welding parameters with the same heat input were obtained, and welding experiments were carried out on them. The formation, microstructure and mechanical properties of weld bead were analyzed. The results show that under the same heat input, the effect of the welding current and voltage on the weld bead is remarkable. With the increase of the two, the penetration, width and spreadability of the weld bead increased, and the low melting point precipitates became more aggregated. At the same time, the average hardness of the weld increased from 98.27 HV to 104.4 HV, i.e., 6.2%.

Crystal structure, Hirshfeld surface analysis, Vibrational studies, Dielectric properties, and AC conductivity of Bis(carbamoyl-guanidine amidinourea salt) diaquatetrachlorocuprate (II)

A new organic-inorganic hybrid compound Bis (carbamoyl-guanidine amidinourea salt) diaquatetrachlorocuprate (II) was successfully synthesized. X-ray diffraction measurements were determined. The compound crystallizes in the monoclinic system, space group P21/n. The structural analysis demonstrated the presence of a layered arrangement perpendicular to the a-axis where plans formed by (C2H7N4O)+ cations alternated with plans formed by [CuCl4(H2O)2]2− anions. The Cu (II) ions were hexa-coordinated with distorted octahedron geometric configuration. The title compound exhibited a three-dimensional structure resulting from the interconnection of molecules through N-H···Cl, N-H···O, O-H···Cl and O-H···O hydrogen bonds. Hirshfeld surface analysis was carried out to explore the different inter molecular interactions. The two-dimensional fingerprint plot revealed the most prominent interactions in the compound. Infrared and Raman spectroscopic measurements were performed to confirm the results obtained by X-ray diffraction. The thermal behavior of the material was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Furthermore, the material electrical properties were characterized through impedance spectroscopy technique in the frequency range 209 Hz-5 MHz and at a temperature ranging from 293 to 408 K. The impedance spectrum was characterized by the appearance of a single semicircle arc which indicated a non-Debye type of relaxation process occurring in the material. Besides, the alternating current (AC) conductivity of the compound was determined using Jonscher's law: σ(ω)=σDC+Aωn. The conduction could be attributed to the ion hopping mechanism.

Experimental investigation on the evolution of vacuum arc in the quench protection switch based on forced current zero

In this paper, the evolution of vacuum arc under different conditions in the quench protection switch (QPS) based on forced current zero was investigated experimentally and analyzed quantitatively. Experiments were conducted with cup-shaped axial magnetic field (AMF) contacts in a demountable vacuum chamber. Images of the arc column were photographed through the observation window with a high-speed digital camera with exposure time of 2 μs. Arc appearance was analyzed quantitatively through digital image processing. Quantified arc appearance and arc voltage characteristics indicated that the high-current vacuum arc evolution in the QPS could be divided into four stages: arc formation stage, arc column merging stage, diffusing stage, and fast extinguishing stage. The influence of AMF on the evolution of high-current vacuum arc in the diffusing stage was also studied. Experiment results indicated that the vacuum arc at relatively low current had a simpler evolution process and the arc column merging had less correlation with voltage stability. It was found that the vacuum arc with a long gap distance developed faster and the time required to enter the stable burning state was shorter. In addition, the vacuum arc with long arcing time tended to constrict again, which is not beneficial to current interruption.

Investigation of Vacuum Arc and Erosion Characteristics of Spiral TMF Contacts With Different Materials

The transverse magnetic field (TMF) can drive the arc to rotate, to reduce the erosion of contact. In this article, TMF contacts of six commonly used materials (CuCr10, CuCr30, CuCr50, WCu10, WCu30, and CuW-WC) are investigated by experiments at the current of 5, 10, and 15 kA. Experimental results show that the contact material has a significant impact on the arc, the arc on CuCr materials rotates, and shows noisy voltage, while the arc on WCu hardly rotates and exhibits a stable arc voltage because of staying in the diffuse mode. Though the erosion of CuCr contacts is more severe than WCu contacts, the results of breaking operations also indicate that CuCr contacts outperform WCu contacts, where CuCr10 contact has a lower breaking capacity than CuCr30 and CuCr50. Moreover, the steel support disk of the interrupter contacts plays a role in the reignition of the arc after a half-cycle of current which is obvious from the erosion of the disk and from records of the arc appearance.

Material realization of double-Weyl phonons and phononic double-helicoid surface arcs with P213 space group

Unconventional chiral quasiparticles with twofold, threefold, and fourfold degeneracies and Chern number ($C$) = $\ifmmode\pm\else\textpm\fi{}2$ have recently sparked interest because of their topological chirality in momentum space. Herein, based on first-principles calculations and symmetry analysis, we propose 14 synthesized topological phonon systems with space group $P2{}_{1}3$ (No. 198) that host two types of almost-ideal double-Weyl points, which are the fourfold degenerate charge-2 Dirac point and the threefold degenerate spin-1 Weyl point. Based on the projected local density of states on the [100] and [101] surfaces of these selected realistic materials, we discovered two visible winding around the projected double-Weyl points, demonstrating the appearance of phononic double-helical surface arcs. Furthermore, we constructed a $\mathbit{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{p}$ model to determine how the two types of double-Weyl point phonons coexist in the system with the $P2{}_{1}3$ space group. We believe that this work provides directions for investigating double-Weyl point phonons and an ideal platform for investigating phononic double-helical surface states in realistic materials.

Investigation on the Arc Appearance During the Arc Slot Crossing Process Between the Spiral Type Contacts

Investigation on the Arc Appearance During the Arc Slot Crossing Process Between the Spiral Type Contacts

Numerical simulation of low-current vacuum arc jet considering anode evaporation in different axial magnetic fields

As the main source of the vacuum arc plasma, cathode spots (CSs) play an important role on the behaviors of the vacuum arc. Their characteristics are affected by many factors, especially by the magnetic field. In this paper, the characteristics of the plasma jet from a single CS in vacuum arc under external axial magnetic field (AMF) are studied. A multi-species magneto-hydro-dynamic (MHD) model is established to describe the vacuum arc. The anode temperature is calculated by the anode activity model based on the energy flux obtained from the MHD model. The simulation results indicate that the external AMF has a significant effect on the characteristic of the plasma jet. When the external AMF is high enough, a bright spot appears on the anode surface. This is because with a higher AMF, the contraction of the diffused arc becomes more obvious, leading to a higher energy flux to the anode and thus a higher anode temperature. Then more secondary plasma can be generated near the anode, and the brightness of the ‘anode spot’ increases. During this process, the arc appearance gradually changes from a cone to a dumbbell shape. In this condition, the arc is in the diffuse mode. The appearance of the plasma jet calculated in the model is consistent with the experimental results.

Functional Properties of Donor (Al) and Acceptor (Cu) Codoped High Dielectric Constant ZnO Nanoparticles

In this work, we have synthesized donor‐acceptor (Al‐Cu) codoped ZnO nanoparticles with a doping concentration of 0%, 0.25%, 0.5%, and 0.75% by coprecipitation method. The synthesized samples were then annealed at 350°C and 600°C. All the samples showed wurtzite structure of ZnO with no secondary phase. The increase in doping concentration led to deterioration of crystalline quality, while improved crystallinity was observed at higher annealing temperature. The morphological study of these samples showed good grain‐to‐grain contact with less isolated pores. These samples were further characterized by impedance spectroscopy for analyzing dielectric properties. The values of the real part of dielectric constant and tangent loss showed decreasing trend with frequency. The appearance of semicircular arcs in the impedance complex plane plots indicates contribution of grains and grain boundaries and presence of different relaxation processes. 0.5% Al and Cu codoped ZnO showed the best dielectric response with a high value of dielectric constant and low tangent loss.

Characterization of Dielectric Oil with a Low-Cost CMOS Imaging Sensor and a New Electric Permittivity Matrix Using the 3D Cell Method.

In this paper, a new method for characterizing the dielectric breakdown voltage of dielectric oils is presented, based on the IEC 60156 international standard. In this standard, the effective value of the dielectric breakdown voltage is obtained, but information is not provided on the distribution of Kelvin forces an instant before the dynamic behavior of the arc begins or the state of the gases that are produced an instant after the moment of appearance of the electric arc in the oil. In this paper, the behavior of the oil before and after the appearance of the electric arc is characterized by combining a low-cost CMOS imaging sensor and a new matrix of electrical permittivity associated with the dielectric oil, using the 3D cell method. In this way, we also predict the electric field before and after the electric rupture. The error compared to the finite element method is less than 0.36%. In addition, a new method is proposed to measure the kinematic viscosity of dielectric oils. Using a low-cost imaging sensor, the distribution of bubbles is measured, together with their diameters and their rates of ascent after the electric arc occurs. This method is verified using ASTM standards and data provided by the oil manufacturer. The results of these tests can be used to prevent incipient failures and evaluate preventive maintenance processes such as transformer oil replacement or recovery.

Safe stroke of vacuum breaking process in DC circuit breaker commutated by intermediate frequency current

The safe stroke between contacts of vacuum switch is the key parameter that can withstand transient recovery voltage (TRV) after arc extinction. In order to determine the minimum safe stroke during direct current (DC) interruption, this paper starts with the characteristic analysis of the commutation process. After breaking current zero crossing, contact gap is used to correlate the dielectric recovery level with TRV. In terms of theoretical description, based on the sheath development analysis of continuous transition model (CTM), different commutation moments and frequency have a perceptible effect on the TRV and dielectric recovery process. The breaking test of DC synthesis circuit with dual power supply is used to further verify the dielectric recovery level of vacuum gap, and the minimum safe stroke corresponding to reliable interruption. Simulation and experimental results show that safe stroke increases with the higher breaking current, TRV and its change rate during the DC breaking process, the corresponding commutation moment should be delayed. Finally, the influence of arc appearance on the safe stroke is discussed by analyzing the arc image of the draw-arc process. The safe stroke is helpful to determine the time setting for commutation moment and reliable breaking process of DC vacuum circuit breaker.

Topological phononic nodal hexahedron net and nodal links in the high-pressure phase of the semiconductor CuCl

By using symmetry analysis and first-principles calculations, we propose that the simple cubic structure of copper chloride (CuCl) in high-pressure phase can be worked as a three-dimensional (3D) topological phononic material, hosting the so-called topological phononic nodal links (TPNLs) in phonon spectra, which are intersected around the center of the Brillouin zone (BZ). More interestingly, another class of nodal-line phonons, i.e., the topological phononic nodal hexahedron net (TPNHN), exists at all the boundaries of 3D BZ and is composed of interconnected quadruply degenerate straight nodal lines. Their topologically nontrivial natures are confirmed by the Berry phase calculations. The TPNHN-induced Dirac cones and the TPNLs-induced drumheadlike surface states are observed in the surface BZ. In addition, the appearance of large surface arcs strongly supports the robustness of nodal-link phonons. Our theoretical results not only pave a route to explore new nodal-line phonons but also reveal that the semiconductor CuCl in high-pressure phase is an ideal material candidate to realize TPNHN and TPNLs.