Discharge Properties Research Articles

Superior Energy and Power Density Realized in Pb(Hf 1- x Ti x )O 3 System at Low Electric Field

The development of antiferroelectric materials with large energy density and fast discharge speed makes dielectric capacitors possess great prospects for applications in pulsed power technology. Here, the PbHfO 3 -based ceramics with compositions of Pb(Hf 1- x Ti x )O 3 (PHT, 0.01 ≤ x ≤ 0.05) were synthesized, and their antiferroelectricity and phase transition behavior were studied. According to the tests of x-ray diffraction, dielectric spectrum, and polarization–electric field hysteresis loops, PHT ceramics gradually transition from an orthorhombic symmetric antiferroelectric phase to a hexagonal symmetric ferroelectric phase at room temperature as Ti 4+ concentration increases. The forward phase switching field of antiferroelectric to ferroelectric phase transition can be markedly regulated by the introduction of Ti 4+ , and the optimal energy storage performance was obtained in Pb(Hf 0.98 Ti 0.02 )O 3 ceramics with a large recoverable energy storage density of W rec ~ 4.15 J/cm 3 and efficiency of η ~ 65.3% only at a low electric field of 190 kV/cm. Furthermore, the outstanding charge–discharge properties with an ultrafast discharge time (71 ns), remarkable discharged energy density (2.84 J/cm 3 ), impressive current density (1,190 A/cm 2 ), and ultrahigh power density (101 MW/cm 3 ) at a low electric field of 170 kV/cm were obtained in studied ceramics. The excellent energy storage performance of PHT ceramics provides a promising platform for the application of dielectric capacitors.

Modified equivalent circuit for coplanar dielectric barrier discharge considering undischarged areas

Coplanar dielectric barrier discharge has a wide range of potential applications in the domains of material surface modification and other areas by producing a thin layer of diffuse plasma with high power density in the air. For a thorough examination of essential variables and discharge properties of coplanar dielectric barrier discharge plasma, an equivalent circuit model is essential. In this paper, a modified equivalent circuit for coplanar dielectric barrier discharge (CDBD) that took into account both the undischarged part and the parasitic capacitance was developed and discussed. The results showed that in the diffusion phase, the discharge area fraction grew quickly with voltage and caused a significant drop in plasma impedance and burning voltage. As the applied voltage increased, the discharge area fraction tended to saturate, the burning voltage slowly rose, and a lot of micro-discharges with greater diameters were present on the dielectric surface during the saturation phase.

Effect of Sn Addition on Anode Properties of SiO<i><sub>x</sub></i> in Sodium-Ion Batteries

Our group has investigated the properties of lithium-ion battery anodes fabricated using Sn/SiOx (SiOx is a mixed phase of Si clusters and amorphous SiO2 matrix). The addition of Sn improves the conductivity of the SiO2 matrix, while the formation of the Li+-conductive Li2Si2O5 phase in the SiO2 matrix improves Si utilization. The charge–discharge cycle life is also extended. In this study, Sn-doped SiOx has been used to fabricate the anode of a sodium-ion battery, and its charge–discharge properties are evaluated. The addition of 3 wt% Sn to SiOx improves the cycle property, as revealed by charge–discharge tests. X-ray diffraction analysis confirmed that the Na+-conductive Na2Si2O5 phase is formed during the charging and discharging processes. These results indicate that adding Sn improves the electronic conductivity of SiO2, and Na2Si2O5 facilitated the movement of Na in the SiO2 matrix. Thus, the utilization of Si is enhanced, and a high discharge capacity is achieved.

Molten salt synthesis of disordered spinel CoFe2O4 with improved electrochemical performance for sodium-ion batteries.

Sodium-ion (Na-ion) batteries are currently being investigated as an attractive substitute for lithium-ion (Li-ion) batteries in large energy storage systems because of the more abundant and less expensive supply of Na than Li. However, the reversible capacity of Na-ions is limited because Na possesses a large ionic radius and has a higher standard electrode potential than that of Li, making it challenging to obtain electrode materials that are capable of storing large quantities of Na-ions. This study investigates the potential of CoFe2O4 synthesised via the molten salt method as an anode for Na-ion batteries. The obtained phase structure, morphology and charge and discharge properties of CoFe2O4 are thoroughly assessed. The synthesised CoFe2O4 has an octahedron morphology, with a particle size in the range of 1.1-3.6 μm and a crystallite size of ∼26 nm. Moreover, the CoFe2O4 (M800) electrodes can deliver a high discharge capacity of 839 mA h g-1 in the first cycle at a current density of 0.1 A g-1, reasonable cyclability of 98 mA h g-1 after 100 cycles and coulombic efficiency of ∼99%. The improved electrochemical performances of CoFe2O4 can be due to Na-ion-pathway shortening, wherein the homogeneity and small size of CoFe2O4 particles may enhance the Na-ion transportation. Therefore, this simple synthetic approach using molten salt favours the Na-ion diffusion and electron transport to a great extent and maximises the utilisation of CoFe2O4 as a potential anode material for Na-ion batteries.

Acute Changes in Motor Unit Discharge Property After Concentric Versus Eccentric Contraction Exercise in Knee Extensor

Acute Changes in Motor Unit Discharge Property After Concentric Versus Eccentric Contraction Exercise in Knee Extensor

Production of runaway electrons and x-rays during streamer inception phase

Streamers play a key role in the formation and propagation of lightning channels. In nature streamers rarely appear alone. Their ensemble behavior is very complex and challenging to describe. For instance, the intricate dynamics within the streamer zone of negative lightning leaders give rise to space stems, which help advance the stepped-leader. Another example is how the increasing morphological complexity of sprites can lead to higher sprite current and greater energy deposition in the mesosphere. Insights into the complex dynamics of a streamer corona can be obtained from laboratory experiments that allow us to control the conditions of streamer formation. Based on simultaneous nanosecond-temporal-resolution photography, and measurements of voltage, current, and x-ray emissions, we report the characteristics of negative laboratory streamers in 88 kPa of atmosphere. The streamers are produced at peak voltages of 62.2 ± 3.8 kV in a point-to-plane discharge gap of 6 cm. While all discharges were driven to the same peak voltage, the discharges occurred at different stages of the relatively slow voltage rise (177 ns), allowing us to study discharge properties as a function of onset voltage. The onset voltage ranged between 24 and 67 kV, but x-ray emissions were observed to only occur above 53 kV, with x-ray burst energies scaling quadratically with voltage. The average delay between the current pulse and x-ray emission was found to be 3.5 ± 0.5 ns, indicating that runaway electrons are produced during the streamer inception phase or no later than the transition stage, when the inception cloud is breaking into streamer filaments. During this short time span, runaway electrons can traverse the gap, hit the ground plate and produce bremsstrahlung x-ray photons. However, streamers themselves cannot traverse more than 3.5 mm across the gap, which supports the idea that runaway electron production is not associated to streamer connection to the ground electrode.

Motor Unit Discharge Characteristics and Conduction Velocity of the Vastii Muscles in Long-Term Resistance-Trained Men.

Adjustments in motor unit (MU) discharge properties have been shown after short-term resistance training; however, MU adaptations in long-term resistance-trained (RT) individuals are less clear. Here, we concurrently assessed MU discharge characteristics and MU conduction velocity in long-term RT and untrained (UT) men. Motor unit discharge characteristics (discharge rate, recruitment, and derecruitment threshold) and MU conduction velocity were assessed after the decomposition of high-density electromyograms recorded from vastus lateralis (VL) and vastus medialis (VM) of RT (>3 yr; n = 14) and UT ( n = 13) during submaximal and maximal isometric knee extension. Resistance-trained men were on average 42% stronger (maximal voluntary force [MVF], 976.7 ± 85.4 N vs 685.5 ± 123.1 N; P < 0.0001), but exhibited similar relative MU recruitment (VL, 21.3% ± 4.3% vs 21.0% ± 2.3% MVF; VM, 24.5% ± 4.2% vs 22.7% ± 5.3% MVF) and derecruitment thresholds (VL, 20.3% ± 4.3% vs 19.8% ± 2.9% MVF; VM, 24.2% ± 4.8% vs 22.9% ± 3.7% MVF; P ≥ 0.4543). There were also no differences between groups in MU discharge rate at recruitment and derecruitment or at the plateau phase of submaximal contractions (VL, 10.6 ± 1.2 pps vs 10.3 ± 1.5 pps; VM, 10.7 ± 1.6 pps vs 10.8 ± 1.7 pps; P ≥ 0.3028). During maximal contractions of a subsample population (10 RT, 9 UT), MU discharge rate was also similar in RT compared with UT (VL, 21.1 ± 4.1 pps vs 14.0 ± 4.5 pps; VM, 19.5 ± 5.0 pps vs 17.0 ± 6.3 pps; P = 0.7173). Motor unit conduction velocity was greater in RT compared with UT individuals in both VL (4.9 ± 0.5 m·s -1 vs 4.5 ± 0.3 m·s -1 ; P < 0.0013) and VM (4.8 ± 0.5 m·s -1 vs 4.4 ± 0.3 m·s -1 ; P < 0.0073). Resistance-trained and UT men display similar MU discharge characteristics in the knee extensor muscles during maximal and submaximal contractions. The between-group strength difference is likely explained by superior muscle morphology of RT as suggested by greater MU conduction velocity.

ESTIMATION OF POWER DEPOSITION IN ICP REACTOR

In the present paper, the power deposited in the inductively coupled radiofrequency (RF) discharges is investigated by a two-dimensional fluid model. The discharge process was sustained in Ar / O2 gases mixture with 50:50 percentage of mixture volume. The discharge properties in the mixture obtained. An operating RF frequency of 13.56 MHz and applied voltage of 20 kV are simulated. A simple known international design of the reactor was chosen with 5 turn coil. Input power of the reactor was 1500 W. This numerical study done using plasma multiphysics model. Results show that the power deposition shows enhancement in behavior as the pressure increased. Keywords: ICP Plasma, Ar Gas, O2 Gas, Power Deposition, Electric Potential

Characterization of an atmospheric pressure plasma jet producing the auroral transition O(1S) to O(1D)

We present a detailed characterization of an atmospheric pressure plasma jet that produces the metastable oxygen states O(1S) and OD) with emission of the ‘auroral’ green line. The device used 99.999 pure argon as a working gas for the plasma generation. Optical emission spectroscopy was used to understand the active species present in the plasma jet and to infer the mechanism of O(1S) creation and destruction. The continuum spectrum was used in conjunction with a method based on machine learning for determining the arbitrary electron probability distribution function. Discharge and plasma properties were estimated from Lissajous plots and using calculations with the BOLSIG+ software. The metastable oxygen forms for all operating parameters of the plasma jet system in a linear electrode configuration. The camera images provided information of the overall plasma jet behavior as parameters were altered. While the metastable oxygen was produced for every iteration, the plasma jet behavior changed considerably when the powered and grounded electrodes are switched. Small admixtures of oxygen and nitrogen were introduced in the plasma jet to understand the kinetic processes of metastable oxygen destruction and the 557.7 nm auroral line. This behavior has implications for plasma reactive chemistry in fundamental areas such as auroral physics as well as technological applications of plasmas.

Study of the Neon Dielectric Barrier Discharge on a Capacitively Coupled Radio Frequency at a Low Pressure with Metastable Atom Density: Effect of the Pressure

We study the neon dielectric barrier discharge with metastable atom density on a capacitively coupled radio frequency at a pressure of about 4–12 Torr. The transport parameters of neon are dependent on the electron energy, and their range is about 0.04–50 eV. A one-dimensional fluid model and the drift-diffusion theory are used to describe the neon dielectric barrier discharge. The effect of the gas pressure on the properties of neon dielectric barrier discharge is presented for the cycle-averaged regime. It is shown that the particle densities, electric potential, and metastable atom density increase with the pressure. In addition, the surface charge concentration and the gap voltage increase as well.

Conjugation of soy protein isolate with carboxymethyl cellulose through dielectric barrier discharge (DBD) plasma

The present study aimed to evaluate the physicochemical properties of dielectric barrier discharge (DBD) plasma grafted carboxymethyl cellulose (CMC) and soy protein isolate (SPI). Therefore, the mixture of SPI and CMC was treated at 16, 18 and 20 kV for 5, 10 and 15 min with DBD plasma. The results of FTIR, XRD, FESEM and SDS-PAGE confirmed the SPI-CMC conjugate formation after plasma treatment, and a glycation degree of about 21 % was obtained after 15 min treatment at 18 kV. Significantly higher levels of emulsifying activity and stability, as well as solubility, were obtained for the conjugates, as compared with the SPI-CMC mixture. Also, the smaller droplet sizes were observed in emulsions obtained from conjugate produced at 18 kV for 5 min, which had the most stability after 14 days of storage at 4 °C. Eventually, it was detected that DBD plasma could graft SPI and CMC in a short time.

Lower motor unit discharge rates in gastrocnemius lateralis, but not in gastrocnemius medialis or soleus, in runners with Achilles tendinopathy: a pilot study.

Deficits in muscle performance could be a consequence of a reduced ability of a motor neuron to increase the rate in which it discharges. This study aimed to investigate motor unit (MU) discharge properties of each triceps surae muscle (TS) and TS torque steadiness during submaximal intensities in runners with Achilles tendinopathy (AT). We recruited runners with (n = 12) and without (n = 13) mid-portion AT. MU discharge rate was analysed for each of the TS muscles, using high-density surface electromyography during 10 and 20% isometric plantar flexor contractions. MU mean discharge rate was lower in the gastrocnemius lateralis (GL) in AT compared to controls. In AT, GL MU mean discharge rate did not increase as torque increased from 10% peak torque, 8.24 pps (95% CI 7.08 to 9.41) to 20%, 8.52 pps (7.41 to 9.63, p = 0.540); however, in controls, MU discharge rate increased as torque increased from 10%, 8.39 pps (7.25-9.53) to 20%, 10.07pps (8.89-11.25, p < 0.001). There were no between-group difference in gastrocnemius medialis (GM) or soleus (SOL) MU discharge rates. We found no between-group differences in coefficient of variation of MU discharge rate in any of the TS muscles nor in TS torque steadiness. Our data demonstrate that runners with AT may have a lower neural drive to GL, failing to increase MU discharge rate to adjust for the increase in torque demand. Further research is needed to understand how interventions focussing on increasing neural drive to GL would affect muscle function in runners with AT.

Influence of B-field on the characteristics of pulsed spark discharges in water

Spark discharges in water have great potential for use in various technological fields, including pollutant degradation, precision micromachining, and nanomaterial production. However, the large-scale application of these discharges is limited by the complexity of the implicated physical and chemical phenomena, which cannot be easily controlled. In this study, we assess the effect of an external B-field on the electrical characteristics of multiple successive discharges, as well as on the erosion of the electrode. In addition to the B = 0 condition, two configurations of the B-field are investigated: B-parallel and B-perpendicular to the electrode axis, both at the magnitude of 125 mT. The obtained results demonstrate that discharge electrical characteristics and electrode erosion are significantly affected by the B-field. Using a W electrode, the highest and lowest discharge currents are measured in the case of B-perpendicular and B = 0, respectively. Meanwhile, the highest erosion volume is obtained in the case of B = 0. To assess the influence of electrode nature and magnetic properties on the discharges, the results obtained using W (paramagnetic) electrodes were compared to those obtained with Ni (ferromagnetic). The comparison shows that the discharge electrical data are tightly distributed when the Ni electrode is utilized, regardless of the B-condition, whereas the data obtained with the W electrode exhibit significant statistical variations in the presence of the B-field. Overall, the data reported herein indicate that the electrical properties of a spark discharge may be varied and controlled by applying an external B-field.

Mechanical property and cutting performance of CNTs reinforced cBN cutting tools by spark plasma sintering

Due to the poor strength and toughness of cubic boron nitride tool, it is easy to have poor tool durability and chipping during machining. In order to solve this problem, carbon nanotubes (CNTs) reinforced cubic boron nitride (cBN) tool was fabricated by spark plasma sintering (SPS). The results show that the uniformly dispersed CNTs enhance the discharge property of the composite powders during SPS sintering, accelerate the material densification process, and improve the sintering effect of cBN. When the sintering temperature was 1475 °C, the fracture toughness and flexural strength of the tool with 0.50 wt% CNTs are 7.16 MPa·m1/2 and 635 MPa, respectively, which are 13.7 % and 75.4 % higher than that of the tool without CNTs. The improvement of mechanical properties of CNTs reinforced cBN tool materials was mainly due to the effect of CNTs drawing, bridging and grain refinement. In the cutting of 45 carbon steel, the effective cutting distance of the tool with 0.50 wt% CNTs was 16,000 m, which was 33.3 % higher than that of the tool without CNTs. The addition of CNTs can improve the abrasion resistance of the tool and machining quality of the workpiece.

Effect of Porous Catalyst Support on Plasma-Assisted Catalysis for Ammonia Synthesis.

We report on the effect of catalyst support particle porosity on the conversion of NH3 synthesis from N2 and H2 in a coaxial dielectric barrier discharge (DBD) plasma reactor. The discharge was created using an AC applied voltage with the reactor at room temperature and near atmospheric pressure (550 Torr). Two different particles of almost equal diameter (∼1.5 mm)─porous silica (SiO2) ceramic beads (average pore size: 8 nm) and smooth, nonporous soda lime glass beads─were compared in the DBD reactor. As the pore size in the SiO2 particles was smaller than the Debye length, penetration of the plasma into the pores of the particles was unlikely; however, reactive species generated in the plasma outside the particles could diffuse into the pores. The N2 conversion and energy yield of NH3 increased with applied voltage for both particle types, and these values were consistently higher when using the SiO2 beads. Discharge and plasma properties were estimated from Lissajous plots and using calculations with the BOLSIG+ software. The effect of these two different catalyst supports on the physical properties of the discharge was negligible. High resolution optical emission spectra revealed that the concentrations of N2+, atomic N, and atomic H (Hα, Hβ) in the plasma discharge were lower with the porous SiO2 beads than with the glass beads at every applied voltage tested. This indicates that these active species participate in heterogeneous reactions at support particle surfaces and that the larger surface area presented by the porous particles led to higher rates of depletion of these intermediates and a higher rate of ammonia synthesis.

Electrochemical properties and discharge performance of Mg-3Sn-xCa alloy as a novel anode for Mg-air battery

In this work, Ca was introduced into the Mg-3Sn alloy as an environmentally friendly element. The electrochemical performance and discharge properties of Mg-3Sn-xCa (x = 0, 0.2, 0.6, 1.0 wt%) as an anode for Mg-air battery were investigated. The results revealed that the Mg-3Sn-1.0Ca alloy exhibited the best activity and the optimum discharge performance, reaching a voltage of 1.46 V at 2.5 mA cm−2 and a peak specific energy of 1277 mA h g−1 at 20 mA cm−2. The Ca element increases the activity of Mg-3Sn through phase modulation, which results in the presence of a large number of cracks in the discharge products and facilitates the maintenance of high and stable voltages. In addition, the refined grains increase the grain boundaries and expand the contact area with the cathode phase, which dissolves the Mg matrix sufficiently and reduces the chunk effect.

Tailoring corrosion and discharge performance of Mg anode by corrosion inhibitor

The effect of various amounts of 5-sulfosalicylic acid (SSA) on the corrosion and discharge property of pure magnesium (Mg) is studied systematically. It was found that SSA plays a vital role in regulating the dissolution kinetics of the substrate and re-deposition rate of discharge product at the metal/electrolyte interface. Low concentration of SSA can be used as corrosion inhibitor for active Mg surface as it chelates with impurity element (Fe3+), while high concentration of SSA increases dissolution rate of Mg since large amount of SSA also acts as complexing agent for the dissolved Mg2+. In terms of discharge performance, addition of 0.1 M SSA improves the utilization efficiency and lowers the discharge potential in the meanwhile under different current densities. The anode demonstrates low and stable discharge potential (-1.83 V) for 10 h at 2.5 mA cm−2 in SSA containing electrolyte. Localized corrosion of the substrate has been significantly facilitated during discharge test. “Thorn-like effect” has been observed for the first time for Mg with addition of complexing agent.

Nanosecond pulsed discharge dynamics during passage of a transient laminar flame

This work presents an experimental study of a nanosecond repetitively pulsed dielectric barrier discharge interacting with a transient laminar flame propagating in a channel of height near the quenching distance of the flame. The discharge and the flame are of comparable size, and the discharge is favoured at a location where it is coupled with the reaction zone and burnt gas. The primary goal is to determine how the discharge evolves on the time scale of the flame passage, with the evolution driven by the changing gas state produced by the moving flame front. This work complements the large body of work investigating the effect of plasma to modify flame dynamics, by considering the other side of the interaction (how the discharge is modified by the flame). The hot gas produced by the combustion had a strong effect on the discharge, with the discharge preferentially forming in the region of hot combustion products. The per-pulse energy deposited by the discharge was measured and found to increase with the size of the discharge region and applied voltage. The pulse repetition frequency did not have a direct impact on the per-pulse energy, but did have an effect on the morphology and size of the discharge region. Two distinct discharge regimes were observed: uniform and filamentary (microdischarges). Higher pulse repetition frequencies and faster-cooling combustion products were more likely to transition to the filamentary regime, while lower frequencies and slower-cooling combustion products maintained a uniform regime for the entirety of the time the discharge was active. This regime transition was influenced by the ratio of the time scale of fluid motion to the pulse repetition rate (with no noticeable impact caused by the reduced electric field), with the filamentary regime preferentially observed in situations where this ratio was small. This work demonstrates the importance of considering how the discharge properties will change due to combustion processes in applications utilizing plasma assistance for transient combustion systems.

Calculation of the Surface Charge Concentration on the Argon’s Dielectric Barrier Discharge: Effect of the Amplitude Voltage

In this work, we study the argon dielectric barrier discharge with metastable atom density on capacitively coupled radio frequency at a pressure of 1 Torr. The parameter transports of argon are depending on the electron energy and their range is about of 0.04-42 eV. A one-dimensional fluid model and the drift-diffusion theory are used to describe the argon dielectric barrier discharge. The effect of the amplitude voltage on the properties of argon dielectric barrier discharge is presented on the cycle-averaged regime. Especially the electron temperature, electric potential and metastable atom density illustrate our results on figures of merits. Consequently, these quantities increase with the increasing of the amplitude voltage. Besides surface charge concentration and the gap voltage increase too.

Optimization of energy storage properties in (1 − x)Na0.5Bi0.5TiO3-xSr0.7La0.2TiO3-relaxed ferroelectric ceramics

Ferroelectric materials are considered to be the most competitive energy storage materials for applications in pulsed power electronics due to excellent charge–discharge properties. However, the low energy storage density is the primary problem limiting their practical application. In this study, (1[Formula: see text])Na[Formula: see text]Bi[Formula: see text]TiO3–[Formula: see text]Sr[Formula: see text]La[Formula: see text]TiO3[(1[Formula: see text])NBT–[Formula: see text]SLT] ferroelectric ceramics are found to exhibit excellent energy storage performances through a synergistic strategy. As the SLT concentration increases, the relaxation characteristic increases significantly and the breakdown strength increases dramatically from 150 kV/cm to 220 kV/cm. The recoverable energy storage density of the 0.55NBT–0.45SLT ceramic is 2.86 J/cm3 with an energy storage efficiency of 88% under an electric field of 220 kV/cm. Furthermore, the ceramic with [Formula: see text] = 0.45 mol exhibited excellent energy storage stability in the ranges of 20–180[Formula: see text]C (temperature) and 1–125 Hz (frequency). These excellent properties demonstrate the potential of (1[Formula: see text])NBT–[Formula: see text]SLT ceramics when used as dielectric capacitors in pulsed power systems.