Breakdown Phenomena Research Articles

A Self‐Recovery Triboelectric Nanogenerator with High Breakdown Resistance for Water Wave Energy Harvesting

AbstractTriboelectric nanogenerator (TENG) harvesting ocean wave energy is an effective method to alleviate the energy crisis. However, the breakdown phenomenon is ubiquitous for the TENG with a large area of dielectric layer, which not only limits the output and reliability but also highly risks the device failure. Here, a self‐recovery TENG (SR‐TENG) featuring high breakdown resistance is designed, which achieves a high output charge density of 4.24 mC m−2 with the assistance of the charge excitation technique, as well as maintains 87% of the initial output even after six times fierce electric breakdown, minimizing the negative impacts of the breakdown phenomenon. Besides, based on the SR‐TENG, a symmetric anaconda‐shaped self‐charge excited TENG is designed for effective water wave energy harvesting. This work not only sheds light on the self‐recovery phenomenon in TENGs, but also represents a significant step toward the high performance TENG featuring high breakdown resistance and ultimate stability, accelerating the practical applications of TENG for blue energy harvesting.

Impact of trapped charge on the breakdown phenomena in HfO2/Al2O3 - based memory capacitors

Impact of trapped charge on the breakdown phenomena in HfO₂/Al₂O₃ - based memory capacitors

High performance Au/mix-phase MgZnO/Ga-doped ZnO/In heterojunction solar-blind UV detector with small work voltage

High performance UVC (220 nm–280 nm) detectors with low work voltage is key problem in wide application of UVC optoelectronic device. Here, Au/MgZnO/Ga-doped ZnO/In heterojunction detector is made with both high UVC sensitivity mix-phase MgZnO and high carrier density Ga-doped ZnO conductive layers. The heterostructure detector possess relative high response(0.36A/W)at 254 nm deep UV light without bias voltage. The avalanche breakdown phenomenon within the heterojunction detector, introduced high deep UV response (1390.3 A/W at 3.3 μW/cm2 230 nm) of the Au/MgZnO/Ga-doped ZnO/In heterojunction detector under 5 V bias voltage. The high response of Au/MgZnO/Ga-doped ZnO/In heterojunction detector under low work voltage, is not only much higher than MSM structure MgZnO detector under bias voltage over 25 V, but also higher than reported deep UV detector under small bias voltage. In addition, because of different internal breakdown mechanism, the peak response position of the Au/MgZnO/Ga-doped ZnO/In heterojunction detector is located at shorter wavelength position compared with MSM structure MgZnO detector. Therefore, Au/MgZnO/Ga-doped ZnO/In heterojunction detector is an ideal device structure in low voltage driven detector with relative high response at short wavelength UV light.

Investigation of Breakdown Phenomenon and Long-Pulse Improvement in Ku-Band TTO

Investigation of Breakdown Phenomenon and Long-Pulse Improvement in <i>Ku</i>-Band TTO

Design perspectives of a system identification approach of the NATO AVT-316 multi-swept wing aerodynamics

Air supremacy requires enhanced maneuvering capabilities at high angles of attack and even beyond the stall angle. High angle-of-attack (high-α) maneuverability can be achieved using swept wings and tailored leading-edge shapes to replace local and disorganized flow separation with controlled separation-induced leading-edge vortices (LEV). Strong leading-edge vortices delay the stall to higher angles and generate a non-linear lift increment up to the angle of attack where the jet-type flow structure of LEV changes to a reversed-flow bubble (vortex breakdown phenomenon). A multi-swept wing configuration has the potential to delay the vortex breakdown to even higher angles as the vortices formed over the front wing can energize vortices formed over the main wing and lead to vortex merging. This article is focused on understanding the unsteady interactions between multiple leading edge vortices formed over multi-swept wing configurations in the subsonic speed regime. Specifically, this article investigates the aerodynamic characteristics of wings being evaluated under the initiative of the NATO STO AVT-316 Task Group. Highly refined meshes, and the use of hybrid turbulence models such as Detached Eddy Simulations (DES) and Delayed DES are required to accurately resolve the vortical flows over these wings. Simulating all flow conditions of interest is a computationally expensive approach. A system identification method was therefore proposed to rapidly and accurately generate aerodynamic models of these wings. The method uses a novel piece-wise chirp (constant amplitude and increasing frequency) motion as an input signal (training maneuver). The motion computational cost is equivalent to the cost of six static CFD simulations, however it can predict aerodynamic responses of the wings over a wide range of angles of attack. The method has been tested for double and triple delta wings. Some design considerations are provided based on predicted flow features and aerodynamic data. Prediction results with different turbulence models, sting geometries, grid resolutions and an adaptive mesh refinement approach are provided.

Destructive dielectric breakdown of 2D muscovite mica

This study investigates the destructive breakdown (DBD) phenomenon in the van der Waals gate dielectric 2D muscovite mica (4–12 nm thick), focusing on its electrical reliability as a gate dielectric material. Capacitor test structures were electrically stressed, and the resulting impact on the physical structure was analyzed using atomic force microscopy. The volume of material removed in a DBD event is found, and the energy required (Ereq) to vaporize the volume was calculated. It is found that Ereq is proportional to the average electrical energy dissipated in the capacitor during breakdown (BD), indicating a direct correlation between damage caused during DBD and the current flow at BD location. In contrast to other thin film dielectrics, the 2D mica is highly susceptible to DBD even at very low current density (&amp;lt;1 A/cm2) and the abrupt, destructive BD more resembles that of thick film dielectric breakdown. An explanation for these finding is proposed in which intercalated K+ ions agglomerate around defects generated by the electrical stressing such that the defect density increases substantially in the local vicinity of BD locations, which leads to increased current and associated Joule heating after the BD event.

From the quantum breakdown model to the lattice gauge theory

The one-dimensional quantum breakdown model, which features spatially asymmetric fermionic interactions simulating the electrical breakdown phenomenon, exhibits an exponential U(1) symmetry and a variety of dynamical phases including many-body localization and quantum chaos with quantum scar states. We investigate the minimal quantum breakdown model with the minimal number of on-site fermion orbitals required for the interaction and identify a large number of local conserved charges in the model. We then reveal a mapping between the minimal quantum breakdown model in certain charge sectors and a quantum link model which simulates the U(1) lattice gauge theory and show that the local conserved charges map to the gauge symmetry generators. A special charge sector of the model further maps to the PXP model, which shows quantum many-body scars. This mapping unveils the rich dynamics in different Krylov subspaces characterized by different gauge configurations in the quantum breakdown model.

Numerical simulations of the region of possible sprite inception in the mesosphere above winter thunderstorms under wind shear

Transient luminous events (TLEs) is the collective name given to mesospheric electrical breakdown phenomena occurring in conjunction with strong lightning discharges in tropospheric thunderstorms. They include elves, sprites, halos, and jets, and are characterized by short lived optical emissions, mostly of red (665 nm) and blue (337 nm) wavelengths. Sprites are caused by the brief quasi-electrostatic field induced in the mesosphere, mostly after the removal of the upper positive charge of the thundercloud by a +CG, and they have been recorded above most of the lightning activity centers on Earth. In wintertime, there are just a few areas where lightning occurs, and of those, sprites have been observed over the Sea of Japan, the British Channel, and the Mediterranean Sea. Unlike their summer counterparts, winter thunderstorms tend to have weaker updrafts and as a result, reduced vertical dimensions and compact charge structures, whose positive and negative centers are located at lower altitudes. These storms are often susceptible to significant wind shear and as a result may exhibit a tilted dipole charge structure and a lateral offset of the upper positive charge relative to the main negative charge. We present results of numerical simulations using a three-dimensional explicit formulation of the mesospheric quasi-electrostatic electrical field following a lightning discharge from a typical mid-latitude winter thunderstorm exhibiting tilt due to wind shear and evaluate the regions of possible sprite inception. Our results show, as numerous observations suggest, that sprites can be shifted a large distance from the location of the parent +CG in the direction of the shear and will occur over a larger region compared with non-sheared storms.

Breakdown of argon by a train of high-repetition long-wave-infrared pulses from a free-electron laser oscillator.

This study presents an experimental demonstration of laser-induced breakdown in argon, employing a free-electron laser with a wavelength of 10 μm and a repetition rate of 2.856 GHz. Despite the fluence of individual laser pulses being an order of magnitude smaller than the breakdown threshold, cascade ionization developed in the pulse train, leading to breakdown. The breakdown probability within a finite pulse train increases with gas pressure, and it was notably enhanced in a gas chamber with poor cleanliness. Numerical simulations of cascade ionization replicated the experimental results. The simulation revealed that breakdown phenomena are governed by the balance between avalanche multiplication of electrons within laser pulses and electron diffusion during pulse intervals.

Thermal and electric field driven rf breakdown precursor formation on metal surfaces

The phenomenon of electric breakdown poses serious challenges to the design of devices that operate in high electric field environments. Experimental evidence points toward breakdown events that are accompanied by elevated temperatures and dark current spikes, which is attributed to high-asperity nanostructure formation that enhances the local electric field and triggers a runaway process. However, the exact mechanistic origin of such nanostructures under typical macroscopic operational conditions of electric field and magnetic-field-mediated heating remains poorly understood. In this work, we simulate the evolution of a copper surface under the combined action of the electric fields and elevated temperatures. Using a mesoscale curvature-driven surface evolution model, we show how a copper surface can undergo a type of dynamical instability that naturally leads to the formation of sharp asperities in realistic experimental conditions. Exploring the combined effect of fields and temperature rise, we identify the critical regimes that allow for the formation of breakdown precursors. The results show that thermoelastic stresses, while not essential, can significantly lower the critical electric field required for runaway surface instability, which is consistent with experimental observations that thermal effects can increase breakdown rates. Published by the American Physical Society 2024

Investigation of a rotating stall in a supercritical CO2 centrifugal compressor

Due to the nonlinear behavior of carbon dioxide properties at its critical point and the size effect of the supercritical carbon dioxide (S-CO2) centrifugal compressor, the stall causation mechanism differs between the S-CO2 centrifugal compressor and a conventional air compressor. The comprehension of the induced principle of the S-CO2 compressor rotating stall holds immense significance in enhancing stall margin and efficiency. This paper employs unsteady simulations to investigate the causes of the impeller rotating stall in the S-CO2 centrifugal compressor. The results show that the leading edge breakdown vortex (LEBV) formed by the tip leakage vortex (TLV) breakdown and the reverse flow in the passage are the reasons for blocking the passage and ultimately causing the rotating stall of the impeller. The migration motion of the LEBV not only induces the leading edge spillage phenomenon but also influences the intensity of the tip leakage flow (TLF) in adjacent passages, causing the propagation of the TLV breakdown phenomenon in the opposite direction to that of impeller rotation. The TLV undergoes intermittent breakdown in flow field, which is influenced by variations in TLF intensity. Additionally, there is a preceding process of breakdown-induced vortex formation and disappearance prior to TLV fragmentation.

Characterization of CuAg Alloys with Low Ag Concentrations.

Copper-based alloys designed to combine high electronic and thermal conductivities with high mechanical strength find a wide range of applications in different fields. Among the principal representatives, strongly diluted CuAg alloys are of particular interest as innovative materials for the realization of accelerating structures when the use of high-gradient fields requires increasingly high mechanical and thermal performances to overcome the limitations induced by breakdown phenomena. This work reports the production and optical characterization of CuAg crystals at low Ag concentrations, from 0.028% wt to 0.1% wt, which guarantee solid solution hardening while preserving the exceptional conductivity of Cu. By means of Fourier Transform Infrared (FTIR) micro-spectroscopy experiments, the low-energy electrodynamics of the alloys are compared with that of pure Cu, highlighting the complete indistinguishability in terms of electronic transport for such low concentrations. The optical data are further supported by Raman micro-spectroscopy and SEM microscopy analyses, allowing the demonstration of the full homogeneity and complete solubility of solid Ag in copper at those concentrations. Together with the solid solution hardening deriving from the alloying process, these results support the advantage of strongly diluted CuAg alloys over conventional materials for their application in particle accelerators.

Simulation study of secondary electron multiplication on microwave dielectric window

The phenomenon of dielectric breakdown in microwave windows restricts the enhancement of power capacity in high-power microwave systems. This process starts with the secondary electron multiplication, which significantly influences the breakdown threshold. In this study, we developed 3D simulation models for rectangular, circular, and annular windows to examine the secondary electron multiplication on their surfaces using the particle-in-cell method. Through a comparative study, we assessed the effects of various input powers, initial emission current densities from particle sources, and magnetic fields. Our findings reveal that the initial field emission current density, which ranges from 10−9 to 109 μA/cm2, marginally affects electron multiplication. However, increased microwave power (with power density ranging from 0.1 to 18.75 MW/cm2) accelerates this multiplication. Strong magnetic fields and non-uniform electric fields further enhance the electron multiplication process.

A study of hollow-cathode electron beam source surface flashover discharge and suppression

As surface flashover discharge limits the performance of hollow-cathode electron beam sources, this work systematically investigates the surface flashover discharge in the hollow-cathode discharge process based on electrostatic field simulations. Experimental research is conducted on designing and investigating hollow cathode discharge cavities featuring structures to prevent surface flashover, both single- and multi-gap. Theoretical analysis found that the vacuum surface flashover discharge will cause an abnormal breakdown phenomenon along the wall of the insulating sleeve. The surface flashover, once formed, would develop dramatically, thus suppressing the formation of hollow-cathode discharge and becoming the main form of discharge. To eliminate the abnormal flashover breakdown, an effective suppression structure is designed regarding the triple point of the surface flashover. Through the special design, the triple points in the corners are always hidden by recessing the corner of the insulator in a notch. Moreover, corrugated structures along the insulating surface are studied, and the proper rectangular slots are designed in the inner insulating surface. The experimental results also indicate that after adopting the insulation scheme, the breakdown voltage of the discharge cavity and its working stability are greatly improved.

Customizing superior surface insulation properties of polymeric dielectric via in-plane molecular chain orientation

Surface flashover is a common breakdown phenomenon on material surfaces for which surface charge migration property, determined by surface composition and molecular chain structure, is crucial. Precise modulation of charge migration property by simple and efficient methods to improve surface flashover voltage is the goal in industry. Here, in-plane molecular chain orientation (MCO) modulation by uniaxial stretching was proposed to achieve this goal and investigate the intrinsic mechanism of charge migration on flashover. Flashover voltage and accompanying leakage current, performed with electrodes oriented at varying angles to the MCO direction, show a consistent trend, which skillfully reveals that the facilitated charge migration is favorable for improving flashover voltage. When the stretching ratio is 3.5, the flashover voltage along the stretching direction (SD) increases by up to 48.7%, while the in-plane minimum flashover voltage remains essentially unchanged with the change in stretching ratio. Molecular chain segment motion properties along different directions further elucidate that the surprising improvement of flashover voltage along SD is primarily due to the MCO that promotes intra-chain charge migration. This work provides a new perspective on anti-flashover modification of polymeric dielectric and will promote the development of surface flashover mechanisms.

The kinetic theory of cathode plasma expansion in a spatially non-uniform geometric configuration of a vacuum diode

This paper presents a theoretical explanation for the occurrence of anomalous ion acceleration in vacuum diodes, leading to the expansion of cathode plasma towards the anode, a characteristic phenomenon of vacuum breakdown. The explanation is derived from first principles based on equations of collisionless physical kinetics, using the example of an axisymmetric vacuum diode. The proposed theoretical interpretation convincingly demonstrates that the primary mechanism behind the anomalous ion acceleration of cathode plasma is the collisionless motion of ions in a self-consistent electric field.

Particle-in-cell/Monte Carlo collision simulation on gap breakdown characteristics of under the conditions of hot-electrode and high-temperature gas medium in low-voltage circuit breaker chamber

The gas composition inside the low-voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the back-arc breakdown and post-arc re-breakdown phenomena occurring inside the LVCB chamber are categorized as the breakdown in the case of high-temperature gas gap of hot electrodes, for which a particle-in-cell/Monte Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization, and other effects, and simulation studies have been conducted. The simulation results show that the gap breakdown is mainly caused by the high-temperature hot free background gas and the cathode thermal electron emission. A plasma sheath layer is formed at the cathode during the breakdown process, and the electric field strength in the sheath layer is higher than that in other regions. With the development of the streamer to the cathode, the thickness of the sheath layer becomes narrower and the electric field strength increases, and finally, a discharge plasma channel is formed in the gap.

Towards the understanding of vortex breakdown for improved RANS turbulence modeling

A triple-delta wing configuration in transonic conditions has been investigated numerically, explicitly focusing on the leading-edge vortices during sideslip flow. Several shock waves manifest over the fuselage, leading to vortex-shock interactions. The primary focus of the analysis centers on the vortex breakdown phenomenon and its underlying causes. The flow field obtained from different turbulence modeling approaches is compared. This study aims to identify the limitations of a standard one-equation model in dealing with such complex applications. It explores physical and modeling reasons leading to the model's inaccuracies. The impact of turbulence treatment on the numerical results is explored, discussing turbulence-related variables. A novel and straightforward modification to the one-equation turbulence model is then introduced and assessed compared to experimental and computational data. The proposed model appears promising for enhancing the accuracy of the one-equation Reynolds Averaged Navier-Stokes outcomes.

Study of partial discharge and breakdown phenomena at triple junctions under various conditions of pressure and temperature

The presence of a triple junction constitutes a potential source of failure in many industrial applications. The reinforcement of the local electric field due to differences in relative permittivity facilitates the formation of partial discharges (PD) which weaken the insulation system and eventually lead to complete breakdown. Additionally, severe environmental conditions (temperature, pressure) associated with certain applications (e. g. nuclear or aeronautical sector) should be considered because of their influence on discharge phenomena occurring at triple junctions. In this study, the behaviour of partial discharge inception voltage (PDIV) and of breakdown (flash-over) voltage (BIV) is compared in the case of a triple junction with an aluminium oxide disc as a solid insulator when the system is heated up to 400 °C. While the PDIV decreases strongly for temperatures above 300 °C, this effect disappears for the BIV. It is proposed that this behaviour is due to the fact that relative permittivity of the aluminium oxide disc increases with temperature at low frequencies, but remains relatively stable at high frequencies, regardless of the temperature.

The interelectrode breakdown mechanism and discharge characteristics of the electrospray thruster

In the actual working process of electric thrusters based on high-voltage electric fields, the discharge breakdown phenomenon is universal and complex, and such phenomena will have a significant impact on the thruster structure, working state and spacecraft system. In order to study the interpolar discharge breakdown characteristics of ionic liquid electrospray thrusters, a basic electrospray model and test system were constructed, and the change curves of discharge characteristic parameters such as breakdown voltage, threshold current, breakdown voltage frequency and so on in the range of 7×10−3~105 Pa with air pressure and transmitter inner diameter were obtained, and the air pressure range that the electrospray model could work in normally was calibrated. The results show that the breakdown voltage characteristic curve of the electrospray model has typical minimum characteristics, and the minimum values all appear around 80 Pa. Lowering the air pressure below 10−2 Pa can effectively increase the breakdown threshold between the poles and the emission current, thereby obtaining a larger voltage regulation range, and when the air pressure is reduced to 7×10−3 Pa, the breakdown can reach more than 3200 V. The 60-μm inner diameter emitter performed better in the discharge experiment, and the breakdown threshold, emission current and operating area range were better than the slightly larger inner diameter emitter under the same working conditions.