Electrical Breakdown Process Research Articles

Review of electron emission and electrical breakdown in nanogaps

With the continual miniaturization of electronic devices, there is an urgent need to understand the electron emission and the mechanism of electrical breakdown at nanoscale. For a nanogap, the complete process of the electrical breakdown includes the nano-protrusion growth, electron emission and thermal runaway of the nano-protrusion, and plasma formation. This review summarizes recent theories, experiments, and advanced atomistic simulation related to this breakdown process. First, the electron emission mechanisms in nanogaps and their transitions between different mechanisms are emphatically discussed, such as the effects of image potential (of different electrode's configurations), anode screening, electron space-charge potential, and electron exchange-correlation potential. The corresponding experimental results on electron emission and electrical breakdown are discussed for fixed nanogaps on substrate and adjustable nanogaps, including space-charge effects, electrode deformation, and electrical breakdown characteristics. Advanced atomistic simulations about the nano-protrusion growth and the nanoelectrode or nano-protrusion thermal runaway under high electric field are discussed. Finally, we conclude and outline the key challenges for and perspectives on future theoretical, experimental, and atomistic simulation studies of nanoscale electrical breakdown processes.

Physical factors influencing dielectric polymer electrical breakdown by generated space charges under a strong electric field

The present work constitutes a contribution in studying the breakdown phenomenon generated by the electron–hole dynamics during their bipolar transport in a polyethylene film subjected to strong dc electrical field. This contribution is addressed to the analysis of the determining physical parameters effects in the electrical breakdown process within a low density polyethylene LDPE film. Indeed, the previous modeling and analysis works for breakdown phenomenon are still limited in this topic. In this regard, using our model of bipolar transport in the charged dielectrics, we present, in this article, a more complete analysis affecting more physical parameters influencing the breakdown transient dynamic process. Theses parameters are namely the applied field, the carrier mobility, the sample temperature, the injection barrier and the coefficients associated with the bipolar transport physical mechanisms. Briefly, our results highlight the existence of two classes of inverse effects and allowed us to establish new power laws. Our validation with previous work is addressed to the effect of the sample thickness on the breakdown field.

The sensitivity analysis of dynamic electric breakdown damage model and simulation of granite by high voltage electric pulse

The use of high-voltage electrical pulse (HVEP) technology for improving the rate of penetration in deep, complex formations has been reported; however, its rock fragmentation mechanism is not fully understood, and the parametric design of electric drilling tools is not perfect. This research paper realized the whole process of single-pulse HVEP rock-breaking by using the electric breakdown model, combining circuit parameter coupling, Kirchhoff’s law, electric breakdown criterion, heat transfer process, and solid mechanical field. The sensitivity simulation of HVEP rock-breaking parameters, which considers the structural parameters of pulse power supply, the deterioration of rock during the electrical breakdown process, the correlation between dynamic dielectric strength of rock and time, and rock heterogeneity, is analyzed. The simulation results indicate that the shape of the plasma channel has little relationship with the pulse peak voltage, and the rock-breaking volume of a single pulse is positively related to the pulse peak voltage; the electrode spacing is positively correlated with the breakdown voltage of the rock in a first-order function shape and has a positive correlation with the failure volume; large electrode spacing can promote HVEP rock-breaking; electrode tilt has little effect on the minimum breakdown voltage and failure volume, and its optimal design should be combined with the flow field analysis of the electric bit structure; the heterogeneity index of granite results in breakdown voltage amplitudes within 3 kV and differences in the fragmentation effect of HVEP. The research results can be used as theoretical support for optimizing HVEP matching drilling tools.

Computational Simulation for Breakdown and Energy Storage Performances with Optimization in Polymer Dielectrics

AbstractThe breakthrough of energy storage technology will enable energy distribution and adaptation across space‐time, which is revolutionary for the generation of energy. Optimizing the energy storage performance of polymer dielectrics remains challenging via the physical process of electrical breakdown in solid dielectrics is hard to be intuitively obtained. In this review article, the application of computational simulation technologies is summarized in energy‐storage polymer dielectrics and the effect of control variables and design structures on the material properties with an emphasis on dielectric breakdown and energy storage performance are highlighted. The prediction and evaluation of material properties by combining various data analysis methods are reviewed. Finally, the outlook and challenges are discussed based on their current developments. This article covers not only an overview of the state‐of‐the‐art advances of breakdown modeling in energy‐storage polymer dielectrics but also the prospects that provide a new knob to synthesize high energy‐storage polymer dielectrics via computational simulation and a new research paradigm.

Quantum breakdown model: From many-body localization to chaos with scars

We propose a quantum model of fermions simulating the electrical breakdown process of dielectrics. The model consists of $M$ sites with $N$ fermion modes per site, and has a conserved charge $Q$. It has an on-site chemical potential $\mu$ with disorder $W$, and an interaction of strength $J$ restricting each fermion to excite two more fermions when moving forward by one site. We show the $N=3$ model with disorder $W=0$ show a Hilbert space fragmentation and is exactly solvable except for very few Krylov subspaces. The analytical solution shows that the $N=3$ model exhibits many-body localization (MBL) as $M\rightarrow\infty$, which is stable against $W>0$ as our exact diagonalization (ED) shows. At $N>3$, our ED suggests a MBL to quantum chaos crossover at small $W$ as $M/N$ decreases across $1$, and persistent MBL at large $W$. At $W=0$, an exactly solvable many-body scar flat band exists in many charge $Q$ sectors, which has a nonzero measure in the thermodynamic limit. We further calculate the time evolution of a fermion added to the particle vacuum, which shows a breakdown (dielectric) phase when $\mu/J<1/2$ ($\mu/J>1/2$) if $W\ll J$, and no breakdown if $W\gg J$.

The fragmentation mechanism of granite in electrical breakdown process of plasma channel drilling

Low rate of penetration (ROP) and high drilling cost are the key problems that encountered in hot dry rock (HDR) geothermal resources exploitation and utilization. Plasma channel drilling (PCD) is a potential technology which has the advantages of high rock-breaking efficiency and ROP. A detailed understanding of the rock-breaking of PCD is essential to optimize the electrical parameters and bit structure. Therefore, this paper uses the probabilistic evolution model and thermo-mechanical coupling model in PFC2D to reveal the generation of plasma channel trajectory and cracks in heterogeneous granite under the high-voltage electric pulse. The results show that increasing temperature on the plasma channel will not alter the trend of initiation and propagation of cracks, but simply reduces the time consumption of crack initiation. The quantity of intragranular shear cracks is always the largest, and they are mainly distributed around the channel. In addition, compared with plasma channels formed when complete electrical breakdown occurs, the maximum depth of the channels of partial electrical breakdown is larger under the same electrode gap. This study also includes an experimental program to examine the granite fragmentation and borehole generation caused by an electrode bit. The research results can provide new ideas and methods for improving the drilling efficiency of HDR formation, and help to design the structural of drill bits based on PCD technology.

The Utilization of a Coupled Electro-Thermal-Mechanical Model of High-Voltage Electric Pulse on Rock Fracture

Our research proposes a unique coupled electro-thermal-mechanical model that takes electric breakdown and heterogeneity into account to show the mechanism of rock fracturing under high-voltage electropulses. Using finite element numerical software, the process of high voltage electrical pulse injection into the rock interior for breakdown is described, and the formation law of plasma channels during the electrical breakdown process is comprehensively analyzed in conjunction with the conductor particles present within the rock. On the basis of electrical, thermal, and mechanical theories, a coupled multi-physical field numerical model of rock failure under the action of high-voltage electrical pulses is developed, and a random distribution model is utilized to simulate the potential occurrence of conductor particles in the rock. Innovative numerical model indicates plasma channel creation in the rock-crushing process. Prior to the formation of the plasma channel, the temperature and stress are approximately 103 k and 10-2 MPa, respectively. Once the plasma channel is formed, the temperature and stress increase abruptly in a short time, with the temperature reaching 104 k and the stress reaching 103 MPa or higher. In addition, it is revealed that the breakdown field strength is the essential factor in plasma channel creation. The heterogeneity of the particles within the rock and the fluctuation in electrode settings are also significant variables influencing the creation of channels. The presented model contributes to a better understanding of the mechanism of rock fragmentation during high-voltage electrical pulses, which has substantial implications for oil exploration and mineral extraction.

Thermal-elastic free energy driven electrical tree breakdown process in epoxy resin under temperature gradient

Thermal-elastic free energy driven electrical tree breakdown process in epoxy resin under temperature gradient

New evidence about the nature of plasma filaments in plasma accelerators of type plasma-focus

In this work, new evidence and information about both the origin and evolution of filamentary structures observed in the current sheath of a small plasma focus (PF) discharge are reported. The experiments were carried out in a small generator of low energy (multipurpose generator) at the PF configuration, under different operating conditions. These include different anode and insulator geometries, without return bars and in a high-performance regime of the generator at high pressures (10 mbar). The evolution of the plasma structures is characterized by means of refractive optical techniques. The electrical behavior of the discharge, as well as its performance, are monitored with conventional electrical diagnostics and neutron and x-ray detectors, respectively. Plasma filaments of the same species are present in all tested configurations, however, in experiments with larger effective anode length (and smaller anode radii), the plasma region containing the filaments moves away from the anode surface and remains confined in a region of the plasma sheath, such as a toroidal plasma belt, without reaching the top of the anode nor participating in the radial compression phase. According to images of the plasma sheath in its early phase, the filaments originate and evolve from a precursor annular plasma formed in the lower part of the anode next to the insulator, during the process of electrical breakdown. The local character that these dense-filamentary structures acquire in the evolution of the plasma sheath would discard the current-filament hypothesis. On the other hand, experiments performed in deuterium gas with anodes of larger effective lengths and without filaments in the radial compression phase allowed the production of neutrons and x-rays at a high performance.

"MODEL ACHIEVEMENT FOR IGNITION AND DEVELOPMENT OF STOCHASTIC DISCHARGE CHANNELS IN CONCRETE AND REINFORCED CONCRETE TAKING INTO ACCOUNT THE PROPERTIES OF THE MEDIUM AND THE GEOMETRY OF THE REINFORCING FRAME"

"The article develops a generalized model of electrodischarge action on concrete, which allows consistently describing phases of electro-explosion in condensed media: initiation and development of discharge channels, expansion, generation of shock waves, interaction of waves with the material being processed, deformation and destruction of solid materials. The model is based on a stochastic deterministic approach to the development of instability. processes associated with the distribution of the electric field, when mechanical stresses break. The flow of the process is considered deterministically on the basis of nonlinear integro-differential equations, local processes leading to the growth of the channel and cracks - stochastically. Equations describing the nature of the discharge development, the change of the channel resistance and its expansion are concordantly solved with the transition equations in the scheme of the real pulse generator. Expansion of the channel in the liquid is based on the law of conservation of energy, mass, pulse, equations of wave dynamics and allows to calculate the temporal and amplitude impact of shock waves from the channel on the barriers. The process of electrical breakdown of condensed dielectrics occurs with the development of a stochastically discharge structure, mainly determined by the emergence of highly conductive plasma channels. The development of the channel structure begins in the area of maximum field tension. In this case, the processes of phase transitions of a material directly determine the quantitative and qualitative processes of image of channels. As part of the study of the model, an analysis of the influence of the movement of electro-discharges on the redistribution of the electrostatic field, conditions leading to the direct formation of discharge channels, fracture formation and complete deformation was conducted. Keywords: model, electro-discharge device, stochastic-deterministic approach, electric field, mechanical voltage, shock wave, channel resistance, dielectric, pulse generator, differential equations."

A Comparison of Electrical Breakdown Models for Polyethylene Nanocomposites

The development of direct current high-voltage power cables requires insulating materials having excellent electrically insulation properties. Experiments show that appropriate nanodoping can improve the breakdown strength of polyethylene (PE) nanocomposites. Research indicates that traps, free volumes, and molecular displacement are key factors affecting the breakdown strength. This study comprehensively considered the space charge transport, electron energy gain, and molecular chain long-distance movement during the electrical breakdown process. In addition, we established three simulation models focusing on the electric field distortion due to space charges captured by traps, the energy gain of mobile electrons in free volumes, the free volume expansion caused by long-distance movement of molecular chains under the Coulomb force, and the energy gained by the electrons moving in the enlarged free volumes. The three simulation models considered the electrical breakdown modulated by space charges, with a maximum electric field criterion and a maximum electron energy criterion, and the electrical breakdown modulated by the molecular displacement (EBMD), with a maximum electron energy criterion. These three models were utilized to simulate the breakdown strength dependent on the nanofiller content of PE nanocomposites. The simulation results of the EBMD model coincided best with the experimental results. It was revealed that the breakdown electric field of PE nanodielectrics is improved synergistically by both the strong trapping effect of traps and the strong binding effect of molecular chains in the interfacial regions.

Numerical electric breakdown model of heterogeneous granite for electro-pulse-boring

The problems of cost, environmental protection and efficiency of hard rock fragmentation in petroleum exploration, drilling and other projects need to be solved urgently. Electro-pulse-boring (EPB) technology has attracted attention due to its advantages of low rock breaking energy consumption, low wear and low time cost. However, there is still no more accurate description model for EPB and rock fragmentation, and the existing models have limited guidance on the parameter optimization of EPB tools. This paper introduces an electric breakdown model, which realizes the whole electric breakdown process under a single high-voltage pulse by coupling the five fields: circuit field, current field, breakdown field, heat transfer field and solid mechanical field. The multi physics model comprehensively considers the circuit structure parameters of the electric impulse generator (EIG), the initiation and development of electric breakdown, the dependence of electric breakdown strength and time, and the heterogeneity of rock. The model results found that the breakdown channel originates from the weak electric strength in the rock, and the development of the channel is highly dependent on the heterogeneity of the rock medium. The rock fragmentation process with a single pulse is accompanied by local electric fragmentation and hydroelectric fragmentation, When the pulse voltage rise time (PVRT) is greater than 500 ns, the hydroelectric fragmentation mode is dominant. The temperature and thermal stress values of the discharge channel are consistent with the previous studies results, and the temperature distribution at the electrode tip is the highest, which shows that the ablation problem of the electrode in EPB process can not be ignored. This model has the potential to establish the relationship between rock-breakingparameters and rock-breaking efficiency of EPB, and can provide a practical method for the development and parameter optimization of EPB and rock breaking tools.

The effects of match circuit on the breakdown process of capacitively coupled plasma driven by radio frequency

The breakdown process of capacitively coupled plasma (CCP) in the presence of a matching network is rarely studied, even though it is the indispensable part of the most laboratory and industrial devices of CCP. Based on the method of Verboncoeur, the solution method of the general “L”-type match circuit coupled with a particle-in-cell/Monte Carlo code is deduced self-consistently. Based on this method, the electrical breakdown process of CCP is studied. Both the plasma parameters and the electric parameters of the matching network during the breakdown are given and analyzed. In the pre-breakdown phase, the entire circuit can be considered as a linear system. However, the formation of the sheath during breakdown significantly enhanced the capacitance of the discharge chamber, which changed the electric signal amplitude of the external circuit. With the stabilization of plasma, the equivalent capacitance of CCP increases, which continues to change the electrical signal until the steady-state is reached. Accompanied by plasma stabilization is the appearance of high-order harmonics of discharge current caused by the gradually oscillating CCP capacitance. The breakdown characteristics can be obviously affected by the capacitance of the matching network. In the case of a breakdown zone, some breakdowns with special characteristics can be obtained by choosing the different capacitors. These works might be a reference for understanding the interaction between the plasma and the external circuit during the breakdown process and how to modulate the gas breakdown by controlling the external circuit.

Analysis of soil impulse discharge characteristics based on optical‐electrical synchronous observation

The impulse performance of grounding electrodes highly depends on soil impulse discharge characteristics. The analysis of soil discharge dynamic process images is helpful to understand the impulse discharge mechanism of grounding electrodes. This paper designed an optical-electrical synchronous observation platform for simulate soil (SiO2 crystal) discharge, and discharge dynamic process images is obtained by high-speed camera. Through analysing breakdown delay time and thermal power before breakdown, it is found that soil impulse discharge is mainly an electrical breakdown process, and soil ionization intensity is positively correlated with the light intensity emitted by whole soil sample in breakdown channel development stage. The time from voltage application to the occurrence of ionization is defined as initial ionization delay time (IIDT). Using image processing technology, the change curve of optical image average grayscale value with time in the process of soil discharge is obtained, and a calculation method of IIDT is proposed by comparing the difference between average grayscale value curve and background image average grayscale value. Experiment results show that IIDT is negatively correlated with impulse voltage, particle size and water content, but not with salt content.

Conductive SiO2/HfO2 distributed Bragg reflector achieved by electrical breakdown and its application in GaN-based light emitters

Owing to the excellent optical reflectivity with wavelength tunability, dielectric distributed Bragg reflectors (DBRs) have attracted considerable interest in GaN-based light emitters. Yet, the non-conductive nature of the dielectric DBRs prevents current from passing through, leading to a current crowding effect and hampering dielectric DBRs from unlocking their full potential. In this paper, a conductive dielectric DBR was fabricated utilizing the electrical breakdown (EBD) technique. With the help of optical simulations, excellent optical properties were demonstrated by optimizing the structural designs with a high reflectivity of 98.3% at 450 nm based on 5.5 pairs SiO2/HfO2 DBRs. The outstanding electrical behaviors after the EBD process were verified by current–voltage curves and conductive atomic force microscopy characterization. Moreover, conductive mechanisms of this type of dielectric DBR were elaborated by comparing the EBD behaviors with different metal electrodes, suggesting that metal filaments play an important role in forming the conducting channels. Besides, 450 nm-emission with conductive 5.5 pairs SiO2/HfO2 DBR was successfully prepared, which proves that a conductive DBR can be successfully applied to GaN-based light-emitting devices. The conductive DBR presented in this work contributes to the acceleration of the development of high-power GaN-based solid-state light emitters.

Experimental study on the effect of high-voltage electrical pulses on the nanoscale pore structure of coal

Research on electric pulse fracturing technology has led to significant advances in the field of coal mine fracturing and permeability enhancement. However, few studies have focused on nanoscale pores. In this study, we investigate the effect of high-voltage electric pulses on the nanoscale pore structure of coal using a custom-built experimental device. The results revealed that the high-voltage electric pulse breakdown process decreased the specific surface area, pore volume, and number of micropores (pore size < 2 nm) and increased the specific surface area, pore volume, and number of macropores (pore size > 50 nm). In particular, the number of pores that were>100 nm increased significantly. Field emission scanning electron microscopy revealed that macropores were widely distributed on the surface of the post-breakdown coal samples and were connected to each other. The number of mesopores (pore size = 2–50 nm) were not significantly altered as they were supplemented by the formation of new pores while simultaneously expanding into larger pores. The electric pulse breakdown process increased the total pore volume, average pore size and pore connectivity, decreased structural complexity, and significantly improved the nanoscale pore structure of the coal samples. Raman spectroscopy further confirmed this observation. From a molecular point of view, post breakdown, the aromatic system in the coal sample dehydrogenated, the directly connected methyl groups broke, the carbon atoms were arranged in a more orderly manner, and the microcrystalline structure gradually improved, thereby providing suitable conditions for convenient gas desorption and diffusion.

Investigation on Charge Transport in Polypropylene Film under High Electric Field by Experiments and Simulation

The charge transport in polypropylene was studied under DC electric fields at different temperatures. By the experimental measurement and simulation of the BCT model, we studied conduction currents, breakdown strength, and space charge distribution. In particular, the conduction characteristics under high temperature and high field, especially the conduction characteristics before the breakdown, were studied by systematic experiments, and the conduction characteristics and the breakdown mechanism were further studied by simulation. The results show that in the process of measuring conduction currents until breakdown, both high temperature and high electric field will promote charge transport. However, the free volume will increase at high temperature, which will easily lead to faster charge transport and breakdown. In the breakdown process at different temperatures, there are different breakdown mechanisms. At 20–60 °C, the electric breakdown process has mainly occurred in polypropylene film, and the breakdown strength is almost unchanged. At 80 °C, electric breakdown and thermal breakdown act together, and the charge transport is faster, and the breakdown field becomes smaller. Finally, we conclude that thermal stress plays a very important role in charge transport. In a high-temperature environment, the volume expansion of polypropylene will promote charge transport, and the insulation of polypropylene capacitor films will be damaged.

On the Mechanism of High-Voltage Pulsed Fragmentation from Electrical Breakdown Process

On the Mechanism of High-Voltage Pulsed Fragmentation from Electrical Breakdown Process

Electrical Breakdown Mechanism of Transformer Oil with Water Impurity: Molecular Dynamics Simulations and First-Principles Calculations

Water impurity is the essential factor of reducing the insulation performance of transformer oil, which directly determines the operating safety and life of a transformer. Molecular dynamics simulations and first-principles electronic-structure calculations are employed to study the diffusion behavior of water molecules and the electrical breakdown mechanism of transformer oil containing water impurities. The molecular dynamics of an oil-water micro-system model demonstrates that the increase of aging acid concentration will exponentially expedite thermal diffusion of water molecules. Density of states (DOS) for a local region model of transformer oil containing water molecules indicates that water molecules can introduce unoccupied localized electron-states with energy levels close to the conduction band minimum of transformer oil, which makes water molecules capable of capturing electrons and transforming them into water ions during thermal diffusion. Subsequently, under a high electric field, water ions collide and impact on oil molecules to break the molecular chain of transformer oil, engendering carbonized components that introduce a conduction electronic-band in the band-gap of oil molecules as a manifestation of forming a conductive region in transformer oil. The conduction channel composed of carbonized components will be eventually formed, connecting two electrodes, with the carbonized components developing rapidly under the impact of water ions, based on which a large number of electron carriers will be produced similar to “avalanche” discharge, leading to an electrical breakdown of transformer oil insulation. The water impurity in oil, as the key factor for forming the carbonized conducting channel, initiates the electric breakdown process of transformer oil, which is dominated by thermal diffusion of water molecules. The increase of aging acid concentration will significantly promote the thermal diffusion of water impurities and the formation of an initial conducting channel, accounting for the degradation in dielectric strength of insulating oil containing water impurities after long-term operation of the transformer.

Flexible Strain Sensor with Tunable Sensitivity via Microscale Electrical Breakdown in Graphene/Polyimide Thin Films.

Carbon-based piezoresistive nanomaterials are widely used for the fabrication of flexible sensors. Although our previous work demonstrated that an electrical breakdown (EBD) process can endow a graphene/polyimide (G/PI) composite with piezoresistivity, the formation of EBD-induced electrical traces with high consistency in bulk nanocomposites remains a technical challenge. With the aim of developing highly sensitive flexible strain sensors using a batch fabrication process, we introduce herein a microscale EBD (μEBD) method to form localized piezoresistors with diverse shapes in a G/PI thin film. The results of scanning electron microscopy, Raman spectroscopy, and electromechanical tests indicate that high piezoresistivity is derived from the high porosity of the carbonized conductive traces generated by the μEBD process. The gauge factor of the μEBD-treated G/PI strain sensor is over 20 times greater than that of the as-prepared G/PI film, and the sensitivities of the strain sensors can be tuned by varying the applied current in the μEBD process. We also demonstrate the potential applications of μEBD-treated G/PI strain sensors in the fields of finger gesture detection, sound pressure measurement, and airflow sensing.