Current Breakdown Research Articles

Recycling of dielectric electroactive materials enabled through thermoplastic PDMS.

In the green transition, actuators and generators play an essential role in the development of sustainable solutions across a broad range of applications. In this context, dielectric transducers are advocated as one of the most promising solutions in terms of effectiveness, lifetime and running costs. However, they are classically produced as sandwich structures, whereby a cross-linked dielectric material is placed between two compliant electrodes. From a materials consumption viewpoint, this is problematic, since it will inherently result in a loss of material during production as well as inhibit the recycling of expended systems when their life comes to an end. Herein, we present a cleaning method employing surfactants and sonication to remove electrodes from the surface of the dielectric material. By applying a thermoplastic silicone elastomer as the dielectric material, it is possible to reprocess the material by hot-pressing, and to prepare new actuators after the rinsing process. This effectively shows that recycling production scrap, for example, is possible. By comparing the cleaned material with a directly recycled material, it is clear that cleaning removes a critical amount of metals from the material and enables recycling for at least five cycles. Comparatively, a directly recycled material is prone to a high leakage current and premature electronic breakdown after only two cycles. This simple cleaning process, in combination with use of a thermoplastic dielectric material, enables less waste from production as well as the possibility of reclaiming and recycling materials in general.

A Review on Palm Oil-Based Nanofluids as a Future Resource for Green Transformer Insulation System

Alternative transformer oil has been investigated universally in past years. Different types of vegetable oil have been proposed and evaluated as replacements for conventional transformer oil (mineral oil) due to increasing exploitation and depleting petroleum reserves. In response to growing concern about global environmental and sustainable issues, this article discusses the suitability of palm oil (PO) and palm oil-based nanofluids (PO-N) as alternative transformer oils. A brief discussion of environmental concerns is provided in this paper, and the detailed properties of PO are thoroughly addressed. The electrical performance (alternating current breakdown voltage and lightning impulse breakdown voltage), physical behaviour (viscosity, flash point, and fire point), tan delta, and relative permittivity of PO and PO-N are also discussed in this paper. Based on reliable data and research, it has been proven that refined, bleached, deodorised palm oil (RBDPO) has been determined to be the most promising type of PO when compared to others. Furthermore, when CuO nanoparticles are added to RBDPO with the use of CTAB surfactant, the AC breakdown voltage increases by 173.42 % compared to RBDPO without CuO. However, there is still scope for further improvement in nanofluid stability. In addition to these studies, future research should focus on other aspects such as ageing studies, partial discharge breakdown voltage, etc. PO has interesting properties that make the industry and scientific community take notice.

Making new history: Contemporary art and the temporal orientations of climate change in Oceania

This article explores artistic production in the region of Oceania that resists the ahistorical and future-oriented temporality of climate change discourse, as it perpetuates colonial structures of power by denying Indigenous futures and ignoring the violent histories that have led to the current climate breakdown. In the video poem Anointed (2018), prominent climate justice activist Kathy Jetñil-Kijiner strategically combines spoken word poetry with visual montage in order to situate Cold War nuclear tests by the US military within the same temporal plane as rising sea levels currently threatening the Marshall Islands. Katerina Teaiwa’s exhibition Project Banaba (2017) similarly mobilizes archival imagery in order to visualize the genealogical relationship between Banabans and the settler landscapes of Aotearoa New Zealand and Australia. Sean Connelly’s architectural and design practice in Hawaiʻi Futures, an ongoing digital design project that engages with the threats of sea level rise and coastal erosion in Hawaiʻi, problematizes linear formations of time and favours a future structured around cyclical, ecological time instead. Interacting with vastly different sites, strategies and temporalities, these three multidisciplinary projects provide critical alternatives to the ahistorical framing of colonial climate change in Oceania and thus play a crucial role in constructing a more just future.

Effects of massive electromagnetic pulses on the structural and chemical properties and leaching efficiency of eudialyte concentrate

Scanning electron microscopy (SEM) and infrared spectroscopy (IR) were used to study the influence of high-power nanosecond electromagnetic pulses (HPEMP) and dielectric barrier discharges (DBD) in air at the atmospheric pressure on the structural and chemical properties of eudialyte. The spectral data analysis has shown that highintensity electric fields initiate mineral surface fracturing due to the weakening and/or breaking of bonds in the structural fragments of the mineral framework (presumably, Si10O27, and Si9MO30). According to the SEM data, HPEMPs cause sample surface strength reduction with the formation of new surface reliefs in the range from parallel (texp = 30 s) to polygonal fractured shapes (texp = 60 and 90 s), depending on the electromagnetic pulse exposure time texp. Eudialyte grain micromorphology after the treatment under DBD conditions is distinctively characterized by the presence of imprints of electrical current breakdown microchannels of up to 3–4 μm, with practically no microcracks or other defects occurring on the mineral surface. The intensifying effect of high-power electromagnetic pulses on the process of eudialyte concentrate acid leaching has been experimentally established. Zirconium recovery into the pregnant solution is improved by 3.4 to 4.3 % through HPEMP pretreatment and by 4.0 % through DBD exposure, with the total recovery of rare earth elements increasing by 1.1 to 1.7 %.This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation, project No. 13.1902.21.0018 (agreement No. 075-15-2020-802).

An Axially Continuous Graphene-Copper Wire for High-Power Transmission: Thermoelectrical Characterization and Mechanisms.

The demand for high-power electrical transmission continues to increase with technical advances in electric vehicles, unmanned drones, portable devices, and deployable military applications. In this study, significantly enhanced electrical properties (i.e., a 450% increase in the current density breakdown limit) are demonstrated by synthesizing axially continuous graphene layers on microscale-diameter wires. To elucidate the underlying mechanisms of the observed enhancements, the electrical properties of pure copper wires and axially continuous graphene-copper (ACGC) wires with three different diameters are characterized while controlling the experimental conditions, including ambient temperature, gases, and pressure. The study reveals that the main mechanism that allows the application of extremely large current densities (>400 000 A cm-2 ) through the ACGC wires is threefold: the continuous graphene layers considerably improve: 1) surface heat dissipation (224% higher), 2) electrical conductivity (41% higher), and 3) thermal stability (41.2% lower resistivity after thermal cycles up to 450°C), compared with pure copper wires. In addition, it is observed, through the use of high-speed camera images, that the ACGC wires exhibit very different failure behavior near the current density limit, compared with the pure copper wires.

Characterizations of a nanocomposite biochemical-sensing membrane of γ-APTES incorporated with silica nanoparticles prepared by ultrasonic liquid atomizer spray

Large-area and uniformly distributed 3-aminopropyltriethoxysilane (γ-APTES) incorporated with poly-dimethylsiloxane-treated hydrophobic fumed silica nanoparticles (NPs) sensing membranes with different mixed ratios were deposited by using ultrasonic liquid atomizer (ULA) spray. Nanoscale current–voltage (I–V) characteristics of the deposited membranes were then characterized by using conductive atomic force microscopy. It is found that the ULA-sprayed γ-APTES plus NPs (γ-APTES + NPs) membrane has smaller leakage current and higher breakdown voltage than does the ULA-sprayed pure γ-APTES membrane. Excellent glucose sensing performances are found when using the deposited ULA-sprayed γ-APTES + NPs as sensing membrane on polysilicon wire sensor. Further sensing performance enhancement was obtained as the γ-APTES + NPs membrane was subjected to UV illumination. Our experiment’s results confirmed that the ULA spray is a promising method for large area deposition of γ-APTES + NPs membrane and that it can be utilized for biomedical sensor applications.

“Breakdown” of stratified electrical explosion products: Plasma development and its mechanical effect

The physical image of breakdown dynamics inside striations is depicted. High-speed photography along with electrophysical and spectral diagnostics reveals three modes for plasma development in Cu wire explosion: current cutoff, initial breakdown (with quenching), and main breakdown (with re-strike). The growth of spatial heterogeneity by electrothermal instability (ETI) provides a stratified structure before the initial breakdown. The characteristic wavelength of the strata is <100 μm for thinner wires (d = 90/130 μm) but in mm level for thicker ones (d = 240/290 μm). By increasing the stored energy from 200 to 220 J, the 290-μm-diameter Cu wire experiences a transition from current cutoff to initial breakdown, with a deposited energy of 2.64 and 3.10 eV/atom. Although the energy is not sufficient to vaporize the wire, axial micro-plasma-channels develop among bright layers (higher temperature but lower density), forming a crossed low-conductive “plasma-network” connecting two electrodes. If the residual energy is enough, the scenario (main breakdown) would be similar to “streamer-spark transition” and enhance the expansion of discharge channel. Two paralleled wires are exploded simultaneously but only one establishes main breakdown; therein, three stronger shock waves are detected, namely, two for vaporization and one for breakdown.

Polypropylene‐based soft ternary blends for power cable insulation at low‐to‐high temperature

AbstractAlthough cross‐linked polyethylene (XLPE) has been widely used as a power cable insulation material in electricity infrastructure for decades, it is necessary to find alternatives that exhibit higher performance than XLPE to meet the increasing demand of the industry. To this end, polypropylene (PP) ternary blends that are soft and exhibit high temperature stability were fabricated by melt blending isotactic PP, ethylene‐1‐octene polyolefin elastomer and ethylene‐propylene random copolymer. These blends exhibited improved higher impact resistance at low temperatures (−40°C) and room temperature than pristine iPP. The blends were mechanically stable even when the temperature was increased to ~120°C, unlike XLPE that exhibited rapid degradation of its modulus above ~90°C. Moreover, the soft ternary blends exhibited increased direct current volume resistivity and breakdown strength. Our work realizes the development of high‐performance insulators for power cables that can be used over a wide range of temperatures from cold to hot environments.

Illumination Dependence of Reverse Leakage Current in Silicon Solar Cells

In the modeling of PV modules under shading and low illumination, a complete description of reverse bias behavior at the cell level is critical to understanding module response. This is particularly important when dealing with high voltage configurations such as tandem and shingled modules. Current simulation studies often do not account for the effects of incident light when dealing with operating voltages approaching cell breakdown. In this article, we investigate the illumination dependence of leakage current at the onset of breakdown in crystalline silicon solar cells. A study of the most popular cell technologies in the market today reveals a light induced effect under reverse bias that is prominent for p-type and small for n-type cells. Additionally, this effect is found to be larger in mono c-Si than multi c-Si cells. Because this phenomenon is not captured in current breakdown models such as Bishop's equation, we propose a split-cell model to describe partial shading in p-type cells. The outlined approach divides the cell into two parallel regions and is advantageous for its procedural simplicity as well as its ability to generalize effects from complex shading profiles.

Computational analysis of direct current breakdown process in SF6 at low pressure

The breakdown of SF6 gas at low pressure is of vital importance to both aerospace and microelectronics industries. However, the breakdown characteristics of SF6 in direct current at low pressure are still seldom studied. In this work, one-dimensional implicit particle-in-cell/Monte-Carlo collision algorithm is used to study the entire direct current breakdown process of low-pressure SF6. The ion-molecule collision, recombination, and external circuit are considered in the model. According to the results, the breakdown process can be divided into three stages: pre-breakdown stage, breakdown stage, and post-breakdown stage. In the pre-breakdown stage, the cathode sheath is not yet formed so the constant electric field exists in the entire area. In the breakdown stage, the formation mechanism of the cathode sheath is analyzed and the electrodes as a whole changes from capacitive to resistive, sharing the voltage with the external resistance. In the post-breakdown stage, the continued growth of positive ions leads to the formation of a thin anode sheath, which further causes the negative plasma potential, different from electropositive gas. The energy production terms including heating power and secondary electron emission (SEE) power are equal to the energy loss terms including collision loss power and boundary loss power, where collision loss power and boundary loss power are almost equal, while SEE power is negligible. In the final, plasma parameters gradually evolve to the last steady-state.

Modified Molecular Chain Displacement Analysis Employing Electro-Mechanical Threshold Energy Condition for Direct Current Breakdown of Low-Density Polyethylene.

In an HVDC environment, space charge accumulated in polymeric insulators causes severe electric field distortion and degradation of breakdown strength. To analyze the breakdown characteristics, here, the space charge distribution was numerically evaluated using the bipolar charge transport (BCT) model, considering the temperature gradient inside the polymeric insulator. In particular, we proposed an electro-mechanical threshold energy condition, resulting in the modified molecular chain displacement model. The temperature gradient accelerates to reduce the breakdown strength with the polarity-reversal voltage, except during the harshest condition, when the temperature of the entire polymeric insulator was 70 °C. The energy imbalance inside the insulator caused by polarity-reversal voltage reduced the breakdown strength by 82%. Finally, this numerical analysis model can be used universally to predict the breakdown strength of polymeric insulators in various environments, and help in evaluating the electrical performance of polymeric insulators.

An improved design for e-mode AlGaN/GaN HEMT with gate stack β-Ga2O3/p-GaN structure

To improve the performance of the conventional p-GaN gate AlGaN/GaN high electron mobility transistors (HEMTs), we propose an improved design for e-mode AlGaN/GaN HEMT with a gate stack β-Ga2O3/p-GaN structure. The simulated results show that the proposed device increases the threshold voltage and the gate breakdown voltage in comparison with the conventional p-GaN gate HEMT due to the use of the β-Ga2O3 layer, which has an additional β-Ga2O3/p-GaN heterojunction and decreases the strength of electric field in the gate region. Moreover, the proposed device exhibits a lower off-state leakage current, which can be attributed to the less donor ionized density. In addition, the impacts of the β-Ga2O3 layer thickness are investigated. There is a trade-off between β-Ga2O3 layer thickness and the performance of the proposed device, including threshold voltage, gate breakdown, and saturation drain current.

Regulation of PANI nanofiber conductivity and its influence on the DC dielectric properties of LDPE

To study the effect of electrical conductivity of nanomaterials on the space charge accumulation in low density polyethylene (LDPE), doped and dedoped polyaniline (PANI) nanofibers with the same diameter and different conductivity were prepared and added into LDPE. The PANI nanofibers and nanocomposites were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscope, thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD) and differential scanning calorimeter (DSC). The space charge distribution, direct current (DC) conductivity and DC breakdown strength of the nanocomposites were measured. The addition of either PANI nanofibers enhanced the crystallization, improved the space charge distribution and reduced the conductivity of LDPE. Doped PANI nanofibers had higher conductivity and could more effectively suppress space charge accumulation than dedoped PANI nanofibers. However, doped PANI nanofibers reduced the DC breakdown strength of PANI/LDPE nanocomposites. Overall, dedoped PANI nanofibers were superior for DC dielectric properties of LDPE.

Simulation and Modeling of Time-Resolved X-Ray Detector for the Saturn Accelerator

We present the technology-aided computer design (TCAD) device simulation and modeling of a silicon p-i-n diode for detecting time-dependent X-ray radiation. We show that the simulated forward and reverse breakdown current–voltage characteristics agree well with the measured data under nonradiation environment by only calibrating carrier lifetimes for the forward bias case and avalanche model critical fields for the reverse bias condition. Using the calibrated parameters and other nominal material properties, we simulated the radiation responses of the p-i-n diode and compared with experimental data when the diode was exposed to X-ray radiation at Sandia’s Saturn facility and the Idaho State University (ISU) TriMeV facility. For Saturn’s Gaussian dose-rate pulses, we show three findings from TCAD simulations. First, the simulated photocurrents are in excellent agreement with the measured data for two dose-rate pulses with peak values of $1.16 \times 10 ^{10}$ and $1.88 \times 10 ^{10}$ rad(Si)/s. Second, the simulation results of high dose-rate pulses predict increased delayed photocurrents with longer time tails in the diode electrical responses due to excess carrier generation. Third, simulated peak values of diode radiation responses versus peak dose rates at different bias conditions provide useful guidance to determine the dose-rate range that the p-i-n diode can reliably detect in experiment. For TriMeV’s non-Gaussian dose-rate pulse, our simulated diode response is in decent agreement with the measured data without further calibration. We also studied the effects of device geometry, recombination process, and dose-rate enhancement via TCAD simulations to understand the higher measured response in the time after the peak dose-rate radiation for the p-i-n diode exposed to TriMeV irradiation.

High-fidelity modeling of breakdown in helium: initiation processes and secondary electron emission

Understanding the role of physical processes contributing to breakdown is critical for many applications in which breakdown is undesirable, such as capacitors, and applications in which controlled breakdown is intended, such as plasma medicine, lightning protection, and materials processing. The electron emission from the cathode is a critical source of electrons which then undergo impact ionization to produce electrical breakdown. In this study, the role of secondary electron yields due to photons (γ ph) and ions (γ i) in direct current breakdown is investigated using a particle-in-cell direct simulation Monte Carlo model. The plasma studied is a one-dimensional discharge in 50 Torr of pure helium with a platinum cathode, gap size of 1.15 cm, and voltages of 1.2–1.8 kV. The current traces are compared with experimental measurements. Larger values of γ ph generally result in a faster breakdown, while larger values of γ i result in a larger maximum current. The 58.4 nm photons emitted from He(21P) are the primary source of electrons at the cathode before the cathode fall is developed. Of the values of γ ph and γ i investigated, those which provide the best agreement with the experimental current measurements are γ ph = 0.005 and γ i = 0.01. These values are significantly lower than those in the literature for pristine platinum or for a graphitic carbon film which we speculate may cover the platinum. This difference is in part due to the limitations of a one-dimensional model but may also indicate surface conditions and exposure to a plasma can have a significant effect on the secondary electron yields. The effects of applied voltage and the current produced by a UV diode which was used to initiate the discharge, are also discussed.

Composite‐channel In 0. 17 Al 0 . 83 N /In 0. 1 Ga 0 . 9 N / GaN /Al 0. 04 Ga 0 . 96 N high electron mobility transistors for RF applications

In this work, we present the high performance of composite channel based In0.17Al0.83N/In0.1Ga0.9N/GaN/Al0.04Ga0.96N high electron mobility transistors (HEMTs) on a sapphire substrate. A numerical simulation is carried out for the proposed and conventional GaN channel-based HEMTs using TCAD. Due to the strong polarization of InAlN/InGaN, enhanced electron confinement and high electron mobility of composite channel based proposed device shows excellent DC and RF characteristics with improved linearity than conventional GaN channel based HEMTs. A 55 nm T-gate device demonstrates 4.45 A/mm drain current density (IDS) at VGS = 0 V, 0.7 S/mm stable transconductance (GM) for a wide range of gate bias, and excellent FT/Fmax of 274/288 GHz. Benefiting from the Al0.04Ga0.96N buffer (back-barrier), the device shows a very low sub-threshold drain leakage current and high breakdown voltage (VBR) of 43.5 V. The combination of high FT/Fmax, stable transconductance, and high breakdown voltage of the proposed HEMTs shows the great promise for high power and wide-bandwidth millimeter-wave applications.

DC Breakdown Characteristic of Air Gap With Water Droplets

Under rain conditions, the sliding water droplets on the insulator’s surface shorten the air insulation distance between the sheds and even cause a flashover. In order to study the mechanism of air gap breakdown with rain droplets, the breakdown process was recorded by a high-speed camera and the influences of rain water droplets (conductivity, volume, and position) were studied. The experimental results show that the impact of the water droplets on the direct current (dc) breakdown voltage is related to the air gap length. The shorter the air gap, the greater the drop of the flashover voltage. Although water conductivity does not affect the breakdown voltages, the arc development path is related to it. This research has significance for revealing the rain flashover mechanism of insulators.

Reliability Analysis on TiN Gated NMOS Transistors

Compared to poly Si gate, metal gate has no gate depletions and experiences inversion capacitance gain, which makes an advantage for devices scaling. In this paper, we investigated the gate oxide leakage current and Time Dependent Dielectric Breakdown (TDDB) characteristics of TiN and poly Si electrodes with a 3.5 to 5 nm SiO2 dielectric thickness range. According to the Transmission Electron Microscope (TEM) analysis there is difference in oxide thickness. The SiO2 thickness of TiN gate electrode has been reduced by ~0.25 nm, considerably because of a scavenging effect. We normalized the reduced SiO2 thickness with an electrical oxide field, and there were no differences between the two electrodes in gate leakage current, accumulation breakdown voltage (BV), and accumulation TDDB lifetime. Therefore, we found the scavenging effect of TiN electrodes seems to affect little the leakage current and TDDB reliability of SiO2 dielectric. On the other hand, the BV and TDDB lifetime of TiN electrode in the inversion region are little bit better than that of the poly electrode. We think this differences are originated from the difference between TiN/SiO2 and poly Si/SiO2 interfaces.

Penerapan Data Mining Dalam Meningkatkan Mutu Perawatan dan Perbaikan Perlengkapan Alat-Alat Kapal Laut Menerapkan Metode K-Means Clustering

This study aims to propose in carrying out sailing activities on the KN. Arcturus ship every week, so that maintenance and maintenance activities need to be carried out properly and scheduled so as not to interfere with ongoing production activities. The current machine breakdown is still relatively high and requires a long repair time, what is proposed is preventive maintenance using the Clustering technique. The method used is K-Means Clustering. By using this method, the data that has been obtained can be grouped into several clusters, based on the similarity of these data, so that data that has the same characteristics are grouped into one cluster and those that have different characteristics are grouped into another cluster. We can use the abundance of data to find hidden information from these data. In order to find out the hidden information from these data, it is necessary to process the data. The data processing process is also known as data mining. With this grouping it will know the results of the analyzed data.

A deterministic breakdown model for dielectric interfaces subjected to tangential electric field

The contact area between solid insulations, namely solid–solid interfaces, affect the dielectric characteristics of an entire insulation system. With the theoretical and experimental studies covered in this paper, we intend to investigate the effects of the elastic modulus, interface contact pressure, and surface smoothness/roughness on the tangential alternating current (AC) breakdown strength of contact surfaces at dielectric interfaces that undergo a tangential electric field. Four distinct solid dielectric specimens with various elastic modulus values were employed. The interfaces between the same materials were subjected to AC breakdown and partial discharge (PD) tests at different contact pressure values. In addition, the interface surfaces were polished using four different sandpapers of various grits to scrutinize the effect of surface roughness. A deterministic model built around the tribology of solid surfaces was proposed to determine the sizes of the interfacial cavities and to simulate the 3D displacement and deformation of the surface protrusions based on the surface roughness, contact pressure, elastic modulus, and hardness of an interface. The estimated sizes of cavities and contact areas were then coupled with a comprehensive breakdown model that addressed the cavity discharge and breakdown of contact areas, separately. Finally, the results by the model were correlated with the results of the AC breakdown and PD experiments to elucidate not only how cavities were linked at solid–solid interfaces but also the effects of roughness, elasticity, contact pressure, and gas pressure inside of the cavities.