Air Breakdown Research Articles

Superior Charge Density of Triboelectric Nanogenerator via Trap Engineering

AbstractTriboelectric nanogenerator (TENG) offers a novel approach for converting high‐entropy mechanical energy into electrical energy, yet achieving high charge density remains critical. Optimizations using dielectrics with high specific capacitance have mitigated air breakdown, but charge loss within dielectrics persists as a limiting factor. Here, based on poly(vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) (P(VDF‐TrFE‐CFE)) with high specific capacitance, (P(VDF‐TrFE‐CFE)) composites’ trap density and energy are engineered using high‐polarity interfaces from barium titanate (BTO) nanoparticles and dense chain segment stacking induced by electrostatic interaction with polyetherimide (PEI) to enhance charge retention capability. With modified high interfacial traps, an ultrahigh charge density of 9.23 mC m−2 is achieved in external charge excitation (ECE) TENG using 0.2 vol% PEI/P(VDF‐TrFE‐CFE) film, marking the highest charge density reported for single‐unit TENGs. This work provides novel material strategies for high‐performance TENGs, paving the way for their large‐scale practical applications.

Numerical study on lightning strike protection method for composite rotor blade based on air breakdown and insulating adhesive layer

The protection effectiveness of traditional Lightning Strike Protection (LSP) for composite rotor blade of helicopter can be diminished due to the explosion risk in overlapping attachment under lightning strike, so a new protection method based on Air Breakdown and insulating adhesive layer (AB-LSP method) was designed to avoid it. In this study, a numerical method was developed to simulate the electrical breakdown, and verified by experiment results. Based on this method, a Finite Element Model (FEM) was established to investigate the effect of two factors (breakdown strength and initial ablation temperature of adhesive layer) on the LSP effectiveness. The results show that the breakdown strength impacts more to the ablation damage in composite than that of high-temperature resistance. Then, another FEM was established to predict the ablation damage by lightning strike in the AB-LSP method protected composite rotor blade. The mechanisms and potential key parameters (magnitude of lightning current, discharge channel location, adhesive layer thickness, and air gap width) that could affect the protection effectiveness were analyzed. The introduction of air breakdown changes the current conduction path and reduces explosion risk. After rational design, this method can offer effective lightning protection for composite helicopter rotor blade and other composite structures.

Single-shot ultrafast imaging of plasma dynamics induced by dual-angle ultrashort laser pulses with subpicosecond delay

Spatiotemporal manipulation of ultrashort laser pulses is crucial for enhancing laser processing and phonon generation. Optimization of these applications requires ultrafast visualization of the underlying processes. In this study, we induced laser ablation using spatiotemporally manipulated double pulses focused from two angles onto a glass surface with a 0.7 ps interval, and captured the images of its dynamics with 5 sequential frames at a frame interval of 0.8 ps. The observed dynamics suggest that the laser profile reflected on the glass surface is influenced by its topography, which in turn affects the behavior of air breakdown plasmas.

A low voltage semiconductor arc discharge plasma actuator with long discharge gap distance

Long-gap spark discharge is beneficial for plasma-assisted combustion. However, the longer the discharge gap, the higher the breakdown voltage required, which is not feasible in practical applications. In the present study, based on a custom-built semiconductor, a long gap discharge plasma actuator is designed, and the breakdown voltage is relatively low compared with the normal spark discharge method. The breakdown discharge voltage for 25 mm gap at atmospheric pressure is only 3.24 kV. The discharge characteristics were investigated in detail. The influence of voltage, capacitance, and the semiconductor geometric parameters on the discharge characteristics is investigated. Based on a high-speed camera, the temporal and spatial long gap discharge process was captured firstly. Combined the discharge waveforms and images, the discharge process of the semiconductor arc discharge plasma actuator is divided into four stages: applying high voltage, surface discharge, air breakdown, and conduction discharge. Using digital image processing techniques, the influence of voltage, capacitance and air gap on surface discharge evolution velocity was studied.

Hydrogen-bond enhanced interior charge transport and trapping in all-fiber triboelectric nanogenerators for human motion sensing and communication

Maximizing charge density output within confined tribolayer areas is crucial for advancing triboelectric nanogenerator (TENG) performance. While conventional methods primarily focus on enhancing current density by modifying the surface properties of tribo-surfaces, the impact of dipole-dipole interactions between polymer molecular chains in the fibrous tribomaterials has been underexplored. This study reveals that intermolecular dipole-dipole interactions, mediated by hydrogen bonding between chitosan and nylon66 molecular chains, serve as effective bridging mechanisms that substantially boost TENG current density. Furthermore, we developed a breathable and antibacterial electrode by depositing silver nanowires (AgNWs) on the tribolayer surfaces. To prevent air breakdown resulting from excessively high current density, multiwalled carbon nanotubes (MWCNTs) were integrated to enhance electron transfer and storage. The structure we constructed achieved an optimized performance with a high voltage of 335 V, current density of 194.5 mA m−2 and power density of 65.1 W m−2, which demonstrates outstanding performance compared to previously obtained results. Finally, the prepared SWS-TENG was attached to the fingertips, wrist, and neck to track the physiological signals of the human state during standing, walking, and running. In addition, the integration of Morse code functionality introduces new possibilities for healthcare, particularly for non-verbal patients, enabling non-invasive communication of symptoms and emotions. This technology demonstrates significant potential as a versatile and non-invasive tool for point-of-care (PoC) and biomedical applications when deployed on various parts of the human body.

Fiberoptic Laser-Induced Breakdown Spectroscopy System for in situ Measurement in a Hazardous Environment

We report the development of a novel fiberoptic laser-induced breakdown spectroscopy (FOLIBS) system for material characterization applications. The system utilizes a 1000-µm optical fiber to transport the laser beam to remote locations for elemental analysis via laser-induced breakdown spectroscopy. Air-fiber interface damage, internal damage, and air breakdown issues during laser-fiber coupling are identified and corresponding solutions are presented. For evaluating the physical properties of the plasma generated by the FOLIBS system, spectroscopic characterization is carried out using a titanium sample. The spectral features collected from a natural uranium sample are also presented. Hence, this rapid, remote, and flexible measurement technique is promising for in situ measurements in hazardous environments in nuclear energy, nuclear safeguards, and nonproliferation applications.

Direct Current Triboelectric Nanogenerator Based on Contact Electrification, Air Breakdown, Electrostatic Induction, and Charge Leakage for Self‐powered Applications

AbstractDiverging from air breakdown‐based triboelectric nanogenerators (TENGs), recent TENG designs present high output power density without requiring precise control over discharge channels. However, existing researches predominantly ascribe its direct current output to electrostatic induction, disregarding the critical factor of charge leakage. This oversight hampers efforts to improve device performance, especially in material selection and optimization. Here, the generation of direct current signals ultimately stems from material charge leakage and spatial electrostatic induction is illustrated. Through theoretical analysis, visualization, and experimental measurement of four phenomena in the device, a quadruple‐effect mechanoelectrical conversion mechanism is established to refine the material selection rule. Under this guideline, the output power density is increased by 34.42% in contrast to the electrostatic induction direct current TENG. For practical applications, a power management circuit is utilized to boost the device's charging rate by up to 18 times. Furthermore, the high voltage of the device can activate discharge‐type UV tubes, demonstrating great potential in developing self‐powered wastewater treatment systems. The multiple charge behaviors proposed in this work, along with the material selection rule, lay a solid foundation for achieving high output power density in direct current TENGs.

Water Microdroplets in Air: A Hitherto Unnoticed Natural Source of Nitrogen Oxides.

Water microdroplets are widespread in the atmosphere. We report a striking observation that micron-sized water droplets obtained from zero-volt spray sources (sonic spray, humidifier, spray bottle, steamer, etc.) spontaneously generate nitrogen oxides. The mechanistic investigation through the development of custom-designed sampling sources combined with mass spectrometry and isotope labeling experiments confirmed that air nitrogen reacts with the water at the air-water interface, fixing molecular nitrogen to its oxides (NO, NO2, and N2O) and acids (HNO2 and HNO3) at trace levels without any catalyst. These reactions are attributed to the consequence of an experimentally detected feeble corona discharge (breakdown of air) at the air-water interface, likely driven by the high intrinsic electric field at the surface of water microdroplets. The extent of this corona discharge effect varies depending on the pH, salinity/impurity, size, speed, and lifetime of microdroplets in the air. Thus, this study discloses that the air-water interface of microdroplets breaks the strong chemical bond of nitrogen (N2), producing nitrogen oxides in the environment, while lightning strikes and microbial processes in soil are considered their dominant natural sources. As nitrogen oxides are toxic air pollutants, their spontaneous formation at the air-water interface should have important implications in atmospheric reactions, requiring further investigations.

ВИЗНАЧЕННЯ ВПЛИВУ РОЗПОДІЛУ ЗОВНІШНЬОГО ЕЛЕКТРИЧНОГО ПОЛЯ ОПОРНО-СТРИЖНЕВОГО ІЗОЛЯТОРА НА ЙОГО СУХОРОЗРЯДНУ НАПРУГУ

A mathematical model has been developed for calculating the internal and external electric field of insulators based on the solution of the Laplace equation with respect to the phasor of the electric potential using the finite element method. The specified model has been used to calculate electric field intensity distributions in the surrounding air spaces of support-rod insulators С4-80-I, C4-80-II and also C4-80-IIСm (Chinese-made). It has been proposed to establish a relationship between the distribution of the electric field around the insulators and their test dry discharge voltage based on the average integral values of the modulus of the electric field intensity along the possible paths of the dis-charge, taking into account the sign of its tangential component. The average integral values of the electric field have been compared with the known experimental values of the air breakdown intensity between two rod electrodes, as well as in the electrode system of the rod and the grounded plane. It has been shown that the most probable path of devel-opment of the discharge for each of the considered insulators is the path closest to the minimum distance in the air between the cap and the flange, the discharge process is two-stage (firstly the section «cap-the rib nearest to the cap» is broken down), and the breakdown intensity of the air around the insulators corresponds to the breakdown intensity between two rod electrodes (the difference in values was 2,1...5,9%). References 10, tables 3, figures 3.

Numerical Modeling of Atmospheric Air Breakdown in a Weakly Nonuniform Electric Field Due to a Positive Lightning Impulse

Numerical Modeling of Atmospheric Air Breakdown in a Weakly Nonuniform Electric Field Due to a Positive Lightning Impulse

Experimental investigation of air breakdown voltage at different altitude conditions

Experimental investigation of air breakdown voltage at different altitude conditions

An Adaptable Charge Source Enabled by Mode‐Switchable TENG for Efficient Self‐Repairing Coating

AbstractSelf‐repairing coatings have received widespread attention due to their ability to repair damaged surfaces. However, film‐forming molecules can only be fixed on the metal surface through relatively weak physical and chemical adsorption. This drawback limits its self‐repairing ability. Here, a mode‐switchable TENG (MS‐TENG) is developed, which has the ability to switch between AC and DC outputs as an adjustable charge source for self‐repairing coatings. Besides the normal sector electrodes of rotational TENG, MS‐TENG has a special design of external electrodes (small extension electrodes on rotator and inner/outer orbit electrodes on stator) and achieves charge accumulation through an excitation circuit and DC output through air breakdown on external electrodes with advantage of the complete release of accumulated charges. Compared with traditional air breakdown TENG, its current output has been improved. In addition, the air breakdown process occurs in the external electrode framework independent of the TENG body. Therefore, the negative impact of air breakdown is suppressed. Finally, MS‐TENG is used to achieve rapid electrostatic adsorption of charged film‐forming molecules through charge injection. MS‐TENG as a charge source effectively improves the performance of self‐repairing coatings, with a corrosion inhibition rate of 96.9%.

Effectively Inhibiting Charge Injection and Dielectric Loss of High Permittivity Inorganic Materials by Rationally Coating Organic Polymer for Achieving High Output Charge Density

AbstractAlthough high permittivity of inorganic materials (possibly two orders larger than organic polymers) is theoretically considered as ideal triboelectric materials, their high leakage property and low contact potential difference with metal electrodes lead to failure to obtain high triboelectric charge density. Besides, the internal space charge accumulation as a result of their defect levels reduces the output charge density and causes dielectric loss or even dielectric breakdown under charge injection in charge‐excitation triboelectric nanogenerator (CE‐TENG). Herein, this study proposes high permittivity and low dielectric loss inorganic materials as triboelectric layers. In order to prevent charge injection passing through the surface of inorganic materials caused by air breakdown under charge excitation, an organic polymer is coated, which has high permittivity, big polarizability, none charge traps, and large work function difference with metal electrodes. After optimizing the high dielectric inorganic layer and the coated organic polymer layer, the output charge of CE‐TENG based on 1 mm PZT‐5H coated with P(VDF‐TrFE‐CFE) achieves 2.83 mC m−2, 6.5 times of CE‐TENG based on 1 mm PZT‐5H, breaking the historical record for inorganic material TENG. This work clarifies the material selection criteria for CE‐TENG and provides a deeper understanding of charge transfer mechanism of inorganic materials.

Formaldehyde degradation by soft-sliding-electrification-induced air ionization

Formaldehyde (HCHO), a highly toxic and carcinogenic gas, is the most common indoor air pollutant and a threat to human health. Developing simple and effective technological routes to achieve sustainable degradation of HCHO has become a common goal. In this work, we reported a self-powered air-ionized HCHO degradation system based on a soft-sliding freestanding mode triboelectric nanogenerator (SSF-TENG). The sliding-electrification process between soft rabbit fur and a robust PTFE film enables the generation of electrical outputs of up to ten thousand volts that can trigger air breakdown. The generated O3, ·OH and other highly oxidizing substances could degrade HCHO into CO2 and H2O. Through a standard ball gap platform based on two hollow Cu balls, the voltage of air discharge was measured to be between 11.2 kV and 14.4 kV. For demonstration, the SSF-TENG was applied to two parallel disk-shaped Cu electrodes to continuously breakdown the air with a peak discharge current of 6 mA. The system can produce a maximum O3 concentration of 1.2 ppm within 50 minutes. Moreover, the HCHO concentration can be reduced from 1.6 ppm to 0 within 20 minutes, and the degradation speed reaches 0.08 ppm/min. This work highlights the application of triboelectric microplasma in pollutant removal, which has great potential in self-powered environmental purification.

Quantifying Dielectric Material Charge Trapping and De-Trapping Ability Via Ultra-Fast Charge Self-Injection Technique.

Recently, utilizing the air breakdown effect in the charge excitation strategy proves as an efficient charge injection technique to increase the surface charge density of dielectric polymers for triboelectric nanogenerators (TENGs). However, quantitative characterization of the ability of dielectric polymers to trap reverse charges and the effect on the startup time of secondary self-charge excitation (SSCE) are essential for extensive applications. Here, an ultra-fast charge self-injection technique based on a self-charge excitation strategy is proposed, and a standard method to quantify the charge trapping and de-trapping abilities of 23 traditional tribo-materials is introduced. Further, the relationship among the distribution of dielectric intrinsic deep, shallow trap states, and transportation of trapped charges is systematically analyzed in this article. It shows that the de-trapping rate of charges directly determines the reactivation and failure of SSCE. Last, independent of TENG contact efficiency, an ultra-high charge density of 2.67 mC m-2 and an ultra-fast startup time of SSCE are obtained using a 15µm poly(vinylidene fluoride-trifluoroethylene) film, breaking the historical record for material modification. As a standard for material selection, this work quantifies the charge trapping and de-trapping ability of the triboelectric dielectric series and provides insights for understanding the charge transport in dielectrics.

Ultrahigh power generation from low-frequency and micro motion by suppressing air breakdown

This work reports a novel and standard metric of plot to evaluate the electrostatic generator's output performance under air breakdown limitation and proposes a strategy to extend the plot for achieving ultrahigh power generation.

Regulation of deep and shallow hole/electron trap states and charge conducting behaviors of dielectric tribo-materials for maximizing retained charges

This work utilizes the UHCSI strategy to quantify the ability of 30 conventional tribo-materials to trap and de-trap positive/negative charges and reveal that the polymer's group composition influences trap states.

Triboelectric nanogenerators exhibiting ultrahigh charge density and energy density

Ultrahigh charge density (8.6 mC m−2) and energy density (0.808 J m−2 per cycle) are achieved in triboelectric nanogenerators by suppressing air breakdown via triboelectric polymer design.

Boosting the Charge Density of Triboelectric Nanogenerator by Suppressing Air Breakdown and Dielectric Charge Leakage

AbstractCharge generation and charge decay are two essential factors that determine the surface charge density of a triboelectric nanogenerator (TENG). However, research mainly focuses on boosting charge generation, and little attention is paid to suppressing charge decay. Here, a strategy of suppressing charge decay, including the air breakdown and dielectric charge leakage, of TENG with high surface charge density (HCD‐TENG) is proposed by utilizing a dual dielectric layer. A series of parameters of different dielectric materials are tested with the assistance of a charge excitation TENG (CE‐TENG) to reveal the relationships between charge generation, air breakdown, and dielectric charge leakage in the atmospheric environment. Further, the phenomenon of dielectric charge leakage limiting the maximum output of TENG prior to air breakdown is observed for the first time. With the simultaneous suppression of the air breakdown and dielectric charge leakage, the output of TENG is enhanced to 2.2 mC m−2. This work not only provides new insight into the performance optimization and material selection of TENG, but also provides significant guidance for obtaining high‐output TENG in the future.

Gamma glycine enhances efficiency of organic hybrid piezoelectric-triboelectric nanogenerators

This study presents a comprehensive exploration of enhancing the electrical output of flexible hybrid piezoelectric-triboelectric nanogenerators (P-TENG) through the incorporation of γ-glycine (γ-GC) into fully organic γ-GC/chitosan (CS) composites. A systematic investigation of the effects of γ-GC content (wt%) on the material characteristics and resulting electrical output signal is conducted. The research demonstrates the pivotal role of optimized γ-GC and CS concentrations in achieving superior performance. Through adherence to the percolation threshold principle, a critical γ-GC content is identified, leading to the attainment of the highest output signal. Three theoretical explanations substantiate this observation: firstly, molecular polarization occurring at the interface; secondly, the establishment of a well-connected filler internetwork; and thirdly, mitigation of air breakdown limitations. The interaction of γ-GC and CS fosters a robust hydrogen bond network, aligning interface polarization coherently. Efficient internetwork connections between γ-GC fillers facilitate facile charge generation and transfer. Furthermore, utilizing an appropriate quantity of γ-GC ensures optimal charge entrapment while circumventing issues related to air breakdown. The optimal electrical output is achieved by using 50% γ-GC, resulting in an open-circuit voltage (VOC) of 79 V and a short-circuit current (ISC) of 64 µA. The maximum power output (Pmax) registers at 705.96 µW under an external load resistance of 1 MΩ. Importantly, practical applications are demonstrated, including capacitor charging (0.22 μF and 0.33 μF), illumination of 100 LEDs, and operation of a scientific calculator-equipped watch.