Breakdown Energy Research Articles

Systematic Characterisation of the Fragmentation of Flavonoids Using High-Resolution Accurate Mass Electrospray Tandem Mass Spectrometry

Flavonoids are a class of polyphenolic secondary metabolites found in plants. Due to their ubiquity in our daily dietary intake and their major anti-oxidative, anti-inflammatory and anti-mutagenic activities, they have been a major focus of wide-ranging research for the past two decades. Mass spectrometry combined with liquid chromatography is one of the most popular techniques for the analysis of flavonoids. In this study, high-resolution accurate mass electrospray tandem mass spectrometry was used to study 30 flavonoids in both positive and negative ionisation modes. From the data obtained, common losses were summarised and compiled. Dominating neutral losses were tabulated. The radical loss of CH3· was observed in flavonoids containing methoxy groups and three key diagnostic product ions were identified. These were m/z 153 (indicative of two OH groups on ring A) m/z 167 (indicative of one OH and one methoxy group on ring A) and m/z 151 (a flavanol, with no ketone oxygen but two OH groups on ring A). These will be useful in structural elucidation of unknown flavonoids and flavonoid metabolites. Energy breakdown graphs were utilised to distinguish between three pairs of structural isomers, and to help rationalise proposed fragmentation pathways. Lastly, a competition of loss of CH3· and methane was reported for rhamnetin and isorhamnetin in the negative ion mode for the first time. Proposed fragmentation pathways were given to rationalise the differences in peak intensities for this competitive process.

Exploring anti-ferroelectric thin films with high energy storage performance by moderating phase transition

Anti-ferroelectric thin films are renowned for their signature double hysteresis loops and sheds light on the distinguished energy storage capabilities of dielectric capacitors in modern electronic devices. However, anti-ferroelectric capacitors are still facing the dual challenges of low energy density and efficiency to achieve state-of-the-art performance. Their large hysteresis and sharp first-order phase transition usually results in a low energy storage efficiency and easy breakdown, severely obscuring its future application. In this study, we demonstrate that anti-ferroelectric (Pb0.97La0.02)(Zr1−xSnx)O3 epitaxial thin films exhibit enhanced energy storage performance through local structural heterogeneity to moderate the first-order phase transition by calculating the corresponding polarization as a function of switching time for the first time. The films exhibit remarkable enhanced breakdown strength (∼3.47 MV/cm, ∼5 times the value for PbZrO3) and energy storage performance. Our endeavors have culminated in the ingenious formulation of a novel strategy, namely, the postponement of polarization processes, thereby elevating the breakdown strength and total energy storage performance. This landmark achievement has unveiled a fresh vista of investigative opportunities for advancing the energy storage prowess of electric dielectrics.

Tuning Dielectric Properties with Nanofiller Dimensionality in Polymer Nanocomposites.

Polymer nanocomposites hold great potential as dielectrics for energy storage devices and flexible electronics. The structural architecture of the nanofillers is expected to play a crucial role in the fundamental mechanisms governing the electrical breakdown and dielectric properties of the nanocomposites. However, the effect of nanofiller structure and dimensionality on these properties has not been studied thoroughly to date. This study explores the critical relationship between nanofiller dimensionality and dielectric properties in polymer nanocomposites. We fabricated polyvinylidene fluoride (PVDF) nanocomposites by incorporating a range of carbon-based nanofillers separately, including zero-dimensional (0D) carbon black (CB), one-dimensional (1D) multiwalled carbon nanotubes (MWCNT), 1D single-walled carbon nanotubes (SWCNT), two-dimensional (2D) reduced graphene oxide (rGO), and three-dimensional (3D) graphite. The frequency-dependent (1 kHz to 1 MHz) dielectric permittivity (k) of the nanocomposites at the same concentration of nanofillers demonstrated a hierarchical order, with MWCNT showing the highest permittivity (∼400%), succeeded by rGO (∼360%), CB (∼290%), SWCNT (∼230%), and graphite (∼70%), respectively. The temperature-dependent (50-150 °C) dielectric spectroscopy revealed high k with increasing temperature due to the enhanced dipole movement. However, their dielectric breakdown strength and energy densities were not correlated to k and exhibited the following order: SWCNT > MWCNT > CB > rGO > graphite. As the electrical breakdown depends upon the nanocomposites' mechanical strength, we correlated the mechanical properties with the nanofiller dimensionality, and Young's modulus followed the 1D ≈ 2D > 0D > 3D order. These findings will provide fundamental insights into designing tunable, conducive nanofiller-based nanocomposites in next-generation flexible electronics and capacitive energy storage devices.

Breakdown strength and energy storage properties of epitaxial lead-based relaxor-ferroelectric films over a wide range of film thickness

Herein, we report the effect of film-thickness, ranging from 0.1 μm to 7.0 μm, on the energy storage performance of epitaxial Pb0.91La0.09Zr0.7Ti0.3O3 (PLZT) films grown on silicon substrates. As the PLZT film-thickness increases, polarization is enhanced and reaches a maximum value at a film-thickness of 1.0 μm, while the breakdown-strength reaches its maximum value at 0.5 μm. A film-thickness of 1.0 μm achieves an optimal volumetric recoverable energy-storage density (Ur,V) of 114.4 J/cm3 and an energy-efficiency of 87.3% at 4.7 MV/cm. Contrastingly, a film-thickness of 4.0 μm exhibits the largest stored recoverable-energy capacity over surface-area (Ur,A) of 34.2 mJ/cm2 (Ur,V = 85.4 J/cm3 at 4.05 MV/cm). Moreover, a film-thickness of 4.0 μm displays a large Ur,V value of 66.8 J/cm3, good thermal stability and excellent fatigue-endurance even at an operational temperature of 200 °C. These results suggest that thick PLZT films hold promise as high-performance energy-storage capacitors capable of operating effectively in harsh conditions.

Yielding optimal dielectric energy storage and breakdown properties of lead-free pyrochlore ceramics by grain refinement strategies

In the quest to develop high-performance dielectrics suitable for high-power applications, its microstructure engineering and understanding the effect on the property have become crucial. However, the trade-off relationship between saturated polarization and breakdown strength with respect to the average grain size complicates defining the ideal microstructure for high-performance energy storage dielectrics. In this study, we investigates the impact of the microstructure of (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 (BZN) pyrochlore ceramics on their energy storage characteristics by adjusting sintering temperatures. Interestingly, dielectric properties, energy storage capabilities, and electrical fatigue characteristics exhibit minimal change, maintaining a high dielectric constant (∼160) and a low dielectric loss (< 10−4). Moreover, BZN ceramics demonstrate quasi-linear dielectric properties up to 250 kV cm−1, with slight fluctuation in energy density as the function of grain size (1.08–1.26 J cm−3). This weak dependence of energy storage on microstructure underscores that the enhancement of BZN ceramics for energy storage devices is more effectively achieved by improving breakdown strength through microstructural refinement rather than grain enlargement, which has limited impact on energy density in BZN systems. The findings from this study offer valuable insights into optimizing the microstructures of multilayer systems that are targeted at augmenting volumetric energy density, laying the groundwork for further advancements in dielectric materials.

Synchronously enhanced breakdown strength and energy storage ability of cellulose acetate flexible films via introducing ultra-low content of carbonized polymer dots

Developing green and environmentally friendly biomass materials for energy storage and application is of great significance to sustainable development. Novel composite films containing cellulose acetate (CA) and carbonized polymer dots (CPDs) are reported herein. The CPDs have strong hydrogen bonding interactions with CA matrix, in which CPDs act as the physical crosslinking points and enhance the entanglement density of the matrix. And the composite films demonstrate a significant enhancement in breakdown strength (Eb), reaching up to 520.58 MV/m with the addition of 0.1 wt% CPDs (1.62 times higher than 321.94 MV/m of pure CA). Furthermore, the discharging energy density (Ud) achieves 2.55 J/cm3 at 450 MV/m, which is 1.36 times higher than that of the pure CA film (1.87 J/cm3 at 400 MV/m) and simultaneously, the energy efficiency (η) is maintained at 73.3 %. The Coulomb-blockade effect induced by the ultra-low content of CPDs effectively inhibiting carrier migration, and the enhanced entanglement density of the matrix improving mechanical properties and reducing polarization loss, mainly contribute to the enhanced dielectric performances. Furthermore, CPDs also improve the mechanical properties of the composite films apparently. This work provides some references for the fabrication of the next generation of environmentally friendly dielectric composite films.

Effect of the anti-Alzheimer drug GSK-3β antagonist on numerical modeling of the energy dissipation through the resin-dentin interface

ObjectivesThe aim of this study was to determine the viscoelastic performance and energy dissipation of conditioned dentin infiltrated with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs). MethodsDentin conditioned surfaces were infiltrated with NPs and TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nano-DMA/complex-loss-storage moduli-tan delta assessment and atomic force microscopy (AFM) analysis. ResultsDentin infiltrated with NPs and load cycled attained the highest complex modulus at hybrid layer and bottom of hybrid layer. Intertubular dentin treated with undoped NPs showed higher complex modulus than peritubular dentin, after load cycling, provoking energy concentration and breakdown at the interface. After infiltrating with TDg-NPs, complex modulus was similar between peri-intertubular dentin and energy dissipated homogeneously. Tan delta at intertubular dentin was higher than at peritubular dentin, after using TDg-NPs and load cycling. This generated the widest bandwidth of the collagen fibrils and bridge-like mineral structures that, as sight of energy dissipation, fastened active dentin remodeling. TDg-NPs inducted scarce mineralization after thermo-cycling, but these bridging processes limited breakdown zones at the interface. SignificanceTDg-based NPs are then proposed for effective dentin remineralization and tubular seal, from a viscoelastic approach.

Enhanced High-Temperature performance of PEI dielectrics via deep trap energy levels and physically crosslinked effects

Dielectric capacitors are indispensable energy storage components in both civilian applications and industrial processes. Under elevated temperatures and intense electric fields, polymer dielectrics usually suffer from an inevitably increase in conductivity, leading to a significant reduction in breakdown strength, energy density and efficiency. This investigation aims to design an all-organic dielectric with enhanced high-temperature capacitive performance by introducing a small molecule P-xylene F (PF) into polyetherimide (PEI). Two mechanisms including the incorporation of deep trap energy levels via wide bandgap fillers and the electrostatic interactions by hydrogen bonding between the fillers and the polymer matrix are proposed to support the enhancement. The hydrogen bonding between PF and polyamic acid (PAA)chains induces the formation of physical cross-linking between PF and the negatively charged benzene rings in PEI after imidization. This influences benzene ring stacking within the polymer chains and enhances the film’s mechanical strength. Additionally, PF’s wider bandgap compared to PEI introduces deep trap energy levels, hindering carrier transport and reducing conductive losses at high temperatures. As results, the dielectric achieves an energy density (Ud) of 4.47 J/cm3 with an efficiency (η) above 90 % at 200 °C. Its excellent stability is also demonstrated with over 210,000 charge–discharge cycles at 200 °C. This study promotes the development of high-performance dielectrics at high temperature.

A two-year dataset of energy, environment, and system operations for an ultra-low energy office building

This paper describes a two-year high-fidelity dataset for an ultra-low energy office building and living laboratory called HouseZero®. The building integrates multiple low-energy technologies, such as natural ventilation with automatic windows, ground source heat pump, and thermally activated building systems. The building’s performance is continuously monitored with an extensive sensor network. The dataset consists of breakdown energy end uses, photovoltaic (PV) production, zone-level indoor environment including indoor air temperature, CO2 concentration, and relative humidity, micro-climatical conditions, building façade temperature, and detailed system operations including zone-level BTU meter, valve status, slab temperature, window/skylight opening status, heat pump, and geothermal well operations. The data can be used to support data analytics of ultra-low-energy building operations, and data-driven modeling of low-energy building systems.

Improved Energy Density at High Temperatures of FPE Dielectrics by Extreme Low Loading of CQDs.

Electrostatic capacitors, with the advantages of high-power density, fast charging-discharging, and outstanding cyclic stability, have become important energy storage devices for modern power electronics. However, the insulation performance of the dielectrics in capacitors will significantly deteriorate under the conditions of high temperatures and electric fields, resulting in limited capacitive performance. In this paper, we report a method to improve the high-temperature energy storage performance of a polymer dielectric for capacitors by incorporating an extremely low loading of 0.5 wt% carbon quantum dots (CQDs) into a fluorene polyester (FPE) polymer. CQDs possess a high electron affinity energy, enabling them to capture migrating carriers and exhibit a unique Coulomb-blocking effect to scatter electrons, thereby restricting electron migration. As a result, the breakdown strength and energy storage properties of the CQD/FPE nanocomposites are significantly enhanced. For instance, the energy density of 0.5 wt% CQD/FPE nanocomposites at room temperature, with an efficiency (η) exceeding 90%, reached 9.6 J/cm3. At the discharge energy density of 0.5 wt%, the CQD/FPE nanocomposites remained at 4.53 J/cm3 with an efficiency (η) exceeding 90% at 150 °C, which surpasses lots of reported results.

Superior dielectric energy storage performance of ultrafine-grained BNT-SBT solid-solution ceramics by solution combustion synthesis

The micrometer scale grain size and large remnant polarization of Bi0.5Na0.5TiO3 (BNT) ferroelectric ceramics severely constrain the breakdown strength and energy efficiency, respectively, restricting their energy storage application despite their large polarization. Hereby, superior energy storage performance is reported by a synergistic strategy of introducing Sr0.7Bi0.2TiO3 (SBT) relaxor ferroelectrics and a solution combustion synthesis (SCS) method. The BNT-SBT solid-solution ceramics are comparatively investigated by the two methods, conventional sintering (CS) and SCS. An ultrafine average grain size of ∼0.39 μm was obtained in the SCS-derived ceramic, and thus exhibits an ultra-high critical electric field of 548 kV/cm, and a high recoverable energy density of ∼5.69 J/cm3. Those key energy storage parameters are superior to those of the previous reported samples prepared by the CS method. Meanwhile, a high energy efficiency ∼90 %, a large power density of ∼130.44 MW/cm3 (at 320 kV/cm), and an ultrafast discharge time of ∼61.7 ns are also achieved. This study indicates that grain engineering combing with chemical design is an effective way to enhance the dielectric energy storage performance.

Engineering multi-ion doping by entropy for high energy storage density with high efficiency in amorphous thin film

In the field of stored energy materials, lead-free amorphous thin films have the advantages of high breakdown strength, excellent stability, environmental protection and pollution-free, and are a very competitive energy storage material. However, the difficulty of simultaneous optimization of polarization and breakdown strength has always been a difficulty in improving the energy storage properties of amorphous thin films. Entropy can be used to design multi-ion doping to improve the energy storage performance of amorphous film. Amorphous films with different entropy are prepared by sol-gel method doped with 50 % Zr4+ and 5 %, 10 %, 15 %, 20 % Bi(Mn0·5Ti0.5)O3. The Bi0·1Ba0·85Sr0·05Mn0·05Ti0·45Zr0·5O3 amorphous thin film prepared at medium entropy (S = 1.37) has a recoverable energy storage density of 107.4 J cm−3 at 8.42 MV cm−1, and the energy storage efficiency is 93.9 %. Under the interaction of multiple elements, entropy design can give full play to the advantages of composite effects, improve breakdown field strength and energy storage efficiency, and is a new method to enhance energy storage performance.

Cost-effective strategy for high-temperature energy storage performance of polyimide nanocomposite films

The performance of most polymer-based film capacitors deteriorates severely at high temperatures, while high Tg polymer capacitors, despite their good performance at high temperatures, but their performance still decays severely after prolonged operation at high temperature. This study involves the deposition of a wide bandgap SiO2 inorganic layer on both surfaces of polyimide (PI) films using electron beam thermal evaporation. The findings indicate a substantial enhancement in the breakdown field strength and energy storage density of the composite films at elevated temperature following the deposition of the SiO2 inorganic layer. Specifically, a 100-nm-thick inorganic layer resulted in a breakdown field strength of 459.65 MV m−1 and an energy storage density of 3.2 J cm−3 at 150 °C. Subsequently, the polyimide film coated with a 100 nm SiO2 inorganic layer was infused with small quantities of SrTiO3 nanoparticles, leading to a breakdown field strength of 504.08 MV m−1 and an energy storage density of 6.75 J cm−3 and maintained an efficiency of 90.9 %. These results surpass the performance of the majority of high-temperature polymer films reported to date, with the inorganic layer deposited via electron beam thermal evaporation matching that of the costly magnetron sputtering method. The study presents a cost-effective method suitable for large-scale industrial production, significantly enhancing the electrical performance of PI at elevated temperatures and offering an economical solution for the commercialization of poly composite-based high-temperature capacitors.

Dynamic interfacial electrostatic energy harvesting via a single wire.

Spontaneously occurred electrostatic breakdown releases enormous energy, but harnessing the energy remains a notable challenge due to its irregularity and instantaneity. Here, we propose a revolutionary method that effectively harvests the energy of dynamic interfacial electrostatic breakdown by simply imbedding a conductive wire (diameter, 25 micrometers) beneath dielectric materials to regulate the originally chaotic and distributed electrostatic energy resulted from contact electrification into aggregation, effectively transforming mechanical energy into electricity. A point-charge physical model is proposed to explain the power generation process and output characteristics, guide structural design, and enhance output performance. Furthermore, a quantified triboelectric series including 72 dielectric material pairs is established for materials choice and optimization. In addition, a high voltage of over 10 kilovolts is achieved using polytetrafluoroethylene and polyethylene terephthalate. This work opens a door for effectively using electrostatic energy, offering promising applications ranging from novel high-voltage power sources, smart clothing, and internet of things.

Selective localization of carbonized polymer dots in amorphous phase towards high breakdown strength and energy density of PVDF-based dielectric composites

In a general way, there is a contradictory between dielectric constant (εr) and breakdown strength (Eb) in dielectric materials, and improving the discharge energy density (Ud) of dielectric polymers has become a great challenge. The semicrystalline ferroelectric polymer polyvinylidene fluoride (PVDF) is favored for its high εr, but its relatively weak Eb in amorphous regions makes it still difficult to obtain appreciable Ud. In response to the fact that the current method of introducing rigid chain amorphous polymers into the amorphous regions of PVDF has limited capability to enhance its Eb, in this work, due to the crystallization induced phase separation, carbonated polymer dots (CPDs) as well as PMMA were introduced into the amorphous region of PVDF, and CPDs/PVDF/PMMA composites were prepared towards high Eb and Ud. It is confirmed that, CPDs significantly increase the entanglement density of molecular chains in amorphous regions of PVDF; in addition, CPDs rely on their inorganic carbon cores with unique electrical properties to resist carrier migration in amorphous regions of PVDF under high electric fields. In brief, CPDs are used as a reinforcing agent for the amorphous region of PVDF to further enhance its Eb and Ud. The composite loaded with 0.1 wt% CPDs exhibits the superior Ud of 12.4 J/cm3 at the Eb of 652.0 MV/m. This work provides new understanding on the dielectric response of ultrasmall-sized CPDs on polymer dielectrics, which could help us design new dielectric polymer composites with suppressed segmental motions for high breakdown strength and high energy density applications.

Electrofracturing of Shale at Elevated Pressure

Electrofracturing deeply buried shale formations could be used to increase reservoir permeability and improve reservoir production without requiring large volumes of freshwater. This paper describes a novel experimental system and initial test results to electrofracture shale under high confining pressures. Core-scale laboratory testing was performed on twelve rock samples recovered from a shale gas reservoir. Each sample was subjected to confining pressures of 20.7 MPa (3000 psi) or 58.6 MPa (8000 psi), representative of overburden pressures at depth. Samples were then subjected to application of high voltage until specimen fracture. The experiments produced deformed samples with multiple fracture types, both parallel and oblique to bedding planes. Electrofracturing increased permeabilities by up to nine orders of magnitude for extended time periods. Rock fracture and throughgoing fractures were demonstrated. Computed tomography images revealed the creation of fractures and tube/tunnel flow channels, which resisted closure under hydrostatic pressures up to 58.6 MPa. The breakdown energy and permeability changes in the sample were independent of applied confining pressure. The cumulative energy input required for fracture depended on applied confining pressure and sample length. The energy required to fracture samples up to 9 cm in length is generally more than 0.5 kJ/cm, but no greater than 1 kJ/cm. Our results show that electrofracture of shales under confining pressure is possible and could be a possible water-free mechanism for reservoir stimulation.

Enhanced energy storage performance, breakdown strength, and thermal stability in compositionally designed relaxor Eu3+ substituted Na0.2K0.3Bi0.5TiO3

Lead-free Eu3+ substituted NKBT ceramics (Na0.2K0.3Bi0.5-xEuxTiO3, x = 0 (Eu 0),0.02(Eu 2),0.04(Eu 4), and 0.06(Eu 6)) were strategically designed via a local random field approach. The structural evolution had been confirmed through X-ray diffraction analysis. The observation of a broad dielectric curve supported the enhanced relaxor nature and the phenomena reflected in the P-E and S-E loops. The diffuse phase transition transforms to the plateau-type feature with excellent thermal stability with ±20 % and ± 40 % variation in dielectric constant over the temperature range of 120 to 500 °C and 90 to 500 °C, respectively in Eu 4. A large recoverable energy density of 1.7 J/cm3 with a high breakdown strength of 188 kV/cm was achieved in the Eu 2 sample at room temperature, making it a potential candidate for energy storage application. Moreover, the frequency stability (0.1 to 500 Hz range), thermal stability (45 °C to 85 °C), and fatigue measurement (10−1 to 106 cycles) were performed from the application point of view. The highest efficiency (82 %) was also achieved in the Eu 6. The negligible Sneg of Eu-rich compositions proves the existence of a relaxor state when the field is removed, and it transforms into the ergodic relaxor state. Furthermore, the SRBRF model is exploited to understand and correlate the transformation from normal to relaxor ferroelectrics with their properties. The current study provides a novel idea for compositional design for energy density, efficiency, and thermal stability ceramics by modifying and creating weakly coupled polar phases with rare earth substitution.

Constructing a dual gradient structure of energy level gradient and concentration gradient to significantly improve the high-temperature energy storage performance of all organic composite dielectrics†

The severe electrical conduction loss at elevated temperature is the initial factor for the degradation of energy storage performance of polymer dielectric films, thus it urgently needs to develop highly heat-resistant polymer capacitive films for meeting the advancing electrical and electronic applications. For reducing conduction loss and improving the high-temperature energy storage performance of dielectrics, the current approaches are focusing on preventing carriers mobility at elevated temperature and high electric field. In this study, the molecular semiconductor ITIC (ITIC is an organic molecular semiconductor 2,2′-[[6,6,12,12-Tetrakis(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene-2,8-diyl]bis [methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propanedinitrile] abbreviation) with high electron affinity was filled into the blends of polyether imide (PEI) and polyethersulfone (PESU). The energy level gradient was constructed due to the different energy bandgap structures among ITIC, PESU and PEI. In addition, the concentration structure gradient was constructed due to the concentration of ITIC which varies along the thickness direction. The results demonstrate that the dual gradients of energy level and concentration can effectively inhibit carrier migration and lower conduction loss, thus significantly improving the electric breakdown strength and energy storage performance at high temperature. The energy storage densities (Ue) of 5.14 J/cm3 and 3.6 J/cm3 at 150 °C and 200 °C, respectively were achieved in PEI/PESU blends with 9 layers of ITIC gradient and 0.25 % ITIC in the outer layer. This study puts forward a novel structural design combining the energy levels gradient with concentration gradient to optimise the high-temperature energy storage properties of all-organic dielectric films.

Enhanced energy-storage properties in (Bi0.5Na0.5)TiO3 ceramics by doping linear perovskite materials Ca0.85Bi0.1(Sn0.5Ti0.5)O3

For energy storage applications in Bi0.5Na0.5TiO3 (BNT)-based materials, the key challenges are the premature polarization saturation and low breakdown electric field (Eb), which confine the energy storage capacity of BNT and significantly restrict progress in advancing pulsed power capacitors. Hence, the cooperative optimization strategy of band structure and defect engineering was proposed, which successfully obtained a high recoverable energy density of 3.83 J/cm3 and an energy efficiency of 77.9 % in the Bi0.5Na0.5TiO3-0.12Ca0.85Bi0.1(Sn0.5Ti0.5)O3 (BNT-0.12CBST) ceramics. Doping the BNT matrix with CBST has been shown to not only reduce grain size but also enhance relaxor behavior, which collectively improves breakdown strength and delays polarization saturation. Furthermore, the x = 0.12 ceramic also exhibits a commendable discharge power density of 91.9 MW/cm3 and a transient discharge time of 40 ns. The higher resistivity and lower oxygen vacancy concentration are conductive to acquire superior breakdown electric field and energy storage performance. We determine the crystal structure, dielectric and ferroelectric properties of the studied ceramics in a wide range of temperatures and concentrations, and a phase diagram is constructed, which illustrates the complex phases present and their transformation behavior. Our work provides an effective strategy to optimize the energy-storage of dielectric ceramics, and shows great potential for practical applications in pulse power systems.

Influence of plasma breakdown on pores and fractures in bituminous coal: A new characterization method of breakdown energy

Plasma technology has a potential application prospect in the field of coal seam permeability enhancement. However, the relationship between plasma breakdown energy and the improvement effect of coal pores and fractures is lack of in-depth research. This study proposed a novel method for characterizing the plasma breakdown energy, and three testing techniques, namely, particle size distribution, mercury intrusion porosimetry (MIP) and low-field nuclear magnetic resonance (NMR), were utilized to examine the pore and fracture distribution of coal samples obtained from Jiulong Mine under varying breakdown energy conditions. The influence between breakdown energy and pores and fractures development is revealed. The results show that: (1) The degree of coal sample fragmentation increases with the increase of plasma breakdown energy. (2) Different breakdown energy induced the development of different pore distribution patterns. At lower breakdown energy, an increase in the volume of macropores dominates. As the breakdown energy increases, there is a rapid increase in the volume of mesopores, a slight increase in minipores, and the least increase in micropores, indicating that plasma treatment primarily improves pores with diameters greater than 100 nm. The test results of the three techniques were mutually verified. (3) Compared with capacitance energy and voltage, the effective breakdown energy obtained by the integral method has a more significant linear relationship with the particle size distribution, total pore volume, and average pore diameter, indicating that the effective breakdown energy is more suitable for characterizing the crushing effect of plasma. During the plasma breakdown process, the expansion stress and thermal stress formed by the effective breakdown energy exceeded the local tensile strength of coal, leading to the generation and development of pores and fractures, which in turn led to the rupture of the coal body. The larger the breakdown energy, the larger the crushing circle formed around the ion channel, the finer the coal is crushed, and the more pore fractures are developed. These nascent pores and fractures provide channels for gas transport, which is extremely favorable for coal mine gas extraction. The research conclusions provide theoretical support for the application of plasma in fracturing and permeability enhancement in coal seams.