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排序方式: 共有1106条查询结果,搜索用时 15 毫秒
91.
文章分析了铝电解电容器等效串联电阻对产品性能的影响,讨论了等效串联电阻的构成及其影响因素,阐述了铝电解电容器生产中控制等效串联电阻的对策,推出了一种改进的铆接工艺,能够有效降低、稳定电极箔与引线间的铆接接触电阻。 相似文献
92.
《Journal of the European Ceramic Society》2023,43(14):6077-6083
Lead-free NaNbO3 (NN) antiferroelectric ceramics provide superior energy storage performance and good temperature/frequency stability, which are solid candidates for dielectric capacitors in high power/pulse electronic power systems. However, their conversion of the antiferroelectric P phase to the ferroelectric Q phase at room temperature is always accompanied with large remnant polarization (Pr), which significantly reduces their effective energy storage density and efficiency. In this study, to optimize the energy storage properties, short-range antiferroelectric (0.95-x)NaNbO3-xBi(Mg2/3Nb1/3)O3-0.05CaZrO3 (xBMN) ceramics were designed to stabilize the antiferroelectric phase, in which the local random fields were simultaneously constructed. The results showed that the antiferroelectric orthorhombic P phase was transformed into the R phase, and the local short-range random fields were generated, which effectively inhibited the hysteresis loss and Pr. Of great interest is that the 0.12BMN ceramics displayed a large recoverable energy storage density (Wrec) of 5.9 J/cm3 and high efficiency (η) of 85% at the breakdown strength (Eb) of 640 kV/cm. The material also showed good frequency stability in the frequency range of 2–300 Hz, excellent temperature stability in the temperature range of 20–110 ℃, and a very short discharge time (t0.9∼4.92 μs). These results indicate that xBMN ceramics have great potential for advanced energy storage capacitor applications. 相似文献
93.
1 000kV晋东南—南阳—荆门特高压交流试验示范工程串补工程一、二次系统均为世界首台首套应用,现场暴露出的控制保护系统若干问题亟需改进。为此,分析了目前线路断路器失灵保护和高抗保护不能退本站串补问题,提出两保护增加退串补逻辑和线路保护收本站远传增加就地跳闸功能,指出线路保护联跳逻辑有时不能退本站串补问题,提出联跳逻辑退本站串补方案,指出串补自动重投逻辑和功能不合理,参照线路重合闸功能提出改进方案,分析了目前线路保护分相联动串补回路不能满足运行方式变化需求,提出线路保护单相跳闸沟通串补三相合闸回路改进方案,给出串补旁路断路器失灵保护判据改进意见。 相似文献
94.
Jun Dong Yalong Jiang Qiulong Wei Shuangshuang Tan Yanan Xu Guobin Zhang Xiaobin Liao Wei Yang Qidong Li Qinyou An Liqiang Mai 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(22)
Developing pseudocapacitive cathodes for sodium ion capacitors (SICs) is very significant for enhancing energy density of SICs. Vanadium oxides cathodes with pseudocapacitive behavior are able to offer high capacity. However, the capacity fading caused by the irreversible collapse of layer structure remains a major issue. Herein, based on the Acid–Base Proton theory, a strongly coupled layered pyridine‐V2O5·nH2O nanowires cathode is reported for highly efficient sodium ion storage. By density functional theory calculations, in situ X‐ray diffraction, and ex situ Fourier‐transform infrared spectroscopy, a strong interaction between protonated pyridine and V?O group is confirmed and stable during cycling. The pyridine‐V2O5·nH2O nanowires deliver long‐term cyclability (over 3000 cycles), large pseudocapacitive behavior (78% capacitive contribution at 1 mV s?1) and outstanding rate capability. The assembled pyridine‐V2O5·nH2O//graphitic mesocarbon microbead SIC delivers high energy density of ≈96 Wh kg?1 (at 59 W kg?1) and power density of 14 kW kg?1 (at 37.5 Wh kg?1). The present work highlights the strategy of realizing strong interaction in the interlayer of V2O5·nH2O to enhance the electrochemical performance of vanadium oxides cathodes. The strategy could be extended for improving the electrochemical performance of other layered materials. 相似文献
95.
Yizhou Xiao Yuanbo Yang Shuai Yang Jinglei Li Dan Liu Jie Wu Mingwen Wang Chunchun Li Fei Li 《International Journal of Applied Ceramic Technology》2023,20(6):3735-3742
Modified BaTiO3 ceramics that possess high dielectric permittivity and acceptable temperature stability have been widely utilized as multilayer ceramic capacitors (MLCCs) for high-frequency bypass and power filtering in automotive applications. However, since the increasing demand for high-capacity and small-size, high-permittivity materials that can serve as dielectric layers in MLCCs are urgently required. In this work, we design and fabricate a special BaTiO3-0.03Mg-0.02Y-0.02CaZrO3 ceramic with a high dielectric permittivity of 3000 and the dielectric variation below ±13% in the temperature range of -55–150°C, fulfilling the requirements of X8R capacitors. To achieve these results, we employed grain size engineering and cation doping, using BaTiO3 precursors with a particle size of 240 nm to prepare the BaTiO3-based ceramics with fine grains, while Mg and Y co-doping was used for improving the temperature stability due to dielectric dispersion. Utilizing these high-permittivity BaTiO3-based materials, we fabricated MLCCs that satisfy the X8R criterion, possessing a high dielectric constant of 2950 and a high breakdown field (410 kV/cm). 相似文献
96.
Yaxi Ding Siwen Zhang Jiazhuo Li Ying Sun Bosi Yin Hui Li Yue Ma Zhiqiao Wang Hao Ge Dawei Su Tianyi Ma 《Advanced functional materials》2023,33(2):2210519
The harsh conditions of large hydrated ion radius of Mg2+ cations and the strong electrostatic interaction with the host material put forward higher requirements for high-performance aqueous magnesium ion (Mg2+) energy storage devices. Herein, substituted aluminium ions (Al3+) doped α-MnO2 materials are prepared. The introduction of Al3+ cations adjust the local chemical environment inside the tunnel structure of α-MnO2 and precisely regulates the diffusion behavior of inserted Mg2+ cations. The shortened oxygens’ distance and abundant oxygen defects result in a substantially enhanced elastic migration pattern of Mg2+ cations driven by strengthened electrostatic attraction, which brings the lower diffusion energy barrier, improved reaction kinetics, and adaptive volume expansion as evidenced by Climbing Image-Nudged Elastic Band density function theory calculations coupled with experimental confirmation in X-ray photoelectron spectroscopy, electron paramagnetic resonance, and galvanostatic intermittent titration technique. As a result, this rationally designed cathode exhibits a high reversible capacity of 197.02 mAh g-1 at 0.1 A g-1 and stable cycle performance of 2500 cycles with 82% retention. These parameters are among the best of Mg-ion capacitors reported to date. This study offers a detailed insight into the local tunnel structure tunning effect and opens up a new path of modification for tunnel-type structural materials. 相似文献
97.
Yang Zhang Li Li Xiaoyu Li Rui Feng Tingting Zhao Meng Pan Lijie Dong 《Advanced functional materials》2023,33(25):2300555
Dielectric polymers with high power density and breakdown strength (Eb) are indispensably used in electrostatic energy-storing systems and devices. However, the discharged energy density (Ue) of dielectric polymers is severely limited due to the relatively low dielectric constant (K). Although current polymer composites improve K, this approach usually faces challenges in enhancing Ue due to the trade-off relation between K and Eb and difficulties in scalable production of dielectric films. Here, a fully melt-extrudable, meter-scale, and high-Ue ferroelectric polymer-based all organic composite film comprising a poly(p-phenylene terephthalamide)-based fluxible polymer (denoted as f-PPTA) is reported. The polymer composite with only 2 wt% of f-PPTA presents a productivity of 12 m2 h−1 and an ultrahigh Ue of 20.7 J cm−3, which outperforms other extruded dielectric polymers reported in the literatures. Such enhancements of dielectric and capacitive properties have been comprehensively investigated and attributed to the crystallization behavior modulations and conformation changes induced by f-PPTA. As a demonstration of real applications, the dielectric capacitors established based on the extruded films enable tens of times higher efficacy on powering electronic devices than biaxially oriented polypropylene capacitors, in addition to long-term cyclic stability. This study opens up new avenue for the design and fabrication of high-Ue polymer dielectrics that are totally compatible with industrial production. 相似文献
98.
Yujing Liu Qi Liu Xiaohui Liu Chengyao Zhao Ruizhi Su Xinwei Luo Zhongqiu Liu Anguo Ying 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(14):2206895
Pore-structure design with the sophisticated and pragmatic nanostructures still remains a great challenge. In this work, porous carbon with Russian-doll-like pores rather than traditional single modal is fabricated via a boiling carbonization approach, accompanied by K+-pre-intercalation. The most important internal factor is that alkali can penetrate into the stereoscopic space of layered Malonic acid dihydrazide and the confinement effect leads to the in-depth development of different dimensional pore structures. The oxygenated and nitrogenated surface guarantees the K+ intercalation behavior. Benefiting from their open framework and enlarged interlayer spacing, K+-pre-intercalated porous carbon with Russian-doll-like pores (denoted as KPCRPs) as anode material exhibits promising potassium storage performance. The assembled KPCRP//activated carbon potassium-ion hybrid supercapacitor in 30 m CH3COOK displays a high energy density of 157.29 Wh kg−1, an ultrahigh power output of 14 kW kg−1, and a long cycling life (99.58% capacity retention after 10000 cycles), highlighting the superiority of Russian-doll-like pore structure. This work sheds light on the designing of 3D pores structure, especially for multimodal pore architectures. 相似文献
99.
Irena Spasojevic José Santiso José Manuel Caicedo Gustau Catalan Neus Domingo 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(30):2207799
The polar discontinuity at any ferroelectric surface creates a depolarizing field that must be screened for the polarization to be stable. In capacitors, screening is done by the electrodes, while in bare ferroelectric surfaces it is typically accomplished by atmospheric adsorbates. Although chemisorbed species can have even better screening efficiency than conventional electrodes, they are subject to unpredictable environmental fluctuations and, moreover, dominant charged species favor one polarity over the opposite. This paper proposes a new screening concept, namely surface functionalization with resonance-hybrid molecules, which combines the predictability and bipolarity of conventional electrodes with the screening efficiency of adsorbates. Thin films of barium titanate (BaTiO3) coated with resonant para-aminobenzoic acid (pABA) display increased coercivity for both signs of ferroelectric polarization irrespective of the molecular layer thickness, thanks to the ability of these molecules to swap between different electronic configurations and adapt their surface charge density to the screening needs of the ferroelectric underneath. Because electron delocalization is only in the vertical direction, unlike conventional metals, chemical electrodes allow writing localized domains of different polarity underneath the same electrode. In addition, hybrid capacitors composed of graphene/pABA/ferroelectric have been made with enhanced coercivity compared to pure graphene-electode capacitors. 相似文献
100.