Hydrous manganese oxide/carbon nanotube composite electrodes for electrochemical capacitors

A novel type of composite electrode based on hydrous manganese oxide and a single-walled carbon nanotube has been prepared and used in electrochemical capacitors. Cyclic voltammetry, galvanostatic charging/discharging tests and electrochemical impedance measurements were applied to investigate the performance of the composite electrodes with different ratios of hydrous manganese oxide and single-walled carbon nanotube. For comparison, the performance of pure hydrous manganese oxide and pure carbon nanotubes was also studied. In this way, the composite electrode with a 6:4 ratio of hydrous manganese oxide to carbon nanotube was found to be the most promising active material for an electrochemical capacitor, which shows both good capacitance and power characteristics.     

A novel concept of hybrid capacitor based on manganese oxide materials

A novel asymmetric hybrid capacitor using LiMn₂O₄ and manganese oxide (MnO₂)/carbon nanotube (CNT) nanocomposite as the positive and negative electrode materials, respectively, and 1 M LiClO₄ in propylene carbonate (PC) as the electrolyte has been developed. To the best of our knowledge, this is the first reported assembly of an asymmetric hybrid capacitor with metal oxides for both electrode materials, and, especially, with MnO₂ as the negative electrode material. The discharge profile of the asymmetric hybrid capacitor shows a typical capacitive behavior with a linear slope. The asymmetric hybrid capacitor was able to deliver a specific energy as high as 56 Wh/kg at a specific power of 300 W/kg, based on the total weight of LiMn₂O₄ and MnO₂/CNT nanocomposite in both electrodes. These results clearly demonstrated a superior performance of this new type of capacitor with a higher specific energy compared to other types of asymmetric hybrid capacitors.     

以多层次聚苯胺颗粒为电极活性物质的超级电容器的电化学性能

以(NH₄)₂S₂O₈为氧化剂用化学氧化法合成了具有多层次结构的聚苯胺颗粒，其二次颗粒由一次颗粒集结而成，一次颗粒的粒径基本上在1 μm以下，一次颗粒由多层微小薄片叠合而成. 用这种聚苯胺为活性物质制成电极，以2 mol•L^-1的H₂SO₄水溶液作电解液，组装成了聚苯胺电极超级电容器. 用循环伏安法、电化学阻抗谱和恒电流充放电技术测试了该超级电容器的电化学性能.在7 mA的充放电电流下，它的比能量可达6.35 Wh•kg^-1，比功率可达132 W•kg^-1，电极材料的比容量可达408 F•g^-1. 在20 mA的充放电电流下，它的比能量可达4.39 Wh•kg^-1，比功率可达328 W•kg^-1，电极材料的比容量可达324 F•g^-1. 在100次的充放电循环中，聚苯胺电极超级电容器的电容量没有下降，电荷充放电效率一直保持在95%左右.     

纳米Co(OH)2/HY复合物的制备及其电化学电容性能

当材料以纳米尺度存在时，某些物理及化学性质将发生根本性变化。因而，纳米技术的概念绝不仅仅是尺寸的缩小，更应体现在物理概念、系统设计、材料合成及制造等方面所发生的根本性革命。随着21世纪的来临，人们正努力地将越来越多的纳米材料功能化，Co(OH)2通常用作Ni(OH）2电池活性材料的添加剂。关于Ni(OH）2的许多电化学性质已有大量报道，而对于Co(OH）2的研究却很少涉及。本文报道了一种新的纳米级Co(OH）2／HY复合物的制备方法，并将制得的复合物制成超级电容器电极，研究了其超电容特性。此外，还初步提出了Co(OH）2各向异性的形貌形成机理。     

Hybrid electrochemical capacitors in aqueous electrolytes: Challenges and prospects

In an internal hybrid capacitor, at least one electrode displays battery-like charge/discharge and the other electrode stores charge reversibly at the electric double-layer (EDL). Recently, a plethora of hybrid cells in aqueous electrolytes have been proposed by coupling an EDL electrode with a battery electrode, the latter made from a variety of redox-active/redox-mediator species either dissolved in the electrolyte or adsorbed/immobilized in nanoporous electrodes. This review presents current opinions, discusses challenges, and supplies recommendation about the hybrid cells with aqueous electrolytes and carbon electrodes.     

Operation of a capacitor bank for plasma metal forming

Previously metal forming has been done using electromagnet in pulsed power mode, better known as magneform [1]. Here we will be presenting a different technique for metal forming. We are using water as a medium for this process. By discharging the stored electrical energy of the capacitor bank in water, we are getting the desired result i.e. to form (expand or compress) a wide range of workpiece to the desired shapes. The advantage of this method over conventional method is that it uses low power (negligible running cost). It does not require any post assembly cleaning degreasing and is hence environmentally ‘friendly’.     

High dV/dt immunity MOS controlled thyristor using a double variable lateral doping technique for capacitor discharge applications

An analysis model of the dV/dt capability for a metal-oxide-semiconductor （MOS） controlled thyristor （MCT） is developed. It is shown that, in addition to the P-well resistance reported previously, the existence of the OFF-FET channel resistance in the MCT may degrade the dV/dt capability. Lower P-well and N-well dosages in the MCT are useful in getting a lower threshold voltage of OFF-FET and then a higher dV/dt immunity. However, both dosages are restricted by the requirements for the blocking property and the forward conduction capability. Thus, a double variable lateral doping （DVLD） technique is proposed to realize a high dV/dt immunity without any sacrifice in other properties. The accuracy of the developed model is verified by comparing the obtained results with those from simulations. In addition, this DVLD MCT features mask-saving compared with the conventional MCT fabrication process. The excellent device performance, coupled with the simple fabrication, makes the proposed DVLP MCT a promising candidate for capacitor discharge applications.     

Cooling rate controlled microstructure evolution through flash DSC and enhanced energy density in P(VDF–CTFE) for capacitor application

Poly(vinylidene fluoride) (PVDF) based polymers are attracting tremendous interest because of their potential applications in advanced energy storage devices. Fundamental understanding of their crystal structure evolution has been proved elusive due to the nature of rapid crystallization rate. Fortunately, flash differential scanning calorimeter (Flash DSC) with a precise control of cooling rate helps to investigate an understanding of structure–property relationships. For the first time, a bimodal distribution of the crystallization rate of P(VDF‐chlorotrifluoroethylene) (CTFE) in the whole temperature range, and a 3D profile of melting point and enthalpy dependence of annealing temperature and time, which is the corresponding crystal structure evolution and the mechanism of crystal nucleation and growth, are revealed by flash DSC. Based on the above conclusions, fast cooling or annealing at low temperature regulates the crystallization behavior, favors a tiny ferroelectric β‐phases, drastically reduces paraelectric spherulite sizes, and leads to greatly enhanced energy storage capacity, but reduction in discharged efficiency. For instance, compared with other processing methods, P(VDF‐CTFE) quenched by liquid nitrogen achieves the highest discharged energy of 10.6 J cm^?3 at the maximum electric field of 270 MV m^?1. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1245–1253     

Structural analysis of unstable norbixin isomers guided by pure shift nuclear magnetic resonance

We report the analysis of complex samples obtained during the microwave irradiation/heating of norbixin, which has been identified as a potential therapeutic target for age-related macular degeneration (AMD). In this context, identifying the different isomers that are obtained during its degradation is of primary importance. However, this characterization is challenging because, on the one hand, some of these isomers are unstable, and on the other hand, the ¹H spectra of these isomeric mixtures are poorly resolved. We could successfully apply 1D pure shift experiments to obtain ultrahigh-resolution ¹H nuclear magnetic resonance (NMR) spectra of the norbixin isomer samples and exploit their information content to analyze complementary 2D NMR data and describe accurately their isomeric composition.