多孔Co(OH)2的制备及其超电容特性

多孔Co(OH)2的制备及其超电容特性;多孔氢氧化钴;电化学电容器;超电容     

1-乙基-3-甲基咪唑三氟乙酸盐作为电化学双电层电容器电解液的电化学性能

应用循环伏安法和直流恒流充放电研究了以离子液体1-乙基-3-甲基咪唑三氟乙酸盐([EMIm]CF3COO)和高比表面活性炭电极构成的电化学双电层电容器的电化学性能.实验表明,[EMIm]CF3COO具有高的比电容、良好的循环特性以及高的充放电效率.在离子液体稳定的电化学窗口内,比电容随电化学窗口的增加而增大.能量密度随电流和电化学窗口的增加逐渐提高,功率密度随电流的增加而减小、随电化学窗口的增加而增加,是一种优良的电化学双电层电解液.     

聚3-(4-氟苯基)噻吩/碳化聚丙烯腈泡沫复合电极的电化学研究

噻吩衍生物是合成导电高分子材料的单体之一,在有机电致发光器件和电能存储等方面有着广泛的应用。聚3-(4-氟苯基)噻吩(PFPT)是一类既可进行p型掺杂又可进行n型掺杂的窄能带聚合物,在导电高分子型电化学电容器方面具有很好的应用前景,聚丙烯腈微孔膜已在锂离子电池方面有了很好的应用。若将它与碳纸复合后,再进行高温碳化和CO2活化,可制得导电性好、比表面积大的片状材料,作为电化学电容器的电极材料具有一定的双电层电容量．本文在三电极电解池中以这种材料的薄片为工作电极使3-(4-氟苯基)噻吩在乙腈溶液中进行电化学聚合,制备了聚3-(4-氟苯基)噻吩／碳化聚丙烯腈泡沫复合电极并研究了电极的电化学特性。     

Efficient decoupling technique applied to the numerical time integration of advanced interaction models for railway dynamics

Railway interaction is characterised by the coupling between the train and the track introduced through the wheel/rail contact. The introduction of the flexibility in the wheelset and the track through the finite element (FE) method in the last four decades has permitted to study high-frequency phenomena such as rolling noise and squeal, whose origin lies in the strongly non-steady state and non-linear behaviour of the contact forces that arise from the small contact area. In order to address models with a large number of degrees of freedom, innovative Eulerian-modal models for wheelsets with rotation and cyclic tracks have been developed in recent years. The aim of this paper is to extend the resulting formulation to an uncoupled linear matrix equation of motion that allows solving each equation independently for each time step, considerably reducing the associated computational cost. The decoupling integration method proposed is compared in terms of computational performance with Newmark and Runge-Kutta schemes, commonly used in vehicle dynamics, for simulations with the leading wheelset negotiating a tangent track and accounting the rail roughness.     

Magic angle spinning NMR with metallized rotors as cylindrical microwave resonators

We introduce a novel design for millimeter wave electromagnetic structures within magic angle spinning (MAS) rotors. In this demonstration, a copper coating is vacuum deposited onto the outside surface of a sapphire rotor at a thickness of 50 nm. This thickness is sufficient to reflect 197‐GHz microwaves, yet not too thick as to interfere with radiofrequency fields at 300 MHz or prevent sample spinning due to eddy currents. Electromagnetic simulations of an idealized rotor geometry show a microwave quality factor of 148. MAS experiments with sample rotation frequencies of ω_r/2π = 5.4 kHz demonstrate that the drag force due to eddy currents within the copper does not prevent sample spinning. Spectra of sodium acetate show resolved ¹³C J‐couplings of 60 Hz and no appreciable broadening between coated and uncoated sapphire rotors, demonstrating that the copper coating does not prevent shimming and high‐resolution nuclear magnetic resonance spectroscopy. Additionally, ¹³C Rabi nutation curves of ω₁/2π = 103 kHz for both coated and uncoated rotors indicate no detrimental impact of the copper coating on radio frequency coupling of the nuclear spins to the sample coil. We present this metal coated rotor as a first step towards an MAS resonator. MAS resonators are expected to have a significant impact on developments in electron decoupling, pulsed dynamic nuclear polarization (DNP), room temperature DNP, DNP with low‐power microwave sources, and electron paramagnetic resonance detection.     

Altitude dependence of electrohydrodynamic flow in an electrostatic lifter

Experiments carried out during the last 50 years have elucidated the basic mechanism of the Biefeld-Brown effect. Recent research has focused on establishing design rules in order to maximize the lifting force resulting from this effect. For this purpose, a numerical estimation that takes the effect of altitude into account is needed. In the present contribution, the thrust due to Biefeld-Brown effect was computed by simulating the corona-discharge-induced electrohydrodynamic flow in a widely used high-voltage asymmetric capacitor with the major goal to elucidate the dependence of thrust on the altitude, pressure, temperature and humidity, respectively. Our numerical results reproduced the experimentally observed decrease of thrust with altitude and shown that this is a consequence of various competing effects.     

Multilayered polycarbonate/poly(vinylidene fluoride‐co‐hexafluoropropylene) for high energy density capacitors with enhanced lifetime

The dielectric lifetime and corresponding damage morphology of polycarbonate/poly(vinylidene fluoride‐co‐hexafluoropropylene) (PC/P(VDF‐HFP)) layered systems are studied under constant direct current (DC) field. Melt blends of the two polymers are also considered for comparison. The dielectric lifetimes of the latter are systematically much shorter than the layered systems. The interfaces between the polymers act as flaws that induce up to two orders of magnitude difference between the layered and blend systems. The capacitance values versus time during breakdown progression exhibit an inversed S‐shape pattern. The three regimes in the S‐shape pattern are consecutively attributed to randomly isolated breakdowns, interconnecting breakdowns, and wearing‐out of the capacitor film. The film breakdown images during dielectric lifetime test confirmed the transition from randomly isolated breakdowns to interconnecting breakdowns. This transition was further evidenced by a bimodal distribution in the Weibull analysis. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

不耦合装药爆炸应力场的动光弹研究

用动光弹方法定量研究了多个不耦合系数下爆炸应力场衰减规律。模型材料为环氧树脂平板。研究表明:当不耦合系数在1～1.75之间取值时,比例距离在15～60范围内,|(?)/(?)|max的值介于3.21～5.00之间,|(?)/(?)|max的值介于小4.61～9.50之间。     

八电极静电陀螺支承系统的建模

八电极静电支承系统沿着四个非正交轴对转子施加静电力,这些作用力相互影响,因此需要对支承坐标进行垂直解耦。针对采用八电极方案的静电陀螺,给出了电极电容的计算公式和位移解算方法,推导了静电力计算公式,最后建立了八电极静电陀螺支承系统的模型并利用Simulink对系统进行仿真。仿真结果表明,在系统中加入解算矩阵和"3-4"变换矩阵后,可以使X、Y、Z三个轴向上对转子位移的控制相互独立,为转子的可靠支承奠定了基础。     

带有轴间动力学解耦的三轴转台自适应控制

针对某型号转台存在的轴间非线性耦合，运用非线性解耦的方法进行了解耦设计，并基于解耦后的系统提出用超稳定性和正性的方法进行自适应模型跟随控制器设计，来解决系统在运行过程中参数发生变化对控制性能影响的问题。仿真结果表明，当系统参数在一定范围变化甚至被控对象模型阶次发生变化时，所设计的自适应模型跟随控制器仍能保证系统具有良好的控制性能。