A piperidinium-based ester-functionalized ionic liquid as electrolytes in Li/LiFePO<Subscript>4</Subscript> batteries

A new functionalized ionic liquid (IL) based on cyclic quaternary ammonium cations with ester group and bis(trifluoromethanesulfonyl)imide ([TFSI]^?) anion, namely, N-methyl-N-methoxycarbonylpiperidinium bis(trifluoromethanesulfonyl)imide ([MMOCPip][TFSI]), was synthesized and characterized. Physical and electrochemical properties, including Li-ion transference number, ionic conductivity, and electrochemical stability, were investigated. The electrochemical window of [MMOCPip][TFSI] was 6 V, which was wide enough to be used as a common electrolyte material. The Li-ion transference number of this IL electrolyte containing 0.1 M LiTFSI was 0.56. The half-cell tests indicated that the [MMOCPip][TFSI] obviously improved the cyclability of a Li/LiFePO₄ cell. For the Li/LiFePO₄ half-cells, after 20 cycles at room temperature at 0.1 C, the discharge capacity was 109.7 mAh g^?1 with 98.7% capacity retention in the [MMOCPip][TFSI]/0.1 M LiTFSI electrolyte. The good electrochemical performance demonstrated that the [MMOCPip][TFSI] could be used as electrolyte for lithium-ion batteries.     

基于Jiles-Atherton理论的铁磁材料塑性变形磁化模型修正

Jiles-Atherton(J-A)模型在磁化建模领域应用广泛,但不同文献给出的J-A模型并不一致,致使采用不同表达式建立的塑性变形磁化模型存在多种版本,其正确性难以甄别.通过对无磁滞磁化方程、能量守恒方程和等效磁场强度方程的梳理与比较,发现原有模型中存在将磁化强度和无磁滞磁化强度混用、将不可逆磁化能量等效于全部的磁化能量、等效磁场强度中应力磁化项界定不清等问题.在此基础上,对上述方程进行了修正,推导了基于J-A模型的塑性变形磁化修正模型.将修正模型计算结果与原模型计算结果、相关文献中的试验结果进行对比,结果表明:与原有计算模型相比,修正模型计算结果的饱和磁化强度和剩余磁化强度随塑性变形增加而减小,矫顽力随塑性变形增大而增大,达到饱和磁化强度时的外磁场强度随塑性变形增大而增大的趋势有所减弱,更符合试验结果,可更准确地反映塑性变形对材料磁化的影响.     

Dc-bias-field-induced dielectric relaxation and ac conduction in CaCu3Ti4O12 ceramics

The dielectric relaxation and ac conduction of CaCu₃Ti₄O₁₂ (CCTO) ceramics were investigated at different temperatures under a dc bias. The dc bias gives rise to space charge accumulation, i.e. an electrode response, resulting in the significant increase of dielectric permittivity and dielectric loss tangent. Two Debye-like relaxations, arising from electrode and grain boundary responses, are present at low frequency with an increase of the dc bias. The electrode and grain boundary relaxations are distinguished according to the impedance spectroscopy and the frequency-dependent ac conductivity. The relaxation times of electrode and grain boundary relaxation are 0.955 ms and 0.026 ms, respectively, with a dc bias of 10 V at 328 K.     

Escape of photo-detached electron from an annular nanomicrocavity

The escaped probability density of the photo-detached electron in an annular nanomicrocavity shows strong oscillations as a function of the length of the escape orbits. We present a semiclassical theory that describes theses oscillations in terms of bundles of escape orbits. Due to the interference effects of the electron waves travelling along different escaped orbits, oscillatory structures appear in the escaped probability density. In addition, the calculation results suggest that the escaped probability density of the photo-detached electron is not only related to the inner radius of the annular microcavity, but also related to the laser polarization. In order to show the correspondence between the escaped probability density and the detached electron’s escaped orbits clearly, we calculate the Fourier transformed semiclassical wave function and find that the peak positions agree well with the length of the detached electron’s orbits. We hope that our results will be useful in understanding the escape and propagation process of particles through semiconductor microjunctions or ballistic microstructure.     

Study of electrochemical performances of multi-doped spinel Li1.1Mn1.85Co0.075Ni0.075O4 at 4.3 and 5 V

Li_1.1Mn_2???2x Co _x Ni _x O₄ (x?=?0, 0.075) spinel powders were successfully synthesized using a liquid stirred tank reactor method. The electrochemical performances of the undoped and doped spinels at 4.3 and 5 V were investigated by X-ray diffraction, field-emission scanning electron microscopy, and electrochemical impedance spectroscopy. The capacity of Li_1.1Mn_2???2x Co _x Ni _x O₄ could be divided into two parts, with 4.3 V as the dividing line in the 3–5 V charge–discharge range. Low capacity and good cyclic performance were obtained when cycled in the 3–4.3 V range for the multi-doped Li_1.1Mn_2???2x Co _x Ni _x O₄ spinel. In comparison with multi-doped spinel at 4.3 V, the results of the cyclic performance worsened at 5 V because the structure underwent further shrinkage, the charge transfer resistance rose and the electrolyte decomposed.     

Exact solutions of （3＋1）-dimensional nonlinear incompressible non-hydrostatic Boussinesq equations

The symmetries and the exact solutions of the (3+1)-dimensional nonlinear incompressible non-hydrostatic Boussinesq (INHB) equations, which describe atmospheric gravity waves, are studied in this paper. The calculation on symmetry shows that the equations are invariant under the Galilean transformations, the scaling transformations, and the space-time translations. Three types of symmetry reduction equations and similar solutions for the (3+1)-dimensional INHB equations are proposed. Traveling and non-traveling wave solutions of the INHB equations are demonstrated. The evolutions of the wind velocities in latitudinal, longitudinal, and vertical directions with space-time are demonstrated. The periodicity and the atmosphere viscosity are displayed in the (3+1)-dimensional INHB system.     

Simultaneous measurement of refractive index and temperature using dual-period grapefruit microstructured fiber grating

By cascading the long period fiber grating (LPFG) and fiber Bragg grating (FBG) in grapefruit microstructured fiber, a novel dual-period fiber grating sensor is proposed. The refractive index and temperature are measured simultaneously by using the different sensitivity of FBG and LPFG. The relationship between dual-period fiber grating transmission spectrum and refractive index, resonant wavelengths and temperature are analyzed theoretically, respectively. The simulation results show that the accuracy of the sensor in measuring refractive index and temperature is estimated to be 2319.6 nm/RIU in a range from 1.33 to 1.36 and 0.017 nm/°C from 0 °C to 100 °C, respectively. Thus, the sensor has high refractive index sensitivity, and can provide the theoretical foundation for the optical fiber biosensor.     

White light interferometry test and analysis of LiNbO3 polarizer

White light interferometer can be used to measure the amplitude extinction ratio (ER) of polarizer and coupling distribution in fiber. A LiNbO₃ polarizer coupled with a polarization maintaining fiber and a silica planar waveguide at the two ends was measured using white light interferometer. According to the principles of optical coherence domain polarimeter (OCDP) technique, the test scheme is analyzed and presented to measure the ER of LiNbO₃ polarizer with its apparatus proposed correspondingly. By analyzing the interference intensity, both the ER of LiNbO₃ polarizer and its coupling crosstalk with optical fiber and waveguide are obtained. The results illustrate that the ER of a 5 mm-long LiNbO₃ polarizer is 71 dB and the crosstalk of the coupling points are around 40 dB. The results have good agreement with analysis.     

Plasmonic planar lens based on stack of metal–insulator–metal waveguides with height tuning

We introduce a technique capable of focusing electromagnetic (EM) waves through plasmonic nanoslits symmetrically arranged along the indented semi-circular surface in silver background. The EM transports through the tuning slits in the form of surface plasmon polaritons (SPPs), and gets the required phase retardations to focus at the focal plane. Due to the subwavelength nature of planar metallic lens, we present the rigorous electromagnetic analysis by using two dimensional (2D) finite difference time domain (FDTD) method. These height-modulated slits with uniform width are demonstrated to have unique advantages in beam manipulation. In combination with previous studies, it is expected that our structure with small number of slits could lead to realization of optimum designs of plasmonic nano-lens.