Nanogravel structured NiO/Ni foam as electrode for high-performance lithium-ion batteries

Nanogravel structured NiO/Ni electrodes were fabricated by using two-step thermal oxidation method of commercial nickel (Ni) foam in air for lithium-ion batteries (LIBs). The macro- and micro-structures of the NiO/Ni foam were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), and Raman spectroscopy. Galvanostatic tests revealed that the electrode exhibits no obvious capacity fading over 40 cycles at 1 C (718 mAg^?1) and 2.5 C (1.8 Ag^?1) current rate. The discharge capacity was higher than the theoretical capacity of NiO even at a high-current rate of 2.5 C. The electrodes can deliver a reversible capacity of 1116.65 mAh g^?1 after 20th cycle at 1 C rate and 1026.20 mAh g^?1 after 40th cycle at 2.5 C rate. The cyclic voltammograms and impedance spectra analysis indicated that a redox reaction of NiO–Ni⁰ with formation and decomposition of Li₂O. The excellent electrochemical performance is mainly attributed to the nanogravel structure of the NiO/Ni foam electrodes as well as its excellent electrical contact between NiO and Ni. The unique nanostructured NiO on the highly conductive metallic Ni in core resulted in the enhanced discharge capacity, coulombic efficiency, cyclic stability, and rate capability when utilized as negative electrodes in LIBs.     

A study of the capacity fade of porous NiO/Ni foam as negative electrode for lithium-ion batteries

High energy density materials such as NiO that undergoes conversion reaction hold promise for lithium (Li)-ion batteries (LIBs). However, porous NiO experiences substantial volume change due to the diffusion-induced stress during electrochemical operation, which causes mechanical fractures and morphological changes of porous NiO electrodes, leading to capacity fade through internal short circuit (ISCr). In this study, both non-destructive and destructive operations were used to visualize and quantify the origins and evolutions of the capacity fading of porous NiO/Ni foam electrodes. Results indicated that charge transfer resistance was dominant among all the internal resistances before ISCr, whereas solid electrolyte interface (SEI) resistance was dominant after ISCr of LIBs. The generation of the large amount of heat and pressure during ISCr caused the volume expansion and the formation of the micro-cracks in the struts of the porous NiO/Ni foam electrodes. Together with the electrolyte decomposition, this led to capacity fade. The results of this study provide insights for developing of NiO/Ni electrode for LIBs.     

金属泡沫圆管换热器性能的数值模拟与分析

氩氦刀低温探针换热器的性能直接影响其探针的降温速率及其治疗温度,采用金属泡沫圆管换热器可简化低温探针的结构并提高换热效率。文中基于氩氦刀的工作原理和金属泡沫圆管换热器的换热特点,采用平行流模型分析该种换热器不同填充圆管长度和工质(氩气)流体回流时间对换热器性能的影响以及温度场分布。     

Novel synthesis and characterization of ZnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoflakes grown on nickel foam as efficient electrode materials for electrochemical supercapacitors

ZnCo₂O₄ nanoflakes were directly grown on Ni foam via a two-step facile strategy, involving cathodic electrolytic electrodeposition (ELD) method and followed by a thermal annealing treatment step. The results of physical characterizations exhibit that the mesoporous ZnCo₂O₄ nanoflakes have large electroactive surface areas (138.8 m² g^?1) and acceptable physical stability with the Ni foam, providing fast electron and ion transport sites. The ZnCo₂O₄ nanoflakes on Ni foam were directly used as integrated electrodes for supercapacitors and their electrochemical properties were measured in 2 M KOH aqueous solution. The ZnCo₂O₄ nanoflake electrode exhibits a high capacitance of 1781.7 F g^?1 at a current density of 5 A g^?1 and good rate capability (62% capacity retention at 50 A g^?1). Also, an excellent cycling ability at various current densities from 5 to 50 A g^?1 was obtained and 92% of the initial capacitance maintained after 4000 cycles. The results demonstrate that the proposed synthesis route is cost-effective and facile and can be developed for preparation of electrode materials in other electrochemical supercapacitors.     

Ultrathin MnO2 nanosheets grown on hollow carbon spheres with enhanced capacitive performance

Ultrathin MnO₂ nanosheets grown on the surface of hollow carbon spheres (MnO₂/HCSs) were fabricated by the redox reaction between carbon spheres with KMnO₄ in aqueous solution. Due to the porous structure and large amounts of active sites, MnO₂/HCSs exhibit excellent capacitive performance with 227.5 F g⁻¹ at 1 A g⁻¹. After 5000 cycles, the capacity retention of MnO₂/HCSs remains 96%, indicating its good cycling stability. These results demonstrate that MnO₂/HCSs are promising supercapacitor electrode material and this work provide a facile method for growth of ultrathin MnO₂ nanosheets on carbon substrate.     

Enhanced electrochemical performance of porous activated carbon by forming composite with graphene as high-performance supercapacitor electrode material

In this work, a novel activated carbon containing graphene composite was developed using a fast, simple, and green ultrasonic-assisted method. Graphene is more likely a framework which provides support for activated carbon (AC) particles to form hierarchical microstructure of carbon composite. Scanning electron microscope (SEM), transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET) surface area measurement, thermogravimetric analysis (TGA), Raman spectra analysis, XRD, and XPS were used to analyze the morphology and surface structure of the composite. The electrochemical properties of the supercapacitor electrode based on the as-prepared carbon composite were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), charge/discharge, and cycling performance measurements. It exhibited better electrochemical performance including higher specific capacitance (284 F g^?1 at a current density of 0.5 A g^?1), better rate behavior (70.7% retention), and more stable cycling performance (no capacitance fading even after 2000 cycles). It is easier for us to find that the composite produced by our method was superior to pristine AC in terms of electrochemical performance due to the unique conductive network between graphene and AC.     

Flower-like Ni3(NO3)2(OH)4@Zr-metal organic framework (UiO-66) composites as electrode materials for high performance pseudocapacitors

Zr-metal organic frameworks (Zr-MOFs, UIO-66) as a kind of crystalline porous material possess controllable porous structure and strong thermal stability up to 753 K. In this paper, we synthesized Ni₃(NO₃)₂(OH)₄, Zr-MOF with high specific surface area (1073 m² g⁻¹) and Ni₃(NO₃)₂(OH)₄@Zr-MOF composite for pseudocapacitor material. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were taken to characterize the structure and morphology of Ni₃(NO₃)₂(OH)₄, Zr-MOF, and Ni₃(NO₃)₂(OH)₄@Zr-MOF. The porous structure of Zr-MOF favors the utilization of the active material Ni₃(NO₃)₂(OH)₄ and interfacial charge transport and provides short diffusion paths for ions, which results in a high specific capacitance. Electrochemical properties are evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge measurement. A maximum specific capacitance (SC) of 992 F/g was obtained from CV at a scan rate of 5 mVs⁻¹, which is higher than Zr-MOF (∼134 F g⁻¹) and Ni₃(NO₃)₂(OH)₄ (∼753 F g⁻¹). Meanwhile, the Ni₃(NO₃)₂(OH)₄@Zr-MOF composite electrode exhibits a good cycling stability over 3000 cycles.

     

The improved output performance of a broad-area vertical-cavity surface-emitting laser with an optimized electrode diameter

The output performance of a 980-nm broad-area vertical-cavity surface-emitting laser(VCSEL) is improved by optimizing the p-electrode diameter in this study.Based on a three-dimensional finite-element method,the current density distribution within the active region of the VCSEL is optimized through the appropriate adjustment of the p-electrode diameter,and uniform current-density distribution is achieved.Then,the effects of this optimization are studied experimentally.The L-I-V characteristics under different temperatures of the VCSELs with different p-electrode diameters are investigated,and better temperature stability is demonstrated in the VCSEL with an optimized p-electrode diameter.The far-field measurements show that with an injected current of 2 A,the far-field divergence angle of the VCSEL with an optimized p-electrode diameter is 9°,which is much lower than the far-field angle of the VCSEL without this optimization.Also the VCSEL with an optimized p-electrode diameter shows a better near-field distribution.     

Current-phase relation of double-barrier Josephson junctions with a two-gap superconductor as intermediate electrode

The current-phase (I-?) relation of a double-barrier Josephson junction with a two-gap superconductor as intermediate electrode is derived by means of a simplified version of Ohta’s model. As in conventional double-barrier Josephson junctions, a marked skewness in the I-? curves is present. Moreover, as in heterotic Josephson devices, a reduction of the maximum Josephson current is predicted. An appropriate experiment to verify the rich behavior of this type of Josephson device is suggested.     

Binaural sensitivity as a function of interaural electrode position with a bilateral cochlear implant user

Experiments were conducted with a single, bilateral cochlear implant user to examine interaural level and time-delay cues that putatively underlie the design and efficacy of bilateral implant systems. The subject's two implants were of different types but custom equipment allowed presentation of controlled bilateral stimuli, particularly those with specified interaural time difference (ITD) and interaural level difference (ILD) cues. A lateralization task was used to measure the effect of these cues on the perceived location of the sensations elicited. For trains of fixed-amplitude, biphasic current pulses at 100 pps, the subject demonstrated sensitivity to an ITD of 300 micros, providing evidence of access to binaural information. The choice of bilateral electrode pair greatly influenced ITD sensitivity, suggesting that electrode pairings are likely to be an important consideration in the effort to provide binaural advantages. The selection of bilateral electrode pairs showing sensitivity to ITD was partially aided by comparisons of the pitch elicited by individual electrodes in each ear (when stimulated alone with fixed-amplitude current pulses at 813 pps): specifically, interaural electrodes with similar pitches were more likely (but not certain) to show ITD sensitivity. Significant changes in lateral position occurred with specific electrode pairs. With five bilateral electrode pairs of 14 tested, ITDs of 300 and 600 micros moved an auditory image significantly from right to left. With these same pairs, ILD changes of approximately 11% of the dynamic range (in microApp) moved an auditory image from the far left to the far right-significantly farther than the nine pairs not showing significant ITD sensitivity. However, even these nine pairs did show response changes as a function of the interaural (or confounding monaural) level cue. Overall, insofar as the access to bilateral cues demonstrated herein generalizes to other subjects, it provides hope that the normal binaural advantages for speech recognition and sound localization can be made available to bilateral implant users.     

Study on the toxic interactions of Ni with DNA using neutral red dye as a fluorescence probe

The interaction between Ni²⁺ and calf thymus DNA (ctDNA) was investigated in simulated physiological buffer (pH 7.4) using the Neutral Red (NR) dye as a spectral probe by UV-vis absorption and fluorescence spectroscopy, as well as CD spectra. The experimental results showed that the conformational changes in DNA helix induced by Ni²⁺ are the reason for the fluorescence quenching of the DNA-NR system. From the experimental results, conclusion can be drawn that Ni²⁺ can cause structural changes of ctDNA and bind with DNA by electrostatic interaction. At the same time, the paper proved that conformation changes of DNA can also lead to the fluorescence decrease of DNA-probe systems.     

Effect of emitting electrode number on the performance of EHD gas pump in a rectangular channel

Previous studies have shown that electric field in the form of corona wind can be used for gas pumping. It has also been shown that the maximal volume flow rate can be achieved by an optimal design and arrangement of electrode(s) involved. In this study, the number of emitting electrodes has been considered for its effects on the pump performance. To seek the relation between the electrode number and pump performance, an EHD gas pump with three configurations (4, 12, and 28 emitting electrodes) is critically evaluated by experimental measurements and numerical simulations.     

Electrophysical characteristics of MIS structures based on graded band-gap MBE HgCdTe with grown in situ CdTe as a dielectric

Capacitance-voltage characteristics of MIS structures based on graded band-gap heteroepitaxial HgCdTe (x = 0.22–0.23 and 0.32–0.36) with grown in situ CdTe as a passivating coating are examined. The average surface-state densities as well as mobile- and fixed-charge densities are determined for the HgCdTe/CdTe, HgCdTe/CdTe–SiO₂–Si₃N₄, and HgCdTe/CdTe–ZnTe systems. It is shown that grown in situ CdTe forms a fairly qualitative interface, and deposition of additional SiO₂–Si₃N₄ and ZnTe layers makes it possible to control the electric strength and charges in the dielectric used.     

电极电压对碳纳米管阴极电离规性能影响的数值模拟

本文基于IE514分离规结构, 建立了碳纳米管阴极电离规物理模型, 根据电离规标准方程, 利用离子光学模拟软件SIMION 8.0分别研究了电极电压对灵敏度和I_grid/I_e的影响. 结果表明, 随着阳极/门极电压比值增大(V_grid/V_gate), I_grid/I_e也将增大, 然而, 当阳极电压增大时, 会导致灵敏度降低, 进而影响真空测量下限的延伸; 该模拟结果与相关文献报道的实验结果符合性很好. 因此, 选择合适的电极电压, 将有利于提高灵敏度, 增大阳极电流, 进一步延伸真空测量下限. 本文所采用的数值模拟方法可推广应用于各种新型碳纳米管阴极极高真空电离规的研发和理论分析中, 为解决极高真空测量难题提供了有效的研究途径. 关键词： 碳纳米管阴极电离规 电极电压 灵敏度 阳极电流     

采用AI／TaN叠层电极提高Si基GePIN光电探测器的性能

金属与Ge材料接触由于存在强烈的费米钉扎效应,导致金属电极与n型Ge接触引入较大的接触电阻,限制了si基Ge探测器响应带宽．本文报道了在SOI衬底上外延Ge单晶薄膜并制备了不同台面尺度的GePIN光电探测器．对比了电极分别为金属Al和A1／TaN叠层的具有相同器件结构的SOI基GePIN光电探测器的暗电流、响应度以及响应带宽等参数．发现在Al与Ge之间增加一薄层TaN可有效减小n型Ge的接触电阻,将台面直径为24um的探测器在1．55um的波长和-1V偏压下的3dB响应带宽提高了4倍．同时,器件暗电流减小一个数量级,而响应度提高了2倍．结果表明,采用TaN薄层制作金属与Ge接触电极,可有效钝化金属与Ge界面,减轻费米钉扎效应,降低金属与n-Ge接触的势垒高度,因而减小接触电阻和界面复合电流,提高探测器的光电性能．     

采用Al/TaN叠层电极提高Si基Ge PIN光电探测器的性能

金属与Ge材料接触由于存在强烈的费米钉扎效应, 导致金属电极与n型Ge接触引入较大的接触电阻, 限制了Si基Ge探测器响应带宽. 本文报道了在SOI衬底上外延Ge单晶薄膜并制备了不同台面尺度的Ge PIN光电探测器. 对比了电极分别为金属Al和Al/TaN叠层的具有相同器件结构的SOI基Ge PIN光电探测器的暗电流、响应度以及响应带宽等参数. 发现在Al与Ge之间增加一薄层TaN可有效减小n型Ge的接触电阻, 将台面直径为24 μ的探测器在1.55 μ的波 长和-1 V偏压下的3 dB响应带宽提高了4倍. 同时, 器件暗电流减小一个数量级, 而响应度提高了2倍. 结果表明, 采用TaN薄层制作金属与Ge接触电极, 可有效钝化金属与Ge界面, 减轻费米钉扎效应, 降低金属与n-Ge接触的势垒高度, 因而减小接触电阻和界面复合电流, 提高探测器的光电性能.     

Flame-fluorescence detection of Mg,Ni, and Pb with a frequency-doubled dye laser as excitation source

The determination of traces of Mg, Ni, and Pb by atomic fluorescence spectrometry using frequency doubled dye laser emission for excitation is reported. Low detection limits and long linear analytical working curves demonstrate the qualification of this method for quantitative analysis.     

Study of the electro-absorption spectrum of a nickel acceptor exciton in a ZnO:Ni crystal based on a calculation of vibrations associated with a Ni+1 impurity

Localized vibrations in ZnO crystals due to the substitution impurity Ni⁺¹ are modeled. The calculations were performed in the shell model using a recursive method for vibrations with A ₁ and E type symmetry. Numerical calculations allowed us to analyze the vibronic structure in the electro-absorption spectra for nickel acceptor excitons in ZnO:Ni. Fiz. Tverd. Tela (St. Petersburg) 41, 986–990 (June 1999)