Morphology Control of TiO_(2)Nanotubes towards High-Efficient Electrodes for Supercapacitor

This article studies the role of electrochemical parameters in controlling the morphology of oxidized TiO_(2)nanotubes and the electrochemical performance of modified TiO_(2)nanotubes.Humidity is a key factor for fabricating TiO_(2)nanotubes.When the relative humidity belows 70%,the TiO_(2)nanotubes can be successfully prepared.What's more,by changing the anodization voltage and time,the diameter and the length of TiO_(2)nanotubes can be adjusted.In addition,the TiO_(2)nanotubes are modified through electrochemical self-doping and loading Pt metal particles on the surface of the nanotubes,which promotes the performance of the supercapacitor.The sample anodized at 100 V for 3 h has a specific capacity of up to 2.576 mF/cm~2 at a scan rate of 100 mV/s after self-doping,and its capacity retention rate still remains at 89.55%after 5000 cycles,demonstrating excellent cycling stability.The Pt-modified sample has a specific capacity of up to 3.486 mF/cm~2 at the same scan rate,exhibiting more outstanding electrochemical performance.

Electrical and mechanical properties of Cu-Cr-Zr alloy aged under imposed direct continuous current

The Cu-Cr-Zr alloys were aged at different temperatures for different time with different current densities. The results show that both the electrical conductivity and hardness are greatly improved after being aged with current at a proper temperature. The electrical conductivity increases approximately linearly with increasing current density while the hardness remains constant. The microstructure observation reveals that a much higher density of dislocations and nanosized Cr precipitates appear after the imposition of current, which contributes to the higher electrical conductivity and hardness. The mechanism is related with three factors： 1） Joule heating due to the current, 2） migration of mass electrons, 3） solute atoms, vacancies, and dislocations promoted by electron wind force.

Effect of linear carboxylic ester on low temperature performance of LiMn_2O_4-graphite cells

To improve the low-temperature performances of Li-ion cells, three types of linear carboxylic ester-based electrolyte, such as EC/EMC/EA（1：1：2, mass ratio）, EC/EMC/EP（1：1：2, mass ratio） and EC/EMC/EB（1：1：2, mass ratio）, were prepared to substitute for industrial electrolyte（EC/EMC/DMC）. Then, 18650-type Li Mn2O4-graphite cells（nominal capacity of 1150 mA ·h） were assembled and studied. Results show that the cells containing three types of electrolyte are able to undertake 5C discharging current with above 93% capacity retention at-20 °C. Electrochemical impedance spectra show that the discharge capacity fading of Li-ion cells at low temperature is mainly ascribed to the charge transfer resistance increasing with temperature decreasing. In comparison, the cells containing electrolyte of 1.0 mol/L LiPF6 in EC/EMC/EA（1：1：2, mass ratio） have the highest capacity retention of 90% at-40 °C and 44.41% at-60 °C, due to its lowest charge-transfer resistance.

Ambient electrical conductivity of carbon cathode materials for aluminum reduction cells

The ambient electrical conductivity (AEC) of carbon cathode materials was investigated in respect to their open porosity, crystal structure and graphite content using hydrostatic method, four-probe technique and X-ray diffraction (XRD), respectively. The AEC is proportional to the specific conductivity (σ0) and the exponential of (1?ε) (ε is porosity) by a quasi-uniform formula based on the percolation theory. Theσ0 can reflect the intrinsic conductivity of the carbon cathodes free of pores, and it depends on the mean crystallite size parallel to the layer (002). The exponentn is dependent on the materials nature of the cathode aggregates, while an averaged value, 4.65, can practically work well with 5 types of cathode materials. The calculation ofσ0 can be extended to the graphitic cathodes containing different aggregates using the simple rule of mixture.

Analytical Model for the Piecewise Linearly Graded Doping Drift Region in LDMOS

A novel 2D analytical model for the doping profile of the bulk silicon RESURF LDMOS drift region is proposed. According to the proposed model, to obtain good performance, the doping profile in the total drift region of a RESURF LDMOS with a field plate should be piecewise linearly graded. The breakdown voltage of the proposed RESURF LDMOS with a piecewise linearly graded doping drift region is improved by 58. 8%, and the specific on-resistance is reduced by 87. 4% compared with conventional LDMOS. These results are verified by the two-dimensional process simulator Tsuprem-4 and the device simulator Medici.

Ionic Conduction and Fuel Cell Performance of Ba0.98Ce0.8Tm0.2O3-α Ceramic

The perovskite-type oxide solid solution Ba0.98Ce0.8Tm0.2O3-α was prepared by high temperature solid-state reaction and its single phase character was confirmed by X-ray diffraction. The conduction property of the sample was investigated by alternating current impedance spectroscopy and gas concentration cell methods under different gases atmospheres in the temperature range of 500-900 ℃. The performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured. In wet hydrogen, the sample is a pure protonic conductor with the protonic transport number of 1 in the range of 500-600 ℃, a mixed conductor of proton and electron with the protonic transport number of 0.945-0.933 above 600 ℃. In wet air, the sample is a mixed conductor of proton, oxide ion, and electronic hole. The protonic transport numbers are 0.010-0.021, and the oxide ionic transport numbers are 0.471-0.382. In hydrogen-air fuel cell, the sample is a mixed conductor of proton, oxide ion and electron, the ionic transport numbers are 0.942 0.885. The fuel cell using Ba0.98Ce0.8Tm0.2O3-α as solid electrolyte can work stably. At 900 ℃, the maximum power output density is 110,2 mW/cm2, which is higher than that of our previous cell using Ba0.98Ce0.8Tm0.2O3-α （x〈≤1, RE=Y, Eu, Ho） as solid electrolyte.

Study of the Conductance Characteristic of Doped Polymer by Monte Carlo Method

The conduct mechanism of the doped polymer is considered. In an asymmetrysystem composed of high polymer and doping conductive matte, chain or congeries framework will beformed between the conductive particles to improve the conductance characteristic. In thisprocession, the conductive particles interact to each other. In this paper, we describe theconductance of the doped polymer by Monte Carlo method. The results accord with the experimentsquite well. It can be concluded that there is an evident change of doped polymer from nonconductorto metal.

Preparation of low-temperature sintered high conductivity inks based on nanosilver self-assembled on surface of graphene

Finer nanoplates of silver are prepared by self-assembly on the surface of graphene,and the low-temperature sintered high conductivity ink containing the silver nanoplates is prepared.Most importantly,graphene is added to the solution before the chemical reduction reaction occurs.Firstly,it is found that silver nanoplates have self-assembly phenomenon on the surface of graphene.Secondly,the Ag nano hexagonal platelets(AgNHPs)with small particle sizes(10 nm),narrow distribution and good dispersion are prepared.Especially,smaller sizes(10 nm)and narrower particle size distribution of AgNHPs particles can be easily controlled by using this process.Finally,the conductivity of the ink is excellent.For example,when the printed patterns were sintering at 150℃,the resistivity of the ink(GE:0.15 g/L)reached the minimum value of 2.2×10^-6 cm.And the resistivity value was 3.7×10^-6Ωcm,when it was sintered at 100℃ for 30 min.The conductive ink prepared can be used for the field of printing electronics as ink-jet printing ink.

Electrical conductivity of (Na_3AlF_6-40%K_3AlF_6)-AlF_3-Al_2O_3 melts

The effects of contents of AlF3 and Al2O3, and temperature on electrical conductivity of （Na3AlF6-40%K3AlF6）- AlF3-Al2O3 were studied by continuously varying cell censtant （CVCC） technique. The results show that the conductivities of melts increase with the increase of temperature, but by different extents. Every increasing 10 ℃ results in an increase of 1.85 × 10^-2, 1.86× 10^-2, 1.89 × 10^-2 and 2.20 × 10^-2 S/cm in conductivity for the （Na3AlF6-40%K3AlF6）-AlF3 melts containing 0%, 20%, 24%, and 30% AlF3, respectively. An increase of every 10 ℃ in temperature results an increase about 1.89× 10^-2, 1.94 × 10^-2, 1.95 × 10^-2, 1.99× 10^-2 and 2.10× 10^-2 S/cm for （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts containing 0%, 1%, 2%, 3% and 4% Al2O3, respectively. The activation energy of conductance was calculated based on Arrhenius equation. Every increasing 1% of AlF3 results in a decrease of 0.019 and 0.020 S/cm in conductivity for （Na3AlF6-40%K3AlF6）-AlF3 melts at 900 and 1 000 ℃, respectively. Every increase of 1% Al2O3 results in a decrease of 0.07 S/cm in conductivity for （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts. The activation energy of conductance increases with the increase in content of AlF3 and Al2O3.

New pretreatment method for high-tension electrical separation of zircon from quartz

Electrostatic separation is one of the mineral processing methods based on mineral conductivity.This method has some significant problems such as being sensitive to humidity,high middling product,and impurity of non-conductive minerals.In this study,a new pretreatment method was proposed for the separation of zircon from quartz before electrostatic separation to solve these disadvantages.In this regard,two stages of pretreatment were applied which involved using collector of sodium dodecyl sulfate(SDS)for adjusting wettability of the zircon surface and spraying electrolyte aqueous solution to increase conductivity of the quartz surface.The effects of important parameters including pH,collector concentration,conditioning time,and concentration and type of electrolyte on the process efficiency were evaluated.The results showed that the optimal conditions of high-tension electrical separation were pH of 4,SDS concentration of 1×10-4 mol/L,conditioning time of 4 min and NaCl as an electrolyte with concentration of 4.27 mol/L.Separation efficiency of 95.12% was achieved in optimum conditions.This pretreatment method can be successfully used before high-tension electrical separation to separate the conductive or non-conductive minerals with various compositions.

Ionic Conduction and Fuel Cell Performance of Ba0.97Ce0.8Ho0.2O3-α Ceramic

The perovskite-type-oxide solid solution Ba0.97Ce0.8Ho0.2O3-α was prepared by high temperature solidstate reaction and its single-phase character was confirmed by X-ray diffraction. The ionic conduction of the sample was investigated using electrical methods at elevated temperatures, and the performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured, which were compared with those of BaCe0.8Ho0.2O3-α. In wet hydrogen, BaCe0.8Ho0.2O3-α almost exhibits pure protonic conduction at 600-1000℃, and its protonic transport number is 1 at 600-900 ℃ and 0.99 at 1000 ℃. Similarly, Ba0.97Ce9.8Ho0.2O3-α exhibits pure protonic conduction with the protonic transport number of 1 at 600- 700℃, but its protonic conduction is slightly lower than that of BaCe0.8Ho0.2O3-α, and the protonic transport number are 0.99-0.96 at 800-1000 ℃. In wet air, the two samples both show low protonic and oxide ionic conduction. For Ba0.97Ce0.8Ho0.2O3-α, the protonic and oxide ionic transport numbers are 0.01-0.11 and 0.30-0.31 respectively, and for BaCe0.8Ho0.2O3-α, 0.01-0.09 and 0.27-0.33 respectively. Ionic conductivities of Ba0.97Ce0.8Ho0.2O3-α are higher than those of BaCe0.8Ho0.2O3-α under wet hydrogen and wet air. The performance of the fuel cell using Ba0.97Ce0.8Ho0.2O3-α as solid electrolyte is better than that of BaCe0.8Ho0.2O3-α. At 1000 ℃, its maximum short-circuit current density and power output density are 465 mA/cm^2 and 112 mW/cm^2, respectively.

Effect of surface treatment for aluminum foils on discharge properties of lithium-ion battery

Aluminum foils having thicknesses of 10-20 μm are commonly employed as current collectors for cathode electrodes in Li-ion batteries. The effects of the surface morphology of the foil on battery performance were investigated by using a foil with roughened surface by chemical etching and a plain foil with smooth surface on both sides. For high-conductivity LiCoO2 active materials with large particle size, there are no significant differences in battery performance between the two types of foils. But for low-conductivity LiFePO4 active materials with small particle size, high-rate discharge properties are significantly different. The possibility shows that optimizing both the surface morphology of the aluminum foil and particle size of active material leads to improvement of the battery performance.

Theoretical Aspects on Doped-Zirconia for Solid Oxide Fuel Cells:from Structure to Conductivity

Solid oxide fuel cells(SOFCs)are regarded to be a key clean energy system to convert chemical energy(e.g.H_(2) and O_(2))into electrical energy with high efficiency,low carbon footprint,and fuel flexibility.The electrolyte,typically doped zirconia,is the"state of the heart"of the fuel cell technologies,determining the performance and the operating temperature of the overall cells.Yttria stabilized zirconia(YSZ)have been widely used in SOFC due to its excellent oxide ion conductivity at high temperature.The composition and temperature dependence of the conductivity has been hotly studied in experiment and,more recently,by theoretical simulations.The characterization of the atomic structure for the mixed oxide system with different compositions is the key for elucidating the conductivity behavior,which,however,is of great challenge to both experiment and theory.This review presents recent theoretical progress on the structure and conductivity of YSZ electrolyte.We compare different theoretical methods and their results,outlining the merits and deficiencies of the methods.We highlight the recent results achieved by using stochastic surface walking global optimization with global neural network potential(SSW-NN)method,which appear to agree with available experimental data.The advent of machine-learning atomic simulation provides an affordable,efficient and accurate way to understand the complex material phenomena as encountered in solid electrolyte.The future research directions for design better electrolytes are also discussed.

Electrochemical study on semiconductive properties of the passive film on rebar in concrete

The electrochemical behavior of metallic passive film on rebar in concrete is characterized by its semiconductive nature. The charge distribution at the interface between a semiconductor and an electrolyte is often determined by measuring the capacitance of the space-charge layer （Csc） as a function of the electrode potential （E）. When the space charge-layer serves as the depletion layer, the relation of Csc^-2 vs E resembles a Mott-Schottky plot （M-S plot）. The semiconductive properties of the passive film on rebar in concrete were analyzed with M-S plots to study the effect of chloride ions and mineral admixtures on rebar passive films. Some rebar electrodes were immersed in simulated concrete pore solutions, while others were embedded in concrete with/without mineral admixtures. In saturated Ca（OH）, solutions, the relation of Csc^-2-E of rebar electrodes shows linear MottSchottky relationship indicating that the passive film on rebar is a highly disordered n-type semiconductor, with donor density （ND） in the order of 10^26m^-3. After adding chloride ions （Cl wt%〈0.2%） in system solutions, the M-S plot slopes significantly decreased and ND increased, suggesting that chloride ion will cause passive film corrosion and breakdown. The M-S plots of the passive film on rebar electrodes embedded in concrete were similar to those immersed in simulated system solution. However, ND of those in concrete with mineral admixtures tended to be a little smaller, indicating that introducing proper quantity admixtures into concrete could make the rebar passive film have a thicker space-charge layer and therefore a thicker passive film layer.

Preparation and properties of PEO/LiClO_4/KH560-SiO_2 composite polymer electrolyte by sol-gel composite-in-situ method

Composite polymer electrolytes based on polyethylene oxide(PEO) were prepared by using LiClO4 as doping salt and silane-modified SiO2 as filler. SiO2 was formed in-situ in (PEO)8LiClO4 matrix by the hydrolysis and condensation reaction of Si(OC4H9)4. The crystallinity,morphology and ionic conductivity of composite polymer electrolyte films were examined by differential scanning calorimetry,scanning electron microscopy,atom force microscopy and alternating current impedance spectroscopy,respectively. Compared with the crystallinity of the unmodified SiO2 as inert filler,that of composite polymer electrolytes is decreased. The results show that silane-modified SiO2 particles are uniformly dispersed in (PEO)8LiClO4 composite polymer electrolyte film and the addition of silane-modified SiO2 increases the ionic conductivity of the (PEO)8LiClO4 more noticeably. When the mass fraction of SiO2 is about 10%,the conductivity of (PEO)8LiClO4-modified SiO2 attains a maximum value of 4.8×10-5 S·cm-1.

Regularity and mechanism of coal resistivity response with different conductive characteristics in complete stress-strain process

The stress,strain as well as resistivity of coal during uniaxial compression process were tested based on self-built real-time testing system of loaded coal resistivity.Furthermore,the coal resistivity regularity and mechanism were analyzed at different stages of complete stress-strain process,which includes the two kinds of coal body with typical conductive characteristics.The results indicate that coal resistivity with different conductive characteristics has different change rules in complete stress-strain process.It is mainly represented at the densification and flexibility phases before dilatation occurs.The variation of resistivity can be divided into two kinds,named down and up.Dilatation of coal samples occurred between 66%σ_(max) and 87%σ_(max).Because of dilatation,coal resistivity involves sudden change.The overall representation is shifting from reducing into improving or from slow improving into accelerated improving.Thus,coal resistivity always shows an increasing tendency at the plastic stage.After peak stress,coal body enters into failure stage.The expanding and communicating of macro fracture causes further improvement of coal resistivity.The maximum value of resistivity rangeability named λ reached 3.49.Through making real-time monitoring on coal resistivity,variation rules of resistivity can be deemed as precursory information so as to reflect the dilatation and sudden change before coal body reaches buckling failure,which can provide a new technological means for forecasting the dynamic disaster of coal petrography.

Mixed Conduction in BaCe0.8Pr0.2O3-α Ceramic

BaCe0.8Pr0.2O3-α ceramic was synthesized by high temperature solid-state reaction. The structural characteristics and the phase purity of the crystal were determined using powder X-ray diffraction analysis. By using the methods of AC impedance spectroscopy, gas concentration cell and electrochemical pumping of hydrogen, the conductivity and ionic transport number of BaCe0.8Pr0.2O3-α were measured, and the electrical conduction behavior of the material was investigated in different gases in the temperature range of 500-900℃. The results indicate that the material was of a single perovskite-type orthorhombic phase. From 500℃ to 900 ℃, electronic-hole conduction was dominant in dry and wet oxygen, air or nitrogen, and the total conductivity of the material increased slightly with increasing oxygen partial pressure in the oxygen partial pressure range studied. Ionic conduction was dominant in wet hydrogen, and the total conductivity was about one or two orders of magnitude higher than that in hydrogen-free atmosphere （oxygen, air or nitrogen）

Self-magnetism and Persistent Photoconductivity

Persistent photoconductivity has been investigated by various models, among which the Macroscopic Barrier model, Large-Lattice-Relaxation model, and Random Local Potential Fluctuations model are mostly well known. Although the three well-known models have played important roles in describing the persistent photoconductivity, they are not the principal cause of persistent photoconductivity. In this paper a classical model originated from ＂selfmagnetism of electron gas＂ is proposed to illustrate the persistent photoconductivity phenomenon. This classical model is based on electron gas pulsation, which depends on the charge density. Different concentrations of current carriers create different frequencies in the system, and thus the system is sensitive to different wave lengths of incident light. Then the construction of different detectors can be possible for different wave lengths of incident light.

An Extended Model for Coexistence of Superconductivity and Paramagnetism in High-T_c Superconductors

In the present work, the total magnetization in superconducting state is separated into critical state and paramagnetic components in terms of an H（x）-dependent magnetic flux density. Utilizing this model, we reproduce successfully M-H curves measured by Sandu et al. [Phys. Rev. B 74 （2006） 184511] and Sandu et al. [J. Supercond. Incorp. Novel Magn. 17 （2004） 701] for different forms of Jc.

Typical application of Rogowski coils in inspection of electrobath

During the aluminum electrolytic roasting process,each component of the electrobath of aluminum performs unsteadily when the electrolytic bath is in the pre-roasting stage. It is important to monitor the currents of the anodes and the cathodes of the aluminum electrobath at regular intervals. Both practice and investigation indicate that Rogowski coil can be adopted to measure heavy direct current of the anodes and the cathodes of the aluminum electrobath. The paper not only introduces the typical application of the Rogowski coil to inspect the state of aluminum electrobath in the roasting process, but also analyzes the principles of the coil sensor including its dynamic properties and some important measurement results respectively. The optimal parameters of the coil can be simulated by means of an advanced simulation tool: simulink tools based on MATLAB soft environment. Based on the gathered current data, an even-current coefficient has been introduced, and the current curve can be drawn. Since they are applied in AL-Electrolyzing, it is possible to distinguish the anode of which the current is not evenly distributed, and to take adjusting measures over a period of time to ensure that the current is evenly distributed.