Electrical Conductivity of Aluminium Alloy Foams

Closed-cell aluminium alloy foams were produced using the powder metallurgical technique.The effect porosity and cell diameter on the electrical conductivity of foams was investigated and the results were compared with a number of models.It was found that the percolation theory can be cussessfully applied to describe the dependence of the electrical ocnductivity of aluminium alloy foams on the relative density,The cell diameter has a negligible effect on the electrical conductivity of foams.     

Effect of γ-Radiation on the Conduction Phenomena of Amorphous As4Se4Te2 at Low Temperatures

The I–V characteristic of amorphous As₄Se₄Te₂ was studied at relatively low temperature ranging from – 158°C to –67°C. Three distinct regions of current-voltage range were observed and discussed on the basis of space-charge limited-current mechanism. A number of conduction parameters were calculated for fresh and γ-radiation samples. The effect of γ-radiation and thermal annealing process on the conduction behaviour of the test sample and on the conduction parameters were also discussed.     

Effect of a Second-Order Phase Transition on the Electrical Conductivity of the Cr–Polymer–Cu Structure

Physics of the Solid State - This report presents the results of studying an anomalous increase in the conductivity in the Cr/polymer/Cu structure near the antiferromagnet/paramagnet phase...     

Comment on ＂Electrical Conductivity and Current-Voltage Characteristics of Individual Conducting Polymer PEDOT Nanowires＂

In ＂Electrical Conductivity and Current-Voltage Characteristics of Individual Conducting Polymer PEDOT Nanowires＂, Long et al. reported the currentvoltage （Ⅰ - Ⅴ） characteristics of individual poly（3,4- ethylenedioxythiophene） （PEDOT） nanowires in the temperature range from 20 to 50K （Fig. 2（a））. The authors stated that at temperatures equal to 50 K and higher, the Ⅰ - Ⅴ curves were linear. With decreasing temperature the Ⅰ - Ⅴ curves gradually became nonlinear. The temperature behavior of Ⅰ - Ⅴ characteristics is not suitably explained.     

Type of Optical Transitions at the Fundamental Absorption Edge in TlGaSe2 and TlInS2 Crystals Subjected to γ-Radiation

Optics and Spectroscopy - The effect of γ-radiation on the optical properties of layered TlGaSe2 and TlInS2 crystals has been studied within a wavelength range of 400–1100 nm at 300 K....     

Electrical and thermoluminescence properties of γ-irradiated La2CuO4 crystals

Abstract

Measurements of the electrical properties of unirradiated as well as γ-irradiated La₂CuO₄ crystals were carried out at different temperatures in the frequency range of 0.1-100 kHz. Thermoluminescence (TL) studies were also performed on such crystals in the temperature range of 300-600K. The conductivity of the unirradiated La₂CuO₄ crystals were found to obey the power law frequency dependence at each measured temperature below the transition temperature (T_c = 450K). The activation energies for conduction and dielectric relaxation time have been calculated. The TL response and the dc resistance were found to increase with γ-irradiation dose up to 9-10 kGy. The results showed that the ferroelastic domain walls of La₂CuO₄ crystal as well as its TL traps are sensitive to γ-raditaion. This material can be used in radiation measurements in the range 225 Gy-10 kGy.     

Effects of γ-ray radiation grafting on aramid fibers and its composites

Armos fiber was modified by Co⁶⁰ γ-ray radiation in the different concentrations’ mixtures of phenol-formaldehyde and ethanol. Interlaminar shear strength (ILSS) was examined to characterize the effects of the treatment upon the interfacial bonding properties of Armos fibers/epoxy resin composites. The results showed that the ILSS of the composite, whose fibers were treated by 500 kGy radiation in 1.5 wt% PF, was improved by 25.4%. Nanoindentation technique analysis showed that the nanohardnesses of the various phases (the fiber, the interface and the matrix) in the composite, whose fibers were treated, were correspondingly higher than those in the composite, whose fibers were untreated. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectrum confirmed the increase in the polar groups at the fibers’ surface. Atomic force microscopy (AFM) results revealed that the surface of the fibers treated was rougher than that of the fibers untreated. The wettability of the fibers’ surface was also enhanced by the treatment. The conclusion that γ-ray irradiation grafting significantly improved the surface properties of Armos fibers could be drawn.     

Apparent Electrical Conductivity of Porous Titanium Prepared by the Powder Metallurgy Method

Porous titanium is produced by thepowder metallurgy method. Dependence of the electrical conductivity on the porosity and pore size is investigated and the experimental results are compared with a number of models. It is found that the minimum solid area model could be successfully applied to describe the relationship between the electrical conductivity and the porosity of porous titanium. This kind of conductivity increases with increasing pore sizes.     

Adsorption and dehydrogenation of 2-propanol on the surface of γ-Al2O3-supported gold

The adsorption and reactions of 2-propanol on γ-Al₂O₃ and γ-Al₂O₃-supported gold samples were investigated by infrared (IR) spectroscopy, modulated differential scanning calorimetry (MDSC) and mass spectrometry. Adsorption of the alcohol on the samples at room temperature led to formation of molecularly adsorbed 2-propanol and 2-propoxide species bonded to Al³⁺ sites. Treatment of γ-Al₂O₃ after alcohol adsorption in flowing He from 25 to 300 °C led to 2-propanol desorption, without evidence of surface reactions. In contrast, when supported gold samples were exposed to the same thermal treatment, formation of acetone and H₂ was observed by mass spectra of the effluent gases from the flow reactor. Concomitantly, IR spectra of the samples showed the appearance of a band at 1698 cm^? 1, assigned to ν_CO vibrations of adsorbed acetone. The formation of acetone occurred by the dehydrogenation of 2-propoxide species bonded to Al³⁺ sites, as evidenced by (a) the decrease in the intensities of their IR bands and (b) the presence of a MDSC peak at approximately the same temperature as that at which acetone was formed and the 2-propoxide species were consumed. It is proposed that gold particles on the γ-Al₂O₃ surface facilitate breaking of the β-CH bond of neighboring surface 2-propoxide species to give acetone. Our results emphasize the bifunctional character of supported gold catalysts for the dehydrogenation of alcohols.     

Effects of ultrasound-assisted H2O2 on the solubilization and antioxidant activity of yeast β-glucan

Yeast β-glucan (YG) possess an extensive range of biological activities, such as the inhibition of oxidation, but the poor water solubility of macromolecular YG limits its application. In this study, through the combined degradation of ultrasonic waves and H₂O₂, and the optimization of the main process parameters for solubilizing YG by response surface methodology (RSM), a new product of YG_UH was generated. The molecular weight, structural characteristics and degradation kinetics before and after solubilization were evaluated. The results showed that the optimal solubilization conditions were reaction time: 4 h, ultrasonic power: 3 W/mL, H₂O₂ concentration: 24 %. Under these conditions, ultrasound-assisted H₂O₂ increased the solubility (from 13.60 % to 70.00 %) and reduced molecular weight (from 6.73 × 10⁶ Da to 1.22 × 10⁶ Da). Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), Congo red (CR), scanning electron microscopy (SEM) revealed that ultrasound-assisted H₂O₂ increased the conformation's flexibility greatly, without changing the main structure of YG. More importantly, solubilization of YG improved free radical scavenging activity with YG_UH exhibiting the highest levels of DPPH and ABTS⁺ free radical scavenging activity. These results revealed that ultrasound-assisted H₂O₂ degradation could be a suitable way to increase the solubility of YG for producing value-added YG.     

Measurement of Electrical Conductivity of Porous Titanium and Ti6A14V Prepared by the Powder Metallurgy Method

Porous titanium and Ti6A14V are produced by the powder metallurgy method. Dependence of the electrical conductivity on the porosity and pore size is investigated and the experimental results are correlative and compared with several earlier models. A newly modified Mori-Tanaka relationship based on the effective field method is proposed, which is successfully applied to describe the dependence of the electrical conductivity of porous titanium and Ti6A14V on the porosity. The pore size has a minor effect on the electrical conductivity of both samples.     

Effects of pressure and gas-jet thickness on the generation of attosecond poulser

We investigate how the intensity and duration of an attosecond pulse generated from high-order harmonic generation are affected by the pressure and thickness of the gas jet by taking into account the macroscopic propagation of both fun- damental and harmonic fields. Our simulations show that, limited by the propagation effects, especially the absorption of harmonics, the intensity of an attosecond pulse cannot be improved by just independently increasing the gas pressure or the medium length. On the other hand, due to good phase-matching conditions, the duration of a generated attosecond pulse can be improved by changing the gas pressure.     

Reply to ＂Comment on ＇Electrical Conductivity and Current-Voltage Characteristics of Individual Conducting Polymer PEDOT Nanowires＇＂

Recently we reported electrical properties of an individual PEDOT nanowire .Ohlckers and Pipinys suggested that the temperature-behavior of I- V curves and resistance can be described in the framework of a phonon-assisted tunneling （PhAT） model. However, there are two points which need to be addressed. First, as shown in Figs. 1 and 2 of Ohlckers and Pipinys＇s Comment, obvious deviations have been observed between the experimental data and the fitting curves obtained from this model especially at low temperatures. Second, the PhAT model is based on the assumption that a source of charge carriers is the local electronic traps in the electrode-nanowire interface layer, the carriers enter the conduction band of the nanowire due to the PhAT through the barrier from these traps. This model has not considered the structure characteristics and conduction mechanism in polymer nanowires.     

Effects of barium on the nonlinear electrical characteristics and dielectric properties of SnO2-based varistors

The effects of barium on electrical and dielectric properties of the SnO_2·Co_2O_3·Ta_2O_5 varistor system sintered at 1250℃ for 60min were investigated. It is found that barium significantly improves the nonlinear properties. The breakdown electrical field increases from 378.0 to 2834.5V/mm, relative dielectric constant (at 1kHz) falls from 1206 to 161 and the resistivity (at 1kHz) rises from 60.3 to 1146.5kΩ·cm with an increase of BaCO_3 concentration from 0mol% to 1.00mol%. The sample with 1.00mol% barium has the best nonlinear electrical property and the highest nonlinear coefficient (α=29.2). A modified defect barrier model is introduced to illustrate the grain-boundary barrier formation of barium-doped SnO_{2}-based varistors.     

Synergetic Effects of Runaway Electron and Vertical Instability on the Wall Damage on HL-2A Tokamak

1 Generation of vertical instability Tokamak experiments show that the energy confinement time and performance are better, and the larger plasma current can be achieved for non-circular cross-sectional shape of plasma than circular cross-section. However, the external magnetic fields which are used to produce the non-circular cross sectional shape also cause the confined plasma to become unstable to small vertical displacement. In general, the ratio of elongation k is larger, the possibility of instability is more. In practice, this vertical displacement mode stabilized by feedback control system or other provided external radial magnetic field to balance out the plasma motion. Under some of situations the control system may be fail due to rapid growth rate of instability exceeding the ability of controlling. The plasma will then move vertically upwards or downwards depending upon the characteristics of instability and control failure.     

Effects of Ag on Electrical Properties of Ag/Ni/p-GaN Ohmic Contact

Properties of the Ag/Ni/p-GaN structure at different temperatures are studied by Auger electron spectroscopy, scanning electron microscopy and high resolution x-ray diffraction. The effect of Ag in ohmic contact on the crystalline quality is investigated and the optimized value of annealing temperature is reported. The lowest specific contact resistance of 2.5 × 10^-4 Ωcm^2 is obtained at annealing temperature of 550^o C.     

Effects of E2 and El-E2 Interference on Coulomb Dissociation of 19C

We investigate the effects of higher order multipole transitions, in particular electric quadrupole （E2） and El-E2 interference, on the Coulomb dissociation of 19 C within the framework of the first order eikonal approximation. The sensitivity of the total Coulomb breakup cross section and the longitudinal momentum distribution of the core fragment to these effects are checked. The breakup occurs predominately through the dipole transition and the contribution of E2 transition to the total cross section is found to be within the range from 1 to 3% of that of El. It is further observed that the El-E2 interference term contributes nothing to the integrated cross section. On the other hand, the longitudinal momentum distribution is observed to be insensitive to the E2 transition while the El-E2 interference introduces a small asymmetry in its shape.     

Effects of charge on the structures and spin moments of Nil3 cluster

The structural stability and magnetic properties of the icosahedral Ni13, Ni13^＋1 and Ni13^-1 clusters have been obtained by utilizing all-electron density functional theory with the generalized gradient approximations for the exchange-correlation energy. The calculated results show that the ground states of neutral and charged clusters all favour a D3d structure, a distorted icosahedron, due to the Jahn-Teller effect. The radial distortions caused by doping one electron and by doping one hole are opposite to each other. Doping one electron will result in a 1/2 decrease and doping one hole will result in a 1/2 increase of the total spin. Both increasing interatomic spacing and decreasing coordination will lead to an enhancement of the spin magnetic moments for Nil3 clusters.     

Impact of the Sintering Additive Al2O3 on the Electrical Conductivity of Proton-Conducting Electrolyte CaZr0.95Sc0.05O3 – δ

Physics of the Solid State - The impact of sintering additive Al2O3 on the electrical conductivity of calcium zirconate-based polycrystalline proton-conducting electrolyte...