Papers by Keyword: Electrical Conductivity

Abstract: Cu-14Fe and Cu-17Fe alloys were produced by casting and processed into in situ composites by hot and cold deformation, and intermediate heat treatment. The microstructures were investigated by using a scanning electron microscope and an optical microscope. The electrical conductivity was evaluated by using a digital micro-ohmmeter. The tensile strength was measured by using an electronic tensile-testing machine. The results show that there are similar cast and deformation microstructures in Cu-14Fe and Cu-17Fe. The tensile strength of deformation-processed Cu-17Fe in situ composite is much higher than that of Cu-14Fe, while the conductivity of deformation-processed Cu-17Fe in situ composite is slightly lower than that of Cu-14Fe at the same cold deformation strain. The Cu-17Fe in situ composite produced by using proper thermo-mechanical processing possesses a good combination of tensile strength and electrical conductivity.

Abstract: On exposure of high-voltage microsecond pulsed fields the molten salts pass into a non-equilibrium state with disappearance of the characteristic peaks of the Raman spectra and increased electrical conductivity. In the course of the relaxation of nonequilibrium melts their Raman spectra and electrical conductivities are restored to the values and features specific to equilibrium systems in over about 10 minutes.

Abstract: (y) Li_0.5Ni_0.7Zn_0.05Fe₂O₄ + (1-y) Ba_0.5Sr_0.5TiO₃ magnetoelectric composites with y = 0.1, 0.3 and 0.5 were prepared by a conventional standard double sintering ceramic technique. X-ray diffraction analysis confirmed the phase formation of ferrite, ferroelectric and their composites. logρ_dc Vs 1/T graphs reveal that the dc resistivity decreases with increasing temperature exhibiting semiconductor behavior. The plots of logσ_ac Vs logω² are almost linear indicating that the conductivity increases with increase in frequency i.e. conductivity in the composites is due to small poloron hopping. Dielectric constant (έ) and dielectric loss (tan δ) were studied as a function of frequency in the range 100Hz–1MHz which reveal the normal dielectric behavior except the composite with y = 0.1and as a function of temperature at four fixed frequencies (i.e. 100Hz, 1KHz, 10KHz, 100KHz). ME voltage coefficient decreases with increase in ferrite content and was observed to be maximum of about 7.495 mV/cmOe for S₁ i.e. (0.1) Li_0.5Ni_0.7Zn_0.05Fe₂O₄ + (0.9) Ba_0.5Sr_0.5TiO₃ composite.

Abstract: Apatite oxides electrolytes La_9.33(SiO₄)₆O₂ was prepared following the Sol-Gel aqueous route. The structure of La_9.33(SiO₄)₆O₂ was evaluated using the X-ray diffraction patterns (PXRD). The main phase is La_9.33Si₆O₂₆ with the Minor impurity phase of La₂SiO₅ as a secondary phase. And dense La_9.33(SiO₄)₆O₂ nanoceramics with grain size of smaller than 100 nm were fabricated by high-pressure sintering, the pressure of 4.5 GPa, the sintering temperature of 1200 ^oC and dwelling time of 10 min were used. The ionic conductivity of the samples is evaluated by AC impedance spectroscopy. The conductivity of dense La_9.33(SiO₄)₆O₂ nanoceramics by high-pressure densification is one multiple higher compared with that of the microcrystalline ceramics. The activation energy in the samples by high-pressure densification and conventional sintering method was 1.06 eV and 1.44 eV, respectively.

Abstract: Dual-frequency ultrasonic assisted ozonation was proposed to degrade pesticide wastewater. The frequencies of ultrasound were 28 kHz and low-MHz (208 kHz, 495 kHz, 679 kHz and 890 kHz). The influence of ultrasound frequency was investigated in this paper. The electrical conductivity of deionized water was measured under different conditions, and degradation rate of acephate solution was used to verify degradation effect of the treatment. The results implied that the 208 kHz system was suitable for ozone dissolving and 495 kHz system was suitable for acephate degradation.

Abstract: Vulcanization methods of conductive silicon rubber are described in this paper. Several common vulcanization agents are also be introduced. The conductivity and mechanical properties of the conductive silicon rubber composite materials are effected by vulcanization systems. The influence degree is introduced by respectively using different vulcanization method, vulcanizing time and vulcanizing temperature. The research progress of vulcanization system of conductive polymer composites is elaborated.

Abstract: Multiwalled carbon nanotubes/Polycarbonate (MWCNTs/PC) nanocomposites were successfully prepared by melting mixing. With the injection speed and temperature changed, different MWCNTs contents MWCNTs/ PC composites were prepared. The electrical conductivity of nanocomposites was compared with different injection speeds and injection temperatures. It was found that the electrical conductivity of the MWCNTs/PC nanocomposites was decreased with MWNTs content increasing, and were both affected by the injection speed and temperature. Besides, at the vicinity of the surface of samples, the resistivity of MWCNTs/PC nanocomposites was the maximum; the closer to the samples inner, the resistivity was smaller and more stabilized. The microstructure and morphology of composites were analyzed by Scanning Electron Microscopy (SEM) techniques, and the MWCNTs’ dispersion in PC matrix and the interfacial interaction between MWCNTs and PC were analyzed.

Abstract: The use of aniline as carbon source has two advantages for the synthesis of carbon materials exhibiting conducting properties: the aromatic ring contributes to the graphitic character and the presence of nitrogen could work as n-dopant, decreasing the band gap of the carbon materials. These conditions contribute to improve their efficiency as electrocatalysts, for example in fuel cells. The objective of this work is to correlate physicochemical characteristics and electrical behavior of carbon samples prepared by nanocasting of aniline in mesoporous silica and its subsequent carbonization under controlled conditions.

Abstract: Yttria-stabilized zirconia is a singular polycrystaline ceramic with a range of technological applications. The combination of its physical properties is responsible for application as solid electrolytes in solid oxide fuel cells. High densification is required for this and other applications. The sintering of this solid electrolyte is still a matter of investigation. To reduce the sintering temperature, the introduction of additives is an effective approach. In this work, the effects of lithium addition on microstructure and electrical conductivity of 8 mol% yttria-stabilized zirconia was studied by scanning electron microscopy and impedance spectroscopy, respectively. Cylindrical pellets were prepared by pressing, followed by sintering at 1200oC without and with 1 and 2 mol% lithium (metal basis). As precursor materials both lithium carbonate and lithium fluoride were used. The main microstructure features were correlated with the results of electrical conductivity.

Abstract: Performances of Ag-SnO₂ electrical contact materials can be strongly affected by the microstructure. In this work, Ag-SnO₂ composite powders were synthesized by chemical reductive precipitation method. During the precipitation process, Ag particle was deposited onto the surface of SnO₂ particle with the assistance of citric acid. The microstructure and properties were analyzed for the prepared Ag-SnO₂ electrical contact materials. Our research reveals that the particle size of SnO₂ has significant influence on the morphology of the Ag-SnO₂ composite powders, and therefore on the microstructure and physical properties of the electrical contact materials. With the decrease of particle size of SnO₂, hardness of the Ag-SnO₂ electrical contact materials increases, while electrical conductivity decreases.