Papers by Keyword: Electrical Conductivity

Abstract: Leakage detection of seawall is important for assessing seawalls present situation, appraisal and strengthening the protection and provide quantitative basis for project engineering management. These papers set forth the work principles of EM34-3 Type earth conductivity detector; and analyzed the detecting results of seawall located on Qiantang River. The research results show that the seawall safety grade is good, and this technology is suitable to assess seawall safety with a good reliability.

Abstract: This study is focused on the elaboration of 8 mol.% yttria stabilized zirconia (YSZ) thin films onto porous supporting NiOYSZ anode substrates using pulsed laser deposition (PLD),and their microstructural and electrical characterizations. Better crystallinity and grain connectivity is observed increasing the deposition temperature until best values are obtained at 500°C. The greater relative conductivity enhancement is found at 300-500°C. The observed an increased conductivity at lower temperatures may be caused by a combination of nanoscaled effect of the YSZ thin film and interfacial effects between YSZ thin film and substrate.

Abstract: Natural graphite, carbon fiber and copper powder as fillers are incorporated into phenolic resin to fabricate conductive polymer composites by hot compression moulding. The effects of the preparing method and mould temperature on the density, electrical conductivity and hardness of composites are investigated. It is found that the density, electrical conductivity and hardness of composites increase as mould temperature increase from 150 °C to 180 °C. Up to 200 °C, the hardness of composite shows a large decrease. At 170 °C, the density, electrical conductivity and hardness of composites are 1.904 g/cm³, 3.43 × 10³ S/m and 54 HS, respectively. Oxidation action occurring in the phenolic resin could be the main reason for the large decrease of hardness as temperature increases up to 200 °C.

Abstract: The electrical properties of nanocomposite SiO₂(Si) films containing Si nanoclusters have been investigated. The films were formed by oxide assisted growth that included ion plasma sputtering (IPS) of Si target and following high temperature annealing. It was determined that electrical conductivity of the films correspond to the mechanism of hopping conductivity with variable hopping length through the traps near the Fermi level (Mott mechanism) due to the large number of silicon dangling bonds in the dielectric matrix. The peculiarities of charge capture in nanocomposite SiO₂(Si) films for their application as the medium for charge storage in memory cells have been investigated by C-V method. The good charge storage possibility of SiO₂(Si) films formed by IPS deposition with followed temperature annealing has been observed. The negative differential capacitance has been revealed in conditions of semiconductor surface accumulation. The physical model for explanation of the negative differential capacitance of MIS structures with nanocomposite SiO₂(Si) films as the dielectric has been proposed. The model is based on the parallel conjunction of the oxide capacitance and nanocrystals capacitance.

Abstract: This work aims to correlate the electrical conductivity and mechanical properties of binary composites made of natural rubber (NR) and carbon black (CB). The samples were prepared using both a wet and dry mixing method before making the composites with a conventional rubber vulcanization process. The dry-mixing method was found to achieve higher electrical conductivity than the wet-mixing method. The composite made by efficient vulcanization (EV) had lower compression set than the composite made by conventional vulcanization (CV) and the compression set increased with an increase of CB. The highest tensile strength of the composite was found at CB content of 20 phr. The percolation threshold concentration of the binary composite was observed at 10 phr CB. Electrical conductivity of the composite depended on sample thickness where thinner samples had higher conductivity than the thick sample.

Abstract: Improvement of the electrostrictive polymer with natural rubber (NR) compliant electrodes can potentially offer advantages for enhancement electromechanical efficiency of elastomer actuators. The NR elastomers are capable of advantageous features such as a high productivity, elasticity, and ease of processing. In this work, the NR composites filled with carbon black (CB) nanopowders at high conductivity was used as compliant electrodes on polyurethane electrostrictive polymer. The compliant NR composites electrodes were fabricated by using spin coating technique. The morphology of the NR composites was observed by the scanning electron microscope (SEM). The mechanical, electrical and electromechanical properties of NR composites were investigated. The electric field-induced strain of sample with compliant NR composites electrodes, and comparison with metallic electrodes was determined by using the photonic displacement apparatus. The results show that the thickness strain of polyurethane electrostriction with compliant NR was higher that with metal electrodes, depending not only on compliance between sample and electrodes, but also good conductivity and adhesion of electrodes. Correlation of the electromechanical properties and the mechanically coupled in stretching and compressing to volume incompressibility of polymer are also discussed.

Abstract: Electrical and mechanical properties of epoxidized natural rubber (ENR-25) filled with conductive carbon black (CCB) have been investigated. SEM was used to analyze dispersion of CCB particles in rubber matrix. The results indicated that the AC conductivity increase with increasing volume fraction of carbon black as well as frequency. The percolation thresholds of the electrical conductivity was found at 0.10 volume fraction of CCB. Furthermore, addition of CCB at volume fraction 0.05 caused the highest tensile strength of the composites. The tensile strength and elongation at break were decreased with increasing content of CCB greater than 0.05 volume fraction. However, the volume fraction of CCB at 0.10 demonstrated the most suitable proportion for the ENR composites with superior electrical and mechanical properties.

Abstract: The dielectric and electric properties of poly (methyl Methacrylate) (PMMA) and Poly (vinyl Pyrrolidione) (PVP) in polar solvent have been studied in the frequency range of 20 Hz to 2 MHz at room temperature. The effect of polar solvent environment on the dielectric and electrical parameters such as the complex dielectric constant (Є*), relaxation times complex electrical modulus (M*) and complex impedance (Z*) has been analysed . Dielectric dispersion curves show that the polymer concentration plays an important role in governing its segmental motion in solvent solution. At low frequencies, the ionic conduction and electrode polarization seems to have dominant influence on the large increase of complex dielectric constant values.

Abstract: Abstract: The magnetic nano-particles of nickel ferrite were synthesized successfully by sol-gel auto-combustion method using high purity metal nitrates and citric acid as chelating agent. The as prepared powder of nickel ferrite was sintered at 5500C for 5 hr to obtain good crystalline phase and was used for further study. The X-ray diffraction technique was employed to confirm the single phase formation of nickel ferrite nano-particles. The X-ray diffraction pattern shows the Bragg’s peak which belongs to cubic spinel structure. The values of lattice constant, X-ray density, oxygen parameter and radii of tetrahedral and octahedral sites were calculated from XRD data. The average crystallite size was estimated using Scherrer’s formula and found to be 6 nm. The temperature dependence of the electrical conductivity plot shows the kink, which can be attributed to ferromagnetic-paramagnetic transition. The activation energy obtained from resistivity plots in paramagnetic region is found to be more than that in ferrimagnetic region. The conduction mechanism in these nickel ferrite nano-particles has been discussed on the basis of hopping of electrons.

Abstract: The complex relative dielectric function ε*(ω) = ε’- jε” of anisole (AN), 1-heptanol (1-HeOH) and their binary mixtures of varying concentration have been measured using Precision LCR meter in the frequency range 20 Hz to 2 MHz at 303 K. The electrical/dielectric properties of the liquid samples are represented in terms of intensive quantities namely, complex relative dielectric function ε*(ω), electrical modulus M*(ω), electrical conductivity σ*(ω) and extensive quantities, i.e. complex admittance Y*(ω) and complex impedance Z*(ω). All of these presentations are used to explore various processes contributed in the electrical/dielectric properties of the mixtures of two polar liquids.