Papers by Keyword: Electrical Conductivity

Abstract: Some conductive MWNT with different loading was filled in epoxy resin through the dispersion technique of surfactant-decoration, high-intensive shear mixing, and bath sonication process. This kind of conductive functional resin coating was then simply brushed on a FRP sheet surface. The electrical conductivity of the cured nanocomposite coating was acquired by four-electrode method to explore the percolation threshold and piezoresistive effect. The change in its longitudinal strain of the coating and FRP sheet was simultaneously sampled under three-point bending. Results reveal that, at the onset percolation threshold (2.0%), the nanocomposite possesses superior piezoresistive effect with high strain-sensitivity (up to 27), which favors to health monitoring to FRP structure used as a novel self-sensing coating.

Abstract: Electrical properties of carbon nanotubes-based epoxy nanocomposites for high electrical conductive plate were investigated. Dispersion and incorporation mechanism between two conductive fillers with different sizes (CNTs and Graphite) in the polymer matrix are the key factors in the fabrication of high electrical conductivity plate. Different variation of carbon nanotubes (CNTs) (1~10 wt %) and Graphite (G) (60 ~ 69 wt %) loading concentration were added into the epoxy resin. Dispersion of CNTs and G in epoxy resin were conducted by the internal mixer with a Haake torque rheometer. The mixture of G/CNTs/EP was poured into the steel mold, and G/CNTs/EP nanocomposites had been fabricated through compression molding. The electrical conductivity of nanocomposites in terms of variation of G and CNTs concentration were measured by the four point probe for in a plane electrical conductivity. The results revealed that addition of G/CNTs and increasing curing temperature are effective ways to produce high electrical conductive nanocomposites. The highest electrical conductivity was reached on 104.7 S/cm by addition 7.5 wt% of CNTs. Dispersion quality of G and CNTs in the epoxy matrix was observed on the fractured surface by scanning electron microscopic.

Abstract: Spark plasma sintering (SPS) is a newly developed technique that enables poorly sinterable tin oxide powder to be fully densified. Sintering without sintering aids is of great importance when SnO₂ ceramics are used as electrodes in the glass melting industry and aluminum electrometallurgy. Dense and good-conductive Antimony-doped SnO2 ceramics can be achieved by SPS at a lower sintering temperature and in a shorter time. When the Sb₂O₃ concentration is 1.0 mol%, the densities of the samples reach their maximum value, which is 98.2% of the theoretical value. When the content of Sb₂O₃ was 2.44mol%, SnO₂ ceramics with densities 97.6% can be obtained at 800°C-1000°C, and the resistivity was about 5.19×10^-2Ω.cm at the sintering temperature of 1000°C. Defined amount of Sb³⁺ used in our research are beneficial to low the sintering temperature and promote the densification of SnO₂ ceramics

Abstract: Electroconductive TiN/O′-Sialon multiphase ceramics were prepared by pressureless sintering from TiN/O′-Sialon powders as the chief raw material which were synthesized by the carbothermal reduction nitridation method using high titania slag, silicon fume and bauxite chalmette. Phase compositions and were analyzed. The effect of microstructure and TiO₂ content in initial raw materials on electrical conductivity were studied by SEM and TEM. The electro-discharge machining (EDM) of the materials was carried out. The results show that the sintered samples consist of O′-Sialon and TiN. O′-Sialon grains exhibit equiaxied morphology and the particle sizes are about 1-3μm. TiN grains exhibit fine granular morphology and most of grains have lower size than 0.5μm. The minimum amount of TiO₂ in initial raw materials is 25wt% for the formation of electroconductive network in the multiphase ceramics, of which the electrical resistivity is 1.8×10^-2 Ω·cm and meets the requirement of electrical discharge machining.

Abstract: Effect of rare earth yttrium on the properties and microstructure of Cu-0.6Cr-0.15Zr-0.05Mg-0.02Si alloy was investigated. The results showed that Cu-0.6Cr-0.15Zr-0.05Mg-0.02Si alloy obtained good comprehensive performance after 80% deformation and then aging at 480°C for 1h, the hardness and electrical conductivity reached 152HV and 85.5%IACS, respectively. The aging time of Y-containing alloy for attaining peak hardness was postponed and the precipitates were finer (2-4nm) and interparticle spacing was shorter than ones of Y-free alloy. The hardness and electrical conductivity of the Y-containing alloy after 80% deformation and then aging at 480°C for 45 min reached 174HV and 82.1%IACS, respectively. The tensile fractures of the two alloys which exhibits the obvious feature of tough fracture.

Abstract: This study used carbon aerogels (CA) and phenolic resin in fixed proportations to produce nano high polymer resin, and used poly ehtylene oxide (PEO) as the modifying agent for phenolic resin to improve the mechanical properties of phenolic resin and promote the surface conductivity. The prepared nano high polymer resin and carbon cloth were made into nano-prepreg by using ultrasonic impregnation method, and a nano-prepreg composite material was prepared by using hot compacting and cut to test pieces to measure its mechanical properties and surface conductivity as well as the influence of temperature-humidity environment (85°C/168hr and 85°C/85%RH/168hr) on mechanical properties. The result showed that the surface conductivity increased by 64.55%, the tensile strength at room temperature increased by 35.7%, the flexural strength increased by 18.4%, and the impact strength increased by 101%. In hot environment (85°C/168hr), the tensile strength decreased by 23.8%, the flexural strength increased by 3.1%, and the impact strength increased by 84.6%. In high temperature-high humidity environment (85°C/85% RH/168hr), the tensile strength decreased by 29.6%, the flexural strength decreased by 17%, and the impact strength increased by 95.7%.Introduction

Abstract: As well known, the weld line defect in injection molding process results detrimental to mechanical properties and surface quality. However, the electrical conductivity of the injection molded part is influenced as well. In this study, in order to reveal the mechanism of the weld line affecting the electrical conductivity of injection molding parts, the conductive polymer composites with various carbon nanofibers filling contents were compounded. Those composites were formed as the tensile samples with and without weld line defects by injection molding process. According to the electrical resistance measurements for the samples, it can be found that at relative low filling content of 10wt%, the weld line contributes to increase the electrical conductivity of the injection molding parts due to its effect on nanofibers’ orientation. However, when the filling content is higher than 20wt%, this effect is not significant any more.

Abstract: The paper researches the processing for leather by utilizing different kinds of tanning materials, retanning and leather fatliquoring, and analyses the effect of leather electroconductibility influenced by water ratio in it and pressure added on the leather. The study illustrates: the greater electric conduction function of tanning materials or amount of polar radical they containing, the better conductivity the leather has. There is a compact relationship between the electric charge of different chemical material which were added in leather and electric conduction function, and the electrical conductivity of leather can be improved obviously by increasing the electric charge and water ratio the leather has.

Abstract: Recently, it has been observed that surface modification of carbon nanotubes（CNTs）influences on CNT’s distribution among epoxy resin and affects the mechanical properties and electrical conductivities of CNTs. Owing to above-mentioned effects, carbon nanotubes treated with oxidizing in organic acids, a kind of surface modification, generates functional groups on the surface of CNTs taht is a major investigation in this study to enhance mechanical properties and electrical conductivities of CNTs. The influence of the different proportion contents of CNTs added into epoxy resin on mechanical properties and electrical conductivities of composites was investigated, and strength of material tested under different temperature environments was observed. Moreover, the creep behavior of carbon fiber（CF）/epoxy resin thermosetting composites tested under different temperature and stress were also concerned to be analyzed. The resulting creep behavior consists of only two stages, including primary creep and steady-state creep. The effects of creep stress, creep time, different humidity treatment on the various temperature creep of composites containing different proportion contents of CNTs were investigated. It is believed that the increased creep strains can be attributed to higher applied stresses, longer creep times, higher humidity, higher temperature and lower hardnesses. The test results also exhibit that mechanical strength and electrical conductivity increase with the increase of CNTs content added into composites. In the influence of temperature effect on specimen, because of different coefficient of expansion among matrix, fiber and CNTs, the overexpansion of matrix caused by high temperature results in crack occurred among matrix. From observation of the fracture surface by SEM image, the debonding occurs and longitudinal fibers are pulled out due to poor interfacial bonding of fiber and matrix, which also results in entire strength degeneration.

Abstract: In the present study, nanocrystalline ceria powder and 10 mol% zirconia-doped ceria (10ZDC) powder were prepared by co-precipitation method from cerium nitrate and zirconium nitrate precursors. The resulting particles with irregular shapes were printed onto alumina substrate for the investigation of oxygen gas sensing behavior. The coating morphology of 10ZDC with a network structure revealed a better connection enhancing the sensing properties. Zirconia doping tended to inhibit the grain growth and decrease the lattice constant of ceria. Such effects may improve the electrical conductivity of 10ZDC under different oxygen partial pressures and shorten the response time of 10ZDC to the change of oxygen partial pressure.