共查询到20条相似文献,搜索用时 0 毫秒
1.
P. Cardoso J. Silva J. Agostinho Moreira D. Klosterman F.W.J. van Hattum R. Simoes S. Lanceros-Mendez 《Physics letters. A》2012
The influence of the dispersion of vapor grown carbon nanofibers (VGCNF) on the electrical properties of VGCNF/epoxy composites has been studied. A homogeneous dispersion of the VGCNF does not imply better electrical properties. The presence of well distributed clusters appears to be a key factor for increasing composite conductivity. It is also shown that the main conduction mechanism has an ionic nature for concentrations below the percolation threshold, while above the percolation threshold it is dominated by hopping between the fillers. Finally, using the granular system theory it is possible to explain the origin of conduction at low temperatures. 相似文献
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建立了electronphononfield(EPF)电子隧穿电导模型,推导了一维无序体系新的交流电导公式.通过计算具有20000—65000个格点的无序体系的交流电导率,分析了交流电导率与温度及外场频率的关系,讨论了无序度对交流电导的影响.计算结果表明,无序体系的交流电导率随外场频率的增加而近似线性的增大;无序体系在低温区出现了负微分电阻特性,电导率随温度的升高而增大,在高温区电导率随温度的升高而减小;无序度对无序体系的交流电导影响明显:在低温区,无序度越小,体系的电导率越大;在高温区,适当增大无序度,
关键词:
无序体系
电子隧穿
跳跃电导 相似文献
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This work reports on the effect of carbon nanotube aggregation on the electrical conductivity and other network properties of polymer/carbon nanotube composites by modeling the carbon nanotubes as hard-core cylinders. It is shown that the conductivity decreases for increasing filler aggregation, and that this effect is more significant for higher cylinder volume fractions. It is also demonstrated, for volume fractions at which the giant component is present, that increasing the fraction of cylinders within clusters leads to a break of the giant component and the formation of a set of finite clusters. The decrease of the giant component with the increase of the fraction of cylinders within the cluster can be related to a decrease of the spanning probability due to a decrease of the number of cylinders between the clusters. Finally, it is demonstrated that the effect of aggregation can be understood by employing the network theory. 相似文献
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《Journal of Electrostatics》2014,72(3):187-191
Several DC electrical conductivity models have been proposed to explain the properties of composite materials. In particular, generalized effective medium model was used, but, in many cases, the obtained parameters do not fit accurately the data. In this paper, we extended the study to Mamunya model, with adjustable parameters. Using different carbon black nanocomposites, we obtained a good agreement with the experimental results, but only for concentrations above the percolation critical concentration. Below this point, the fit is not accurate. 相似文献
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《Solid State Ionics》2006,177(19-25):1613-1617
The thermal diffusivity and electrical conductivity have been measured for two ion conducting polyethylene oxide (PEO) based polymer–ceramic composites viz. (PEO:NH4I) + xAl2O3, (PEO:LiBF4) + xBa0.70Sr0.30TiO3 and two solid–solid composites viz. AgI + xAl2O3, AgI +xBa0.70Sr0.30TiO3. The thermal diffusivity has been measured by the novel photoacoustic technique while the electrical conductivity has been measured by impedance spectroscopy technique using complex impedance plots. The pattern of variation in the electrical conductivity (σ) vs. composition plot and that in the thermal diffusivity (αs) vs. composition plot are similar. Interestingly, the correlation between αs and σ is not only qualitative but is quantitative as well in the sense that the ratio (αs / σ) remains constant for all the samples within the same system (though their conductivities are different) similar to Wiedmann–Franz law applicable to metallic conductors. 相似文献
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Wet acid oxidation treatment methods have been widely reported as an effective method to purify and oxidize the surface of industrial multi-walled carbon nanotubes. This work examines the use of a concentrated HNO3/H2SO4 mixture in an attempt to optimize the purification procedure of industrial multi-walled carbon nanotubes with diameter distribution statistics. It is shown that acid treatments of several hours are enough to purify the nanotubes. The electrical and thermal conductivities of epoxy composites containing 0.05–0.25 wt% of an acid-treated multi-walled carbon nanotube have been studied. The electrical conductivity of the composites decreases by more than three orders, whereas the thermal conductivity of the same specimen increases very modestly as a function of the filler content. 相似文献
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The interaction between the hot electrical conductivity and the residual electric field have been investigated in lower hybrid current drive (LHCD) experiments with non-zero loop voltage in the HT-7 tokamak. It has been found that the hot electrical conductivity contribute significantly to the current drive in partial non-inductively sustained plasmas. The hot electrical conductivities under different lower hybrid power levels and different parallel refractive indexes have been obtained. It is comparable to the Spitzer conductivity in high power LHCD experiments. 相似文献
11.
Manuela Ferrara Heinz-Christoph Neitzert Maria Sarno Giuliana Gorrasi Diana Sannino Vittoria Vittoria Paolo Ciambelli 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):66
The effect of the electrical field on the conductivity of linear low-density polyethylene/carbon nanotubes/ (LLDPE/CNT) composites during temperature cycling has been investigated. Under applied voltage a positive resistivity temperature coefficient was observed during heating already at low (2–3 wt%) CNT content, followed by a large negative temperature coefficient during cooling whose value depends on the applied voltage. The resistivity values after thermal cycling were markedly lower, while they slightly increased in the absence of an electrical field. The effects of thermal cycling on structural and physical properties of the composites have been evaluated by X-ray diffraction and differential scanning calorimetry. 相似文献
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Charles E. Starrett Romain Perriot Nathaniel R. Shaffer Tammie Nelson Lee A. Collins Chris Ticknor 《等离子体物理论文集》2020,60(3):e201900123
A new Sesame-type table for the electrical conductivity of aluminium is described. The table is based on density functional theory calculations and ranges from 10−3 to 1 times solid density (2.7 g/cm3), and from 10−2 to 103 eV in temperature. The table is compared with other those of simulations and to experiments and is generally in good agreement. The high-temperature, classical limit of the conductivity is recovered for the highest temperatures and lowest densities. The table is critically evaluated, and directions for improvements are discussed. 相似文献
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《Heat Recovery Systems and CHP》1992,12(6):497-503
Zeolite tuff-PTFE composites as adsorbing solids are investigated. Three zeolite tuffs, respectively rich in phillipsite, chabazite and clinoptilolite, were used as starting materials in preparing these composites. Their main features are discussed and compared with those of usual commercial adsorbents, emphasizing some of the advantages arising from their use. Parameters of significant importance in these materials such as water vapour adsorption capacity, thermal conductivity and bulk density are measured and related to each other. Useful indications in the choice of the most proper zeolite tuffs to be used as starting materials are collected. 相似文献
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Since the graphene nanoplates (GNPs) are usually folded and wrinkled, we propose a factor, flatness ratio, to theoretical analyze the thermal conductivity of GNP composites. An analytical model for the thermal conductivity of GNP composites is presented, which shows an excellent agreement with the experimental data. Theoretical analysis reveals that flatness ratio acts as a dominant role in determining the influence of other factors. We further show that the two-dimensional geometry is the primary factor for GNP outperforming one-dimensional carbon nanotubes as thermal conductive filler, rather than the other factors of thickness, length and interfacial thermal resistance. 相似文献
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Alexander A. Redkin Elena V. Nikolaeva Alexander E. Dedyukhin Yurii P. Zaikov 《Ionics》2012,18(3):255-265
The interrelationship between electrical conductivity, molar volume and enthalpy of mixing was studied for molten chlorides
and their mixtures. The dependence of electrical conductivity and activation energy on the molar volume is different for various
groups of salts. The dependence of specific conductivity on molar volume obtained for molten alkali chlorides was found to
be similar to other chloride salts. The specific conductivity of binary mixtures that lack strong chemical interactions between
the components can also be described by the proposed empirical equation. The enthalpy of mixing should be taken into consideration
for these chemical interactions. 相似文献
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Paleo A. J. Samir Z. Aribou N. Nioua Y. Martins M. S. Cerqueira M. F. Moreira J. Agostinho Achour M. E. 《The European physical journal. E, Soft matter》2021,44(5):1-8
The European Physical Journal E - The phenomenon of a precursor spreading in front of an advancing droplet is still not fully understood. We recently used a driven lattice-gas model to study the... 相似文献
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We have studied the dynamic conductivity of a composite consisting of well- and weak-conducting components with random fractal structure. In order to calculate effective properties of composite medium, we used hierarchic structure model and innovative iterative averaging method based on renormalization group transformations idea. Our results show, that the behavior of a composite over a magnetic field become even more complicated.Unusual peaks and oscillations appear in frequency dependencies of effective conductivity, permittivity and other properties. We discuss the influence of fractal parameters of the composite structure on such unusual behavior of effective properties. 相似文献
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T. Feurer R. Sauerbrey M. C. Smayling B. J. Story 《Applied Physics A: Materials Science & Processing》1993,56(3):275-281
When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The conduction mechanism is phonon-assisted variable range hopping, evident from the observed temperature and electric field dependence of the resistivity at low conductivities. The laser-induced conductivity depends on the ambient atmosphere during irradiation. Transmission spectroscopy in the visible region and infrared Fourier transform spectroscopy have been used to characterize the material. A thermal mechanism is proposed for the formation of conducting polyimide, by excimer-laser irradiation. 相似文献