Electric conduction in copper gallium telluride thin films

P type copper gallium telluride (CuGaTe₂) synthesized from the elements was used as a source for the preparation of films by flash evaporation. Films of different thicknesses were prepared and their electrical conductivity was measured in the temperature range 100–300 K. While in the case of thin films the low temperature conduction could be explained by a variable range hopping process, for thicker films the conduction process could be attributed to thermally assisted tunnelling through the grain boundary barrier. The high temperature conductivity data fits well to the process of transport by thermionic emission over the grain boundaries.     

The role of conductive fillers on the rheological behavior and electrical conductivity of multi-functional shear thickening fluids (M-STFs)

Multi-functional shear thickening fluids (M-STFs) with both shear thickening behavior and electrical conductivity have a great potential for usage in a variety of applications ranging from intelligent anti-impact and vibration damping structures to effective electric mechanical platforms. However, the influences of conductive fillers on the rheological behavior and electrical conductivity of M-STFs remained unclear. In this study, the role of conductive fillers including multi-walled carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), and mixtures of MWCNT/CNF was investigated through the response surface methodology (RSM) in the temperature range of 0 °C to 60 °C. The individual and combined effects of filler content, temperature, and type of fillers on the electrical resistance and rheological behavior of M-STFs were studied. The results revealed the significant role of conductive fillers on the rheological properties and electrical conductivity of M-STFs. It is found that the initial viscosity of M-STF increases with increasing the filler content. Moreover, the M-STFs containing CNF exhibits higher electrical conductivity and lower percolation threshold (0.4 wt%). The results of this work provide new insights for the development of novel STF-based systems with multi-functional properties.     

The electrical behavior of laminated conductive polymer composite at low temperatures

The study deals with the electrical characteristics of laminated conductive polymer composites consisting of epoxy and carbon fibers with different concentration. The composites contain 7, 17.5, and 25.2 wt% carbon fibers (10, 25, and 36 layers of carbon fibers), respectively. The DC electrical conductivity was studied as a function of filler concentration in low temperature range 25–275 K. It was found that the composites exhibit negative temperature coefficient of resistivity (TCR) and electrical conductivity enhancement with temperature and carbon fibers concentration. The semiconducting behavior of the observed electrical conductivity is characterized by two different regions: high temperature range where the conductivity increases gradually (thermal process) and low temperature range where the conductivity increases with a less rate (Motts hopping process) with increasing of temperature.     

Influence of thermal treatment on the structure and electrical conductivity of thermally expanded graphite

Thermally expanded graphite (TEG) is a promising filler beneficial to electrically conductive materials due to its high electrical conductivity, low density, and cost. In this work, the electrically conductive TEG was prepared by thermal treatment of the expandable graphite in the range of temperatures from 400 to 800 °C in air. Effects of the temperature treatment on the morphology and chemical structure of TEG were thoroughly characterized. Thermal treatment of the expandable graphite resulted in thermally expanded graphite formation with up to 6 times higher electrical conductivity than the precursor. Optimal conditions of thermal treatment were established at 600 °C providing material with the highest electrical conductivity, high expansion volume, and a well-ordered and defect-less structure.     

Manufacturing techniques and property evaluations of conductive composite yarns coated with polypropylene and multi-walled carbon nanotubes

This study uses a melt extrusion method, a method for producing wires, to coat polyester (PET) yarns with polypropylene (PP) and multi-walled carbon nanotubes (MWCNTs). The resulting PP/MWCNTs-coated PET conductive yarns are tested for their tensile properties, processability, morphology, melting and crystallization behaviors, electrical conductivity, and applications. The test results indicate that tensile strength of the conductive yarns increases with an increase in the coiling speed that contributes to a more single-direction-orientated MWCNTs arrangement as well as a greater adhesion between PP/MWCNTs and PET yarns. 8 wt% MWCNTs results in an 18 °C higher crystallization temperature (T_c) of PP and an electrical conductivity of 0.8862 S/cm. The test results of this study have proven that this form of processing technology can prepare PP/MWCNTs-coated PET conductive yarns that have satisfactory tensile properties and electrical conductivity, and can be used in functional woven fabrics and knitted fabrics.     

The effect of Bi2O3 on the microstructure and electrical conductivity of ZrO2-Y2O3 ceramics

ZrO₂-Y₂O₃ ceramics with varying Bi₂O₃ contents were prepared and their microstructures and electrical conductivities investigated. The phase stability of cubic fluorite zirconia was disturbed by the introduction of Bi₂O₃ and tetragonal or monoclinic second phases appeared. The effect of the second phases on the intragrain and the grain boundary conductivities was investigated in the 300–550 C range using complex plane analysis in the frequency range of 5 Hz to 13 MHz. It showed that conductivity data could readily be interpreted in terms of possible physical models and electrical equivalent circuits. Tetragonal phases had a small positive influence on the intragrain conductivity. The grain 9boundary resistivity could be diminished by discrete monoclinic second phases which offered more conductive intergranular contacts.     

导电混凝土的导电性能及影响因素研究进展

导电混凝土是具有导电、电热、电磁屏蔽等诸多特性或功能的复合材料,在道路融雪化冰、电气设备接地、结构健康监测以及电磁屏蔽等领域具有广阔的应用前景。导电混凝土应具有适宜的导电性能和电阻率稳定性,但是导电材料类型、形态和掺量以及导电混凝土含水率和环境温湿度等诸多因素都可能导致导电性能和电阻率稳定性降低,从而制约导电混凝土的工程应用。分类对比了常见导电材料的性能差异以及用不同导电材料制备的导电混凝土的导电性能差异,在此基础上,探讨了导电混凝土的导电性能和制备方法的研究现状,较为系统地分析了导电材料类型和掺量等因素对导电性能的影响,并提出了改善导电性能和电阻率稳定性的建议。     

Estimation of compensation ratio by identifying the presence of different hopping conduction mechanisms in SnO2 thin films

The electrical properties of undoped SnO₂ thin films prepared by the sol-gel technique were investigated by conductivity measurements in a temperature range of 50-200 K. Structural characterizations of the films were performed by atomic force microscopy and X-ray diffraction. Optical properties of the samples were also characterized by optical absorption spectroscopy. The different hopping models were used to investigate the characteristics of electrical conduction by hopping in employed temperature range. It was shown that three types of behavior can be expected, nearest-neighbour hopping at high temperatures, the Mott variable-range hopping at low temperatures and Efros-Shklovskii variable-range hopping at lower temperatures. The criteria for the observation of these three regions were established and the transitional behavior of the conductivity was determined. The experimentally determined critical transition temperatures were at the orders of magnitudes with what could be expected based on hopping conduction calculations. Under these analyses, the compensation ratio of the films was determined.     

Manufacture of high sensitive Ag-Fe3O4-PDMS nanocomposite pressure sensor through morphology control of conductive filler

Silver nanowire (AgNW) has been proposed as a promising conductive filler candidate based on its excellent electrical and thermal conductivity properties. However, residual PVP (polyvinylpyrrolidone) exists on the surface of AgNW synthesized through the polyol process. As a result, there is a problem in that the contact resistance (R_C) is increased. This problem can be solved by improving the contact area between AgNWs. Therefore, in this study, the electrical conductivity characteristics of AgNW were to be improved by etching which can increase the contact area of AgNW. The concentration of etchant was adopted as the main parameter, and ideal etching parameter was derived by analyzing the microstructure and electrical conductivity characteristics of the etched AgNW. The etched AgNW showed a minimum resistance of 0.034 kΩ/□, and the etched AgNW showed about 23% improved surface area compared to the as-prepared AgNW. In addition, by controlling the ultrasonic milling parameters, it was intended to produce Fe₃O₄ nanoparticles (Fe₃O₄ NP) that make the conductive structure less dense and prevent stacking between AgNWs by acting as a nano-spacer. The prepared Fe₃O₄ NP showed an average particle size distribution of 150 nm or less. Ag-Fe₃O₄-PDMS (Polydimethylsiloxane) nanocomposite was prepared through such a conductive filler. As a result of analyzing the response characteristics of Ag-Fe₃O₄-PDMS nanocomposite, the resistance decreased linearly as the applied pressure increased, and the root-mean-square was 0.99 or higher.     

颗粒填充型聚合物的导热性能与摩擦磨损性能研究

采用蒙特卡罗可控空间分布算法,生成网链构型的三维代表体积单元(RVE)模型,数值研究了非均匀分布下不同组分氮化铝/石墨/银导热硅脂的导热性能。制备了氮化铝、氮化铝/石墨、氮化铝/石墨/银三种填料体系的导热硅脂,并测试所有样品的热导率和体积电阻率。采用往复摩擦磨损试验机对室温下导热硅脂在钢-钢摩擦副上的载流摩擦磨损性能进行研究。利用扫描电子显微镜(SEM)观察金属表面并利用能谱分析仪(EDS)对表面元素成分进行分析。结果表明:导热填料形貌越丰富,硅脂中的导热网络越致密,氮化铝/石墨/银硅脂的最大热导率可达1.623 W/(m·K),可实现在较少填充量下获得较高热导率;氮化铝/石墨/银有限元模型模拟的结果更贴近实验测量值,可以用来预测球状/片状/棒状颗粒填充导热硅脂的导热性能;氮化铝/石墨/银导热硅脂的载流摩擦磨损性能最优,这归结于其导热性能和导电性能协同减轻电弧对金属表面的侵蚀。     

Electrical conductivity of single crystal nickel tungstate

Measurements of a.c. and d.c. electrical conductivity in crystals of nickel tungstate, in the temperature range 300 to 1100 K, are presented. NiWO₄ is found to be a semiconductor with a band gap of 2.10 eV. The nature of the electrical conduction is discussed in the light of various conduction models.     

Microstructural image analysis and structure–electrical conductivity relationship of single- and multiple-filler conductive composites

The electrical conductivity of polypropylene/graphite (PP/G) composites and polypropylene/graphite/carbon black (PP/G/CB) was investigated in this paper. The conductivity experimental data of PP/G composites was correlated to theoretical models, which exist in the literature, and the results showed higher values of the exponent t compared to the expected typical values. Moreover, these analytical models were unable to describe the electrical behaviour for multiple-filler conductive composites such as PP/G/CB composites. A 2D computer simulation to numerically compute the electrical conductivity based on digital image analysis was found to be somewhat useful to describe the mechanism of conduction in PP/G/CB composites and to determine the critical factors in developing high electrically conductive composites.     

Electrical conductivity enhancement of a polymer using butyl glycidyl ether (BGE)–lithium hexafluorophosphate (LiPF<Subscript>6</Subscript>) complex

In this study, we investigated the improvement in electrical conductivity of a polymer with the addition of dissolved lithium hexafluorophosphate (LiPF₆) in an ether based solvent, butyl glycidyl ether (BGE). Thin film samples were fabricated by adding LiPF₆ (up to 1 wt%) to poly (methyl-methacrylate) (PMMA). Film with 0.75% LiPF₆ showed the highest improvement of electrical conductivity by three orders of magnitude. Both FTIR spectra and X-ray diffraction studies confirmed the formation of BGE–LiPF₆ complex. Differential Scanning Calorimetry was used to characterize the PMMA/LiPF₆ specimens further. Dielectric experiments revealed the existence of multiple composition dependent relaxation processes: β (high frequency) and β (low frequency) relaxation processes. The results suggest that electrical conductivity could be improved without influencing the domain polymer and the composite materials, including their processability. This work suggests that the conductivity of nanocomposites with various solid conductive fillers may be sufficiently enhanced in combination with this ion conduction approach involving a “liquid conductive filler.” Since BGE is compatible with epoxy molecules, further study is expected to lead to an effective solution to conductive epoxy composites in their wide field of applications including aircraft and multifunctional energy sources such as structural batteries.     

Low-field D. C. conductivity in the bulk amorphous GexTe10Se90-x System

D. C. conductivity measurements have been made as a function of temperature and electric field on bulk amorphous Ge_xTe₁₀Se_90?x (10? x ?40) samples, in order to identify the conduction mechanism and to study the effect of the electric field on the conductivity. In the entire range of temperature (80–300 K) the conduction in all the samples is found to take place $\text{via}$ thermally assisted tunnelling of the charge carriers in the localized states of the band tails. The addition of germanium results in an increase in the localized state density and hence an increase in conductivity. An increase in the electric field decreases the activation energy, thereby increasing the conductivity of the samples. The conductivity shows an exponential dependence on the electric field.     

Electrical Relaxation in Mixed Alkali Bi2O3-K2O-Li2O-Fe2O3 Glasses

A new glass system(Bi2O3)50(Fe2O3)10(Li2O)x(K2O)40-x, where x changes in steps of 5 mole fraction between 0 and 40, was selected to study the electrical relaxation and the mixed alkali effect(MAE)phenomena.Measurements of ac conductivity σac, dielectric permittivity ε' and loss factor tanδ in the frequency range of 0.12～102 kHz and in the temperature range of 300～650 K were carried out. The temperature dependence of the ac conductivity shows a slow increasing rate at low temperature and high frequency and a rapid increase at high temperature and low frequency. At constant temperature, the ac conductivity is found to be proportional to ωs, where s is the frequency exponent, which is less than 1. Analysis of the conductivity data and the frequency exponent shows that the overlapping large polaron tunnelling(OLPT)model of ions is the most favorable mechanism for the ac conduction in the present glass system. The ac response, the dc conductivity and dielectric relaxation have the same activation energy and they originate from the same basic transport mechanism. The results of the dielectric permittivity show no maximum peak in the temperature and frequency range studied. This absence of maximum peak is an indication of non-ferroelectric behavior of all the studied samples. The MAE has been detected in the ac conductivity, which is the same as the classical MAE in the dc conductivity. The electrical parameters such as dielectric permittivity ε' and real dielectric modulus M'show a typical minimum deviation from linearity by about two orders of magnitude. The loss factor tanδ and the imaginary dielectric modulus M" are insignificantly dependent on composition even at the same transition temperature Tg.     

Influential Factors on Electromagnetic Properties of Selected 3D Reticulated Ceramics

3D reticulated ceramics (3DRCs) with the composition containing SrFe12O19-SiC-TiO2 were prepared by a replication process with polyurethane sponges as the template in ceramic slurry. The electrical conductivity, dielectric and magnetic parameters of 3D reticulated ceramics (3DRCs) were measured with changes in cell size of the sponges, contents in the slurry and sintering temperature in this paper. Discussions about the influential factors of those parameters were focused on their electrical conductivity. The experimental results indicated that the electrical conductivity of 3DRCs raised with the increase of cell size, SiC/SrO.6Fe2O3 with weight ratio and sintering temperature. X-ray diffractions and SEM were used to investigate the relationship between electrical conductivity and sintering temperature. Deoxidizing reactions of SrO.6Fe2O3 caused the increasing electrical conductivity. The real part of permittivity (ε′) and imaginary part of permeability (μ") raised with the increase of electrical conductivity (σ). The imaginary part of permittivity (ε") has a maximum at 10° S/cm with the increase of σ, and the real part of permeability (μ′)changes slightly with the increase of σ. When σ is at the range of 10-4 S/cm to 100 S/cm (a semi conductive state),both the imagine part of permittivity and permeability raises with increasing σ, therefore, the 3DRCs present their high electromagnetic loss properties.     

Electrical Conductivity of a Carbon Reinforced Alumina Resistive Composite Material Based on Synthetic Graphite and Graphene

We have prepared samples of carbon reinforced alumina ceramics with different volume fractions of synthetic graphite (0–20%) and graphene (0–4%) and measured their electrical conductivity. It has been shown that increasing the volume percent of the conductive component increases the electrical conductivity of the samples from 10^–8 to 2 × 10^–3 S/cm. The results have been analyzed in terms of percolation theory and tunneling conduction theory. The synthetic graphite-based samples show linear current–voltage behavior and their electrical conductivity increases by a factor of 1.4 to 2.8 in the temperature range 300–550 K, with a sharp rise above 550 K. The temperature dependences of their electrical conductivity are analyzed in terms of hopping transport and thermally induced tunneling conduction mechanisms. The conclusion is made that the conduction mechanism in the corundum–carbon ceramics differs significantly from that in polymer composite materials.     

具有隔离结构的超高分子量聚乙烯/镍高导电复合材料

采用化学镀手段制备金属镍包覆的超高分子量聚乙烯复合粒子,通过热压成型方法制得具有隔离结构的超高分子量聚乙烯(UHMWPE)/镍(Ni)高导电复合材料。通过调节金属(镍)镀层厚度及加工温度考察不同Ni含量及加工温度对复合材料导电性能的影响。结果表明,复合材料具有明显的导电逾渗行为;通过化学镀工艺可有效提高金属填料与基体的结合力,同时实现金属镍在聚合物基体中的选择性稳定分布,构建具有隔离结构的导电网络,使得复合材料的逾渗值降低至1.02%(体积分数)。基于金属填料优异的导电性能,在Ni体积分数仅为2.53%时,复合材料的电导率达到2648S/m。此外,降低复合材料的加工成型温度有助于减少加工过程对导电网络的破坏作用,从而有效降低复合材料的导电逾渗值,对提高复合材料导电性能具有重要意义。     

Temperature dependence of electrical conductivity in double-wall and multi-wall carbon nanotube/polyester nanocomposites

The aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (–NH₂). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model.     

Charge transport in CaTiO3: I. Electrical conductivity

The present paper reports the electrical conductivity of polycrystalline undoped CaTiO₃ in the temperature range 973–1323 K under controlled oxygen partial pressure (10–10⁵ Pa). The electrical conductivity data are considered in terms of defect disorder and related semiconducting properties of CaTiO₃. The values of the p(O₂) exponent of electrical conductivity at high p(O₂), that vary between 1/4.3 and 1/6.2 at 973 and 1323 K, respectively, are considered in terms of theoretical defect disorder model of p-type CaTiO₃ and increasing effect of minority charge carriers (electrons) with temperature on p-type conduction. The activation energy of the electrical conductivity, assuming 125.3 kJ/mol at 10 Pa and 94.4 kJ/mol at 72 kPa, has been considered in terms of the formation of defect and their mobility. The band gap, determined from the minimum of electrical conductivity corresponding to the n–p transition is equal to 2.77 eV.