Composite Conductors Research Articles

Quasi-Continuous Metasurfaces for Orbital Angular Momentum Generation

A quasi-continuous composite perfect electric conductor-perfect magnetic conductor metasurface and a systematic metasurface design process are proposed for the orbital angular momentum (OAM) generation. The metasurfaces reflect the incident left circularly polarized (LCP)/right circularly polarized (RCP) plane wave to RCP/LCP vortex beams carrying OAM at normal or oblique direction. Unlike conventional metasurfaces that are composed of discrete scatterers, the scatterers on the proposed metasurface form a quasi-continuous pattern. The patterning of the metasurface is calculated through grating vectors, and no optimization of single scatterer is required. Furthermore, the distortions from local-response discontinuity of discrete scatterers are avoided. This letter provides great convenience to high-quality OAM generation.

Review on fiber-optic sensing in health monitoring of power grids

Fiber-optic sensing technology is best adapted to health monitoring and evaluation of power grids because of its immunity of electromagnetic interference, capabilities of multiplexing and distributed sensing, and tolerance to harsh environments. We review key fiber-optic sensing technologies, including fiber Bragg gratings, fiber-optic interferometers, optical time domain reflectometries, and their applications in three main parts of power grids, transformers, power towers, and overhead transmission lines, during the past 20 years. In particular, optical fiber composite overhead ground wire and optical phase conductor applied in power grids are the areas of great potential to go further. The perspectives of an intelligent fault diagnosis subsystem for power grids based on a fiber-optic sensing network are discussed, and related on-going work is described. The review shall be of benefit to both engineers and researchers in power grids and fiber-optic sensing.

MAGNETIC-PULSE PRESSING OF ELECTRICAL CONNECTIONS FOR STRANDED WIRES

Purpose. The research of the process peculiarities of magnetic- pulse fitting of electric stranded conductor joints, made of different materials, using couplings. Evaluation of loading optimal parameters, providing high operational reliability of electric connecting units. Methodology. In order to carry out simulation and research of the process of magnetic-pulse fitting of electric stranded conductor joints CRUG24 software package was used, which was developed to estimate impact interaction. Handling the problem was carried out numerically using finite differences. Metallographic study of collected cross-sectional cuts was performed with the use of optical microscope МЕТАМ ЛВ-71, equipped with digital-still camera, connected to the computer, which used image analysis system IMEGE Expert Pro3. The electrical tests of wire joints were carried out using the thermal bench from exposure to two factors: heating with rated current and expansion by operating load. Results. It was ascertained that magnetic-pulse pressing of electric joints was followed by partial self-purification and bedding component contacting surfaces of electric joints. Oxides and contaminating impurities were expelled into small localized zones between wires, between a wire and a coupling, which resulted in the contact of juvenile surfaces. Upon mutual deformation and displacement of metal wire surface capacity size and coupling tight mechanical contact was created, which provided minimal transient resistivity. The existence of residual compression stress provides the longstanding high-quality electric contact in joints. While using magnetic-pulse pressing of electric joints, due to high speed of deformation and impact of great inertial forces, deformation containment of connected components takes place in the zone of load action. The wires in contact with each other and with couplings generate faceting, but coupling sidewall hardly has any thinning. Filled density of cross-section is approximately 100 %. This fact provides a high degree of sealing capacity of joints, which to a wide extent prevents the oxidation of contacting surfaces and the rise of transient resistivity of electric joints in the operational process. As a result of processing of the results of thermal and electrical tests it was ascertained that pressed joint factors of defectiveness with all types of wires according to thermal impact and resistivity, are significantly lower than unity. Practical value. Magnetic-pulse pressing of unattended joints in electric stranded monometallic, bimetallic and composite conductors provides high operational reliability of connecting units and it may be used while mounting overhead system of railways, transmission lines and fitting connecting components of electrical transport electric circuits.

High-Efficiency Composite Anodic Conductor in an Aluminum Electrolyzer

A composite anodic conductor is proposed for an aluminum electrolyzer. The new anode reduces the power losses and the costs since smaller quantities of nonferrous metals are required, the strength is increased, and the electrical contact area is stable. The economic efficiency of the new design is established.

Monitoring of Overhead Transmission Conductors Subjected to Static and Impact Loads Using Fiber Bragg Grating Sensors

It has previously been shown that the next-generation polymer core composite high-voltage transmission line conductors under severe transverse impact conditions develop complex failure modes strongly dependent on the type and magnitude of external multiaxial loads. In this paper, we greatly improve our understanding of the dynamic structural response of the conductor subjected to low-velocity impacts. We successfully demonstrate that fiber Bragg grating (FBG) sensors could be a viable technique for in-service monitoring of the conductors subjected to a variety of static and impact situations. It is shown that under static and low-energy/velocity conditions, the sensors can accurately measure strains both on the bare rods and inside the conductors. The accuracy of the sensors is independently verified by performing finite-element calculations of associated strains in the rods under axial tension and three- and four-point bend loading conditions. The tests on the full-scale conductors under low-energy impact also show that the sensors can identify the location and magnitude of impact with a very high degree of sensitivity. These results, combined with the intrinsic properties of optical sensors and fibers, indicate the FBG sensors could be especially useful in the monitoring of low- and high-energy impact events in service.

Sol-gel synthesis and electrical characterization of doped-carbon decorated mixed conductor ceramics

New mixed composite conductors of compositions: Li3V2−x [Cu]x (PO4)3/C and Li3V2−x [Nb]x(PO4)3/C (x = 0.1; 0.2 and 0.3) have been synthesized by the sol-gel method using Citric and Oxalic acids as a primary carbon source and Carbon Black or Carbon Nano-Fibers as secondary carbon sources. The combination of these carbon forms with the Nb doped-polyanion material boosts their electrical behavior up to 10−3 S.m−1 that is two orders of magnitude higher than the Li3V2(PO4)3/C at a room temperature. SEM, TEM and Micro-Raman Spectroscopy evidence that Carbon Nano-Fiber blend is better conductor than Carbon Black blend, which is also revealed by complex conductivity spectra. The conductivity behavior of Nb-doped ceramic is better than the Cu-doped one. The obtained niobium composites have a much more stable structure compared to the copper ones because the niobium atoms fit well in the vanadium position, whereas copper atoms are expelled from the structured.

Micro X-Ray Diffraction Study of Polycrystalline MgB <sub>2</sub> Wire and Evaluation of Carbon Doping Effect Via Low-Temperature Sintering

Simple and efficient characterization of local structural states in materials is desirable for evaluating and tailoring the material performance. Herein, we have focused on micro X-ray diffraction and conducted a local structure characterization for superconducting wires having MgB2 polycrystalline cores. The critical current properties of the superconducting materials were controlled and improved by a low-temperature sintering approach with malic acid doping as a carbon source. The transport performance depending on the sintering and doping effects was found to be closely associated with the characterized properties of the local structures. The evaluation method will therefore be useful to develop composite conductors.

Characterization of innovative rotary swaged Cu-Al clad composite wire conductors

Cu/Al composites are perspective for applications in a wide range of industrial and commercial branches, from transportation to elecatrotechnics. This study focuses on Cu/Al clad composite wires with 5 mm in diameter featuring unique sequencing produced via the technology of rotary swaging at the processing temperatures of 20 °C and 250 °C. During the swaging process, we continuously acquired samples for investigations and used our own KOMAFU S600 system for dynamic detection of swaging forces. The composite wires subjected to electrical resistivity measurement were further analysed via electron microscopy, neutron diffraction, and mechanical testing. The results showed that both the total imposed strain (swaging degree) and swaging temperature influenced the investigated parameters non-negligibly. The samples subjected to high reduction ratios (swaging degree > 3) at the temperature of 250 °C exhibited formation of intermetallics at the interfaces, which deteriorated the electric conductivity. However, the conductivity was also affected by structural phenomena, such as work hardening, texture development, dislocations density, and recrystallization. All the final 5 mm samples exhibited sufficient bonding of both the components and recrystallized ultra-fine grained structures providing them with the ultimate tensile strength of >200 MPa.

Structure and Properties of Cu/Mg Composites Produced by Hydrostatic Extrusion

Two Cu/Mg-composite rods of different content of components were produced by hydrostatic extrusion. The volume proportion of the copper sheath and magnesium core was almost equal in one of the two composite samples. Seven thin magnesium fibers were located in the copper matrix of another composite. Estimate calculations of the strength properties and electrical resistance of deformed composites were carried out and compared with the experimental results. The influence of anneals on the microstructure and electrical and mechanical properties of composites was also studied. This work has shown that a temperature rise causes sequential formation of the intermetallic compounds CuMg2 and Cu2Mg at the Cu/Mg interface, which, according to the phase diagram, results in eutectic reactions. The results of this work can be used in the development of high-strength composite conductors.

Simulation of the Transport and Magnetization Loss in Bi2223 High-Temperature Superconducting Composite Conductors

The development of high-temperature superconductors (HTSs) brings us a new material to make high-field magnets. Some conceptual HTS composite conductors have been developed for large-scale magnets with high field, such as fusion magnets. In this paper, we propose three models of Bi2223 high-temperature superconducting composite conductors that may be applied to the China Fusion Engineering Test Reactor. We analyze the transport and magnetization loss of these high-temperature superconducting composite conductors during the charging process and in an alternating magnetic field by the finite element method, respectively. This provides simulated data for analyzing the stability of Bi2223 high-temperature superconducting composite conductors.

VSIE-Based Domain Decomposition Method With Simplified Prism Vector Basis Functions for Planar Thin Dielectric-Conductor Composite Objects

A nonoverlapping and nonconforming volume-sur-face integral equation (VSIE) domain decomposition method (DDM) using simplified prism vector (SPV) basis functions is presented for complex electrically large composite planar thin dielectric-perfect electric conductor objects. Compared with the recently developed SPV-based VSIE, this scheme considerably accelerates the convergence of iterative solutions by an effective preconditioner resulted from the DDM. Moreover, this DDM does not require imposing continuity conditions at the interfaces between adjacent subdomains, and the use of discontinuous Galerkin approach allows the nonconforming volume discretizations. Due to the nonconforming nature, subdomains can be built up separately, resulting in a flexible and convenient geometrical modeling. For composite subdomains involving thin dielectric layers, the full/half SPV basis is applied so that, in comparison with the generally used Schaubert–Wilton–Glisson basis, the number of unknowns is remarkably reduced. Several numerical examples are reported to illustrate the efficiency and fast convergence of this scheme.

Elastic Conductors: A Composite Elastic Conductor with High Dynamic Stability Based on 3D‐Calabash Bunch Conductive Network Structure for Wearable Devices (Adv. Electron. Mater. 9/2018)

Elastic Conductors: A Composite Elastic Conductor with High Dynamic Stability Based on 3D‐Calabash Bunch Conductive Network Structure for Wearable Devices (Adv. Electron. Mater. 9/2018)

Load bearing characteristics study on novel deepwater composite drilling conductor by simulation and experimental methods

A novel design of composite drilling conductor (CDC) was carried out for improving the vertical and lateral bearing capacity. Bearing characteristics of CDC was investigated when subjected to lateral and longitudinal loads based on the ultimate subgrade reaction method and pile foundation bearing theory. Theoretical models for lateral displacement and vertical load were established. Finite element analysis (FEA) was conducted, and bearing capacity and influencing factors of the composite structure were studied. Through laboratory experiments, the interaction between the structure and the soil as well as the regularity of soil deformation and stress variation in the surrounding soil were studied during installation, vertical and lateral load application. The results showed that the vertical bearing capacity increased with increasing depth of the bucket foundation under the combined effect of the composite structure. Meanwhile, the depth of the embedded point of the composite conductor increased with an increased bending moment when subjected to a combined load with a constant vertical force. When the bending moment on the structure top was constant, the lateral displacement of the structure as well as the depth of the embedded point would increase with increasing vertical force. Furthermore, the bending moment change on the top of the CDC was more significant than the vertical force regarding the lateral displacement. It is also showed that the internal bucket foundation produced an "elastic plugging" effect when the CDC was subjected to vertical loading, while soil pressure transmission occurred from the upper soil to the underlying strata soil. When subjected to lateral loads, the earth pressure on the bucket sidewall was redistributed, and the bucket foundation produced a lateral supporting effect on CDC. The composite structure effectively reduced the conductor vertical and lateral displacement and improved the lateral and vertical bearing capacity. These results provide useful theoretical references for further development and optimization of the CDC structure.

A Composite Elastic Conductor with High Dynamic Stability Based on 3D‐Calabash Bunch Conductive Network Structure for Wearable Devices

AbstractAs an indispensable basic component of wearable devices, the composite elastic conductor is widely used for elastic electrode and elastic wire. The ideal elastic conductor is expected to have high conductivity and stretchability, and maintain the resistance constant during stretching. However, it's difficult for the current composite elastic conductors filling solid conductive materials. Here, a composite elastic conductor filling liquid‐metal alloy is reported. Highly conductive and freely deformable liquid‐metal filler achieves the elastic conductor with excellent conductivity and stretchability (electrical conductivity of 1.34 × 103 S cm−1, sheet resistance of 17.59 mΩ □−1, and breaking elongation of 116.86%). Importantly, the filler forms novel three‐dimensional Calabash Bunch conductive network structure in elastic matrix, which enables the elastic conductor to have excellent dynamic stability during stretching. The relative resistance variation is only 4.305% at 116.86% strain. This variation is 2–5 orders of magnitude smaller than that of the reported composite elastic conductor at the same strain, which is important for wearable devices to remain performances fairly unchanged undergo large deformation. Finally, it served as elastic electrodes of a stretchable capacitive strain sensor and elastic wires of a stretchable earphone respectively to demonstrate its potential in wearable devices.

A Calculation Method on High-Frequency Loss of Double-Layer Composite Conductor

In order to reduce resistance loss due to skin effect and proximity effect in high-frequency inductive wireless transmission coils, an impedance calculation model is built in this paper for analyzing the electromagnetic field and resistance loss of the double-layer composite conductor in the frequency range of less than 100 kHz. The analytical formulas on calculating high-frequency resistance and power loss of the composite conductor are obtained. It is found that there is a critical frequency above which the resistance of the double-layer composite conductor is significantly lower than that of a pure copper conductor. The loss density within the aluminum layer is lower than that of a copper conductor, and will increase sharply at the interface between copper and aluminum layer. The wiring mode, coil shape factor, and the magnetic field angle determine the distribution of the magnetic field intensity around the composite conductor. When the angle of magnetic field vector varies from 0° to 360°, the magnetic field intensity will vary in a spiraling way. Finally, the high-frequency resistances of the two double-layer composite conductor coils are measured and are consistent with the analytical results, which is helpful to the high-frequency coil design in inductive wireless power transmission.

Tensile and conductivity properties of epoxy composites containing carbon black and graphene nanoplatelets

Adding conductive fillers to an insulating polymer matrix produces composites with unique properties. Varying amounts of carbon black (0.33, 0.67, and 1 wt%) and graphene nanoplatelets (5, 10, 15, and 20 wt%) were added to epoxy. In addition, a few carbon black/graphene nanoplatelet/epoxy formulations were also fabricated. The conductivity and tensile properties were determined and analyzed. The single filler composites containing 5 and 10 wt% graphene nanoplatelet and 0.33 wt% carbon black could be used for electrically insulating applications. Composites containing 15 and 20 wt% graphene nanoplatelet could be used for static dissipative applications. The following composites could be used for semi-conductive applications: 0.67 wt% carbon black/epoxy, 1 wt% carbon black/epoxy, 0.33 wt% carbon black/5 wt% graphene nanoplatelet/epoxy, and 0.33 wt% carbon black/10 wt% graphene nanoplatelet/epoxy. At the 95% confidence level, the combination of 0.33 wt% carbon black with 5 wt% graphene nanoplatelet caused the composite electrical resistivity (1/electrical conductivity) to significantly decrease from ∼1015 ohm-cm to ∼104 ohm-cm. It is likely that the highly branched, high surface area carbon black is forming an electrically conductive network with graphene nanoplatelets. Concerning single filler composites, adding ≤1 wt% carbon black did not significantly lower the composite tensile strain; however, adding graphene nanoplatelet did decrease tensile strain and increase modulus. One possible application for the 10 wt% graphene nanoplatelet/epoxy composite is in Polymer Core Composite Conductors for power transmission lines, which need to be electrically insulating, have improved thermal conductivity (increased from 0.2 to 0.3 W/m-K), increased tensile modulus (increased from 2.7 to 3.3 GPa), and good tensile strength (70 MPa) and strain (3.3%).

Quantum Conductance of Copper–Carbon Nanotube Composites

Carbon nanotube (CNT)-based conductors are the focus of considerable ongoing experimental research, which has demonstrated their potential to offer increased current carrying capacity or higher specific conductance, as compared to conventional copper cabling. Complementary analytical research has been hindered by the high computational cost of large-scale quantum models. The introduction of certain simplifying assumptions, supported by critical comparisons to exact solutions and the published literature, allows for quantum modeling work to assist experiment in composite conductor development. Ballistic conductance calculations may be used to identify structure–property relationships and suggest the most productive avenues for future nanocomposite conductor research.

Application of DTA/DSC and dilatometry for optimization of Ba–Ce–Y–P–Si–O glass phase for composite protonic conductors based on BaCe0.9Y0.1O3−δ

The aim of this work was to determine the influence of chemical composition on thermal and electrical properties of selected glass from the BaO–CeO2–Y2O3–P2O5–SiO2 system. Properties of the investigated glasses were optimized in terms of glass-BaCe0.9Y0.1O3 composite protonic conductor preparation. Three types of glasses with different P2O5/SiO2 ratio were prepared and investigated. The DSC and XRD measurements indicated limited tendency to crystallization of obtained glasses up to T = 1023 K. The dilatometry measurements led to determination of the thermal expansion coefficients (TEC) and the softening point. It was found that obtained glasses soften in temperature range of 903–923 K, depending on the composition which is advantageous from the viewpoint of further preparation and formation of the composite material. The Electrochemical Impedance Spectroscopy measurements done as a function of temperature and gas atmosphere allowed to determine the activation energy of the electrical conductivity. Observed fluctuations of the activation energy with gas atmosphere suggest the possible role of the protonic defects in total conductivity. Based on the obtained results it can be stated that proposed glass system may be considered as the modifying phase for improvement of BaCe0.9Y0.1O3-based materials.

A new percolation model for composite solid electrolytes and dispersed ionic conductors

Composite solid electrolytes (CSEs) including conductor/insulator composites known as dispersed ionic conductors (DICs) have motivated the development of novel percolation models that describe their conductivity. Despite the long history, existing models lack in one or more key areas: (1) rigorous foundation for their physical theory, (2) explanation for non-universal conductor–insulator transition, (3) classification of DICs, and (4) extension to frequency-domain. This work describes a frequency-domain effective medium approximation (EMA) of a bond percolation model for CSEs. The EMA is derived entirely from Maxwell’s equations and contains basic microstructure parameters. The model was applied successfully to several composite systems from literature. Simulations and fitting of literature data address these key areas and illustrate the interplay between space charge layer properties and bulk microstructure.

Alumina Particle Reinforced Cu Matrix Conductors

The high strength conductors used in pulsed magnets in the US National High Magnetic Field Laboratory (MagLab) are manufactured from Cu matrix composites. One of the composites is made from particle-reinforced Cu. The fabrication of these composite conductors requires high deformation strain, which creates high densities of dislocations and reduced particle spacing. Both mechanical strength and electrical conductivity can be predicted from particle spacing and dislocation density. When dislocation density reaches a certain value, the particle size, distribution, and shape become important to mechanical properties. We studied the particle size, distribution, and shape in high-strength conductors with respect to the properties of the conductors. The two most important factors related to the above parameters were dislocations near the interface between particle and matrix and stress concentration near the particles. By engineering these variations, the properties of the conductors can be optimized. This paper reports our understanding of the relationship between critical properties and particle distribution in composite conductors for high field pulsed magnets.