Conductive Carbon Fiber Research Articles

High‐Performance Fiber‐Shaped All‐Solid‐State Asymmetric Supercapacitors Based on Ultrathin MnO2 Nanosheet/Carbon Fiber Cathodes for Wearable Electronics

Flexible fiber‐shaped supercapacitors have shown great potential in portable and wearable electronics. However, small specific capacitance and low operating voltage limit the practical application of fiber‐shaped supercapacitors in high energy density devices. Herein, direct growth of ultrathin MnO2 nanosheet arrays on conductive carbon fibers with robust adhesion is exhibited, which exhibit a high specific capacitance of 634.5 F g−1 at a current density of 2.5 A g−1 and possess superior cycle stability. When MnO2 nanosheet arrays on carbon fibers and graphene on carbon fibers are used as a positive electrode and a negative electrode, respectively, in an all‐solid‐state asymmetric supercapacitor (ASC), the ASC displays a high specific capacitance of 87.1 F g−1 and an exceptional energy density of 27.2 Wh kg−1. In addition, its capacitance retention reaches 95.2% over 3000 cycles, representing the excellent cyclic ability. The flexibility and mechanical stability of these ASCs are highlighted by the negligible degradation of their electrochemical performance even under severely bending states. Impressively, as‐prepared fiber‐shaped ASCs could successfully power a photodetector based on CdS nanowires without applying any external bias voltage. The excellent performance of all‐solid‐state ASCs opens up new opportunity for development of wearable and self‐powered nanodevices in near future.

Ordered Polypyrrole Nanowire Arrays Grown on a Carbon Cloth Substrate for a High-Performance Pseudocapacitor Electrode.

Highly aligned nanoarchitecture arrays directly grown on conducting substrates open up a new direction to accelerate Faradaic reactions for charge storage as well as address "dead volume" limitations for high-performance pseudocapacitor electrodes. Here we reported the electrochemical fabrication of well-ordered polypyrrole (PPy) nanowire arrays (NWAs) on surfaces of carbon fibers in an untreated carbon cloth to construct hierarchical structures constituted by the three-dimensional conductive carbon fiber skeleton and the atop well-ordered electroactive polymer nanowires. The morphologies, wetting behaviors, and charge-storage performances of the polymer were investigated by scanning electron microscopy, transmission electron microscopy, contact-angle measurement, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The well-ordered PPy NWA electrode exhibited a high specific capacitance of 699 F/g at 1 A/g with excellent rate capability, and 92.4% and 81.5% of its capacitance could be retained at 10 and 20 A/g, respectively. An extremely high energy density of 164.07 Wh/kg could be achieved by the PPy NWAs at a power density of 0.65 kW/kg. It also displayed a quite high energy density of 133.79 Wh/kg at a high power density of 13 kW/kg. The assembled symmetric supercapacitor of PPy NWAs//PPy NWAs also exhibited excellent rate capability, and only 19% of its energy density decreased when the power density increased 20 times from 0.65 to 13 kW/kg.

Prussian Blue Analog Batteries on Thread Substrates for Wearable Electronic Applications

Flexible, wearable electronics are starting to reach mass consumer markets but an adequate solution to power these devices remains a challenge. The size constraints in traditional mobile devices impose a premium on high energy density batteries to capitalize on limited space. These energetically dense systems often require bulky, rigid casings for robust protection against fire and chemical hazards. Thus we target energy storage in textiles, where size constraints are less stringent, battery real estate is scalable to requirements, and safer materials may be used. We demonstrate a zinc/Prussian blue analog battery on a thread/fiber architecture that can be woven into clothing/textiles. First, we show a cell that consists of a copper hexacyanoferrate (CuHcf) cathode dyed or coated on to conductive carbon fibers and a counter zinc electrode, suspended in a sodium-rich agarose hydrogel electrolyte at neutral pH. Agarose is a seaweed based gel known to conduct ions such as Na+. We introduce sodium salt loaded agarose gels as a potential high rate battery electrolyte. Preliminary charge/discharge tests of the 1.7 V cells in a flooded 2 cell setup show an initial specific discharge capacity of 51 mAhr/g of CuHcf, and 43 mAhr/g after 25 cycles. Further optimization is likely to improve cycle life significantly. Next, we demonstrate simple woven structures with CuHcf and Zn coated threads with Agarose/Na+ electrolyte as a proof of concept towards realizing wearable and washable electronics. We characterize the physical properties of the fiber electrodes and gel electrolyte with SEM, stress loading, and washing with sodium salt based laundry detergents. A range of electrochemical characterization is performed on the woven structures to analyze their cycle life, energy and coulombic efficiencies and specific capacities.

Synthesis of 3D Cos/CNF Electrode for Efficient Oxygen Evolution

In order to achieve a high efficiency oxygen production, 3D electrode was designed and synthesized by electrodeposition of cobalt sulfides (CoS) onto the conductive carbon fiber paper (CFP) substrate (1×1 cm2) by cyclic voltammetry at different scan rate of 5, 10, 20, 30 mV s-1 in 12.5 mM Co(NO3)2 and 12.5 mM thiourea. The CoS/CFP was directly used as anode to highlight the merits of the novel architecture, showing a rather low Tafel slope (~60 mV dec-1) and low overpotential (~0.3 V). The high electrochemical performance of CoS/CFP electrode will be discussed in detail with the analysis of SEM, XRD and XPS.

The Effects of Hydrophobic Coatings on an Insulative Skirt Layer to Decouple Galvanic Corrosion Between Mechanically-Coupled Aluminum Alloy and Carbon-Fiber Reinforced Polymer-Matrix Composites

Lightweight metals such as aluminum (Al) are being frequently coupled to polymer-matrix composites (PMCs) to reduce weight and improve performance in a multitude of applications in the defense, aerospace, automotive and civil-infrastructure industries. The intimate contact of carbon-fiber reinforced (CFR) PMCs with Al alloys can result in galvanic corrosion of the Al alloys. The electrically conductive carbon fibers in the CFR PMCs serve as cathodes and induce galvanic corrosion of the Al. The galvanic corrosion between 6061-T6 Al and CFR PMC can be effectively attenuated by decoupling Al from CFR PMC using an insulating skirt layer. The deposition of salts on the insulative skirt, however, can create a continuous ionically-conductive electrolyte film that can bridge the CFR PMC and Al, thus reducing the effectiveness of the skirt. The utilization of hydrophobic coatings on the skirt can help to attenuate galvanic corrosion by breaking up the continuous electrolyte film. In this study, the effect of hydrophobic coatings on insulative skirt materials was investigated to attenuate galvanic corrosion between mechanically coupled 6061-T6 Al and CFR PMC. Experiments were conducted in accelerated laboratory and outdoor conditions. The galvanic corrosion rates were monitored for coatings of different degrees of hydrophobicity, various skirt lengths, and exposure conditions and. Initially, the galvanic corrosion rates for couples with different insulating-skirt lengths coated with a silane-based ceramer (i.e., Siloxel) were monitored in a humidity chamber at 30o C and 90% RH over a period of up to 3 days using the zero resistance ammeter (ZRA) technique. The couples were sprayed with salt solutions of different concentrations. Results from this accelerated humidity ZRA experiment showed that a skirt length of only 0.5 inch was very effective in attenuating galvanic corrosion. To study the effectiveness of different coatings, specimens were fabricated with a 0.5-inch long skirt and coated with either Siloxel, epoxy, polyurethane or latex. The resulting galvanic corrosion rates were then compared. The two best coatings in attenuating galvanic corrosion (i.e., Siloxel and polyurethane) were selected for outdoor exposure. CFR PMC/Al galvanic couples with 0.5 inch insulating skirts (with either the Siloxel or polyurethane coatings, or no coatings) were exposed at rain forest (Manoa) and severe marine (MCBH) environments for 2 months. The CFR PMC/Al galvanic specimens at the severe marine site were exposed in two conditions: sheltered and unsheltered. The sheltered specimens were subjected to significant salt build up; whereas, the unsheltered specimens were subjected to cleansing effects of rain. The effect the salt deposition characteristics on galvanic corrosion between the sheltered and the unsheltered conditions was studied.

Substrate Selection and Management Strategies for Aqueous EPD

Classical EPD has typically been conducted in organic solvent media. Many suitable solvents are volatile and highly flammable and this limits the industrial application of the technique on the basis of safety alone. Aqueous EPD may be seen as a safer method, but issues relating to electrolysis and surface energy phenomena become prominent and can create interferences and variability unless the substrate type and its preparation are compatible with the aqueous EPD chemistry and its deposition method. As EPD layers become thinner, factors such as substrate surface structure and wettability become more critical. Industrial processes utilising some principles of EPD for applying paint from water-based preparations are well established in the metal finishing sector. Consequently there is a significant body of practical experience available from this sector that can be of use in translating classical EPD from a solvent to an aqueous technique while avoiding interferences inherent in the use of water as the deposition medium. In this paper, substrate selection is discussed in relation to the electrolyte content of the system where phenomena such as dissolution and micro-arcing can occur. The initial wetting of the substrate must be considered prior to applying voltage. Surface preparation techniques and the methods of introducing the substrate into the EPD dispersion all can have an impact on the final result. Note: This paper is based on the authors’ personal and practical experience of industrial electrophoretic painting over more than 40 years. Only metal substrates are discussed because these have been almost exclusive in this sector during that time. Non-metal substrates such as conductive plastics, graphite and carbon fibre have also been coated with electrophoretic paints but this is not yet at any significant scale and so no general principles have been established

A two-stage stochastic PDE-constrained optimization approach to vibration control of an electrically conductive composite plate subjected to mechanical and electromagnetic loads

A new two-stage stochastic partial differential equation (PDE)-constrained optimization methodology is developed for the active vibration control of structures in the presence of uncertainties in mechanical loads. The methodology relies on the two-stage stochastic optimization formulation with an embedded first-order black-box PDE-constrained optimization procedure. The PDE-constrained optimization procedure utilizes a first-order active-set algorithm with a conjugate gradient method. The objective function is determined through solution of the governing PDEs and its gradient is computed using automatic differentiation with hyper-dual numbers. The developed optimization methodology is applied to the problem of post-impact vibration control (via applied electromagnetic field) of an electrically conductive carbon fiber reinforced composite plate subjected to an uncertain, or stochastic, impact load. The corresponding governing PDEs consist of a nonlinear coupled system of equations of motion and Maxwell's equations. The conducted computational study shows that the obtained two-stage optimization solution allows for a significant suppression of vibrations caused by the randomized impact load in all impact load scenarios. Also, the effectiveness of the developed methodology is illustrated in the case of a deterministic impact load, where the two-stage strategy enables one to practically eliminate post-impact vibrations.

Direct electrical cure of carbon fiber composites

This paper presents a study of the cure of carbon fiber composites by the direct application of an electric current. The conductivity of carbon fiber enables the individual fibers to act as heating elements. The result is a large number of heating elements throughout the composite structure. These heating elements locally heat the resin surrounding them, resulting in the resin curing. This study shows that cure of composites is achieved in samples up to 60 × 25 cm. Initially, the required contact arrangement to obtain a uniformly heated panel is assessed and an optimum arrangement achieved. Following this, the change in required energy as the sample thickness and sample length are changed is measured. The degree of cure is compared to conventionally cured composites using differential scanning calorimetry (DSC). Three-point bend testing is used to determine the flexural strength and modulus of the composite samples. The results show that a comparable level of cure can be obtained using direct application of an electrical current as that obtained using autoclave cure and oven cure processes.

A conductive interwoven bamboo carbon fiber membrane for Li–S batteries

Natural bamboo, as a sustainable precursor, is used to prepare porous bamboo carbon fibers (BCFs) that are subsequently interwoven into a BCF membrane (BCFM) as a captor interlayer for the lithium polysulfide intermediates between the sulfur cathode and the separator in Li–S batteries.

Development of Guidelines to Attenuate Galvanic Corrosion between Mechanically-Coupled Aluminum and Carbon-Fiber Reinforced Epoxy Composites Using Insulation Layers

The use of an insulating skirt to attenuate galvanic action between mechanically-coupled 6061-T6 aluminum (Al) and electrically conductive carbon fiber reinforced (CFR) polymer-matrix composites (PMCs) was assessed, analyzed and modeled. The galvanic-corrosion current as a function of time between the 6061-T6 Al and CFR PMCs for a range of insulative skirt lengths, ls, and sodium chloride (NaCl) salt loadings, m′, in a humidity chamber at 30°C and 90% relative humidity (RH) were monitored. Polarization experiments were conducted on 6061-T6 Al and conductive CFR PMC electrodes to study the mechanisms governing galvanic corrosion in solutions ranging from 0 ppm chloride (Cl−) to 20,000 ppm Cl− concentrations. Based on the electrochemical characteristics of Al and the CFR PMC and the ohmic loss within the galvanic couple, a model was developed that related the galvanic corrosion rate (iGalv) to the value of ls/m′, which is the ratio of the insulating skirt length to salt loading. Experimental data from the polarization experiments as well as data from monitoring the galvanic couples in the humidity-chamber galvanic experiments were used to generate plots of log ls/m′ vs log iGalv, which can be used in design to determine proper skirt length for various environments (based on salt-loading levels) to limit the galvanic corrosion rate to a specified value.

Effect of synthesis temperature and N2/O2 flow on morphology and field emission property of SnO2 nanowires

A large amount of tin oxide (SnO2) nanowire arrays were synthesized on the flexible conductive carbon fiber substrate by thermal evaporation of tin powders in a tube furnace. The temperature, as well as the flow rate of the carrier N2 gas and the reaction O2 gas, plays an important role in defining the morphology of the SnO2 nanowires. Morphology and structure of the as-grown SnO2 samples are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Results show that all the samples possess a typical rutile structure, and no other impurity phases are observed. The morphology changes from rod to wire with the increase of reaction temperature. Ratio of length to diameter of the nanowires increases first and then decreases with the flow ratio of N2/O2 gas. The optimum synthesis conditions of SnO2 nanowire are: reaction temperature 780 ℃, N2 and O2 flow rates being 300 sccm and 3 sccm respectively. In our growth process, the nanowire grows mainly due to the vapor-liquid-solid (VLS) growth process, but both the VLS process and surface diffusion combined with a preferential growth mechanism play the important role in morphology evolution of the SnO2.Field emission measurements for Samples 1-6 are carried out in a vacuum chamber and a diode plate configuration is used. Relationship between the growth orientation, aspect ratio, density and uniformity of the arrays and field emission performances will be investigated first. Results reveal that the field emission performance of SnO2 nanostructures depends on their morphologies and array density. The turn-on electric field (at the current density of 10 upA/cm2) decreases and the emission site density increases with tin oxide array density, and the turn-on electric field of Sample 5 (synthesized at 780 ℃, nitrogen and oxygen flow rates being 300 sccm and 3 sccm respectively) is about 1.03 V/m at a working distance of 500 m. By comparison, for the turn-on electric fields of the not well-aligned SnO2 nanowire arrays we have 1.58, 2.13, 2.42, 1.82, and 1.97 V/m at 500 m. These behaviors indicate that such an ultralow turn-on field emission and marked enhancement in (～ 4670) can be attributed to the better orientation, the good electric contact with the conducting fiber substrate where they grow, and the weaker field-screening effect. Our results demonstrate that well-aligned nanowire arrays, with excellent field-emission performance, grown on fiber substrate can provide the possibility of application in flexible vacuum electron sources.

Process and Structure of Electromagnetic Shielding Plywood Composite Laminated with Carbon Fiber Paper

Carbon fiber paper (CFP), a type of flexible planer electromagnetic shielding material with thin thickness, low density, and good adhesion property and permeability, was laminated with wood veneer to produce a plywood composite with good shielding effectiveness (SE). It was found that a hot-press pressure of 1.2 MPa and a double-sized adhesive concentration of 380 g/m2 were most appropriate for the production of CFP plywood composites. SE of plywood composite laminated with single layer CFP was better than that before hot pressed, which result from the formation of three-dimensional and smaller conductive carbon fiber circuitries. The space between two-layer CFPs and the thickness of the surface-layer veneer had significant influence on SE. The SE of the composites laminated with two-layer CFPs was significantly higher than those with one-layer CFPs. The SE in the frequency range of 30 MHz to 1 GHz reached above 30 dB depending on the space between two-layer CFPs and the thickness of the surface veneer, which was sufficient SE for commercialization and the use of plywood composites.

Three-phase composite conductive concrete for pavement deicing

The use of electrically conductive concrete for pavement deicing is an emerging material technology. Three kinds of electrically conductive concrete composites, namely, steel fiber, carbon fiber, and steel fiber-graphite, are measured, and the factors that affect conductivity are analyzed. A three-phase composite conductive concrete containing steel fiber, carbon fiber, and graphite is developed for pavement deicing. The conductive property test and the compressive strength of this concrete in the laboratory show that the dispersion uniformity of the carbon fiber, as well as the concrete voids, significantly affects conductivity. The composition ratio, preparation techniques and electrode layout mode of the three-phase composite conductive concrete are introduced and studied. A specimen consisting of a three-phase composite conductive concrete with an electrical resistivity of 322Ωcm is used in the heating experiment and is proven to render satisfactory heat effects that meet the requirements of pavement deicing.

Monolithic Composite Electrodes Comprising Silicon Nanoparticles Embedded in Lignin‐derived Carbon Fibers for Lithium‐Ion Batteries

AbstractWe report direct manufacturing of high‐capacity carbon/silicon composite fiber electrodes for lithium‐ion batteries produced via a flexible low‐cost melt processing route, yielding low‐cost stable silicon particles coated in situ by a 10 nanometer thick protective silica layer. The core–shell silicon/SiO2 islands are embedded in electrochemically active and electronically conductive carbon fiber derived from lignin precursor material. The silicon–silica–carbon composites exhibit capacities exceeding 700 mAh g−1 with Coulombic efficiencies in excess of 99.5 %. The high efficiency, stability, and rate capability are linked to the nanocrystalline structure and abundant, uniform nanometer‐thick SiO2 interfaces that are produced during the spinning and subsequent pyrolysis of the precursor blend.

3D Si/C Fiber Paper Electrodes Fabricated Using a Combined Electrospray/Electrospinning Technique for Li‐Ion Batteries

Although the theoretical capacity of silicon is ten times higher than that of graphite, the overall electrode capacity of Si anodes is still low due to the low Si loading and heavy metal current collector. Here, a novel flexible 3D Si/C fiber paper electrode synthesized by simultaneously electrospraying nano‐Si‐PAN (polyacrylonitrile) clusters and electrospinning PAN fibers followed by carbonization is reported. The combined technology allows uniform incorporation of Si nanoparticles into a carbon textile matrix to form a nano‐Si/carbon composite fiber paper. The flexible 3D Si/C fiber paper electrode demonstrate a very high overall capacity of ≈1600 mAh g‐1 with capacity loss less than 0.079% per cycle for 600 cycles and excellent rate capability. The exceptional performance is attributed to the unique architecture of the flexible 3D Si/C fiber paper, i.e., the resilient and conductive carbon fiber network matrix, carbon‐coated Si nanoparticle clusters, strong adhesion between carbon fibers and Si nanoparticle clusters, and uniform distribution of Si/C clusters in the carbon fiber frame. The scalable and facile synthesis method, good mechanical properties, and excellent electrochemical performance at a high Si loading make the flexible 3D Si/C fiber paper batteries extremely attractive for plug‐in electric vehicles, flexible electronics, space exploration, and military applications.

Effect mechanism of mixing on improving conductivity of asphalt solar collector

This paper investigates the influence of different mixing parameters of 1 forced mixing on the conductivity of asphalt solar collector (ASC). Graphite powder and carbon fibers were used to improve the conductivity of asphalt concrete. The conductivity of ASC was measured with the same mix gradation, mixing procedure but different mixing parameters. The rational vibrating mixing parameters are obtained according to orthogonal experiments of the conductivity. A laboratory test of volume index and conductivity was performed after determining the rational mixing parameters. The effects of common forced mixing the on microstructure of ASC were investigated using scanning electron microscopy (SEM) and computed tomography (CT). The results obtained show that the mixing parameters have a major impact on the conductivity of asphalt concrete, among which the temperature have the strongest influence, while the revolutionary speed has less influence. The rational mixing parameters include: Bitumen temperature T1 160°C, aggregate temperature T2 180°C, mixing time t 90s and mixing revolution speed v 45r/min. ASC can obtain good conductivity and volume index with rational mixing parameters. The resistivity drops from insulation to 39.8ohmm and the thermal conductivity increases from 1.531W/mK to 2.120W/mK. The microstructure of ASC showed that the conductive fillers have uniform distributions in the sample. Conductive particles and carbon fibers promote the formation of conductive networks, because fibers may bridge up several isolated conductive particles.

Study on lowering the percolation threshold of carbon nanotube-filled conductive polypropylene composites

Conductive polymer composites (CPCs) consist of a polymeric matrix and a conductive filler, for example, carbon black, carbon fibers, graphite or carbon nanotubes (CNTs). The critical amount of the electrically conductive filler necessary to build up a continuous conductive network, and accordingly, to make the material conductive; is referred to as the percolation threshold. From technical and economical viewpoints, it is desirable to decrease the conductive- filler percolation-threshold as much as possible. In this study, we investigated the effect of polymer/conductive-filler interactions, as well as the processing and morphological development of low-percolation-threshold (Φc) conductive-polymer composites. The aim of the study was to produce conductive composites containing less multi-walled CNTs (MWCNTs) than required for pure polypropylene (PP) through two approaches: one using various mixing methods and the other using immiscible polymer blends. Variants of the conductive PP composite filled with MWCNT was prepared by dry mixing, melt mixing, mechanofusion, and compression molding. The percolation threshold (Φc) of the MWCNT-PP composites was most successfully lowered using the mechanofusion process than with any other mixing method (2-5 wt%). The mechanofusion process was found to enhance formation of a percolation network structure, and to ensure a more uniform state of dispersion in the CPCs. The immiscible-polymer blends were prepared by melt mixing (internal mixer) poly(vinylidene fluoride) (PVDF, PP/PVDF, volume ratio 1:1) filled with MWCNT.

Advanced, Flexible Ultracapacitor Electrodes on Carbon Fiber Cloth Using Nano-Architectured MnO2/CNT

The critical “energy-prosperity-environmental dilemma” has prompted academicians, policy makers, and industrial leaders worldwide to institute R&D programs and policies to meet the global energy challenge [1]. The transient nature of renewable energy sources like solar and wind cause detrimental fluctuations in power grids that lead to reliability problems. To mitigate these effects, energy storage systems are critically needed to store electricity and smooth out the abrupt changes in energy demand. Moreover, demand for EVs and HEVs as well as flexible and ‘wearable’ solutions to meet requirements of the military for providing power to the personnel, or unmanned aerial vehicles, space missions, etc., have further accelerated the search for next-generation energy storage devices, specifically batteries and supercapacitors, with high energy and power density, safety, low cost, and environmental friendliness. Though LIBs provide the highest energy density, they suffer from low specific power and poor safety [2-5]. Supercapacitors, on the other hand, have high power density, cyclability, and safety but suffer from low energy density and high production cost [2-5].Ultracapacitors can be classified into electrical double layer capacitors (EDLCs), pseudocapacitors, and hybrid supercapacitors, based on the electrode design and charge storage mechanism. Recently, nanostructured electrode materials have played a key role in the advancement of supercapacitor technologies; these nano-scaled materials have higher capacities and better response rates than traditional bulk materials. In this paper, we present the innovative approach of using 3D nano-architectured double-sided MnO2/CNT electrodes on a free-standing conductive carbon fiber (CF) cloth which eliminates the need for a metal substrate conductor layer, thereby reducing cost and weight, and allows for multilayer stacking of electrodes to further enhance areal capacitance. The use of CF cloth also allows flexibility in cell design. The 3D nano-structured electrodes allow shorter ion diffusion distance, lower contact resistance, faster electron transfer kinetics, and high specific surface area for optimum loading of the MnO2nanoparticles to boost energy and power density.Hot-filament CVD process was used to synthesize CNT on a piece of woven carbon fiber cloth. Electrochemical deposition was performed for thin-film coating of MnO2 on the CNTs. SEM micrographs in figure 1 show the section of the CF cloth, with and without the vertically aligned CNTs and an overview of the CF cloth post CNT synthesis. The SEM images of the electrode after MnO2 deposition can be seen in figure 2. The porous structure of the MnO2 deposited uniformly on the CNTs is evident. Electrochemical characterization was performed in a modified cell in 3 electrode configuration in 0.1M KCl electrolyte and also after assembling the electrodes in a symmetric configuration in a pouch cell prototype with 1M TEATFB in acetonitrile. Excellent values of the areal and specific capacitances of 455 mF/cm2 and 1035 F/g, respectively, were obtained at a scan rate of 5mV/s. The electrode also retains more than 67% of its capacity at a higher scan rate (the areal and specific capacitance drop to 305 mF/cm2and 694 F/g when the scan rate increases from 5 to 100mV/s). Detailed fabrication and material analysis of the advanced, flexible electrodes and the prototype cell will be presented. Results from electrochemical characterization will also be discussed.

Microstructure and Thermal Expansion of Hybrid - Copper Alloy Composites Reinforced with both Tungsten and Carbon Fibres

Tungsten as refractory material and high thermal conductive carbon fibres are promising candidates for production of copper matrix composites for high temperature applications. Three types of rod-like samples were prepared by gas pressure infiltration of different carbon/tungsten fibre preforms with copper and/or copper alloy (Cu-0.5Cr) respectively. The fibres are aligned parallel to rod axis and were combined with the tungsten wire cloth. The microstructure of prepared hybrid composites was examined. The samples were thermally cycled 3 times up to 550 °C at a relatively high heating/cooling rate (10 K/min) to touch real condition in applications where high heat is formed during short time. The thermal expansion behaviour in radial direction was also analysed. Results show that a combination of both types of reinforcements in rod-shapes samples insures good protection against composite disintegration during high temperature thermal loading.

Heterogeneously structured conductive carbon fiber composites by using multi-scale silver particles

This paper reports a new approach to enhance the through-thickness thermal conductivity of laminated carbon fabric reinforced composites by using nanoscale and microscale silver particles in combination to create heterogeneously structured continuous through-thickness thermal conducting paths. High conductivity of 6.62W/(mK) with a 5.1v% silver volume fraction can be achieved by incorporating these nanoscale and microscale silver particles in EWC-300X/Epon862 composite. Silver flakes were distributed within the inter-tow area, while nanoscale silver particles penetrated into the fiber tows. The combination of different sizes of silver fillers is able to effectively form continuous through-thickness conduction paths penetrating fiber tows and bridging the large inter-tow resin rich areas. Positive hybrid effects to thermal conductivity were found in IM7/EWC300X/sliver particle hybrid composites. In addition, microscale fillers in resin rich areas showed less impact on tensile performance than nanoscale particles applied directly on fiber surface.