Single Carbon Fiber Research Articles

Measuring Redox Flow Battery Kinetics on Single Carbon Fibres

Vanadium redox flow batteries (VRFB) provide large scale energy storage with a long lifecycle, by storing redox couples in large tanks and converting chemical to electrical energy at a solid electrode. VRFB have a higher levelized cost of storage (LCOS), than pumped hydro energy storage (PHES) and Li-ion batteries, preventing wider adoption (1). Improving the LCOS of VRFB would enable greater levels of renewable power generation into electricity grids. In VRFB, the cost of energy storage ($kWh-1) is independent of the cost of power ($kW-1) (2). Typically, VRFB have V2+/V3+ in the anolyte and V4+/V5+ in the catholyte, both dissolved in sulfuric acid (3). If the V4+/V5+ couple was replaced by Fe2+/Fe3+, the storage cost would be reduced as iron chloride is significantly cheaper than vanadium pentoxide (4). Using iron will lower the cell operating potential and lead to chemical cross-over, negatively impacting the performance (4). Thus, efforts to reduce the cost of VRFB should be focussed on the cost of the cell unit that produces power (3). These cells typically use carbon felt electrodes and if the power density of the can be increased, the cell and hence battery cost will also decrease (4). It has been shown that treating carbon fibres can improve the kinetics of redox reactions, with carbonyl and hydroxyl groups (5), nitrogen doping (6) and metal catalysts (7) all credited with improving kinetics. The experimental methods used to calculate kinetic parameters can vary significantly and may lack the precision required to identify why different treatments alter performance. In addition, the morphology and structure of carbon felt complicates the measurement of kinetic parameters due to complex flow behaviour through the felt. In this work, single carbon fibres are used as electrodes to precisely investigate the effect different surface modifications have on electrode kinetics, for both vanadium and iron redox reactions. This should enable greater control over surface functionalization and more accurate testing of kinetic parameters. For planar electrodes, the standard rate constant can be found from the variation of the peak separation during cyclic voltammetry at different scan rates (8). For micro-fibre electrodes, clear current peaks are not always observed, thus a numerical model has been developed using the underlying Nernst, Butler-Volmer and diffusion equations, to enable the determination of the kinetic parameters. The validity of the model is confirmed by using the standard rate constant calculated from a planar gold electrode, in a solution of Fe2+/Fe3+ in sulfuric acid, and comparing the simulated CV for a gold micro-electrode, to an experimentally recorded CV, under the same conditions. This approach allows chemical, thermal and electrochemical treatments of the carbon fibre electrodes to be precisely carried out and the effect measured on individual carbon fibers, enabling quick and efficient screening of different activation methods. If a treatment method leads to improved kinetic activity, the increase in current density of an operational cell can be estimated based on a two-dimensional stationary model (9) and then compared to experimental data from a small-scale test cell. References Lazard, Lazard's Levelized Cost of Storage, in (2016). C. Jizhong, X. Ziqiang and L. Bei, Journal of Power Sources, 241, 396 (2013). K. J. Kim, M.-S. Park, Y.-J. Kim, J. H. Kim, S. X. Dou and M. Skyllas-Kazacos, J. Mater. Chem. A, 3, 16913 (2015). V. Viswanathan, A. Crawford, D. Stephenson, S. Kim, W. Wang, B. Li, G. Coffey, E. Thomsen, G. Graff, P. Balducci, M. Kintner-Meyer and V. Sprenkle, Journal of Power Sources, 247, 1040 (2014). X. W. Wu, T. Yamamura, S. Ohta, Q. X. Zhang, F. C. Lv, C. M. Liu, K. Shirasaki, I. Satoh, T. Shikama, D. Lu and S. Q. Liu, Journal of Applied Electrochemistry, 41, 1183 (2011). J. Jin, X. Fu, Q. Liu, Y. Liu, Z. Wei, K. Niu and J. Zhang, ACS Nano, 7, 4764 (2013). C. Flox, J. Rubio-Garcia, R. Nafria, R. Zamani, M. Skoumal, T. Andreu, J. Arbiol, A. Cabot and J. R. Morante, Carbon, 50, 2372 (2012). R. S. Nicholson, Analytical Chemistry, 37, 1351 (1965). D. You, H. Zhang and J. Chen, Electrochimica Acta, 54, 6827 (2009).

Multiphysics modeling of mechanical and electrochemical phenomena in structural composites for energy storage: Single carbon fiber micro-battery

This paper presents a framework for multiphysics modeling of a novel type of multifunctional composite material, structured on microscale, with ability to function as battery cell in addition to carry mechanical load. The micro-battery consists of a single carbon fiber surrounded by very thin solid electrolyte coating and embedded in a matrix which is a porous material containing active particles able to intercalate lithium. During battery operation (discharging and charging) the structural battery constituents undergo volume changes, caused by lithium-ion movement. The presented mathematical model is solved numerically using COMSOL software and results are used to analyze the physical phenomena occurring in the structural battery material. Parametric analysis is performed to reveal the significance of geometrical parameters like fiber volume fraction in the battery and the porosity content in the matrix on the multifunctional performance of the composite unit including its swelling/shrinking during charging/discharging.

Single Carbon Fibers with a Macroscopic-Thickness, 3D Highly Porous Carbon Nanotube Coating.

Carbon fiber (CF) grafted with a layer of carbon nanotubes (CNTs) plays an important role in composite materials and other fields; to date, the applications of CNTs@CF multiscale fibers are severely hindered by the limited amount of CNTs grafted on individual CFs and the weak interfacial binding force. Here, monolithic CNTs@CF fibers consisting of a 3D highly porous CNT sponge layer with macroscopic-thickness (up to several millimeters), which is directly grown on a single CF, are fabricated. Mechanical tests reveal high sponge-CF interfacial strength owing to the presence of a thin transitional layer, which completely inhibits the CF slippage from the matrix upon fracture in CNTs@CF fiber-epoxy composites. The porous conductive CNTs@CF hybrid fibers also act as a template for introducing active materials (pseudopolymers and oxides), and a solid-state fiber-shaped supercapacitor and a fiber-type lithium-ion battery with high performances are demonstrated. These CNTs@CF fibers with macroscopic CNT layer thickness have many potential applications in areas such as hierarchically reinforced composites and flexible energy-storage textiles.

Compression test of a single carbon fiber in a scanning electron microscope and its evaluation via finite element analysis

A longitudinal compression test for a single polyacrylonitrile-based carbon fiber (T300) was performed using a scanning electron microscope. The compressive stress/strain behavior was initially linear, but subsequently became nonlinear. The longitudinal tangent modulus decreased with increasing compressive strain. A cyclic compression test revealed that the T300 carbon fiber deformed elastically up to ~90% compressive strength. The variability in the compressive strength was evaluated using Weibull analysis. The representative compressive strength of the T300 carbon fiber was nearly the same as the tensile strength. The compressive strength of the T300 carbon fiber was almost same as that of the high-tensile strength T800S carbon fiber. Finite element analysis was performed to investigate the validity of the test method. The results showed that the longitudinal compressive stress on the carbon fiber varied during longitudinal compressive loading. The maximum longitudinal compressive stress in the carbon fiber was slightly higher than the average compressive strength applied at the end. However, the variability in the measured compressive strength was much higher than that in the longitudinal compressive stress on the carbon fiber, which does not affect the former.

Real time electrochemical investigation of the release, distribution and modulation of nitric oxide in the intestine of individual zebrafish embryos

Nitric oxide (NO) is an important signaling molecule that has been implicated in a variety of physiological and pathophysiological processes in living organisms. NO plays an important role in embryonic development in vertebrates and has been reported to influence early organ development and plasticity. Quantifying NO in single embryos and their developing organs is challenging because of the small size of the embryos, the low dynamically changing concentration and the short life-time of NO. Here, we measured the distribution of NO in the intestine of live zebrafish (Danio rerio) embryos in physiological conditions and under the influence of therapeutic agents. NO measurements were performed using a miniaturized electrochemical sensor fabricated on a single carbon fiber (CF) which enables quantitative real time in vivo monitoring, and by fluorescence imaging using the 4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate (DAF-FM-DA) dye. NO production was detected in the middle segment the intestine at a level of 3.78 (±0.64) μM, and at lower levels in the anterior and posterior segments, 1.08 (±0.22) and 1.00 (±0.41) μM respectively. In the presence of resveratrol and rosuvastatin, the intestinal NO concentration decreased by 87% and 84%, demonstrating a downregulating effect. These results indicate the presence of variable micromolar concentrations of NO along the intestine of zebrafish embryos and demonstrate the usefulness of CF microelectrodes to measure quantitatively the NO release at the level of a single organ in individual zebrafish embryos. This work provides a unique approach to study in real time the modulatory role of NO in vivo and contributes to further understanding of the molecular basis of embryonic development for developmental biology and drug screening applications.

Comparison of shear strengthening techniques of reinforced concrete beams with carbon fibre reinforced polymers (CFRPs)

Reinforced concrete beams can be strengthened in shear by externally bonded fibre reinforced polymer (FRP) composites in the forms of side-bonded FRP strips, FRP U-jackets or FRP wraps. This study aims to the most efficient shear strengthening of beams with Fibre Reinforced Polymers (FRP) using the less possible drilling operations to the existing load bearing element and taking also into account the cost analysis. Theoretical and experimental investigation took place on different ways of beam strengthening with single and double carbon fibre ropes mounted onto the notch at angles of 45o and 90o. Also, study of strengthening with carbon fibre fabric strips, rope anchored was performed. Reinforced concrete beams with dimensions 15x15x70 cm, with concrete classified C30/37 were constructed, each of which was reinforced only under bending with 3Ø10 B500c steel bars.

Carbon Fiber Ionization Mass Spectrometry for the Analysis of Analytes in Vapor, Liquid, and Solid Phases.

Various ionization methods in mass spectrometry (MS) are available for the analysis of analytes with different properties. Nonetheless, the use of a single ionization method to analyze mixtures containing analytes with different polarities and volatilities in different phases at atmospheric pressure remains a challenge. Exploring an ionization method that can ionize small organics and large biomolecules with different properties for MS analysis is advantageous. Carbon fiber ionization mass spectrometry (CFI-MS), which uses a carbon fiber bundle as the ion source, is useful for the analysis of small organics with low polarities. Voltage needs to be applied on the carbon fiber bundle to initiate corona discharge for ionization of analytes. In this study, we explore the suitability of using CFI-MS in the analysis of analytes in vapor, liquid, and solid phases using a single carbon fiber (length : ∼1 cm; diameter: ∼10 μm) as the ion source. Furthermore direct electric contact on the carbon fiber is not required. We demonstrate that CFI-MS is useful for analyzing not only small and low-polarity organics but also polar biomolecules, such as peptides and proteins. The limits of detection for analytes with high polarities such as dodecyl trimethylammonium bromide and bradykinin are estimated to be ∼16 and ∼53 pM, respectively. Ionization mechanisms, including corona discharge and electrospray, are involved in the ionization of analytes with the polarity from low to high. Furthermore, sesame oil containing aromatic volatiles and compounds with different polarities is used as a model sample to demonstrate the capability of the developed ionization method to provide comprehensive chemical information from a complex sample. In addition, the feasibility of using the developed method for quantitative analysis of nonpolar as well as medium and high polarity analytes is also demonstrated. The sensitivity of the developed method toward analytes with high polarity is higher than those with low polarity. The method precision was estimated to be ∼7.8%.

Morphology design of isotactic polypropylene composites

In this article, the high-performance polymer composites were prepared based on the morphology designing method. To begin with, the beta transcrystalline morphology in the interfacial region of isotactic polypropylene (iPP) composites supported by single carbon fiber was formed by the induction of beta nucleating agent (NA) and verified using the polarized light microscopy. Then, to further explore the application of the beta transcrystalline morphology, the way of induction by supported NA was introduced into the iPP injection-molded samples. The result showed that a certain number of interfacial beta transcrystallinity was formed in the adjacent region of carbon nanotubes–modified iPP injection-molded samples. Herein, the mechanical properties are closely related to the interfacial beta transcrystalline morphology, the convective evidence was the improvement of the sample’s impact strength by seven times. Therefore, this work gives a new perspective for the preparation of high-performance composites materials via morphology designing.

Stress analysis and fracture toughness of notched polyacrylonitrile (PAN)-based and pitch-based single carbon fibers

The stress analysis and fracture toughness of high tensile strength polyacrylonitrile (PAN)-based (T1000GB, IMS60, and T300), high modulus PAN-based (M60JB), high modulus pitch-based (K13D), and high ductility pitch-based (XN-05) single carbon fibers were investigated using notched specimens and a focused ion beam. The maximum stress of T1000GB, IMS60, T300, M60JB, K13D, and XN-05 single fibers was calculated as 30.5, 29.4, 25.6, 44.3, 68.6, and 15.5 GPa, respectively. The critical stress intensity factor of T1000GB, IMS60, T300, M60JB, K13D, and XN-05 single carbon fibers was calculated as 1.91, 1.82, 1.67, 3.09, 4.84, and 1.02 MPa m1/2, respectively. The critical energy release rate of T1000GB, IMS60, T300, M60JB, K13D, and XN-05 single carbon fibers was calculated as 478, 502, 763, 3064, 13266, and 237 J/m2, respectively. These results indicate that a linear relationship exists between the fracture toughness (critical stress intensity factor and critical energy release rate) and tensile modulus and maximum stress. The results indicate that the maximum stress is an effective parameter for evaluating the fracture toughness of PAN-based and pitch-based single carbon fibers.

Size effect on tensile strength of parallel CFRP wire stay cable

The paper studies the size effect on the tensile strength of parallel carbon fiber reinforced polymer (CFRP) wire stay cable in the macroscale. First, an asymptotic weakest-link Weibull model that incorporates a statistical length effect for the tensile strength of longitudinal composites is proposed in this research. For the proposed model, the weakest-link effect gradually becomes dominant and causes a decrease in strength that increases along the length of the longitudinal elements. The asymptotic threshold length Lρ on the strength analysis can be evaluated by the asymptotic weakest-link Weibull model. The strength data of single carbon fibers and impregnated bundles with different lengths obtained by previous studies are employed to validate the proposed model and the log-likelihood ratio test and the Bayesian information criterion (BIC) are used as the criteria for the validation of the proposed model. The tensile strengths of CFRP wires with different lengths are obtained and analyzed by using the proposed model, and the results obtained from the random strength field model proposed by Vořechovský and Chudoba are illustrated and discussed in detail. Finally, the actual strengths of two parallel CFRP wire cables are compared with the simulated results to illustrate the Daniels’ effect on the strengths of parallel CFRP wire cables. To evaluate the strengths of parallel CFRP wire stay cables, the length effect and Daniels’ effect should be considered in the design of the CFRP cables to ensure safety and reliability.

Effect of high pressure hydrogen on the mechanical characteristics of single carbon fiber

In this study, carbon fiber was exposed to a pressure of 7MPa for 24h in high pressure chamber. The tensile test for carbon fiber was conducted to estimate the effect on the high pressure hydrogen in the atmosphere. To determine the tensile strength and Weibull modulus, approximately thirty carbon fiber samples were measured in all cases, and carbon fiber exposed to high pressure argon was evaluated to verify only the effect of hydrogen. Additionally, carbon fiber samples were annealed at 1950°C for 1h for a comparison with normal carbon fiber and then tested under identical conditions. The results showed that the tensile strength scatter of normal carbon fiber exposed to hydrogen was relatively wider and the Weibull modulus was decreased. Moreover, the tensile strength of the annealed carbon fiber exposed to hydrogen was increased, and these samples indicated a complex Weibull modulus because the hydrogen stored in the carbon fiber influenced the mechanical characteristic.

Nanoindentation derived elastic constants of carbon fibres and their nanostructural based predictions

Elastic constants of single carbon fibres were estimated by a novel nanoindentation based method and subsequently predicted by modified two- and three-phase Eshelby-Mori-Tanaka (EMT) micromechanical models which takes into account both crystalline, amorphous phases and microvoids of the fibre structure. This case study was carried out on a T-300 PAN-based carbon fibre reinforced SiC composite material at room temperature. Transversal and longitudinal cross-sections of individual fibres were indented by a sharp Berkovich tip up to the maximum depth of 150 nm. Assuming transverse isotropy of the fibres, their five elastic constants were deduced from the measured indentation moduli using numerical (Vlassak-Nix) and analytical (Delafargue-Ulm) models, and finite element method simulations. The elastic constants were estimated to c11 = 30.9, c12 = 9.7, c13 = 12.2, c33 = 237.3 and c44 = 10.9 GPa. The complete set of measured elastic constants were analyzed and then predicted by the proposed modified EMT models. The application of anisotropic nanoindentation coupled with the amorphous-crystalline structure model is unique to carbon fibre which revealed that an anisotropic ‘amorphous′ matrix should be assumed to achieve an appropriate fit with experimental results. This matrix was considered as a mixture of microvoids and aligned graphite planes, and their volume ratio was determined.

Friction of carbon tows and fine single fibres

The aim of this study conducted on carbon tows and single fibres is to highlight some friction behaviours to help better understand the friction mechanisms that occur during the manufacture of carbon composites. These mechanisms are responsible for damage that reduces the specifications and lifetime of mechanical parts. An experiment has been developed in order to rub together two carbon tows, or two single carbon fibres (with a diameter down to 5µm), at an angle of 90°. The influences of friction velocity, normal load, and type of carbon fibre have been studied. For both tows and fibres the friction follows the Coulomb’s law because there is no influence of the velocity and the normal load in the tested range. The rearrangement of fibres within the tow has been shown to be fundamental. For the single fibre, the role of the Young’s modulus and the sizing treatment is important.

Transverse compressive properties of polyacrylonitrile (PAN)-based and pitch-based single carbon fibers

In this study, transverse compressive properties of high tensile strength polyacrylonitrile (PAN)-based (T1000GB), high modulus PAN-based (M60JB), high modulus pitch-based (K13D), and high ductility pitch-based (XN-05) single carbon fibers were measured using a direct compression test. The transverse compressive modulus, Ef (TC), of T1000GB, M60JB, K13D, and XN-05 single fibers corresponded to 8.94 GPa, 3.30 GPa, 1.44 GPa, and 17.49 GPa, respectively. The transverse compressive strengths, σf (TC), of T1000GB, M60JB, K13D, and XN-05 single fibers corresponded to 0.894 GPa, 0.999 GPa, 0.037 GPa, and 1.438 GPa, respectively. The results indicate that the high ductility pitch-based, the high strength PAN-based, and the high modulus PAN-based single carbon fibers possess high compressive modulus and strength. In contrast, the high modulus pitch-based single carbon fiber possess low compressive strength and modulus. Statistical distributions of transverse compressive strength were characterized. The Weibull modulus for T1000GB, M60JB, K13D, and XN-05 single fibers corresponded to 6.86, 7.57, 9.72, and 5.41, respectively. The result indicate that the structure/microstructure parameters are clearly correlated with transverse compressive properties of PAN-based and pitch-based single carbon fibers and especially with the transverse compressive modulus/strength and the Weibull modulus of transverse compressive strength.

Experimental characterization of single ply out‐of‐plane permeability through gaseous flow

A new approach to measure out‐of‐plane permeability of single ply unidirectional fiber material under tensile load has been investigated. Single ply permeability is an important material parameter in prepreg fabrication processes where the polymer impregnates the fiber reinforcement. Fibers are processed under tension changing the flow behavior of the resin into the porous media. The experimental characterization cell developed for these processes is mounted to a universal testing machine allowing application and continuous variation of the tensile load applied to the fiber sample. The article outlines the setup including the sensing and data acquisition concept, and implements the data reduction procedure based on Darcy's flow in porous media to obtain the transverse permeability as a function of tension loading. Transverse permeability was determined for single glass and carbon fiber tows for a wide range of tensile loading. The smaller diameter carbon tow permeability showed an order smaller permeability compared to glass fibers. In addition, permeability for both materials changed up to two orders as tensile loading was applied. The results can be used to optimize the impregnation behavior of single ply infusion processes. POLYM. COMPOS., 39:3247–3258, 2018. © 2017 Society of Plastics Engineers

Study on microstructure of transition zone and its strong contrast of single T700 carbon fibers

The transition zone (TZ) between the skin and core of Toray T700 carbon fiber was investigated by transmission electron microscopy. The higher basal-plane orientation was identified in the TZ compared with the skin and core, but it disappeared after heat treatment at 2800°C. Plasmon peak energy in the TZ was higher than that in the skin and core about 0.7–0.8eV, indicating the TZ with higher density. No element concentration existed in the TZ. The TZ with strong contrast manifests itself before and after heat treatment, and formation mechanism of its strong contrast was proposed.

Direct observation of nanoparticle migration in epoxy based fiber reinforced composites using fluorescence microscopy

The preferential accumulation of nanoparticles at carbon fiber surfaces, induced by the addition of a thermoplastic “migrating agent” to an epoxy resin, was monitored via in situ fluorescence microscopy. (3-Glydidyloxypropyl)trimethoxysilane functionalized fluorescent silica nanoparticles (GFCSP) were synthesized by a modified Stöber method to track the spatiotemporal abundance of nanoparticles. Single carbon fibers were embedded in an uncured epoxy mixture consisting of tetraglycidyl-4,4-diaminodiphenylmethane and 4,4’-diamnodiphenyl sulfone, as well as thermoplastic migrating agent, poly(ether sulfone), and GFCSP. A heated microscope stage was used to monitor the fluorescence in the local vicinity of the fiber as the epoxy begins to cross-link and solidify upon heating. Our results show that the synthesized GFCSP accumulate at fiber surfaces only in the presence of poly(ether sulfone), as verified using scanning electron micrographs of Mode I fiber fracture surfaces.

A suspended carbon fiber culture to model myelination by human Schwann cells.

Understanding of myelination/remyelination process is essential to guide tissue engineering for nerve regeneration. In vitro models currently used are limited to cell population studies and cannot easily identify individual cell contribution to the process. We established a novel model to study the contribution of human Schwann cells to the myelination process. The model avoids the presence of neurons in culture; Schwann cells respond solely to the biophysical properties of an artificial axon. The model uses a single carbon fiber suspended in culture media far from the floor of the well. The fiber provides an elongated structure of defined diameter with 360-degree of surface available for human Schwann cells to wrap around. This model enabled us to spatially and temporally track the myelination by individual Schwann cells along the fiber. We observed cell attachment, elongation and wrapping over a period of 9 days. Cells remained alive and expressed Myelin Basic Protein and Myelin Associated Glycoprotein as expected. Natural and artificial molecules, and external physical factors (e.g., p atterned electrical impulses), may be tested with this model as possible regulators of myelination.

A Novel Pickering Emulsion for Carbon Fiber Sizing Agent Stabilized by Graphene Oxide Sheets.

In this paper, a method was proposed for obtaining a stable and homogeneous Pickering emulsion for carbon fiber (CF) sizing agent. Graphene oxide (GO) sheets and surfactants as the mixed emulsifiers system, epoxy resin as the primary film former, the CF sizing agent emulsion was developed by phase inversion emulsification method based on the stability principle of Pickering emulsion. Meanwhile, the factors that affected the performances of the emulsion, including the size of GO sheets and pH value, were investigated intensively by centrifuge, electrophoresis apparatus and laser particle size analyzer. According to scanning electron microscope observation, the CF surface was coated with GO and film former. The static contact angle tests indicated the wetting performance between the sized CF and epoxy resin was improved. Moreover, the tensile strength of single CF sized with the Pickering emulsion showed an increase compared with that of T700 CF. This research shows the huge potential for the fabrication of GO-based Pickering emulsion for CF sizing agent.

Smart composites materials: A new idea to add gas-sensing properties to commercial carbon-fibers by functionalization with ZnO nanowires

Commercial carbon fibers have been coated by a brush-like layer of ZnO nanowires using a seeded chemical bath deposition. Both single carbon fibers or large tows can be functionalized in such a way. Exploiting the electrical conductivity of carbon fibers and the functional properties of ZnO nanostructures, we demonstrated that the intersection at the crossing of two functionalized carbon fibers can act not only as a piezoelectric strain sensor, but also as a chemoresistive gas sensor. The small volume of added nanostructures prevents delamination issues. The “crossing” configuration, which is typical of carbon fiber fabrics used for composites, paves the way to transform a typical texture with simple mechanical and structural properties into a “smart” material with noninvasive integrated arrays of micron-scale sensors.