Solid Carbon Fiber Research Articles

Energy storaging multifunctional carbon fiber composites based on Nano‐SiO2 reinforced epoxy matrix structural electrolytes

AbstractMultifunctional carbon fiber composite materials capable of storing energy and carrying structural loads have advantages for aerospace structures. In this paper, a structural supercapacitor that consists of an epoxy‐based solid polymer electrolytes (E‐SPEs) and carbon fiber was proposed. To develop an E‐SPEs with better mechanical properties and ionic conductivity, Nano‐SiO2 was introduced into the solid polymer electrolytes. Nano‐SiO2 reinforced E‐SPEs (Nano‐SiO2/E‐SPEs) show improved mechanical properties (Young's modulus [E] = 0.85 GPa) and ionic conductivity (4.99 × 10−4 S cm−1), compared to E‐SPEs without Nano‐SiO2. Structural supercapacitors were further prepared by combining E‐SPEs with carbon fibers. The structural supercapacitor prepared with Nano‐SiO2/E‐SPEs exhibits the higher power and energy density (261.93 W kg−1 and 2.11 Wh kg−1) compared to the structural supercapacitor prepared with E‐SPEs without Nano‐SiO2 (51 W kg−1 and 0.34 Wh kg−1), indicating improved mechanical and energy storage properties for structural supercapacitors after incorporation of Nano‐SiO2. This strategy has great potential in enhancing performance of structural energy storage composite materials for application in next‐generation aerospace vehicles.

Synergistic effects of carbon fiber and polytetrafluoroethylene on the friction and wear behavior of polyarylene ether nitrile under dry lubrication condition

AbstractThe synergistic effects of carbon fiber (CF) and polytetrafluoroethylene (PTFE) on the friction and wear behavior of polyarylene ether nitrile (PEN) under dry lubrication condition were studied. According to the scanning electron microscopy (SEM) on the composites' surface after wear, the wear mechanism of the composites under dry sliding condition was analyzed. The research results show that the addition of solid lubricants PTFE and carbon fibers to PEN helps to enhance the properties of friction and wear. The specific wear rate is decreased to 5.7 × 10−7 mm3/N m at a PTFE composition of 5 wt%, which is optimized by 33.4% more than PEN/CF composites. In addition, wear mechanisms are mainly abrasive wear, accompanied by adhesive wear and plowing of the friction ring.

Boosting microbial electrocatalysis via localized high electron shuttles concentration by monolithic electrode based on nanostructured nitrogen-doped carbon microtubes

Electrode materials capable of increasing the electricigens loading and accelerating the extracellular electron transfer (EET) are urgently required for microbial electrocatalytic technologies. In this work, a monolithic electrode (MDC800AM) based on three-dimensional (3D) interconnected N-doped carbon microtubes (NCMTs) derived from nanostructured polyaniline (PANI)-coated cotton fibers is prepared by a facile and scalable method. The PANI-coating layer and subsequent manganese (Mn)-catalyzed graphitization is helpful in doping the surface with nitrogen atoms and improving its graphitization degree, which contributes significantly to the hydrophilicity, biocompatibility and electronic conductivity of the electrode. Because of the hollow structure and large inner diameter of NCMTs, the MDC800AM is able to buffer the electrolyte facilitating well-localized electron shuttles (ES) within the electrode region as well as increase the surface area for electricigens to inhabit. Based on these advantages, the as-prepared MDC800AM exhibits enhanced microbial electrocatalytic activity and stability such as to outperform its counterpart made up of solid carbon fibers. This work not only provides a monolithic electrode manifesting greatly accelerated activity toward microbial electrocatalysis, but also a proof-of-concept demonstration of boosting the microbial fuel cell (MFC) performance via localized high ES concentration. • A electrode consisting of nanostructured N-doped carbon microtubes was obtained. • It increased surface area for bacteria to live and localized electron shuttles in it. • It exhibited greater power density and stability than that made of solid fibers.

Preparation and Evaluation of the Tensile Characteristics of Carbon Fiber Rod Reinforced 3D Printed Thermoplastic Composites

The most common method to fabricate both simple and complex structures in the additive manufacturing process is fused deposition modeling (FDM). Many researchers have studied the strengthening of FDM components by adding short carbon fibers (CF) or by reinforcing solid carbon fiber rods. In the current research, we sought to enhance the mechanical properties of FDM components by adding bioinspired solid CF rods during the fabrication process. An effective bonding interface of bioinspired CF rods and polylactic acid (PLA) was achieved by triangular interlocking sutures and by employing synthetic glue as the binding agent. In particular, the tensile strength of solid CF rod reinforced PLA samples was studied. Critical parameters such as layer thickness, extruder temperature, extruder speed, and shell thickness were considered for optimization. Significant process parameters were identified through leverage plots using the response surface methodology (RSM). The optimum parameters were found to be layer thickness of 0.04 mm, extruder temperature of 215 °C, extruder speed of 60 mm/s, and shell thickness of 1.2 mm. The results revealed that the bioinspired solid CF rod reinforced PLA (CFRPLA) composite exhibited a tensile strength of 82.06 MPa, which was approximately three times higher than the pure PLA (28 MPa, 66% lower than CFRPLA), acrylonitrile butadiene styrene (ABS) (28 MPa, 66% lower than CFRPLA), polyethylene terephthalate glycol (PETG) (34 MPa, 60% lower than CFRPLA), and nylon (34 MPa, 60% lower than CFRPLA) samples.

Flexible and Integrated Sensing Platform of Acoustic Waves and Metamaterials based on Polyimide-Coated Woven Carbon Fibers.

Versatile, in situ sensing and continuous monitoring capabilities are critically needed, but challenging, for components made of solid woven carbon fibers in aerospace, electronics, and medical applications. In this work, we proposed a unique concept of integrated sensing technology on woven carbon fibers through integration of thin-film surface acoustic wave (SAW) technology and electromagnetic metamaterials, with capabilities of noninvasive, in situ, and continuous monitoring of environmental parameters and biomolecules wirelessly. First, we fabricated composite materials using a three-layer composite design, in which the woven carbon fiber cloth was first coated with a polyimide (PI) layer followed by a layer of ZnO film. Integrated SAW and metamaterials devices were then fabricated on this composite structure. The temperature of the functional area of the device could be controlled precisely using the SAW devices, which could provide a proper incubation environment for biosampling processes. As an ultraviolet light sensor, the SAW device could achieve a good sensitivity of 56.86 ppm/(mW/cm2). On the same integrated platform, an electromagnetic resonator based on the metamaterials was demonstrated to work as a glucose concentration monitor with a sensitivity of 0.34 MHz/(mg/dL).

Structural analysis of hexagonal and solid carbon fibers composite

This paper is showed to explore the relationship between materials and their properties. The elements are defined by their features. It identifies the composition of the pyrolysis products obtained through pyrolysis in the structure of different designs. Two design specimens of carbon fibers structure with different directional load were fabricated, solid carbon fibers and hexagonal carbon fibers structure. The deformation behavior is well-known and has been analyzed. 3D finite element (FE) models were used to investigate both structures. There was some impact on the specimens used, and the behavior of the strain and stress line was captured. These results show that the positive Poisson's ratio of both composites structures obtained when appropriate yarn structure in the 3D material system is adopted in both designs. The main purpose of the experiment was to define and test the structure's use in industries that require carbon fiber material that has excessively excellent mechanical and thermal properties. DMA tests have been conducted, and both the thermal and mechanical properties investigated. The compositions can improve carbon vs the adhesion of the polymer matrix for carbon fibers structure, which allows the use of such fibers for the reinforcement of plastics without extra processing.

Matrix and interface microcracking in carbon fiber/polymer structural micro-battery

In this paper, the propagation of radial matrix cracks and debond cracks at the coating/matrix interface in unidirectional carbon fiber structural micro-battery composite are studied numerically. The micro battery consists of a solid electrolyte-coated carbon fiber embedded in an electrochemically active polymer matrix. Stress analysis shows that high hoop stress in the matrix during charging may initiate radial matrix cracks at the coating/matrix interface. Several 2-D finite element models of the transverse plane with different arrangements of fibers and other matrix cracks were used to analyze the radial matrix crack growth from the coating/matrix interface of the central fiber in a composite with a square packing of fibers. Energy release rates of radial cracks along two potential propagation paths are calculated under pure electrochemical loading. The presence of a radial matrix crack imposes changes in the stress distribution along the coating/matrix interface, making debonding relevant for consideration. Results for energy release rates show that the debond crack growth is governed by mode II.

Failure Analysis of a Composite Rudder Stock Using 3D X-ray Microcomputed Tomography

A failure analysis investigation was performed on the remnants of a carbon fiber rudder stock that fractured during operation on a vessel in an offshore sailing race. 3D X-ray microcomputed tomography, light microscopy and scanning electron microscopy techniques were utilized to characterize manufacturing quality, mode(s) of failure, fracture surfaces and design geometry. The CT scan slices showed signs of large-scale air entrapment, porosity and voids in the order of 10% by volume. CT gray-scale variations indicated material density differences, which allowed for differentiation between air entrapments, resin rich locations, fiber plies and shifting of material during manufacturing. The analysis also revealed the use of a solid, cylindrical balsa wood core, with unidirectional carbon fiber plies oriented around the core and off-axis bias plies along the outer circumference of the rudder stock. Fracture of the rudder occurred near the transition from the blade to post at the bearing interface. Fractographic analysis revealed signs of fractured carbon fibers—brooming and longitudinal splitting with areas of both adequate residual fiber matrix adhesion, and areas of dry fibers indicating poor wet-out. Manufacturing flaws found within the rudder post and along the fracture surface suggest it was a likely contributing factor leading to premature failure during service. Review of the intended design drawings shows that a hollow rhomboid stock design was specified; however, a solid cylindrical carbon fiber design was built, with a rapid transition and area reduction near the bearing interface. The manufacturing process used was a hand layup technique with vacuum consolidation. This process utilized with the size and geometry of a solid core design limited overall compaction of the resin and fibers, which exacerbated air entrapment and void formation. Fracture occurred at the bearing interface, due to the constraint and transition from a round solid core to a reduced area rhomboid “neck” geometry of the blade under hydrodynamic forces.

General Metal-Ion Mediated Method for Functionalization of Graphene Fiber.

Graphene fibers (GFs) are attractive materials for wearable electronics because of their lightness, superior flexibility, and electrical conductivity. However, the hydrophobic nature and highly stacked structure endow GFs similar characteristics in nature to solid carbon fibers. Therefore, the interior functionalization of GFs so as to achieve synergistic interaction between graphene nanosheets and active materials thus enhance the performance of hybrid fibers remains a challenge. Herein, a general metal-ion mediated strategy is developed to functionalize GFs and nanoparticles of Cu, Fe2O3, NiO, and CoO are successfully incorporated into GFs, respectively. As proof-of-concept applications, the obtained functionalized GFs are used as electrodes for electrochemical sensors and supercapacitors. The performances of thus-devised fiber sensor and supercapacitor are greatly improved.

Multiscale Numerical Model for Contact Resistance Prediction in the Proton Exchange Membrane Fuel Cell

Proton exchange membrane (PEM) fuel cell is considered to be a promising power source for vehicles, portable application and stationary by virtue of its zero pollution, low operating temperature, fast start-up and high efficiency. Contact behavior between gas diffusion layer (GDL) and bipolar plate (BPP) is of significant importance to the performance of PEM fuel cell. Most current studies for contact behavior are conducted by experiments and finite element analysis (FEA), which lead to high cost and huge computation for the whole fuel cell [1,2]. Comparatively speaking, the more generalized and effective analytical methods are deficient in this field because of multiscale features (from several-μm fiber to hundreds-mm fuel cell) and complex diverse mechanical properties of the components (such as the fibrous GDL and solid bipolar plate) [3]. The objective of this study is to build a numerical model to predict the contact behavior via a micro scale model for the “mechanical-electrical” relation between fibrous carbon paper and solid surface, as well as a macro scale model for the electrical contact resistance (ECR) of whole fuel cell. For the micro scale model, mathematical descriptions of solid surface topography and carbon fiber structure are established according to actual features of the components at the interface. Solid surface profile is modeled by the classic Greenwood & Willamson rough surface. Carbon paper is simulated by the random line network model based on the multi-layer construction. Contact pressure and resistance are calculated to generate the “mechanical-electrical” relation based on the Hertzian theory and statistical methods. In the micro model, the effects of carbon paper compression and internal fiber contact on contact resistance are given necessary attention, which are not considered in previous studies [4]. For the macro scale model, the ECR of whole fuel cell is calculated based on the predicted “electrical-mechanical” constitution relation. First, channel configuration of widespread metallic BPP is described according to the forming process and measurement of channel configuration. Then, nonlinear contact pressure distribution is obtained based on the interface deformation characteristic and Winkler surface model. Finally, ECR considering the channel configuration is calculated based on the “electrical-mechanical” constitution relation from micro model. Experiments of metallic BPP fabrication and ECR measurement are conducted to validate the multiscale numerical model. In the comparison, the model results show good agreement with the experimental results as shown in Fig.1 (b). During the experiments, the measurement results also show obvious dependence on the micro topography and channel configuration of the contacting BPP and GDL. Hence, influences of interface topography, material property, GDL deformation, and channel configuration are systematically studied based on the multiscale model. As shown in Fig.1 (c), it is found that lower ECR would be generated by reducing of surface roughness and softening of material, and significant increase occurs in ECR as the channel width decreases because of the growing contribution of channel gradient region. Size factor is proposed to evaluate the influence of various feature scale to the contact behavior in the fuel cell. Moreover, the assembly process of fuel cell could also be evaluated by the multiscale model.

Comparative study of carbon fiber structure on the electrocatalytic performance of ZIF-67

In this study, novel ZIF-67@carbon fiber composites were fabricated by a simple and facile approach. In order to explore the influence of carbon fiber structure on enhancing the electrocatalytic efficiency of the ZIF-67, different structural carbon fibers (hollow porous carbon fiber (PCF) and solid carbon fiber (SCF)) were used for preparing ZIF-67/carbon fiber catalysts. ZIF-67/carbon fiber composites were characterized via X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. Thanks to excellent hollow structural characteristic of PCF, ZIF-67/PCF possesses more exposed active sites, smaller particle size of ZIF-67, better conductivity, electrochemical stability, more mass transport channels as well as superior electrocatalytic abilities than ZIF-67/SCF. Furthermore, ZIF-67/PCF(1:1) sample-modified glassy carbon electrode presents a linear range to nitrobenzene that is composed by two line segments, i.e. from 0.3 to 50 μM with a sensitivity of 454.7 μA mM−1 and from 50 to 390 μM with a sensitivity of 132.0 μA mM−1, and a low detection limit of 0.16 μM. It also exhibits a wide linear response to l-cysteine in the range of 5–160 μM and 160–1580 μM with a rapidly response within 1.0 s as well as high catalytic rate constant, good stability and anti-interference ability. Our work provides useful information for searching and choosing carbon materials with excellent structure benefit to electrochemical applications.

Low-density and high-modulus carbon fibers from polyacrylonitrile with honeycomb structure

The density of commercially available polyacrylonitrile-based carbon fibers is in the range of 1.75–1.93 g/cm3. It will be of great benefit to reduce the density of carbon fiber without compromising mechanical properties, so that high-performance structures made from such fibers can be lighter than those made from the solid carbon fibers. With the goal to produce high-strength and high-modulus carbon fibers with densities in the range of 0.9–1.3 g/cm3, polyacrylonitrile (PAN) based precursor fibers were produced with a honeycomb structure. Using dry-jet wet spinning and an islands-in-a-sea geometry bi-component spinning method, honeycomb precursor fibers were manufactured that consisted of PAN as the sea component and poly(methyl methacrylate) (PMMA) as the islands component. Subsequently, the precursor fibers were stabilized and carbonized to produce hollow carbon fibers. Resulting carbon fibers have an estimated density of around 1.2 g/cm3 with high tensile modulus of up to 209 N/tex. Raman spectroscopy mapping of the carbonized honeycomb fiber cross-section exhibited a strong Raman G-band intensity not only at the outer surface of the carbon fiber but also at the surface of inner walls of the honeycomb structure, suggesting that highly ordered graphitic structure was developed at these regions.

SU‐E‐T‐777: Use of Tennis Racket and Air Gap Between the Body and Carbon Fiber Couch for Skin Sparing in Radiation Therapy of Prone Breast

Purpose:To reduce the skin dose from the carbon fiber couch scatter in radiation treatment of breast cancer in the prone position. If this issue is not addressed, the prone breast touching the solid carbon fiber couch can absorb significant dose to the skin and cause the skin reaction.Methods:1. Use of “tennis racket” instead of the solid couch. To check this hypothesis, we measured the dose at the depth of 5 mm in solid water phantom placed on the couch, using a Farmer chamber. A plan for a patient with 6MV beams, gantry angles of 113 and 286 degrees Varian scale was used. It was found that treatment with “tennis racket” instead of the solid carbon fiber couch reduces the surface dose by 5–7%, depending on the beam direction. 2. Use of the air gap between the couch and the body was analyzed using radiochromic film on the surface of the solid water phantom 10 cm thick. Initially the phantom was placed on the couch with the film sandwiched in between. Two fields at the angles of 135 and 315 degrees were used. The measurements were repeated for the air gap of 2 and 5 cm and 6 and 15 MV beams.Results:It was found that a 2‐cm gap decreased the surface dose by 3% for a 6 MV beam and by 5.5% for a 15 MV beam. A 5‐cm gap reduced the dose by 9% for 6 MV and 13.5% for 15 MV.Conclusion:Use of both methods (combined if possible) can significantly reduce the surface dose in radiation therapy of the prone breast and possible skin reaction. We plan to explore dependence of the dose reduction upon the angle of incidence.

Research on the Preparation of Calcium Silicate Hydrates Insulating Material

The hard silicon calcium stone slurry were synthesized by dynamic hydrothermal synthesis in this article, the influence of water solid ratio and carbon fiber on the performance of the calcium silicate thermal insulation material was studied. The results showed that when the water-solid ratio of 40, sodium dodecyl benzene sulfonate cited as a foaming agent, the sphericity of spherical particles was well, and xonotlite fiber developed well. The added carbon fiber could significantly increase the flexural and compressive strength and coefficient of thermal conductivity of the material. The microstructure of calcium silicate insulation material was observed and analyzed by scanning electron microscope.

Characteristic of Porous Carbon Fiber and its Microwave Absorption as Filler for Composite

As a specific morphology, the porous carbon fiber was prepared through carbonization of polyacrylonitrile/polymethyl methacrylate (PAN/PMMA) blend fiber with the PAN weight of 70%. The morphology and crystalline structure of the obtained porous carbon fibers were investigated by SEM, XRD, and Raman. The obtained porous carbon fiber produced at carbonization temperature of 1000-1400°C as well as the solid carbon fiber were cut into millimeter size and used as fillers to add to epoxy in order to make composite with the weight of 6%. The complex permittivity of these composites was measured using a network analyzer. The results reveal that the cross section of obtained carbon fiber from PAN/PMMA (70/30) is full of pores with size of 0.1-1um. The graphite crystalline degree becomes high with increasing the carbonization temperature. The composite filled by the porous carbon fiber shows better microwave absorption than that filled by the solid carbon fiber, the lowest reflection loss is-24.5dB and the band width with reflection loss below-10dB is 1.9GHz as the porous carbon fiber is the filler. Among three carbonization temperature: 1000°C, 1200°C, 1400°C, the porous carbon fiber prepared at 1200°C gives the best microwave absorbing performance.

Preparation of mesohollow and microporous carbon nanofiber and its application in cathode material for lithium–sulfur batteries

Mesohollow and microporous carbon nanofibers (MhMpCFs) were prepared by a coaxial electrospinning with polyacrylonitrile (PAN) and polymethylmethacrylate (PMMA) as outer and inner spinning solutions followed by a carbonization. The carbon fibers were thermal treated with sublimed sulfur to form S/MhMpCFs composite, which was used as cathode material for lithium–sulfur batteries. Electrochemical study shows that the S/MhMpCFs cathode material provides a maximum capacity of 815mAh/g after several cycles of activation, and the capacity retains 715mAh/g after 70cycles, corresponding to a retention of 88%. The electrochemical property of the S/MhMpCFs composite is much superior than the S-incorporated solid carbon fibers prepared from electrospinning of single PAN. The mechanism of the enhanced electrochemical property of the S/MhMpCFs composite is discussed.

A new softening agent for melt spinning of softwood kraft lignin

AbstractKraft lignin obtained from the pulping of wood is an interesting new precursor material for carbon fiber production because of its high carbon content and ready availability. However, continuous spinning of softwood kraft lignin (SKL) has been impossible because of its insufficient softening characteristics and neat hardwood kraft lignin (HKL) has required extensive pretreatments to enable fiber formation. Softwood kraft lignin permeate (SKLP) and hardwood kraft lignin permeate (HKLP), fractionated by membrane filtration, were continuously melt spun into fibers. To improve the spinnability of SKL and HKL, HKLP was added as a softening agent. SKL‐ and HKL‐based fibers were obtained by adding 3–98 wt % HKLP. A suitable temperature range for spinning was 20–85°C above the Tg of the lignin samples, and this range gave a flawless appearance according to the SEM analysis. Smooth, homogeneous fibers of SKLP, HKLP, and SKL with HKLP were successfully processed into solid carbon fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effects of diameter and hollow structure on the microwave absorption properties of short carbon fibers

A series of polyacrylonitrile (PAN)-based solid or hollow carbon fibers were prepared with outer diameters ranging from sub-micrometer to two hundred micrometers. They have similar compositions and intrinsic conductivities. Their electromagnetic parameters and microwave reflections were measured and compared. It was found that both the real and imaginary parts of the complex permittivity increased with decreasing diameter, especially at around 1.0μm. The microwave absorption peaks moved to lower frequencies as well. However, some different properties were observed among the hollow carbon fibers with similar outer diameters. For example, the imaginary part of the complex permittivity increased much more gently and the microwave absorption peak located at the lower frequency had a stronger absorption. A connected network was finally proposed to understand these diameter-dependent properties. That is, a finer diameter means more fibers and a denser network, which produces a higher increase of the complex permittivity, especially for its imaginary part. Hollow structures could accelerate the increasing rate of the real part while lowering that of the imaginary part. It can be concluded that decreasing diameter and introducing a hollow or porous structure are both beneficial to the strong absorption at lower frequencies.

Increased beam attenuation and surface dose by different couch inserts of treatment tables used in megavoltage radiotherapy

The use of solid carbon fiber table materials in radiotherapy has become more common with the implementation of image‐guided radiotherapy (IGRT), since the solid materials give less imaging artifacts than the so‐called tennis racket couchtops. The downside of the solid carbon fiber couch inserts is that they increase the beam attenuation, resulting in increased surface doses and inaccuracies in determine the dose in the patient. The purpose of this study was to evaluate the interaction of 6 and 15 MV photons with eight different couch inserts. The presented results enable direct comparison of the attenuation properties of the studied couchtops. With a direct posterior beam the maximum attenuations reach 3.6% and 2.4% with 6 and 15 M V, respectively. The measured maximum attenuation by a couchtop with an oblique gantry angle was 10.8% and 7.4% at 6 and 15 MV energies, respectively. The skin‐sparing effect was decreased substantially with every couchtop. The highest increases in surface doses were recorded to be four‐ and threefold, as compared to the direct posterior open field surface doses of 6 and 15 MV, respectively. In conclusion, the carbon fiber tabletops decrease the skin‐sparing effect of megavoltage photon energies. The increased beam attenuation and skin doses should be taken into account in the process of treatment planning.PACS number: 07.90.+c

Effect of Hydroxyapatite Matrix on the Growth of Carbon Nanotubes via a CVD System

This paper reports the fabrication of carbon nanotubes (CNTs) /hydroxyapatite (HA) composites via in-situ process in a chemical vapor deposition (CVD) system and the effect of HA matrix on the growth of CNTs. When the HA matrix is fabricated by a chemical coprecipitation method, deficient HA (D-HA) crystals in nano size have been observed in these composites. There are about 20% weight percent of multi-walled CNTs with a mean diameter of 40~60 nm. When the matrix used as catalyst for CNTs growth without HA in the same way, no CNTs but solid carbon fibers in submicrometer scale have been produced in these composites. Only Fe and MgO crystals can be observed in these composites. When the HA matrix is fabricated by a physical mixing with the presence of D-HA crystals, hollow CNTs with the diameter of 180~210 nm are also produced in these composites. Fe and MgO besides P2O5, D-HA and C crystals can be observed in the composites.