Polyacrylonitrile Carbon Fibers Research Articles

Carbon nanofiber electrodes without commercial polymer precursors deliver superior electrochemical performance

Carbon nanofiber (CNF) electrodes are conductive and electrochemically stable, making excellent supercapacitor components. However, such fibers are commonly made from commercial polymer precursors, such as polyacrylonitrile (PAN), which are expensive to produce. Further, PAN carbon fibers are inert and lack porous surfaces, limiting their use as supercapacitor electrodes without further modification. We demonstrate the use of coal-derived polyurethane (CPU) in lieu of PAN, producing a cheap alternative precursor. Electrospinning and carbonization of this precursor produces porous fibers which are rich in nitrogen and oxygen species, creating an active surface facilitating fast faradaic reactions (FFRs). These electrodes offer superior electrochemical performance, with 604 F g−1 at 1 A g−1. After an initial activation period, this capacitance is stable over 10,000 cycles. In a symmetrical two electrode cell, this activated carbon offers superior rate performance and power-energy density trade-off compared to commercial and literature activated carbon electrodes with 20.9 Wh kg−1 energy density at a power density of 0.5 kW kg−1.

A novel cost-effective flow-through electrode based on polyacrylonitrile carbon fiber for enhancing micropollutant degradation via electro-Fenton

Electrochemical filtration is an effective technology for treating the wastewater that containing low-concentration organic micropollutants. However, its practical application has been hindered by the lack of feasible flow-through electrodes. Herein, a physically assembled flow-through cathode, based on commercial polyacrylonitrile-based (PAN) carbon fiber (CF), was introduced in an electro-Fenton (EF) system. The conductive filtration element, created by coiling the FeOCl-functionalized CF onto a cylindrical support, exhibited effective and consistent degradation of diverse micropollutants (77.9–94.5 %, TOC: 32.4–50.5 %) after a single-pass filtration. The excellent two-electron (2 e−) oxygen reduction reaction (ORR) performance of PAN-CF, along with the enhanced mass transfer in the flow-through configuration, contributed to the pollutant degradation by generating considerable reactive oxygen species (ROSs, including H2O2 and •OH) and facilitating adequate contact between pollutants and ROSs. The integration of electrochemistry significantly improved the antifouling performance of the filter, making it promising for real wastewater treatment. Detailed calculations and comparisons further confirmed the cost advantages of the proposed flow-through electrodes. This study provides a unique solution for the design and fabrication of engineeringly and economically feasible flow-through electrodes in electrochemical filtration systems.

Effect of oxygen content on the preoxidation structure of polyacrylonitrile fibers

AbstractDuring the preoxidation process of polyacrylonitrile (PAN) fibers, the diffusion behavior of oxygen from skin to core can lead to the formation of radially uneven structure of fibers, which affects the mechanical properties of subsequent PAN carbon fibers. Here we examine the effect of oxygen content on the subsequent structure evolution of fibers with different preoxidation structure, by using13C Solid‐state NMR analysis (13C‐NMR), optical density characterization, differential scanning calorimetry analysis, and thermalgravimetric analysis. The results show that increasing the oxygen content during the subsequent heat treatment can effectively reduce the radial structure difference of fiber, its efficiency is related to the preoxidation degree of fibers. For fibers with lower preoxidation degree, namely less heat treatment work (W), the radial structure difference disappears when the oxygen content reaches 29%. Further study shows that the improvement of radial structure of preoxidized fibers improved fiber thermal stability, its efficiency is also related to theWof fibers; when theWof fibers is 5, the carbonization yield at 800°C increased from 56.79% to 62.61%, which is 10.25% higher; when theWof fibers is 20, under the same oxygen content range, the carbonization yield increased from 68.97% to 69.60%, which is only 0.913% higher.

Study of microstructure evolution and mechanical behaviour changes of PAN-based carbon fibers after high-temperature heat treatment (up to 2950 °C)

The quantitative relationship between the microstructure behaviour and mechanical properties of polyacrylonitrile (PAN) carbon fibers (CF) after being heat treated in the range of 2000–2950 °C was studied. The surface morphology, elemental composition, orientation of graphite microcrystallites (Π), carbon interlayer spacing distances (d002), crystallite dimension (Lc and La), skin-core structure, pore structure and mechanical properties were characterised and evaluated after high-temperature heat treatment (HHT). The study found that increasing temperature resulted in an increase in the orientation of graphite crystals and the stress component of microcrystalline strong bonding direction along the fiber axial direction, leading to Young’s modulus of T300 and M40J increases of 18.7% and 7.7%, respectively. Meanwhile, the decrease in tensile strength by 53.9% and 29.4%, respectively, can be attributed to the deterioration of the homogeneity of the CF radial structure and a reduction in the stress dissipation path inside the CF. Finally, we have developed a theoretical model to predict the CF tensile strength and Young’s modulus based on Griffith’s fracture theory and uniform stress model, and it was verified with a relative error between the calculated and measured values less than 10%.

The Investigation of General Properties of Carbon Fiber (CF) Composites - Preliminary Study

The most commonly used materials in the production of high-performance CFs are cellulose, polyacrylonitrile, and pitch. Polyacrylonitrile (PAN)-based fibers dominate the market (representing nearly 90% of total CF production), with some companies producing more than 10,000 tons per year. However, the current technique's high cost (the combined cost of the precursors and stabilization accounts for 70% of total CF synthesis cost) limits the technology's applicability. Carbon fiber manufacturing is characterized by a high energy demand due to long processing times and energy intensive thermal processes. PAN-based CFs are difficult to commercialize due to the time-consuming pre-oxidation step, which significantly raises the manufacturing cost. As a result, advanced processing technologies aimed at reducing CF production costs should be developed. They were consisting of a thin but strong crystalline filament of carbon. This experimental study was to learn the mechanical properties of carbon fiber using Universal Testing Machine (UTM). There was a section where we made a phone case out of Polyacrylonitrile (PAN) carbon fiber and compared it to other materials for phone cases. The phone cases of carbon fiber composites as the one examples of consumer product was made from the woven carbon fiber then was hardened by hard epoxy mixed with resin epoxy. Then, the phone cases were tested with UTM machine to compare the tensile strength and high modulus. Other than that, there were few samples with different composition of PAN powder mixed with different composition of sodium thiocyanate. The results of the testing shows that the carbon fiber had the high tensile strength than the other materials of phone cases which were silicone and thermoplastic polyurethanes (TPU). The microstructure of carbon fiber has a significant impact on its mechanical properties.

Innovative and efficient preparation of high-performance polyacrylonitrile-based carbon fiber paper by centrifugal spinning

Polyacrylonitrile (PAN) carbon fibers are often used to prepare high-performance paper-based materials owing to their high strength, good electrical and thermal conductivity, and superior comprehensive properties. In this study, a novel method for preparing PAN-based carbon fibers by centrifugal spinning was developed, and a stable and homogeneous PAN carbon fiber paper was successfully obtained. Subsequently, the formation process, microscopic morphology, electrical conductivity, electrochemical performance and hydrophobicity of the PAN carbon fiber paper were studied and evaluated. The results showed that the electrical conductivity of the PAN carbon fiber paper prepared via this method reached 43.250 s·cm−1, resistivity was as low as 0.023–0.033 Ω·cm, and contact angle exceeded 140°. This study adopted a new method to prepare PAN carbon fiber paper, which provided another method for the preparation of high-performance fiber paper.

Lignin molecular design to transform green manufacturing

<h2>Summary</h2> Lignin is the most abundant phenolic biopolymer on earth, representing an abundant feedstock for green manufacturing. Nevertheless, the diverse chemical linkages, heterogeneous functional groups, variable molecular weights, and amphiphilic structures all prevent the synthesis of fungible materials from lignin, leaving it as a predominantly low-value resource. On the basis of structure-property relationship, we synergistically overcome these challenges by chemical design of a type of lignin, high-molecular weight esterified linkage lignin (HiMWELL), with more uniform esterified linkages, larger molecular weight, and much lower OH group content via interunit substucture replacement. HiMWELL transforms lignin into a precursor for manufacturing renewable materials with drastically improved properties and functionality. The HiMWELL-based carbon fiber achieved a record tensile strength and better mechanical properties than the control polyacrylonitrile carbon fiber. HiMWELL also uniquely improved mechanical properties of the recyclable polymer blends and achieved UV-shading effects.

Preparation and electromagnetic microwave absorption performances of sulfurated and oxidized polyacrylonitrile carbon fibers

Polyacrylonitrile carbon fibers (PAN CFs) were sulfurated at high temperatures and then oxidized with an H2O2 solution. Thermal and chemical analysis showed high thermal stability and the sulfur content up to 4 mmol g−1. From the microwave absorption studies, the voltage standing wave ratio and the attenuation through one adsorbent layer decrease almost linearly with increasing frequency. The reflection coefficient equals 0.79 ± 0.017 and 0.473 ± 0.02 at 10 and 30 GHz. "Transparency windows" with a bandwidth of about 300 MHz are observed at 30 and 36 GHz. The 1000 times attenuation of the signal power is found at 30 GHz.

Impact of the Manufacturing Processes of Aromatic-Polymer-Based Carbon Fiber on Life Cycle Greenhouse Gas Emissions

Carbon fibers (CFs) are promising lightweight materials to reduce vehicle fuel consumption. However, the most widely used polyacrylonitrile (PAN)-based CF production process consumes a considerable amount of energy. A novel production process for CFs from aromatic polymers (APs) is proposed as an alternative. In this study, the greenhouse gas (GHG) emissions from PAN-based CFs, from APs using the classical benzidine method, and from APs using the coupling method on a cradle-to-gate basis, were analyzed. The results indicate that the AP CFs with the classical benzidine method generated 11% fewer GHG emissions compared with the conventional PAN CFs. Emissions were further reduced by 42% using a large-tow production process. As the classical benzidine method for manufacturing CFs from APs uses a monomer synthesized via benzidine, which is carcinogenic, we examined a different synthetic route using the coupling method for monomer synthesis to avoid the benzidine intermediate. The GHG emissions from the AP CFs manufactured by the coupling method showed a 51% increase compared with PAN-based CFs, indicating a trade-off between GHG emissions and carcinogenicity. However, with proper chemical management, the classical method of CF manufacturing from APs via benzidine showed reduced GHG emissions.

Многоэмиттерные катодно-модуляторные узлы

The solution to the problem of creating an alternative to existing light sources is considered, consisting in the development of environmentally friendly energy-saving cathodoluminescent light sources of a new generation based on the glow of a phosphor under the action of electrons obtained by field emission from an autocathode with a large number of emission centers. To create cathodoluminescent light sources, it is proposed to use a field-emission multi-emitter cathode, which includes a number of separate cathodes made of polyacrylonitrile carbon fibers located on one common flat surface. The technical feasibility of using these multibeam electron guns in cathodoluminescent lamps has been substantiated.

A one-step hot pressing molding method of polyacrylonitrile carbon fibers: influence on surface morphology, microstructure and mechanical property

A one-step hot pressing molding method of polyacrylonitrile carbon fibers: influence on surface morphology, microstructure and mechanical property

Design of Low Cost Carbon Fiber Composites via Examining the Micromechanical Stress Distributions in A42 Bean-Shaped versus T650 Circular Fibers

Recent advancements have led to new polyacrylonitrile carbon fiber precursors which reduce production costs, yet lead to bean-shaped cross-sections. While these bean-shaped fibers have comparable stiffness and ultimate strength values to typical carbon fibers, their unique morphology results in varying in-plane orientations and different microstructural stress distributions under loading, which are not well understood and can limit failure strength under complex loading scenarios. Therefore, this work used finite element simulations to compare longitudinal stress distributions in A42 (bean-shaped) and T650 (circular) carbon fiber composite microstructures. Specifically, a microscopy image of an A42/P6300 microstructure was processed to instantiate a 3D model, while a Monte Carlo approach (which accounts for size and in-plane orientation distributions) was used to create statistically equivalent A42/P6300 and T650/P6300 microstructures. First, the results showed that the measured in-plane orientations of the A42 carbon fibers for the analyzed specimen had an orderly distribution with peaks at |ϕ|=0∘,180∘. Additionally, the results showed that under 1.5% elongation, the A42/P6300 microstructure reached simulated failure at approximately 2108 MPa, while the T650/P6300 microstructure did not reach failure. A single fiber model showed that this was due to the curvature of A42 fibers which was 3.18 μm−1 higher at the inner corner, yielding a matrix stress that was 7 MPa higher compared to the T650/P6300 microstructure. Overall, this analysis is valuable to engineers designing new components using lower cost carbon fiber composites, based on the micromechanical stress distributions and unique packing abilities resulting from the A42 fiber morphologies.

Reinforcing carbonized polyacrylonitrile fibers with nanoscale graphitic interface-layers

Carbon fibers going through stabilization, carbonization, and graphitization heat-treatment stages will form continuous graphitic layers that are closely packed and preferentially aligned along the fiber axis, forming high mechanical stiffness or strength and electrical or thermal conductivity. The alignment of noncontinuous, powder-like graphene layers in polymers has been challenging due to the low bending modulus of a few- or even single-layered graphene, which causes aggregations or folding behaviors. This research demonstrates the leveraging of polymer-nanoparticle interactions to align graphene nanoplatelets (GNPs) in the polyacrylonitrile (PAN) matrix. An in-house designed spinning method produces a three-layered fiber that utilizes the interfacial interactions between each layer for graphene alignment between graphitic layers. This composite containing oriented GNPs significantly improves modulus (i.e., 42.3 to 74.6 GPa) and increases electrical conductivity for enhancing volatile organic compounds (VOCs) sensing behaviors. This research opens up a new scalable fabrication method for multilayered composites.

Nonlinear elastic response of pan based carbon fiber to tensile loading and relations to microstructure

In this study, wide- and small-angle scattering (WAXS, SAXS) are used to analyze the structure of polyacrylonitrile (PAN) carbon fiber. Wide angle scattering is used to identify lattice parameters such as d-spacings, stacking height of crystalline planes (Lc), average crystallize size (Lc), and various other features (void content, degree of graphitization). Small angle scattering results show orientation and size distributions of pores/amorphous regions. Several analysis techniques were applied to small angle scattering results to ensure accuracy. XRD Data collected is correlated to single fiber mechanical properties and a fiber model is developed. Fiber modulus is heavily related to crystallite dimensions and orientation as well as pore structure. Authors hypothesize that the non-linear elasticity observed in the fiber direction of carbon fibers arises from elastic planar motion within turbostratic carbon. As crystalline regions grow and expand, the lattice structure improves lowering the barriers for (002) quasi-graphene plane motion. This miniscule elastic planar motion can lead to a large nonlinear response to tensile loading especially for high crystallinity carbon fibers and underlying deformation mechanics is addressed considering transverse-isotropy of turbostatic graphite crystals.

Textile-Grade Carbon Fiber-Reinforced Polycarbonate Composites: Effect of Epoxy Sizing

Epoxy-sized textile-grade polyacrylonitrile (PAN) carbon fiber (TCF) with 450 K filaments (CFTF, ORNL) was reinforced in the polycarbonate (PC) matrix using a compression molding technique. The epo...

Delicacy Management on Kiloton Dry Wet Spinning Bath Liquid

During the dry-jet wet spinning process of polyacrylonitrile carbon fiber precursor, the fluctuation of the coagulation bath liquid level affects the stability of the nozzle directly. The motion trajectory and the motion intensity in all directions of the fluid during the movement of the fiber in the coagulation bath fluid field were studied. A three-dimensional model of the cross flow and jet collision motion trajectory was established, and the impact of fluids with different strengths on the surface of the coagulation bath was analyzed. Solidification of the liquid surface in the fitting strength of the peak effect of the return wave overflow trough coupled superimposed to determine the coagulation bath surface to eliminate interfering fluctuations affecting factors. Based on the above analysis, a smart device for real-time monitoring of the coagulation bath air layer has been developed by using the damping equipment in the coagulation bath, where the impact of various fluid waves on the liquid surface can be eliminated on fixed point or position. According to the understanding of kiloton dry-jet wet spinning precursor fiber production line, in-depth exploration has been made to control the high dynamic coagulation bath level effectively from the perspective of technology and delicacy management.

Field emission properties of polyacrylonitrile carbon fibers at different processing temperatures

Field emission properties of polyacrylonitrile carbon fibers at different processing temperatures

Analysis of carbon fiber structure based on dynamic laser Raman spectroscopy

AbstractThe in‐plane modulus and inter layer shear modulus are the intrinsic properties determining the carbon fiber's characterization, but could not be gotten for a single sample. With the addition of dynamic Raman spectra, the parameters are obtained from five carbon fibers individually, which interpret perfectly that the Young's modulus and conductivities are not consistent according to the normal views. The mesophase pitch‐based graphitized carbon fiber has thermal conductivity of 635 Wm−1 K−1, much higher than 78 Wm−1 K−1 of the polyacrylonitrile graphitized carbon fiber, even the modulus of the latter is higher than the former. The Young's modulus of polyacrylonitrile carbon fiber and rayon‐based graphitized carbon fiber are 260 and 140 GPa; however, their thermal conductivities are lower than 1.0 Wm−1 K−1. With these two intrinsic properties, the structure of a carbon fiber can be understood clearly, so that the properties can be enhanced accordingly.

Electro-thermal–mechanical performance of a sensor based on PAN carbon fibers and real-time detection of change under thermal and mechanical stimuli

Structural health monitoring (SHM) is a vastly growing field consisting of sensors embedded in or attached with the structure which respond to the strain or other stimuli to monitor the deformation in real-time. In this study, a carbon fiber (CF) sensor was developed using unidirectional Polyacrylonitrile (PAN) carbon filaments aligned straightly together and its sensitivity was calculated experimentally, with the gauge factor (GF) in 10.2–10.8 range. The electro-thermal behavior of this CF sensor showed distinct performance and detected the change in the surrounding temperature. There is a good reproducibility in the results in both piezoresistive and electro-thermal behavior of the CF sensor and its electrical performance showed real-time detection of both mechanical and thermal stimuli. The results established that the CF exhibited good potential as a flexible strain sensor for in-situ monitoring of damage or energy release during the failure of composites.

Semimetal Bi/carbon fibers derived from electrospinning polyacrylonitrile and its visible light photocatalytic performance

A series of semimetal Bi-doped carbon fibers (Bi/CFs) were prepared by electrospinning-calcined polyacrylonitrile technique and characterized by XRD, SEM, EDS, XPS and UV–Vis DRS spectra to probe the morphology, structure and optical properties. Then, the Bi/CFs hybrids as photocatalysts were investigated the photocatalytic performances for degradation of representative environmental contaminants (Congo red dye and antibiotics sulfanilamide) under visible light irradiation (λ > 420 nm). In different compositions, the photocatalytic efficiencies have followed the order as Bi (5%)/CFs > Bi (10%)/CFs > Bi (1%)/CFs > polyacrylonitrile carbon fibers, that was mainly for the surface plasmon resonance effect of semimetal Bi, which made Bi/CFs hybrids had high light-harvesting properties and effective separation abilities of photogenerated carriers. According to the results of optical performance and the scavengers trapping experiments, the feasible photocatalytic mechanism was deduced. This study provided semimetal Bi, a new plasmonic co-catalyst, as a well substitute for Au and Ag noble metal to be a promising potential for environmental contaminants treatment.