Low-cost Carbon Fibers Research Articles

Effect of acid soak treatment of the precursor on the structure and properties of polypropylene-based carbon fibers

Polyolefin fibers have received wide attention as the precursor for low-cost carbon fiber, and cross-linking of linear polyolefin by strong acid has been proven to be an effective way to stabilize the precursor fiber prior to carbonization. However, the conventional temperature used in sulfonation process is too high and could result in severe decomposition of the linear chain of the polymer, which further deteriorated the mechanical properties of the as-prepared carbon fiber. Thus, reducing the duration of sulfonation process operated at high temperature may alleviate the degradation behavior, conferring the polyolefin-based carbon fibers with better performance. In this paper, polypropylene (PP) fibers were soaked in sulfuric acid at 50 °C–90 °C, before the conventional preparation protocol of PP-based carbon fiber. The structural evolution from PP to carbon fiber were characterized by Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The mechanical and conductive properties of carbonized fibers where further measured. The results showed that the soak in sulfuric acid resulted in swelling of PP fibers in diameter direction, as well as reducing the crystallinity of the fibers, both of which were physical transformation, and could be easily controlled by soak temperature. The subsequent sulfonation at conventional temperature was fastened for the soaked PP fibers, and the duration of sufficient sulfonation were almost reduced by half. The obtained carbon fibers exhibited better thermal conductivity and mechanical properties, which were enhanced by 25 % and 40 %, respectively, compared with that without soak pretreatment.

Carbon Fibers Based on Cellulose–Lignin Hybrid Filaments: Role of Dehydration Catalyst, Temperature, and Tension during Continuous Stabilization and Carbonization

Lignocellulose has served as precursor material for carbon fibers (CFs) before fossil-based polymers were discovered as superior feedstock. To date, CFs made from polyacrylonitrile have dominated the market. In search of low-cost carbon fibers for applications with medium strength requirements, cellulose and lignin, either as individual macromolecule or in combination, have re-gained interest as renewable raw material. In this study, cellulose with 30 wt% lignin was dry-jet wet-spun into a precursor filament for bio-based carbon fibers. The stabilization and carbonization conditions were first tested offline, using stationary ovens. Diammonium sulfate (DAS) and diammonium hydrogen phosphate were tested as catalysts to enhance the stabilization process. Stabilization is critical as the filaments’ strength properties drop in this phase before they rise again at higher temperatures. DAS was identified as a better option and used for subsequent trials on a continuous carbonization line. Carbon fibers with ca. 700 MPa tensile strength and 60–70 GPa tensile modulus were obtained at 1500 °C. Upon further carbonization at 1950 °C, moduli of >100 GPa were achieved.

Carbon fibers from bitumen-derived asphaltenes: Strategies for optimizing melt spinnability and improving mechanical properties

The demand for low-cost carbon fibers with exceptional mechanical properties continues to grow across various industries. Bitumen-derived asphaltenes have emerged as a promising alternative to polyacrylonitrile (PAN), yet asphaltenes are a complex mixture of compounds, and the fundamental understanding of which asphaltenes are melt spinnable is not clearly understood. In this study, we utilized three distinct types of asphaltenes, each exhibiting notably distinct thermal softening temperatures (Ts) and aromaticity. The optimal melt processing conditions of asphaltenes were determined by dynamic rheology tests. Moreover, we introduced a novel strategy to facilitate the melt spinning of non-spinnable samples by preparing 100 % asphaltene blends with a low Ts asphaltene at different weight fractions. By this means, we achieved continuous melt spinning of precursor fibers. After careful selection of the stabilization and carbonization conditions, uniform carbon fibers were obtained from asphaltenes, which had the highest tensile strength (∼570 MPa) and modulus (∼60 GPa) values, comparable to isotropic pitch-based carbon fibers. Further post-processing of the as-spun fiber resulted in a significant increase in tensile properties, ∼1.1 GPa for strength and ∼91 GPa for modulus. Overall, this study identified spinnable asphaltene precursor characteristics and fiber post-processing methods for achieving low-cost, high-quality carbon fibers from asphaltenes.

Introducing thermo-mechanochemistry of lignin enabled the production of high-quality low-cost carbon fiber

A surprisingly simple approach to increasing the mechanical properties of lignin-based carbon fiber by leveraging a newly discovered thermo-mechanochemistry of lignin.

The development of a techno-economic model for the assessment of asphaltene-based carbon fiber production

Carbon fiber is a material consisting of strong filaments made essentially of atoms of carbons. Asphaltene is as a potential precursor in the manufacturing of carbon fiber. The technology for production of carbon fiber from asphaltene is in the early stage of development, therefore the economic feasibility of the process at large-scale production has not yet been stablished. This information is critical for those making investment decisions and for policy formulation, and is required for the further development of this pathway. A techno-economic assessment of the production of asphaltene-based carbon fiber derived from bitumen to estimate the production cost was performed through the development of process models. The material and energy requirements, sizing of the main equipment, and capital and operating costs were obtained from a data-intensive process model. The results show that for a plant capacity of 3,000 tonnes per year, the production cost is $10.16 per kg of carbon fiber. This cost estimate is most sensitive to the stabilization time, the process yield, and the flow of nitrogen required to set the atmosphere of the carbonization operation. The effect of scale and tow size were also studied; production cost decreased with those parameters. For a 12 k tow and capacities greater than a 890 t/y plant, the production cost is lower than the current market price of polyacrylonitrile (PAN)-based carbon fiber, while for capacities above 3,060 t/y, the production cost would be below $10/kg CF. The uncertainty analysis shows that production cost would likely range between 11.50 and 14.80 $/kg CF, indicating that it is potentially cheaper to produce carbon fiber from asphaltene than from polyacrylonitrile. These results are useful for making investment decisions, policy formulation, and identifying process variables important for low-cost carbon fiber.

Compressive strength improvements from noncircular carbon fibers: A numerical study

The benefits of high-performance unidirectional carbon fiber composites are limited in many cost-driven industries due to the high cost relative to alternative reinforcement fibers. Low-cost carbon fibers have been previously proposed, but the longitudinal compressive strength continues to be a limiting factor or studies are based on simplifications that warrant further analysis. A micromechanical model is used to (1) determine if the longitudinal compressive strength of composites can be improved with noncircular carbon fiber shapes and (2) characterize why some shapes are stronger than others in compression. In comparison to circular fibers, the results suggest that the strength can be increased by 10%–13% by using a specific six-lobe fiber shape and by 6%–9% for a three-lobe fiber shape. A slight increase is predicted in the compressive strength of the study two-lobe fiber but has the highest uncertainty and sensitivity to fiber orientation and misalignment direction. The underlying mechanism governing the compressive failure of the composites was linked to the unique stress fields created by the lobes, particularly the pressure stress in the matrix. This work provides mechanics-based evidence of strength improvements from noncircular fiber shapes and insight on how matrix yielding is altered with alternative fiber shapes.

Development of low-cost electrospun carbon nanofibers using asphaltene precursor

This study reports for the first time the development of low-cost nano-scale carbon fibers from petroleum asphaltene precursors using the simple and cost-effective electrospinning technique. Firstly, the green nanofiber nonwoven mats were electrospun without any prior treatment of the asphaltene feedstock. The nanomats were then heat treated at different temperatures to optimise their thermostabilisation and carbonisation conditions. Based on extensive mechanical and analytical (DSC, TGA, ATR-FTIR) characterisations, it was found that thermostabilisation of fibers at 250 °C in air followed by carbonisation at 1000 °C in nitrogen resulted in nanofibers with the best tensile properties (∼340 MPa) and good morphology as also confirmed by SEM micrographs. Moreover, the nanofiber mats exhibited relatively good electrical conductivity (5.88 ± 0.43 S cm−1), which could be useful for energy storage applications. The average diameter of the carbonised nanofibers was found to be 700 nm, and the carbonised nanofiber mats were flexible and showed good handleability despite the inherent brittleness of asphaltenes. Overall, the present work opens new avenues for the valorisation of asphaltene waste into high-value nanofiber materials with the potential for multi-functional applications in the composite and energy industries.

Modification of large tow textile grade polyacrylonitrile fiber by dopamine hydrochloride to prepare low-cost carbon fibers

Owing to high specific strength and modulus, low density, corrosion resistance, etc., polyacrylonitrile (PAN)-based carbon fibers (CFs) have been widely used in aerospace, new energy, sporting goods, and other fields. However, their application in some civil fields is limited due to their high price. Textile grade polyacrylonitrile fiber (TPF) has a structure similar to the PAN precursor of PAN-based CFs and its cost is also comparatively low, which could be expected to replace the PAN precursor in the preparation of low-cost CFs. However, the lack of active groups in the initial copolymer of TPFs leads to rapid cyclization and extremely exothermic reaction in the pre-oxidation process, which further results in the danger of fiber melting and combustion. In the present work, surface impregnation of TPFs in dopamine hydrochloride aqueous solution together with a further ultrasonic treatment were carried out, and successive pre-oxidation and carbonization resulted in the formation of TPF-based CFs. The results showed that the cyclization temperature of modified TPFs decreased significantly and the exothermic peak also widened with the introduction of oxygen anion of dopamine hydrochloride during the pre-oxidation process, and the microstructure characterization detected by FTIR, XRD and Raman confirmed that the functional groups of dopamine hydrochloric were helpful to accelerate the formation of a ladder structure. Owing to the controllable evolution of fiber architectures during the whole heat treatment process, the final tensile strength and tensile modulus of obtained TPF-based CFs were 3.31GPa and 223.80GPa, respectively.

Carbon Fibers: From PAN to Asphaltene Precursors; A State-of-Art Review

Due to their outstanding material properties, carbon fibers are widely used in various industrial applications as functional or structural materials. This paper reviews the material properties and use of carbon fiber in various applications and industries and compares it with other existing fillers and reinforcing fibers. The review also examines the processing of carbon fibers and the main challenges in their fabrication. At present, two main precursors are primarily utilized to produce carbon fibers, i.e., polyacrylonitrile (PAN) and petroleum pitch. Each of these precursors makes carbon fibers with different properties. However, due to the costly and energy-intensive processes of carbon fiber production based on the existing precursors, there is an increasingly growing need to introduce cheaper precursors to compete with other fibers on the market. A special focus will be given to the most recent development of manufacturing more sustainable and cost-effective carbon fibers derived from petroleum asphaltenes. This review paper demonstrates that low-cost asphaltene-based carbon fibers can be a substitute for costly PAN/pitch-based carbon fibers at least for functional applications. The value proposition, performance/cost advantages, potential market, and market size as well as processing challenges and methods for overcoming these will be discussed.

Compatibility of mesophase pitch and linear low-density polyethylene for low-cost carbon fiber

Compatibility of mesophase pitch and linear low-density polyethylene for low-cost carbon fiber

An Investigation of Mechanical Properties of Recycled Carbon Fiber Reinforced Ultra-High-Performance Concrete.

Carbon fiber-reinforced concrete as a structural material is attractive for civil infrastructure because of its light weight, high strength, and resistance to corrosion. Ultra-high performance concrete, possessing excellent mechanical properties, utilizes randomly oriented one-inch long steel fibers that are 200 microns in diameter, increasing the concrete's strength and durability, where steel fibers carry the tensile stress within the concrete similar to traditional rebar reinforcement and provide ductility. Virgin carbon fiber remains a market entry barrier for the high-volume production of fiber-reinforced concrete mix designs. In this research, the use of recycled carbon fiber to produce ultra-high-performance concrete is demonstrated for the first time. Recycled carbon fibers are a promising solution to mitigate costs and increase sustainability while retaining attractive mechanical properties as a reinforcement for concrete. A comprehensive study of process structure-properties relationships is conducted in this study for the use of recycled carbon fibers in ultra-high performance concrete. Factors such as pore formation and poor fiber distribution that can significantly affect its mechanical properties are evaluated. A mix design consisting of recycled carbon fiber and ultra-high-performance concrete was evaluated for mechanical properties and compared to an aerospace-grade and low-cost commercial carbon fiber with the same mix design. Additionally, the microstructure of concrete samples is evaluated non-destructively using high-resolution micro X-ray computed tomography to obtain 3D quantitative spatial pore size distribution information and fiber clumping. This study examines the compression, tension, and flexural properties of recycled carbon fibers reinforced concrete considering the microstructure of the concrete resulting from fiber dispersion.

Green and Low-Cost Natural Lignocellulosic Biomass-Based Carbon Fibers-Processing, Properties, and Applications in Sports Equipment: A Review.

At present, high-performance carbon fibers (CFs) are mainly produced from petroleum-based materials. However, the high costs and environmental problems of the production process prompted the development of new precursors from natural biopolymers. This review focuses on the latest research on the conversion of natural lignocellulosic biomass into precursor fibers and CFs. The influence of the properties, advantages, separation, and extraction of lignin and cellulose (the most abundant natural biopolymers), as well as the spinning process on the final CF performance are detailed. Recent strategies to further improve the quality of such CFs are discussed. The importance and application of CFs in sports equipment manufacturing are briefly summarized. While the large-scale production of CFs from natural lignocellulosic biomass and their applications in sports equipment have not yet been realized, CFs still provide a promising market prospect as green and low-cost materials. Further research is needed to ensure the market entry of lignocellulosic biomass-based CFs.

Influence of Line Processing Parameters on Properties of Carbon Fibre Epoxy Towpreg

This paper explores the performance of low-cost unidirectional carbon fibre towpregs with respect to line production speed and fibre volume fraction. Using an automated production line, towpregs were produced at different production speeds, resulting in modified fibre volume fractions. The towpregs were used to manufacture unidirectional composite plates, which were then tested to evaluate mechanical performance. The fibre straightness and interfacial void ratio of the composite plates were determined by statistical analysis of the samples’ optical micrographs. The results demonstrate that adjusting the line production speed enables targeted fibre volume fractions (FVF) to be reached, resulting in the composites having different mechanical performances (2039 MPa and 2186.7 MPa tensile strength, 1.26 and 1.21 GPa flexural strength for 59.8% and 64.4% FVF, respectively). It was shown that at lower production speeds and FVF, composites exhibit good consolidation and low porosity, which is highlighted by the better interlaminar shear strength performances (8.95% increase), indicating the limitations of manufacturing very high FVF composites. Furthermore, it was concluded that fibre straightness plays a key role in mechanical performance, as samples with a lesser degree of fibre straightness showed a divergence from theoretical tensile properties.

Direct deposition of low-cost carbon fiber reinforced stainless steel composites by twin-wire arc spray

Metal matrix composites (MMCs), combining the unique advantages of two or more constituents, have been recognized as a promising structural material system. Particularly, MMCs reinforced by carbon fibers (CFs) have opened new material design routes towards increased strength-to-weight ratios. Here, we demonstrate a low-cost one-step deposition of CF reinforced stainless steel (CFRSS) composites by twin-wire arc spray on low-alloy steel (LAS) substrates. The CFs are self-assembled and grow coherently, up to 100 s of μm in length, along the splat-domain boundaries with enhanced bonding to their vicinals through partial oxidation. Structural and electrochemical studies reveal a pitting corrosion of the CFRSS layer in aqueous NaCl (3.5 wt.%) electrolyte and the corrosion passivation is apparently larger than that of the LAS substrate. Both the micro- and nano-hardness of the CFRSS layer are improved to over 4 times higher than that of the LAS substrate. These property enhancements indicate that this low-cost one-step process could revolutionize protective coatings on LAS against corrosion and/or erosion under aggressive conditions.

Exploring polymer precursors for low-cost high performance carbon fiber: A materials genome approach to finding polyacrylonitrile-co-poly(N-vinyl formamide)

Traditional single batch trial-and-error experiment has failed to screen promising copolymer candidates for polyacrylonitrile (PAN)-based carbon fiber at high efficiency. In this work, theoretical computation coupled with high-throughput experiments were employed to accelerate the searching of new potential polyacrylonitrile (PAN) copolymer precursor for low-cost and high-performance carbon fiber. A series of target PAN copolymers involving the pre-screened comonomers were synthesized using a custom-made ten channel polymerizer. With the designed three-step screening, a N-vinyl formamide (NVF) PAN copolymer producing low onset cyclization temperature (155.5 °C), high extent of stabilization (94%) and heat-resistant stabilized products (T5% of 434.5 °C and residual of 78.9% at 700 °C) was discovered. The new P(AN-co-NVF) copolymer has a lower activation energy of 22.21 kcal/mol than traditional P(AN-co-IA) (26.71 kcal/mol) and P(AN-co-AM) (25.98 kcal/mol) copolymer at a wide range of NVF content, accounting for its low-temperature cyclization. This work verified the feasibility of the materials genome approach in the exploration of suitable carbon fiber precursors.

Continuous, pilot-scale production of carbon fiber from a textile grade PAN polymer

Presented here is an investigation into the successful wet spinning and carbonization of a low-cost textile grade (TG-PAN) polyacrylonitrile (PAN) polymer blended with a more traditional carbon fiber (CF-PAN) grade precursor. Both wet spinning and carbonization were performed using continuous pilot scale facilities directly analogous to larger scale industrial processes which provide validation for further scale-up. The blended precursor fibers (TG-CF) showed consistently uniform cross-sections with the benchmark CF grade PAN precursor exhibiting mechanical properties similar to a commercially available precursor fiber. Despite a TG-PAN only precursor failing to adequately stabilize, the benchmark CF-PAN and the blended (TG-CF) precursor fibers and carbon fibers produced are high quality and exhibit uniform properties. The corresponding TG-CF carbon fiber containing 70 wt% of TG-PAN has a tensile strength of 2.2 GPa, a tensile modulus of 210 GPa and a 1% elongation to failure. Although less than the CF-PAN carbon fiber, the mechanical properties of TG-CF affirm that this approach has the potential to develop scalable low-cost carbon fiber suitable for a range of important applications.

Transformation of petroleum asphaltenes to carbon fibers

Petroleum asphaltenes, a by-product of crude oil extraction, are a promising feedstock for the development of high-value carbonaceous materials because of their high carbon content and aromaticity. In this work, we have studied the efficacy of low-value petroleum asphaltenes as raw materials in producing carbon fibers. We present a facile, yet effective, method to produce carbon fibers without the need of expensive pre-treatment processing. To do this, extensive physicochemical characterizations were carried out to evaluate asphaltene properties throughout the entire process. Continuous spinning of green fibers with different diameters (∼10–200 μm) was optimized according to the rheological characteristics of asphaltenes. We originally developed a multi-step stabilization process to cross-link the asphaltene-derived green fibers. This was followed by carbonization of the fibers resulting in fibers with mechanical strength of ∼400 MPa and Young's modulus of ∼70 GPa. These are relatively high values obtained without any pretreatment or high temperature carbonization/graphitization. This study presents a previously unexplored avenue to develop low-cost carbon fibers from low-value petroleum asphaltenes.

Preparation of Biodegradable and Low-Cost Lignin-Based PVOH Carbon Fibers Prepared by Electrospinning

A polyvinyl alcohol (PVOH)/lignin nanofiber was prepared by the electrospinning method as a precursor for biodegradable and low-cost carbon fibers. PVOH 15% was dissolved in water, and various concentration of lignin (5, 10, 15, 20, and 25%) was added. The presence of lignin in PVOH solution increased the viscosity and conductivity. From SEM analysis, PVOH solution produced smooth fiber, whereas the addition of lignin produced fibers in bead forms. The presence of lignin above 20% in PVOH did not produce spun-fiber. FTIR analysis confirmed that lignin was able to form hydrogen bonds with PVOH. TGA analysis showed that PVOH/lignin nanofibers had the highest residual mass, i.e., 40% at 600 °C. The morphology of the carbon fibers showed flake forms with many pores and had 58.07% carbon content.

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.

Anodic production of hydrogen peroxide using commercial carbon materials

The electrochemical production of hydrogen peroxide (H2O2) from water is an appealing alternative to substitute the classic anthraquinone process. Herein, we show a process development to maximize the efficiency of the anodic production of H2O2. Carbon materials were used as anodes to optimize process parameters such as current density, electrolyte concentration, and the pH. We found that the electrolyte concentration, pH, and the presence of a chemical stabilizer have a substantial effect on the selectivity of water oxidation to H2O2. The addition of Na2SiO3 as a stabilizer increased the H2O2 production significantly at high pH regimes. A direct relationship between CO32− ion activity and enhanced production of H2O2 was also observed. We report H2O2 concentrations in the anolyte up to 33 mmol L−1 at a current density of 100 mA cm−2 using commercial and low-cost carbon fiber paper.