Low-cost Carbon Fibers Research Articles

Preparation of Isotropic Carbon Fibers from Kerosene-Purified Coal Tar Pitch by Co-Carbonization with Pyrolysis Fuel Oil.

An inexpensive and general-purpose carbon fiber was prepared using coal tar pitch. In contrast to the solvent extraction process employing expensive solvents, a low-cost centrifugal separation method facilitated the reduction of loss due to the pitch purification and an overall yield increase. The coal tar pitch purified by centrifugation and subsequently co-carbonized with pyrolysis fuel oil improved in spinnability. Moreover, the resulting spinnable pitch had a softening point of 250 °C. The obtained carbon fibers were heat-treated at 1000 °C for 5 min, resulting in a tensile strength of approximately 1000 MPa and an average diameter of 9 μm. In this study, we present an effective method for obtaining low-cost general-purpose isotropic carbon fibers.

Stable Electrodes Fabricated from Carbon Fibers for Electrochemical Double Layer Supercapacitors, Pseudocapacitors and Zn-Air Batteries

The ever-increasing demand for sustainable energy has led to the development of inexpensive energy storage devices. The electrode material is one of the most important parts of an energy storage device; the electrode material has a major impact on the device’s price, sustainability, environmental friendliness, performance and lifetime.Asphaltene, as a high carbon content by-product of the oil sands industry, currently has a higher supply than demand. Furthermore, asphaltene can be used to prepare low-cost carbon fibers (CFs) as the electrode material in energy storage devices. Electrochemical double layer supercapacitors (EDLCs), pseudocapacitors and the air-electrode in Zn-air batteries (ZABs) were prepared in this study by using asphaltene based CF.Activated carbon fibers (ACFs) were prepared by chemically activating the CF derived from asphaltene produced in Alberta, Canada. ACFs were used to prepare stable, high performance and flexible EDLC and birnessite MnO2 type pseudocapacitors. CFs were also used as a conductive base layer for spinel type MnCo2O4, which is an efficient electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). MnCo2O4 coated CFs were used to prepare stable and high efficiency homemade air electrodes for ZAB.ACFs, that were used as the active material in an aqueous EDLC, had a specific surface area of 2290 m2 g-1 and total porosity (pore volume) of 1.27 cm3 g-1, which includes 0.88 cm3 g-1 of micropores (pore width < 2 nm) and 0.29 cm3 g-1 of mesopores (2 nm < pore width < 50 nm). The maximum specific capacitance (Cs) reached was 311 F g-1 at a specific current (is) of 0.04 A g-1; this was reduced to 248 F g-1 at a specific current of 1 A g-1. Capacitance retention of this EDLC was 91% after 10,000 cycles. This material was later used in an EDLC device with an ionic liquid electrolyte (EMIMBF4, 1-ethyl-3-methylimidazolium tetrafluoroborate); ionic liquid electrolytes provide wider voltage windows. As a result, a specific energy (Es) of 35.7 Wh kg-1 was achieved at a power density (Ps) of 525.4 W kg-1. These values are comparable to energy and power values delivered by some batteries.Birnessite-type MnO2 (δ-MnO2) is a promising material for charge storage devices like pseudocapacitors (slower charge/discharge compared with EDLCs but faster charge/discharge compared with batteries). However, the insulating nature of δ-MnO2 limits its electrochemical performance. Because of the high performance and high conductivity of ACF used in EDLC devices, this material was chosen to fabricate ACF/δ-MnO2 composite electrodes to enhance capacitive performance of δ-MnO2. δ-MnO2 was coated onto ACFs through a hydrothermal process. The crystal structure of δ-MnO2 was subsequently thermally modified to reduce its crystallinity by introducing oxygen deficient defects. These defects acted as active sites to enhance electrolyte ion adsorption/desorption, which improved the capacitive performance. The maximum Cs reached for the composite electrode was 327 F g-1 at a specific current of 0.04 A g-1, which was significantly improved compared to the δ-MnO2 powder (not coated on ACF, 195 F g-1 at 0.04 A g-1). Capacitance retention for the composite electrode was 93% (initial capacitance of 298 F g-1 and final capacitance of 279 F g-1 at 1 A g-1), while the retention for the δ-MnO2 powder was 64% (from 154 F g-1 to 98 F g-1) after 10,000 cycles.CFs were utilized to prepare homemade gas diffusion layers (GDLs) for use in air electrodes in ZABs. Air electrodes were prepared with CF carbonized at three different temperatures, i.e., 500 oC, 800 oC and 1500 oC. the ORR and OER activity of the homemade air-electrodes, as well as commercially purchased electrodes, were tested in 1 M KOH. All homemade electrodes showed much better OER activity than the purchased ones. ORR activity was similar for both commercial electrodes and homemade electrodes prepared with CF at 1500 oC (CF-1500). CF-1500 was coated with spinel type MnCo2O4 via a facile sonication procedure. MnCo2O4 coated CF-1500 had excellent catalytic activity towards both ORR and OER, outperforming the bench mark Pt-RuO2 catalyst. The cycling behavior of CF-100 was very stable with initial and final efficiencies of ~63% and ~58%, respectively, after 200 cycles (100 h) of charge and discharge at 10 mA cm-2.

Asphaltene thermal treatment and optimization of oxidation conditions of low-cost asphaltene-derived carbon fibers

This investigation is aimed at determining the conditions for the oxidation/stabilization of asphaltene fibers through extensive physicochemical characterization and evaluation of mechanical properties of the resulting carbon fibers. Melt spinning was used to fabricate green fibers using asphaltenes, from both straight solvent-de-asphalting (SDA) processing and subsequent thermal treatment. Thermal pretreatment of SDA asphaltenes was found to yield much improved carbon fiber properties. An oxidation treatment of HT300-derived (thermal pretreatment at 300 °C) carbon fibers provided the best mechanical properties with an average tensile strength of ∼1130 MPa and an average Young’s modulus of 71 GPa. Thermal treatment of SDA asphaltenes led to much lower sulfur content in both oxidized and carbonized fibers when oxidation was performed at ∼300 °C. BET, XPS, and XRD analyses showed that carbon fibers fabricated from treated asphaltenes with improved mechanical properties had a lower surface area, lower pore volume, higher amount of stable functional groups than SDA asphaltene-derived carbon fibers.

Influence of the carbonization temperature on the properties of carbon fibers based on technical softwood kraft lignin blends

Lignin is an interesting renewable resource for carbon fibers. In this work we investigate the usage of unpurified softwood kraft lignin Indulin AT for melt-spinning of lignin-fibers and the properties of resulting lignin and carbon fibers. Indulin AT is blended with 10, 15 and 20 wt% polyethylene glycol (PEG) and melt-spun on a pilot plant. The obtained as-spun lignin fibers are stabilized in air and afterwards transformed to carbon fibers at carbonization temperatures of 900 °C, 1500 °C, 2000 °C and 2300 °C. Along the process chain the fibers are characterized by mechanical testing, scanning electron microscopy, X-ray diffraction (XRD) and Raman spectroscopy to provide insight into the structure and quality of the lignin and carbon fibers. Additionally, analytical studies show strong intermolecular interactions between Indulin AT and polyethylene glycol. Despite the high ash content the resulting carbon fibers exhibit promising mechanical properties. XRD and Raman show the increase in ordered carbon structures with an increasing carbonization temperature. Blends of unpurified Indulin AT and PEG are successfully used for melt-spinning of lignin fibers and production of low-cost carbon fibers thereof.

Improvement of interfacial adhesion of unidirectional textile grade carbon fiber (TCF) with unsized, epoxy and urethane sizing reinforced in thermoset urethane composites

This work considers a unique wide tow (450k filaments) form of low-cost carbon fiber intended for non-aerospace applications. TCF is currently produced in epoxy and urethane sizing, and there is a need to understand its resulting composite properties. In this study, the interfacial adhesion of sized TCF reinforced in thermoset urethane (TSU) composites are examined through the surface, thermal and mechanical characterization techniques. Atomic force microscopy (AFM) results showed an increase in surface roughness for urethane (276%) and epoxy sized (78%) versus unsized TCF. XPS results showed 531% increase in O in epoxy sized TCF and 250% N content in urethane sized TCF compared to unsized TCF. The surface energy of epoxy and urethane sized TCF is enhanced by 78% and 96%, respectively compared to unsized TCF. The storage modulus showed improvement for urethane (23%) and epoxy (21%) sized than unsized TCF-TSU composites. The flexural, interlaminar shear strength (ILSS), and impact properties of urethane sized TCF increase by 24%, 50%, and 273%, respectively, than unsized TCF. The results demonstrate that the surface and thermal properties correlate with the mechanical properties of TCF-TSU composites and sizing enhances the wettability of the composites.

Carbon Fibers Derived from Oleic Acid-Functionalized Lignin via Thermostabilization Accelerated by UV Irradiation

Lignin is a biorenewable precursor source suitable for the production of low-cost carbon fibers. In this work, softwood lignin was chemically modified with fatty acids to employ UV-triggered oxidative reactions occurring at long alk(en)yl chains as a pretreatment prior to thermostabilization. The chemical transformation of oleic acid-functionalized lignin (OAFL) under the UV irradiation was the free radical-based cross-linking reaction assisted by atmospheric oxygen, which successfully formed oxidatively cross-linked networks of lignin derivatives at the surface of the fiber. We observed that OAFL showed more rapid oxidative cross-linking than stearic acid-functionalized lignin (SAFL) because the presence of carbon–carbon double bond in OAFL contributed to the formation of more stable allyl radicals in addition to alkyl radicals under the UV irradiation. This UV pretreatment played a pivotal role in the conversion of flexible pristine OAFL fibers into infusible fibers during the subsequent thermostabilization step at the elevation rate of 2 °C/min without melt deformation. As the elevation rate of 2 °C/min is among the fastest thermostabilization process for lignin-derived carbon fibers, the duration of the thermostabilization of the OAFL-derived fibers in this study (∼2 h) is considerably less than previously reported ones. In addition, the UV irradiation process in this study requires less power (150 W) and exposure time (8 min), which can be appreciated by carbon fiber manufacturers aiming to reduce the fabrication cost. Therefore, the chemical functionalization with fatty acids envisages the possibility to produce carbon fibers from lignin precursors via a rapid stabilization step with spending less amount of time and energy.

Development of low cost carbon fibers based on chlorinated polyvinyl chloride(CPVC) for automotive applications

CPVC fibers were prepared using a low-cost chlorinate polyvinyl chloride (CPVC) precursor using wet spinning, and various elongation rates were applied (0%, 50%, 100%, and 125%) to improve the physicochemical properties. CPVC fibers were carbonized in a nitrogen atmosphere to prepare CPVC carbon fibers, and physicochemical changes were observed by applying the same elongation rates. The CPVC fiber changed from aliphatic to aromatic carbon chemically, such as C-Cl peak intensity disappeared after carbonization and C = C bonding peak was newly discovered. After CPVC carbonization, CPVC carbon fiber, which has an elongation of 125%, has the maximum mechanical properties (tensile strength of up to 1.83GPa, modulus of 172GPa) by inducing a change in the carbon fiber structure, so it can be applied to the automotive industry in the future.

On the structural evolution of textile grade polyacrylonitrile fibers during stabilization and carbonization: Towards the manufacture of low‐cost carbon fiber

We made an attempt to produce low cost carbon fibers using textile grade polyacrylonitrile (Tex-PAN) fibers. Here, we examined fibers collected from each zone of the stabilization and carbonization furnaces and mechanical and physical properties were measured with the aim to evaluate their chemical stability and final properties. Thermal studies revealed a cyclization peak at 308 °C and an extent of reaction of 66.2% after stabilization process. The apparent crystallite size after carbonization was determined by X-ray diffraction and it was found to be smaller in Tex-PAN fibers than commercial PAN fibers. Raman spectroscopy confirmed the development of the graphitic structures within the carbon fibers produced from Tex-PAN. Interestingly, the tensile properties (3.25 GPa) of carbon fibers from Tex-PAN fibers were found to be comparable with those of commercial PAN fibers. Precursor fibers take more than half of total production cost for producing carbon fibers (CFs), Tex-PAN precursor can be an indispensable candidate for low cost CF production.

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) polyacrylonitrile (PAN) polymer blended with a more traditional carbon fiber (CF) grade PAN 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 PAN 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 TG-CF carbon fiber containing 70wt% 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 nonetheless very good mechanical properties of TG-CF affirm that this approach has the potential to develop scalable low-cost carbon fiber suitable for a wide range of important applications.

Effect of boric acid on the stabilisation of cellulose-lignin filaments as precursors for carbon fibres

The increasing demand for a low-cost and renewable carbon fibre precursor has driven the focus on bio-based precursors. Cellulose-lignin composite fibres are a new approach toward this direction. The combination of cellulose and lignin into a composite fibre could solve some of the current limitations for pure cellulose and lignin fibres. This study investigated the treatment of the composite fibres with boric acid with focus on carbon yield, stabilisation rate and fibre fusion, which is a typical defect in carbon fibre production. The influence of boric acid on the mechanism of stabilisation was studied. The stabilisation time was reduced by 25% through treatment with the reduction of fibre fusion, while the carbon yield increased significantly in comparison to the untreated fibres.

Concept of limit stress for the tensile behavior of carbon fiber composite tows

A new criterion, the limit stress, is presented for characterizing the mechanical performance of carbon fibers via the impregnated tow method. A description of the method and its underlying connection to actual single carbon fiber mechanical performance is given and an initial demonstration of the technique is implemented. For implementation, a commercial 24k tow carbon fiber was interrogated mechanically, and prepared using two independent approaches, resulting in two cross-sectional geometries; flat (ribbon) and round. The average ultimate failure stress and average limit stress from round to flat were reduced by 5.76% and 16.8%, respectively. Hence, the limit stress approach is between 2–3x more sensitive to induced variations in tow performance compared to the peak load approach. This method gives critical insight to the nuances of carbon fiber performance, important to the understanding of fiber types (for example low-cost carbon fibers) and coupled fiber surface optimization.

Controlled acetylation of kraft lignin for tailoring polyacrylonitrile-kraft lignin interactions towards the production of quality carbon nanofibers

Lignin/polyacrylonitrile (PAN) precursors can provide a green solution for lowering the cost while adequately maintaining the mechanical performance of carbon fibers, opening the gates for energy efficient lightweight materials to reach price-sensitive markets. We anticipated that improving the interactions between hydrophobic PAN chains and lignin, abundant in hydrophilic –OH groups, is important issue for obtaining a more aligned polymeric network, advantageous for the mechanical performance of carbon fibers. A controlled acetylation using acetic anhydride or isopropenyl acetate (IPA; in DMSO/EmimOAc) allowed us to step-by-step increase the degree of substitution of lignin and fine-tune the thermal characteristics as well as the miscibility of the blends, thus tailoring the mechanical properties of the resulting electrospun carbon fiber mats, along with the morphological evolution of the fibrous network. Differential scanning calorimetry and rheometry results indicated that by increasing the amount of substituents, the complex hydrogen bonding network connecting lignin molecules gradually breaks down leading to an increase in lignin/PAN polymer blend miscibility. However, it also became apparent that by masking hydroxyl groups important free radical mediated processes during the stabilization step might be inhibited, this phenomenon appeared to be more pronounced when aliphatic hydroxyl groups are selectively acetylated (IPA in DMSO/EmimOAc). Carbon fiber mats with the best mechanical performance were obtained only via controlled partial acetylation of kraft lignin with an almost 3-fold improvement in tensile strength (about 2-fold increase in elastic modulus) compared to the unmodified lignin-based fibrous materials. Our study holds promise for the realization of potentially low-cost quality carbon fibers.

Discovering Biomass Structural Determinants Defining the Properties of Plant-Derived Renewable Carbon Fiber

SummaryTraditional lignocellulosic feedstock research has focused on biomass characteristics essential for improving saccharification efficiency, yet the key biomass features underlying high-quality renewable lignin materials remain unknown. Nevertheless, modern biorefinery cannot achieve sustainability and cost-effectiveness unless the lignin stream can be valorized. We hereby addressed these scientific gaps by investigating biomass characteristics defining lignin-based carbon materials properties. Lignin from eight sorghum samples with diverse characteristics was fabricated into carbon fibers (CFs). Remarkably, only lignin uniformity was found to define CF mechanical performance, highlighting the new structure-property relationship. Contrarily, lignin content and composition did not impact on carbon material properties. Mechanistic study by XRD and Raman spectroscopy revealed that higher lignin uniformity enhanced CF microstructures, in particular, turbostratic carbon content. The study for the first time highlighted lignin uniformity as an important biomass structure determinant for renewable products, which opened up new avenues for feedstock design toward diverse products enabling sustainable and cost-effective bioeconomy.

Characterization of textile-grade carbon fiber polypropylene composites

In this work, we consider low-cost carbon fiber produced with a textile-grade precursor. The objective of the study is to investigate textile-grade carbon-fiber-reinforced-polypropylene composites (TCF-PP) from compounded pellets for mechanical and thermal characterization. Four sets of pellets with 1%, 5%, 10%, and 15% reinforcement were manufactured using textile-grade carbon fiber (TCF) and polypropylene (PP) by twin-screw compounding. The addition of TCFs through gravimetric feeder directly in the extruder resulted in lower fiber content; however, side feeder has shown good potential. The pellets were further processed in extrusion compression molding to manufacture plaques. An increase in fiber loading has a negligible effect on fiber attrition as fiber length distribution variation between 1% and 15% reinforced pellets was very small. The addition of TCFs in PP showed a significant improvement in mechanical properties. The tensile strength and modulus of the composite were 26% and 161%, respectively, improved by the addition of 10 wt% TCF. Similar results were observed in the flexure test. However, the impact properties were reduced by 25.54% by the addition of 15% TCF.

Composites made from CF prepreg trim waste tapes using sheet molding compounds (SMC) technology: Challenges and potential

This study explores the use of carbon fiber (CF) prepreg trim waste to manufacture lightweight, high performance and low cost CF composites using sheet molding compound (SMC) technology. First, the modifications of a typical SMC and a flow study to determine the charge in size and mass of the sheets are determined. Then, the effect of the age of the prepreg tapes, aspect ratio of cut chips and pressure during compression molding on the tensile and impact properties of the composites is determined and these properties are compares with those of typical SMC composites. It is concluded that (i) the standard SMC production line needs to be modified in order to successfully convert CF tapes into sheets and (ii) the produced CF composites can meet the high stiffness and acceptable strength for not strength-critical applications without the need to store the prepreg trim waste in controlled conditions.

Improved structure and highly conductive lignin-carbon fibers through graphene oxide liquid crystal

Lignin is considered as a promising bio-sourced precursor for more sustainable and low-cost carbon fibers (CFs). However, lignin-based CFs generally have a poor graphitic structure, compared to polyacrylonitrile CFs. In this paper, we present an original approach that uses graphene oxide liquid crystal (GOLC) as a templating agent to promote the formation of graphitic structure in the fibers at low carbonization temperature. Both lignin and hybrid lignin/GOLC CFs were carbonized/graphitized up to 2700 °C. Structural analyses by X-ray diffraction, Raman spectroscopy and electrical measurements manifest a significant improvement in graphitic structure and a preferred orientation of graphene planes for lignin/GOLC fibers. These effects are the result of axial propagation of the templated graphitic order nucleated by the large GO flakes. The current approach reveals the possibility of preparing low-cost lignin-based CFs with improved graphitic structure and high electrical conductivity at low temperature for electrochemical or smart textile applications.

Open-ended capstone project: designing and manufacturing of a low-cost carbon fiber reinforced composite suborbital rocket payload housing using a 3D printed core

Open-ended capstone project: designing and manufacturing of a low-cost carbon fiber reinforced composite suborbital rocket payload housing using a 3D printed core

Structural Transformation of Polyacrylonitrile (PAN) Fibers during Rapid Thermal Pretreatment in Nitrogen Atmosphere.

The modification before the stabilization process could tune the exothermic behavior and the structural evolution of PAN fibers during stabilization. In this study, we demonstrate that a rapid thermal pretreatment in nitrogen can effectively mitigate the exothermic behavior of PAN fibers, such as decreasing the initial temperature, broadening the exothermal peak, and decreasing the nominal heat release during heating the fibers in air. The color of fibers has shown gradual changes from white to light yellow, yellow and brown during thermal pretreatment in nitrogen with the increase of pretreating temperature and time. The differential scanning calorimetry (DSC), Fourier Transform Infrared Spectrometer (FTIR), X-ray diffraction (XRD), and Thermogravimetric Analysis (TG) characterization have been applied to analyze the thermal properties, chemical and physical structural difference between PAN, and thermally pretreated PAN fibers. The thermal pretreatment of PAN fibers in nitrogen could induce cyclization, dehydrogenation, and cross-linking reactions, in which the cyclization play an important role on improving the cyclization index of stabilized PAN fibers. Meanwhile, the pretreatment can result in noticeable changes of the aggregation structure of PAN fibers, as indicated by the increase of crystallinity and crystalline size. These structural modifications can benefit the main cyclization reaction during stabilization and enhance the carbon yield in resultant carbon fibers. The rapid thermal pretreatment in nitrogen could increase efficiency of modification on PAN fibers, and that could save much time and energy. It is beneficial to manufacture low-cost carbon fibers and to spread the applications of carbon fibers.

Puck의 파손기준에 기반한 풍력발전기용 복합재 블레이드의 점진적 파손 평가

Composites combined physically with a reinforcing material and base material are very different from existing metal materials and show complex damage and damage patterns. To explain this, the Tsai-Hill and Tsai-Wu failure condition equations were introduced using the correlation between the vertical and shear stress and strength, and Puck’s theory was introduced to explain the damage and failure mode under a combined load. In this paper, progressive failure analysis was performed to examine the damage mode of the composite blade for a wind turbine designed and manufactured as a fiber-reinforced composite material and the change in the failure mode due to the increase in load using the theory of Puck’s. For this purpose, 30 kW composite blades were stacked using newly developed low-cost and high-strength pitch-based carbon fibers, and the load was acquired using a simple load calculation method according to the IEC61400-2 standard. A structural safety evaluation was performed through structural analysis under the calculated load. In addition, the damage mode was evaluated using the damage standard theory of Puck’s, and progressive damage analysis was performed in the initial damage progressing gradually with a 10% and 20% increase in the load condition.

Honeycomb carbon fibers strengthened composite phase change materials for superior thermal energy storage

Phase change materials (PCMs) have shown promising applications for thermal energy storage and management. With the purposes of solving the critical leakage problem and improving the thermal conductive property of paraffin PCM, composite PCMs as-supported by carbon fiber bundles were fabricated by a simple vacuum impregnation. The porous and honeycomb-shaped carbon fibers were prepared by the direct carbonization of biomass sisal fibers. As beneficial from the carbon supporting scaffolds, the composites illustrated great thermal conductivity increasement (1.73 W m−1 K−1) over pure paraffin (0.25 W m−1 K−1). The composite PCMs show satisfying latent heat (192.2 J g−1 at a carbon ratio of 12.8%), good shape stability, favorable thermal reliability and cyclability. Moreover, due to the one-dimensionally arranged carbon fiber bundles, the composites also showed anisotropic thermal conductive property. All of those could reinforce the use of the low-cost sisal-derived carbon fibers as thermal conductive scaffolds to PCMs, which will promote their practical applications for advanced thermal energy storage in collecting solar energy and industrial waste heat.