Low-cost Carbon Fibers Research Articles

Coupled photothermal and joule-heating process for stable and efficient interfacial evaporation

Access to water and clean energy is a major concern in modern society. Although there have been huge improvements in the efficiency of solar interfacial evaporation as a technique to obtain clean water, it remains challenging for solar-driven interfacial evaporation systems to maintain stable steam generation and water production without an energy storage system. To overcome these issues, we propose a coupled tunable photothermal and joule-heating process for interfacial evaporation using a low-cost commercial carbon fiber (CF) material. The CF material had a high porosity, good water absorption, salt-rejection ability, and high total absorption (93%) and electrical conductivity (1666 S/m), which make it suitable for photothermal and joule-heating conversion. By coupling photothermal and joule-heating processes through the same CF material as the evaporation medium, a stable and efficient interfacial evaporation performance could be achieved, in which the input power of the electrical energy could be adjusted to match the loss of solar energy. Through coupled evaporation experiments, it was found that the evaporation rate reached 1.36 kg m−2 h−1, with sun irradiation power of 1 kW m−2. For photothermal conversion or joule-heating conversion, the efficiency first decreased and then increased. “Cold Vapor’’, with a lower input power, resulted in a higher efficiency, whereas heat localization led to a significant decrease in the relative ratio of the thermal losses and improved the efficiency at a higher input power. This work has further improved the multi-process coupling and multi-energy complementary process and will promote its actual application.

Design and numerical evaluation of recycled-carbon-fiber-reinforced polymer/metal hybrid engine cradle concepts

The design and evaluation of polymer-metal hybrid (PMH) engine cradles are realized via the design of concept models and finite element (FE) analyses. The structures consider a low-cost recycled carbon fiber (rCF) and PMH technologies. The initial conceptual design consists of creating C-type/hollow-type inserts and modifying the plastic components by considering the dimensions and thickness of insert and inclusion of plastic ribs as the design parameters. The PMH engine cradles are then evaluated by performance criteria, including weight reduction, stiffness, natural frequency and strength. The integration of rCF with injection-molding over metal inserts promoted weight reduction. The hollow-type and C-type PMH engine cradles achieved the weight reduction of 19 and 16% compared to the reference steel engine cradle, respectively, while they fulfilled the evaluation criteria. The results contribute to the advance of lightweight engine cradles with improved structural performance, fabricated with low-cost carbon fiber and fast manufacturing processes.

Functional Properties of a Pitch-Based Carbon Fiber-Mortar Composite as a Thin Overlay for Concrete Pavement.

This experimental study investigated the utility of a pitch-based carbon fiber–mortar composite, which could replace polyacrylonitrile carbon fiber, as a thin overlay for concrete pavement. The objective was to explore the utility of the low-cost carbon fiber, which was produced via a melt-blown method, i.e., blowing at high pressure after melting the pitch residue following crude oil purification. The mechanical properties, durability, and thermal properties of the pitch-based carbon fiber were explored to maximize strength, durability, functionality, and economy by using micro-sized fibers that are closer in size to the constituents of cementitious materials. Melt-blown pitch-based carbon fiber has low individual fiber strength but generally excellent thermal conductivity. Thermal conductivity tests were conducted on mortar panels (560 mm × 560 mm; thickness = 25, 40 or 60 mm) containing 0, 0.4, 0.5 or 0.6 wt % pitch-based carbon fiber. The absolute thermal conductivity tended to improve with higher wt % of pitch-based carbon fiber, in the range of 9~11 W/°C. However, thermal conductivity tended to be lower under the 0.6 wt % condition, possibly due to the effect of dispersion. Compressive strength degradation was tested over 350 cycles of freezing and thawing: the strength of the 0.4, 0.5 or 0.6 wt % samples was 91, 89, and 82%, respectively, relative to the control specimen (0 wt %). Thus, all specimens had a compressive strength of 80% or more after 350 cycles compared to the control specimen. To test the adhesion performance for new thin overlays and old concrete surfaces, concrete cylinders (100 × 200 mm; thickness = 10 mm) were cut at an angle of 46 degrees, and the pitch-based carbon fiber-mortar composite was used to bond the various sections. The bond strength of the test specimens was more than twice that of the reference specimen.

Low-Cost Carbon Fibre Derived from Sustainable Coal Tar Pitch and Polyacrylonitrile: Fabrication and Characterisation.

Preparation of high-value pitch-based carbon fibres (CFs) from mesophase pitch precursor is of great importance towards low-cost CFs. Herein, we developed a method to reduce the cost of CFs precursor through incorporating high loading of coal tar pitch (CTP) into polyacrylonitrile (PAN) polymer solution. The CTP with a loading of 25% and 50% was blended with PAN and their spinnability was examined by electrospinning process. The effect of CTP on thermal stabilization and carbonisation of PAN fibres was investigated by thermal analyses methods. Moreover, electrospun PAN/CTP fibres were carbonised at two different temperatures i.e., 850 °C and 1200 °C and their crystallographic structures of resulting such low-cost PAN/CTP CFs were studied through X-ray diffraction (XRD) and Raman analyses. Compared to pure PAN CFs, the electrical resistivity of PAN/25% CTP CFs significantly decreased by 92%, reaching 1.6 kΩ/sq. The overall results showed that PAN precursor containing 25% CTP resulted in balanced properties in terms of spinnability, thermal and structural properties. It is believed that CTP has a great potential to be used as an additive for PAN precursor and will pave the way for cost-reduced and high-performance CFs.

Carbon Fibers from Lignin-Cellulose Precursors: Effect of Stabilization Conditions

There is an increasing demand for lightweight composites reinforced with carbon fibers (CFs). Due to its high availability and carbon content, kraft lignin has gained attention as a potential low-cost CF precursor. CFs with promising properties can be made from flexible dry-jet wet spun precursor fibers (PFs) from blends (70:30) of softwood kraft lignin and fully bleached softwood kraft pulp. This study focused on reducing the stabilization time, which is critical in CF manufacturing. The impact of stabilization conditions on chemical structure, yield, and mechanical properties was investigated. It was possible to reduce the oxidative stabilization time of the PFs from about 16 h to less than 2 h, or even omitting the stabilization step, without fusion of fibers. The main reactions involved in the stabilization stage were dehydration and oxidation. The results suggest that the isothermal stabilization at 250 °C override the importance of having a slow heating rate. For CFs with a commercial diameter, stab...

Development of Tungsten Oxide Nanoparticle Modified Carbon Fibre Cloth as Flexible pH Sensor

A reagent-less pH sensor based on disposable and low cost carbon fibre cloth (CFC) is demonstrated for the first time, where tungsten oxide nanoparticles were grown directly onto the CFC substrate. For comparison purpose, tungsten oxide nanoparticle modified glassy carbon electrode (GCE) was also fabricated as a pH sensor, where hydrothermally synthesized tungsten oxide nanoparticles were drop casted onto the GCE surface. The corresponding equilibrium potential using tungsten oxide/CFC as a pH sensor was measured using open circuit potential (OCP), and was found to be linear over the pH range of 3–10, with a sensitivity of 41.38 mVpH−1, and response time of 150 s. In the case of tungsten oxide/GCE as a pH sensor, square wave voltammetry (SWV) was used to measure the shifts in peak potential and was found to be linear with a pH range of 3–11, and a sensitivity of 60 mVpH−1 with a potential drift of 2.4–5.0% after 3 hour of continuous use. The advantages of tungsten oxide/CFC and tungsten oxide/GCE as pH sensing electrode have been directly compared with the commercial glass probe based electrode, and validated in real un-buffered samples. Thereby, tungsten oxide nanoparticles with good sensitivity and long term stability could be potentially implemented as a low cost and robust pH sensor in numerous applications for the Internet of Things (IoT).

Safer and more effective route for polyethylene-derived carbon fiber fabrication using electron beam irradiation

As a precursor constitutes 50% of total production cost, adopting low-cost precursors for carbon fiber (CF) fabrication has been used as a major strategy to translate exotic carbon fiber technology into a commercial market. Polyethylene (PE), one of the cheapest and the most widely used plastics, has gained lots of tractions as a low-cost CF precursor ensuring stable price and supply. However, the major problem is that the only known CF fabrication protocol using PE includes sulfonation process, which generates toxic SOx fumes. Such toxic fuming does not comply safety and environmental regulations, thereby obstructed bringing PE based CFs into the real world applications. In this study, for the first time, we could demonstrate the fabrication of PE based carbon fiber without SOx fume generation by adopting electron beam pre-treatment. Electron beam technology served various industry fields for decades and it has been well known that active radicals are introduced into polymer chains by electron beam irradiation. Those active radicals are speculated to enable stabilization under significantly mild condition where no toxic fumes were generated. As a result, carbon fiber with sound properties reaching tensile strength of 1.3 GPa could be fabricated through shorter processing time.

Effects of ultraviolet irradiation on stabilization of textile-grade polyacrylonitrile fibers without photo-initiator for preparing carbon fibers

The ultraviolet (UV) was irradiated on textile-grade polyacrylonitrile (PAN) fibers without photo-initiators to demonstrate the effective stabilization for preparing carbon fibers (CFs). The irradiation for as short as 20 min at 75 °C generated radicals in the textile-grade PAN fibers, which accelerate stabilization, resulting in significant reduction of process time. In addition, stepwise irradiations from 75 to 200 °C by increasing UV power, and following thermal treatments to mimic continuous stabilization for 30 min total provided CFs with tensile strength and modulus of 2.43 ± 0.4 and 195 ± 8.6 GPa. Considering conventional thermal stabilization for at least 60 min and 5 h with special and textile PAN fibers, respectively, the incorporation of UV irradiation into the present system could effectively advance stabilization process to shorten duration and to produce low-cost CFs based on textile-grade PAN fibers as one of cheap precursors.

Hydrothermal base catalysed treatment of Kraft Lignin for the preparation of a sustainable carbon fibre precursor

Industrial Kraft Lignin (KL) prepared by LignoBoost® technology was treated via hydrothermal base catalysed depolymerisation (HBCD). KL was dried and divided into methanol soluble and insoluble fractions. The insoluble fraction was treated in 1 M NaOH (aq) at 300 °C. After precipitation with HCl (aq), the solids yield was ca. 60 wt%. These solids demonstrated improved thermal stability and carbon content, increased solubility in MeOH and reduction in polydispersity. With a view to the use of the product in the preparation of carbon-based materials (e.g. carbon fibres (CF)), thermal analysis was undertaken, revealing a lack of a glass transition below the decomposition temperature, excluding melt pinning. However, a high solubility in organic solvents renders the product a suitable candidate for solvent spinning and for the production of renewable low-cost CFs. Additionally, the process generated an oily liquid phase with yields of ca. 10 wt% containing valuable catechol and methylated derivatives.

Thermal behavior and thermal stabilization of guanidine hydrochloride-modified acrylic fiber for preparation of low-cost carbon fiber

A commercial textile-grade acrylic fiber was modified with guanidine hydrochloride for the preparation of low-cost carbon fibers. Thermal behavior of the modified acrylic fiber was studied by simultaneous differential scanning calorimetry and thermogravimetric analysis, and the effect of guanidine hydrochloride on the thermal stabilization of acrylic fiber was investigated by Fourier transform infrared spectrometry and densimetry. The results indicated that guanidine hydrochloride could initiate the cyclization reaction of nitrile groups at lower temperature and promote the thermal stabilization of acrylic fiber. Compared with the carbon fibers prepared from the original acrylic fiber, the tensile strength and tensile modulus of the carbon fibers prepared from the modified acrylic fiber had been increased by about 72% and 34%, respectively. The guanidine hydrochloride-modified acrylic fiber was expected to be a practical low-cost carbon fiber precursor.

Microstructure and mechanical properties of carbon fiber needled felt reinforced sol-derived YAG composite

The study concerning the second phase reinforced YAG matrix composites is few although YAG is well known as a desirable thermo structural ceramic. In this paper, low-cost 3D carbon fiber needled felt was used as reinforcement to improve the fracture toughness of YAG, and the carbon fiber needled felt reinforced YAG (C/YAG) composite was fabricated through vacuum impregnation-drying-heat treatment, using the Y2O3-Al2O3 sol with a high solid content as raw material. The microstructure, mechanical properties, thermal stability and oxidation resistance of C/YAG composite were carefully investigated. Due to the characteristics of reinforcement and the microstructure, the as-fabricated C/YAG composite showed non-catastrophic failure behavior and much higher fracture toughness compared with monolithic YAG ceramic. The flexural strength of C/YAG composite was well retained after annealed at 1700 °C and 1800 °C under inert atmosphere. Although the chemical inertness between carbon fiber and YAG was confirmed up to 1800 °C, the physical bonding of interface was enhanced during annealing, which led to the decrease of fracture work, especially at 1800 °C. The oxidation resistance of C/YAG composite was related to the cracks and pores since YAG is immune to oxidation. The changes of microstructure and flexural strength after oxidation at 1200 °C, 1400 °C and 1600 °C were characterized and analyzed.

Reinforcement Systems for Carbon Concrete Composites Based on Low-Cost Carbon Fibers

Carbon concrete polyacrylonitrile (PAN)/lignin-based carbon fiber (CF) composites are a new promising material class for the building industry. The replacement of the traditional heavy and corroding steel reinforcement by carbon fiber (CF)-based reinforcements offers many significant advantages: a higher protection of environmental resources because of lower CO2 consumption during cement production, a longer lifecycle and thus, much less damage to structural components and a higher degree of design freedom because lightweight solutions can be realized. However, due to cost pressure in civil engineering, completely new process chains are required to manufacture CF-based reinforcement structures for concrete. This article describes the necessary process steps in order to develop CF reinforcement: (1) the production of cost-effective CF using novel carbon fiber lines, and (2) the fabrication of CF rebars with different geometry profiles. It was found that PAN/lignin-based CF is currently the promising material with the most promise to meet future market demands. However, significant research needs to be undertaken in order to improve the properties of lignin-based and PAN/lignin-based CF, respectively. The CF can be manufactured to CF-based rebars using different manufacturing technologies which are developed at a prototype level in this study.

Preparation of low-cost carbon fiber precursors from blends of wheat straw lignin and commercial textile-grade polyacrylonitrile (PAN)

Abstract Low-cost precursor fibers (PFs) were prepared from blends of a wheat straw lignin (WSL) and a commercial textile-grade polyacrylonitrile (PAN) by wet spinning, and then the precursors were converted into carbon fibers (CFs) by thermal stabilization and carbonization. The PFs were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The lignin content in the blends was found to play an important role in the PF structure, which was closely related to the change of intermolecular forces in the spinning solution. The lignin, acting as the carboxylic acid comonomer, had significantly promoted the thermal stabilization of the lignin/PAN blend PFs, which helped to further decrease the production cost of CFs. With increasing lignin contents, the carbon content of CFs remained at about 95%. The carbon of lignin could be utilized for the preparation of CFs.

Direct evidence of IR-driven hot electron transfer in metal-free plasmonic W18O49/Carbon heterostructures for enhanced catalytic H2 production

Plasmonic nanostructures have received significant attention in the field of solar-to-fuels conversion, because they can collect and utilize abundant low-energy photons to generate high-energy hot electrons for producing green chemical fuels. However, the ultrafast relaxation process of hot electron often leads to poor quantum yields of plasmonic nanostructures. Herein, we construct the one-dimensional W18O49/Carbon heterostructure for employing low-cost electrospun carbon fibers as the “electron mediator” to hinder the relaxation of hot electron in plasmonic W18O49 nanowires. We confirm that the IR-excited plasmonic hot electrons in W18O49 nanowires can quickly transfer to carbon fibers within only ∼50 fs in the W18O49/C heterostructure. This kinetics time is much shorter than the relaxation time of these hot electrons from high-energy surface plasmon (SP) to the ground state in W18O49 nanowires (∼5.5 ps). As a result, upon low-energy IR-light excitation, the W18O49/C heterostructures exhibit nearly 2-fold enhancement on the catalytic H2 production from ammonia borane as compared to single W18O49 nanowires. Wavelength-dependent catalytic tests further indicate that this plasmon-enhanced catalytic activity is induced by the ultrafast transport process of plasmonic hot electron due to the localized surface plasmon resonance.

The Role of Tension and Temperature for Efficient Carbonization of Polyacrylonitrile Fibers: Toward Low Cost Carbon Fibers

We report the production of automotive grade carbon fibers in a low temperature carbonization furnace by making use of the influence of various levels of tensions and temperatures on polyacrylonitrile (PAN) precursor fibers. The experiments were performed at two different temperatures during a low temperature carbonization process to understand the effect of differences in temperature as well as tension. The effect of oxidative stabilization and carbonization processes on the structure, mass retention, and mechanical properties of precursor fibers was analyzed. Fibers were collected from each zone of the low and high temperature furnaces, and physical properties were measured for carbon fibers along with precursor and oxidized fibers. The infrared studies revealed the variation in the chemical structure of the fibers during the stabilization, and the aromatization index of 65.5% was calculated from thermal studies of the stabilized fibers. It was found that an increase in tension during low temperature (L...

Molecular and thermal studies of carbon fiber precursor polymers with low thermal‐oxidative stabilization characteristics

ABSTRACTIn this investigation, terpolymers, copolymers, and homopolymer of acrylonitrile with dimethylaminopropyl acrylamide (DMAPA), itaconic acid (IA) viz., poly(acrylonitrile‐ran‐3‐dimethylaminopropyl acrylamide‐ran‐itaconic acid) [P(AN‐DMAPP‐IA)], poly(acrylonitrile‐co‐3, dimethylaminopropyl acrylamide) [P(AN‐DMAPP)] were synthesized with varying amounts of comonomers using solution polymerization process. The chemical structure, composition, bonding network were determined employing infrared, 1H and, 13‐carbon nuclear magnetic resonance spectroscopic techniques. Molecular characteristics of as‐synthesized polymers such as different kinds of average molecular weights, molecular weight distribution were estimated applying solution viscometry and size exclusion chromatography. The influence of comonomers (DMPAA, IA) on the thermal stabilization characteristics of acrylonitrile terpolymers in comparison with copolymers and homopolymers of acrylonitrile were studied using differential scanning calorimetry (DSC), hyphenated thermal techniques (thermal gravimetry coupled with differential thermal analyzer).The DSC curves of P(AN‐DMAPP‐IA) exhibit a distinct broader bimodal peaks with thermal exotherm initiating at as low as 165 °C, and followed by two peaks with temperature difference of 42 °C, releasing the evolved heat at a release rate of 0.7–0.11 J g−1s−1over 10 min as compared to 1.2, 7.5 J g−1s−1 in 4.5, 2 min as observed in P(AN‐DMAPP), polyacrylonitrile, respectively. The thermal stability of P(AN‐DMAPP‐IA) and P(AN‐DMAPP), as evidenced by TGA‐DTA was found to be higher than PAN homopolymers. Specific heat capacity measurements confirmed the DSC results. Bulk densities of P(AN‐DMAPP‐IA) were in the range 0.31–0.35 g/cc. These results confirm the low‐temperature stabilization characteristics and suitability of P(AN‐DMAPP‐IA) as low cost carbon fiber precursor polymers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46381.

Phosphorus functionalization for the rapid preparation of highly nanoporous submicron-diameter carbon fibers by electrospinning of lignin solutions

Rapid preparation of low-cost carbon fibers by electrospinning of lignin solutions thanks to the functionalization with H3PO4.

A revolution in low-cost carbon fiber production

LeMond Composites’ patent pending manufacturing process will produce low-cost, high performance carbon fiber for a range of industries, from transportation to renewable energy.

Thermal Treatment of Melt-Spun Fibers Based on High Density PolyEthylene and Lignin

The purpose of this study was the synthesis of novel low-cost carbon fibers along with the investigation of the optimal parameters of temperature and time for the stabilization of hybrid high-density polyethylene (HDPE) and lignin melt-spun fibers. These fibers were manufactured by physical compounding of HDPE and chemically-modified softwood kraft lignin (SKL) in order to produce green fiber precursors for carbon fiber synthesis. Stabilization tests were performed with respect to thermal treatment (physical method) and sulfonation treatment (chemical method). The results revealed that only chemical methods induce the desired thermal process-ability to the composite fibers in order to manufacture carbon fibers by using a simple method. This investigation shed light on the stabilization techniques of polymeric fibers in the absence of any cyclic groups in terms of environmentally-friendly mass production of carbon fibers using low-cost and green raw materials. This study facilitates incorporation of softwood lignin in homegrown polymeric fibers by a low-cost production process via melt-spinning of composite fibers, which were successfully stabilized using a facile chemical method and carbonized. Additionally, a comprehensive investigation of the thermal behavior of the samples was accomplished, by examining several ways and aspects of fiber thermal treating. The properties of all studied fibers are presented, compared, and discussed.

Effects of stabilization variables on mechanical properties of isotropic pitch based carbon fibers

Optimization of the stabilization process for manufacturing low-cost carbon fibers was performed. By simply varying both heating rate (0.5–10°C/min) and starting temperature (25–230°C), the resulting fibers possessed different properties such as densities, oxygen contents, and weight gains due to the oxygen up-takes. Subsequent oxidative reactions led to changes in chemical compositions of the fibers. Therefore, this study suggests that more concerned design with complementary parameters such as starting temperature and heating rate, significantly reducing stabilization time down to 56.5min with the comparable mechanical properties of the conventional isotropic pitch based CFs.