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Carbon fibers (CFs) have been considered as a next-generation material in high-performance applications such as aerospace, defense, sporting goods, wind energy, automobiles, electronics, and civil engineering industries due to their superior mechanical properties including high tensile strength and modulus and characteristics such as low density, good corrosion and low impact resistance, low coefficient of thermal expansion, and high electric conductivity. In this paper, we introduced the brief overview of the most widely produced and used polyacrylonitrile(PAN)-based CFs. In particular, the studies on developing high performance CFs by theoretical and experimental approaches were presented. Theoretical tensile strength of CFs can be ideally up to 100 GPa with the perfectly developed graphitic structure and its orientation along fiber direction. However, commercially available CFs reveal only tensile strength of 7 GPa because of the existing defects, misordered carbon crystals, and turbostratic structure. Those originate from manufacturing processes such as spinning, stabilization, and carbonization, which generate significant morphological and structural defects in both exterior and interior of CFs. The review covered the research on parameters related with the tensile properties and optimizing processes to increase the tensile strength of PAN-based CFs. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrospinning is a simple, versatile, and cost-effective technology which generates ultrasound fibers with high surface area to volume ratio, porosity and tunable porosity. Solution and processing parameters such as viscosity, molecular weight, concentration of the polymer, applied voltage, distance from tip to collector, conductivity, significantly affect the fiber morphology. An optimization of these parameters is required to obtain materials with desired properties for specific applications. In this study we synthesized electrospun fibers with different concentrations of PAN, our purpose being the obtaining of carbon fibers, needed for producing the gas diffusion layers for Proton Exchange Membrane Fuel Cell. The electrospun fibers obtained were subjected to carbonization at two different temperatures, 1200°C and 1400°C, in order to establish the temperature influence on removing all non-carbonaceous matter and to obtain a sample with higher carbon concentration and pure carbonaceous material. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile/graphene (PAN/GP) composite nanofiber filaments were spun continuously by a homemade eight‐needle electrospinning device with an auxiliary electrode, and then, yarns were obtained by plying and successive twisting. Subsequently, the composite yarns were stabilized at 250–280°C for 1–2 h and then carbonized at 800–1100°C for 1–3 h. The diameter of yarns significantly decreased by over 60% after carbonization and the structure became more compact. The optimum stabilization conditions were at 270°C with holding for 1.5 h. The addition of GP at a low mass fraction (<1%) promoted the formation of ladder‐like structures and ordered graphitic structures during stabilization and carbonization. It seems there were defects in the pristine CNF, and the addition of GP reduced the defects. The conductivity of the composite CNF yarn sharply increased with the increase of GP content to 1%, and then decreased. The maximum value was 66.44 ± 13.16 S/cm at 1100°C held for 3 h. The mechanical properties for composite CNF yarns were performed. The maximum stress and modulus were 59.49 MPa and 14.63 GPa, respectively. POLYM. ENG. SCI., 58:903–912, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The present work deals with the characterization of multi‐walled carbon nanotubes (MWCNTs) filled and unfilled short carbon fiber reinforced epoxy resin composites. Short carbon fibers (10 mm) were selected at various processing stages such as (i) white color polyacrylonitrile fibers (PAN); (ii) pre‐carbonized carbon fibers (Precarb‐CF); (iii) oxidized carbon fibers (OCF); (iv) fully carbonized carbon fibers (CF‐low); and (v) sized carbon fibers (CF Sized). The investigated composites were characterized by three points bending test, hardness test, dynamic mechanical thermal analysis (DMTA), electrical conductivity test, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results show that the mechanical and electrical properties of the investigated materials markedly depend on the type of short carbon fibers and on the presence of MWCNTs. POLYM. COMPOS., 39:E817–E825, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

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 (LT) carbonization has increased fiber density and produced a higher modulus and high tensile strength fiber up to 2200 cN. It was also seen that increasing the temperatures during the initial carbonization did not affect tensile strength and produced lower modulus fiber once high temperature (HT) carbonization was completed. However, this study revealed that it is possible to produce fibers with a tensile strength of 3.28 GPa and tensile modulus of 222 GPa just within LT carbonization, which are desirable for automotive applications. Moreover, by eliminating the HT carbonization, additional energy consumption and manufacturing time can be reduced, which further lowers the cost of the final carbon fibers. [ABSTRACT FROM AUTHOR]

Electrospun fibers of mixed polyacrylonitrile/polyvinyl pyrrolidine (PAN/PVP) sheath and silicone oil core were obtained by coaxial electrospinning. PVP and silicone oil were then removed from the coaxial electrospun fibers via phase separation and carbonization processes, respectively, to make the hollow-porous multilayered ultrafine carbon fibers. The relationship between the morphology and electrochemical performance of ultrafine carbon fibers was investigated. Results show that the supercapacitor based on electrode of hollow-porous multilayered ultrafine carbon fibers exhibits high conductivity, fast ion diffusion, high specific capacitance (231.6 F·g −1 ), high charging/discharging efficiency (99.7%), and low internal resistance (0.2 Ω) using tetraethylammonium tetrafluoroborate in acetonitrile as electrolyte. Additionally, this work also demonstrates a great potential in the preparation of carbon nano-materials with graphene-like multilayer structure. [ABSTRACT FROM AUTHOR]

Several studies have shown the importance of carbon fibres (CF) for different high technology markets. In recent years, different fibre types with improved properties have been developed for those markets. Polyacrylonitrile (PAN) copolymers are the basic raw material (precursor) for these fibres in the predominant case. Improvements of the mechanical fibre properties have mainly been achieved by defect reduction during the manufacturing process. Thus, commercial carbon fibres with tensile strengths up to approx. 7000 MPa are currently available. It can be shown that the strengths can be further increased (in the direction of graphene properties) when the relationship between process conditions and defects due to manufacturing of the fibres is better understood. In this context, novel processes like electron beam crosslinking or UV-activation have proven to be very promising. The article gives an overview about the current situation in the field of carbon fibres development and particularly shows recent shortcomings with respect to novel applications. [ABSTRACT FROM AUTHOR]

Carbon fibers (CFs) were prepared from polyacrylonitrile fibers pre-irradiated with γ-ray irradiation in air prior to heat treatment and then by continuous stabilization and carbonization. The structural changes of fibers during heat treatment and the mechanical properties of the resultant CFs were investigated using dynamic mechanical analysis, wide-angle X-ray diffraction, small-angle X-ray scattering, and universal testing machine. It is found that not only the stabilization time was shortened with the increasing absorbed doses, but also the preferred orientation of carbon layers in the CFs was increased initially with the increasing absorbed doses and then decreased. Consequently, the tensile strength and Young's modulus of CFs were increased by 13.2 and 2.6 % at an appropriate dose, respectively, in which skin-core structure in CFs was relieved according to SEM images. Hence, it is believed that irradiation technology-assisted stabilization has a significant potential in CF industry. [ABSTRACT FROM AUTHOR]

Unidirecitonal pre-preg carbon fibers of ten peel plies were laid up at 0-, 45-, −45-, and 45-degree stacking sequences on a flat and smooth aluminum (Al) plate, and then carbonized electrospun polyacrylonitrile (PAN) nanofibers were placed on top of the last ply prior to vacuum curing in a vacuum oven. The PAN electrospun fibers were oxidized at 280°C in an ambient condition for 1 hr and then carbonized at 850°C for 1 hr in an argon (Ar) gas atmosphere. The resultant composite panels were cut into small pieces and subjected to a number of different characterization techniques. Thermal mechanical analysis (TMA) measurements clearly showed that significant reinforcement was achieved for the pre-preg/carbonized PAN fiber composites because of the enhanced interfacial bonding between the PAN nanofibers and the matrix. Dynamic mechanical analysis (DMA) tests exhibited a shift of the glass transition temperature of the carbonized PAN nanofiber/composite, which may be helpful for high-temperature applications of the present composites. A Raman spectroscopy peak around 897 cm−1 indicated formation of the γ-phase of the carbonized PAN fibers. The highest stretching peak of the CH2 group was recognized within the range of 2,500-2,800 cm−1 for the carbonized fibers. The vibration peak of the CN group also appeared at 1,452 cm−1 spectrum. TMA determined the coefficient of thermal expansion (CTE), indicating an improvement in stability of the composite material, which can be useful for structural health monitoring (SHM) as well as lightning strikes and electromagnetic interference shielding applications of new carbon fiber composites. [ABSTRACT FROM AUTHOR]

Carbon fiber is expected to increase its importance as a lightweight substitute material. The significant market potential in the automotive industry is strongly dependent on carbon fiber cost. A decrease of about 50% from the present cost level of polyacrylonitrile (PAN)-based carbon fibers is needed. This ambitious target is only achievable with high-cost transparency in the production chain. This paper reviews published cost models and identifies the need for a consistent methodology and transparency over input parameters. A new cost model with a modular structure covering all process steps by cost type and disclosing all process parameter assumptions is introduced. The most cost-intense steps are polymerization, including raw material (25%), carbonization (22%) and fiber washing after coagulation (19%). Most important cost types are energy (34%), raw material (19%) and capital costs for equipment (18%). The high-cost share of 54% for carbon fiber PAN precursor is consistent with most reviewed models. [ABSTRACT FROM AUTHOR]

Aligned electrospun nanofibrous bundle was used as the raw material for pretreatment, preoxidation and carbonization processes to prepare carbon nanofibers in a procedure temperature-controlled sintering furnace. Effect of carbonization temperature on themorphology and structural performance of nanofiberswas investigated in present study. Results showed that R1 (the relative intensity radio between Disordered peak and Graphite peak) of nanofibers carbonized at 1000 °C is 0.90, carbon content is up to 85.67%, conductivity is 105.44 S·cm-1, Young's modulus is 68.8 ± 0.42 GPa, and fiber strength is 306.0 ± 9.0 MPa, all of which endow the fibers with a superior comprehensive property. [ABSTRACT FROM AUTHOR]

Reducing the price of carbon fiber (CF) is crucial to the wider application of CFRP in automobiles for energy reduction. Because process costs account for 46% of the total cost of CF, interest has increased in the development of affordable processes such as microwave plasma carbonization, which can reduce the cost. In this study, the concept of a two step microwave plasma carbonization process is suggested to enhance the mechanical properties of the CF made with the plasma process. Compared with single step carbonized CF, the two step carbonized CF had 171% improved tensile strength because of the synergetic effect of the low power and high power carbonization steps. Two step or multi step carbonization process is expected to be another improvement of the microwave plasma carbonization process in that it not only reduces the energy consumption of the process but also improves the mechanical properties of CF. [ABSTRACT FROM AUTHOR]

The paper presents the results of the manufacture of carbon fibers (CF) from polyacrylonitrile fiber precursor containing bioactive ceramic nanoparticles. In order to modify the precursor fibers two types of bio-glasses and wollastonite in the form of nanoparticles were used. The processing variables of the thermal conversion of polyacrylonitrile (PAN) precursor fibers into carbon fibers were determined using the FTIR method. The carbonization process of oxidized PAN fibers was carried out up to 1000 °C. The carbon fibers were characterized by a low ordered crystalline structure. The bioactivity tests of carbon fibers modified with a ceramic nanocomponent carried out in the artificial serum (SBF) revealed the apatite precipitation on the fibers' surfaces. [ABSTRACT FROM AUTHOR]

Sheath-core polyacrylonitrile (PAN)/poly(methyl methacrylate) fibers were spun through bi-component dry-jet gel-spinning method and were used for fabricating hollow carbon fibers. After optimizing stabilization and carbonization conditions, the resulting PAN-based hollow carbon fibers possessed an average strength and modulus of 3.16 and 275 GPa, respectively. Additionally, 1 wt% carbon nanotubes (CNTs) were added to PAN portion to form PAN+CNT sheath. The PAN+CNT-based hollow carbon fiber had an average strength of 3.24 GPa and modulus of 254 GPa. These hollow carbon fibers can be used for fabricating low density and high performance structural composite materials. [ABSTRACT FROM AUTHOR]

Microwave heating is investigated as an alternative method of carbonization process for carbon fiber (CF) in order to reduce the energy costs. In this study, a microwave plasma system is designed for the carbonization process, and stabilized polyacrylonitrile fiber is carbonized using the system. Compared with the CF fabricated by conventional thermal carbonization process, plasma-carbonized CF has higher surface roughness, which can enhance the mechanical interlocking between resin and CF and increase the mechanical properties of the CF Reinforced Polymer (CFRP). Furthermore the mechanical properties of the CF didn't fall behind that of the conventionally carbonized one. As a result, microwave plasma carbonization is a good candidate for the next-generation carbonization processes in the CF industry. [ABSTRACT FROM AUTHOR]

Carbon papers (CPs) have been fabricated using wet-laying carbon fibers (CFs) and polyacrylonitrile (PAN) fibers. Scanning electron microscopy revealed that the PAN fibers tightly interconnected the CF junctions with the pores between the fibers. The tensile strength of the carbon webs (CWs) increased as the fraction of PAN fibers used as the binder increased. The CW fabricated with 0.15 wt% PAN fibers had a tensile strength six times greater than that of the CW without PAN fibers. Moreover, by mixing the CFs with PAN fibers in water, the CFs separated from each other in the webs due to the interruption of hydrophobicity between the CFs. After mixing with PAN fibers, the CWs were carbonized at 1200 °C in the presence of a phenolic resin. The PAN fibers maintained their morphology due to their high carbon content after carbonization. The electrical resistivity of the CPs with high PAN fiber content was significantly lower than that of a CP without PAN fibers due to the interconnection of the CFs by the carbonized PAN fibers. [ABSTRACT FROM AUTHOR]

Due to its unique structure, hollow-mesoporous carbon fibers would enlarge the applications of hollow fiber in the areas operating in the harsh environment. In this paper, polyacrylonitrile (PAN) -based hollow-mesoporous carbon fibers (HMCFs) with various carbonization temperatures were firstly fabricated by heat treatments including stabilization and carbonization with the hollow-mesoporous precursor fibers preparing with blending alkali lignin (AL). Unlike previously, a small amount of residue of AL (less than 1%) in the hollow-mesoporous fiber (HMF) would reduce the degree of cyclization although the activation energy of cyclization reaction reduces, and thus accelerate the thermal decomposition of HMF which shows a lower carbon yield eventually compared with PAN. The oxidative stability of fibers improves a lot when HMF is transformed into HMCF which is beneficial to use it in the poor conditions. This work explains the effects of residue of AL existing in the precursor fiber on the processes of stabilization and carbonization of HPCMs, and the relationships between basic properties of HMCFs including physical structure, chemical composition and relevant properties and carbonization temperature. It provides a new insight to fabricate HMF into HMCF by the heating treatments of stabilization and carbonization with the existence of AL. • PAN-based hollow-mesoporous carbon fibers were fabricated firstly by heat treatments with blending alkali lignin. • A small amount of residue of AL (less than 1%) in the hollow-mesoporous fiber (HMF) would accelerate the thermal decomposition of HMF which shows a lower carbon yield eventually compared with PAN. • The oxidative stability of fibers improves a lot when HMF is processed into HMCFs. • The tensile strength and modulus reach to 2.99 and 215.37 cN/dtex when the carbonization temperature is 800 °C, respectively. [ABSTRACT FROM AUTHOR]