Surface Morphology Of Carbon Fibers Research Articles

Electrical transport behaviors of Ni layer on carbon fiber

Recently, carbon materials have been employed for the core of metal wires, contributing to their weight reduction. Low weight is a required characteristic for cables used in air, water, and ground transportations, in order to maximize fuel efficiency. Nowadays, the hybridization of C with metal for the creation of C-based metal wires is achieved through different approaches. A thin metal layer of Ni is usually applied through electroless plating on the surface of C fibers (CFs; diameter = 7 μm). Transport studies conducted on a single strand of Ni-coated CFs (Ni-CF) have indicated that, depending on the grain size, phonon-supported hopping or phonon-driven electron scattering transport can dominate. At a given P concentration (∼11 at.wt.%) and when the average grain size is < 100 nm, phonon-driven electron scattering transport dominates: as the temperature increases, the resistance increases as well, resulting in a positive temperature coefficient of resistance (TCR) (∼1.5 × 10 −3 /K at 300 K). This is a conduction behavior typically observed in metals. However, when the average grain size is > 100 nm, impurity-related variable range hopping (VRH) transport dominated, leading to a negative TCR (∼1.0 × 10 −4 /K at 300 K); in this case, the resistance decreases with increasing temperature, as in a semiconductor. Our results imply that, by controlling the plating condition and surface morphology of CF, it is possible to modulate metal properties (i.e., the metal-insulator transition (MIT)). • A Ni layer was deposited on the outside of carbon fibers (CFs) by electroless electrochemistry. • The temperature-dependent resistance of the Ni-CFs was measured in a closed-cycle refrigerator (CCR). • Transport studies conducted on a single strand of Ni-coated CFs have indicated that, depending on the grain size, phonon-supported hopping or phonon-driven electron scattering transport can dominate.

Mechanical characteristics of high strength concrete incorporating recycled CFRP fibers

AbstractThe current research article assesses the feasibility of recycled CFRP (Carbon‐Fiber‐ Reinforced‐Polymer) fibers in high‐strength concrete. Different dosages of recycled CFRP fibers (0.2%, 0.4%, 0.6%, 0.8%, and 1%) as well as different aspect ratios of CFRP fibers with 10 and 20 mm fiber lengths is assessed for hardened state characteristics of reinforced high‐strength concrete. Furthermore, ultrasonic pulse velocity test, compression test, flexure test, and impact resistance test are performed to understand the hardened properties of specimens. The chemical composition of various elements present in the various kinds of concrete samples is qualitatively and quantitatively found with the help of energy‐dispersive X‐ray spectroscopy (EDX) equipment. To understand the surface morphology of carbon fibers incorporated in concrete samples, Scanning electron microscope (SEM) photographs are obtained to examine the prepared samples thoroughly. Linear regression analysis, an analytical analysis technique, is incorporated to linearly correlate the different hardened mechanical characteristics of specimens taking into account varying lengths and different dosages of recycled CFRP fiber. The findings reveal that increasing the CFRP fiber dosage and the aspect ratio of recycled CFRP fiber improves the reinforced mix composition's mechanical characteristics.

High‐epoxy value bio‐based epoxy emulsion reinforced interfacial properties of carbon fiber/epoxy composites

AbstractThe development of new bio‐based epoxy resins and the search for new application areas have become important research directions for bio‐based epoxy resins. Using protocatechuic acid (PA) as a bio‐based raw material, brominated alkenes with different chain length were introduced into PA through substitution reaction, and then oxidized to obtain epoxy resins (PA‐EP) with different epoxy values. After that, it was introduced into epoxy resin (diglycidyl ether bisphenol A [DGEBA]) sizing agent to replace part of DGEBA to prepare new sizing agents. Sizing amount test and sizing CF surface morphology show that the introduction of PA‐EP with high‐epoxy value made it easier be adhered to carbon fiber (CF) surface during sizing process. Interfacial shear strength and interlaminar shear strength of composite made of sizing CF (20 wt% PA‐EP‐3) were 56.86% and 30.29% improvement against the bare CF, which was attributed to the increase in surface energy and epoxy groups after CF sizing. Therefore, PA‐EP with high‐epoxy value was applied as sizing agent for improving interface performance of CF for the first time, and this application was less affected by its low‐output problem compared to its application as a matrix resin in the field of composite manufacturing.

Study on production technology and surface morphology of carbon fiber

Since the 21st century, China’s carbon fiber industry has begun to develop rapidly. The research and development of carbon fiber is a major project related to national strategic security. Carbon fiber production technology has been mature, among which PAN based carbon fiber has the largest capacity. However, compared with the imported carbon fiber materials, there is still a certain gap in the performance of domestic carbon fiber materials. The purpose of this paper is to compare the properties of domestic carbon fiber and its composites. Firstly, the production process of carbon fiber is introduced, including monomer polymerization, spinning, oiling, preoxidation, carbonization, graphitization and other steps. Then, the T700 Carbon Fibers of Toray, Japan and two kinds of domestic T700 Carbon Fibers of Hengshen and Weihai were characterized and analyzed, and the surface morphology of three kinds of carbon fibers was compared. It is found that the domestic carbon fiber of Weihai adopts the similar technology of thousand spray wet spinning, and the fiber surface is smooth. However, Hengshen carbon fiber adopts the wet spinning process. There are grooves on the surface of the fiber, which will increase the mechanical meshing force between the fiber and the resin, and have a positive significance for the interface performance of the composite. However, it will increase the probability of fiber defects, such as fine lines, and have a negative impact on its tensile properties and other mechanical properties.

Influence of surface modification of carbon fiber based on magnetron sputtering technology on mechanical properties of carbon fiber composites

To improve the interfacial performance of carbon fiber (CF) and epoxy resin, the surface of CF was modified using magnetron sputtering technology, and a CF epoxy resin (CFER) composite was prepared using injection molding technology. The influence of magnetron sputtering technology on the surface properties of CF was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamic contact angle analysis (DCAA). The influence of the surface modification of the CFs by magnetron sputtering on the mechanical and interfacial properties of CF composites was analyzed by testing the tensile and bending properties of the CFER composites. The results indicated that the surface morphology of CF can be modified by magnetron sputtering, and a nano sized carbon film was deposited on the surface of the CFs. The morphology of the carbon film on the surface of the CFs was different from that on the silicon pellet. The surface roughness of the CF increased after it was modified by magnetron sputtering. The surface wettability of the CFs may be improved by increasing the surface free energy of the fiber owing to the deposition of the carbon film. Tests of the tensile and bending properties of the CFER composites showed that the surface modification of CFs by magnetron sputtering can effectively improve the mechanical properties of the CFER composites, which not only improves the tensile strength and bending strength, but also increases the tensile modulus and bending modulus. The SEM images showed that the interfacial adhesion between the modified CF and the epoxy resin was significantly improved. The stress–strain curves showed that the failure mode of the CFER composite modified by magnetron sputtering CF surface changed, and a stress yield phenomenon was observed.

Reinforced interface and mechanical properties of high strength carbon fiber composites

Based on the surface analysis of carbon fiber, an epoxy resin matrix with good wettability to carbon fibers had been developed and studied, and the influence of winding tension on the interface and mechanical properties of the composite were studied. The surface morphology of carbon fiber and the active functional groups of sizing agent were analyzed. In order to form a good interface combination, the wettability between carbon fibers and epoxy resin matrix was characterized by dynamic contact angle. The winding tension played an important role in the mechanical properties of composites. Therefore, a kind of carbon fiber reinforced composites, Naval Ordnance Laboratory (NOL) rings were fabricated using different winding tensions. Particularly, when the winding tension was 30 N, the interfacial bonding between carbon fibers and resin matrix was the most compact and firm. The tensile strength and interlaminar shear strength (ILSS) of NOL rings reached high values, 2712 MPa and 75 MPa, respectively.

The effect of the concentration of water in the silica sol–gel solution on the formation of an oxide film on the surface of carbon fibers

Studies of SiO2 films deposited on the surface of carbon fibers from a PAN precursor were carried out. Sol-gel solutions with different H2O/TEOS molar ratios were obtained and studied. The hydrolysis-condensation reaction in a sol–gel solution leads to viscosity changes and the formation of Si-O-Si bonds in the IR spectrum. Using SEM, we studied the surface morphology of carbon fibers after deposition of a SiO2 film. The effect of water concentration on the completeness of the reaction in a sol–gel solution and the quality of the oxide film formed on the surface of the fibers are analyzed.

The effect of self-resistance electric heating on the interfacial behavior of injection molded carbon fiber/polypropylene composites through molecular dynamics analysis

The impregnation of carbon fabric reinforcements in an injection mold through self-resistance electric (SRE) heating opens the way for manufacturing carbon fiber reinforced thermoplastics in quantities and low cost. The surface morphology evolution of carbon fiber under SRE heating may affect the interfacial properties of resulting composites. In this work, molecular dynamics was introduced to investigate the atomic-level interaction between carbon fiber (CF) and polypropylene (PP) in composites. The influence of CF surface morphology on the interfacial impregnation ability, mechanical properties and interface failure mechanism were explored. Simulation results reveal that increasing the aspect ratio or the amount of grooves of CF surface can enhance the quality of composite interface. The interface failure mode was found to be related to CF surface morphology. In addition, the high kinetic energy enrichment area was used to predict the evolution of micro-void inside the polymer bulk.

Effect of sol-gel solution parameters on the formation of films on the surface of carbon fibers

In this study to apply an oxide film to the surface of carbon fibers a sol-gel solution was used. Sol-gel solutions were prepared according to the described procedure from tetraethoxysilane (TEOS) and ethanol at various H2O concentrations. The molar ratio H2O/TEOS ratio was changed in the range from 2 to 20. After coating and drying, the surface morphology of carbon fibers was investigated. The relationship between the concentration of sol-gel solutions and the amount of deposited SiO2 on the surface of carbon fibers was analyzed.

Enhanced interfacial strength of carbon fiber/PEEK composites using a facile approach via PEI&ZIF-67 synergistic modification

As a kind of metal-organic frameworks (MOFs) which possess large specific surface area and excellent thermal stability, zeolitic imidazolate framework-67 (ZIF-67) shows great application potentials because it can be synthesized in aqueous solutions at room temperature. In this work, we propose a synergistic strategy by taking advantages of polyetherimide (PEI) and ZIF-67 to enhance the interfacial strength of carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites via a facile route. The bare CF is simply immersed into PEI solution and the aqueous solution of ZIF-67 precursors stepwise at room temperature to wrap PEI intermediate sizing layer and in situ grow ZIF-67 crystals. The surface morphology of CF indicates that regulating the concentration of PEI sizing agents can control the relative amount of ZIF-67 adhered onto CF surface. After modification, the tensile strength of single CF shows no deterioration and the interfacial shear strength (IFSS) of as-prepared modified CF/PEEK reveals an increase of 40.5%. Besides, the enhanced interfacial interaction mechanism might be ascribed to miscible feature of PEI with PEEK and rough structure from ZIF-67. This work may shed some light on establishing a facile and effective synthetic approach to modify CF and improve the performance of composites without degrading the mechanical property of pristine CF.

Preparation and characterization of spinnable pitch for general‐purpose carbon fiber from refined pitch

ABSTRACTFour types of spinnable pitches (MP‐N‐A, MP‐A, MP‐A‐H, and MP‐A‐N) for general‐purpose carbon fiber have been prepared under certain conditions with the refined pitch as the raw materials. Fourier transform infrared spectrum and solid‐state nuclear magnetic resonance spectra combined with curve‐fitting analysis have been used to characterize the average molecular structure (Iar, CH3/CH2, SAR, and SHFG) of spinnable pitches. Thermogravimetric analyses and polarizing microscope have been used to observe the thermal stability and the microstructure of spinnable pitches, respectively. The X‐ray diffraction combined with curve‐fitting analysis have showed that, the stacking heights (Lc) of these four kinds of spinnable pitches were 2.21, 1.78, 1.79, and 1.76 nm, respectively. The parallel layers (N) of each spinnable pitch were 7.30, 6.02, 6.06, and 5.97. What is more, the numbers of aromatic ring in each layer (n) were 17.03, 11.61, 11.75, and 11.41. Finally, the scanning electron microscopy has been used to characterize the surface morphology of carbon fibers which obtained by each spinnable pitches. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47880.

Enhanced interfacial interactions of carbon fiber reinforced PEEK composites by regulating PEI and graphene oxide complex sizing at the interface

The interfacial interactions and bonding of carbon fiber (CF) reinforced poly(ether-ether-ketone) (PEEK) composites is improved by applying polyether imide (PEI) and graphene oxide (GO) complex sizing at different ratios at the interface. The thermally stable polyether imide (PEI) and graphene oxide (GO) complex sizing is prepared and then coated on carbon fiber surfaces homogeneously. The sizing layer forms on the fiber surfaces, and multiple GO sheets are introduced successfully surrounding the carbon fibers. The surface morphologies of carbon fibers change distinctly with different GO contents. The interfacial shear strength (IFSS) increases from 43.4 MPa for bare fiber reinforced PEEK composites to 49.4 MPa for composites reinforced by carbon fibers coated with PEI only. However, a significant improvement is achieved when GO sheets are introduced to the CF surfaces, making the IFSS grow up to 63.4 MPa. Furthermore, the dynamic mechanical tests show that the normalized damping area results of carbon fibers coated with complex sizing decrease remarkably by about 50%. DMA results, interlaminar shear strength (ILSS) test and flexural test results are in agreement with each other, suggesting better interface bonding of composites by applying PEI and GO complex sizing. Besides, the interfacial interaction mechanism in modified composites is proposed. The enhanced interfacial performance is caused by the positive effect of complex interface layer.

Preliminary experimental study of a carbon fiber array cathode

The preliminary experimental results of a carbon fiber array cathode for the magnetically insulated transmission line oscillator (MILO) operations are reported. When the diode voltage and diode current were 480 kV and 44 kA, respectively, high-power microwaves with a peak power of about 3 GW and a pulse duration of about 60 ns were obtained in a MILO device with the carbon fiber array cathode. The preliminary experimental results show that the shot-to-shot reproducibility of the diode current and the microwave power is stable until 700 shots. No obvious damage or deterioration can be observed in the carbon fiber surface morphology after 700 shots. Moreover, the cathode performance has no observable deterioration after 700 shots. In conclusion, the maintain-free lifetime of the carbon fiber array cathode is more than 700 shots. In this way, this carbon fiber array cathode offers a potential replacement for the existing velvet cathode.

Influence of surface properties of graphene oxide/carbon fiber hybrid fiber by oxidative treatments combined with electrophoretic deposition

An effective way to prepare graphene oxide/carbon fiber hybrid fiber was proposed by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition process. Surface functional group, surface roughness, and surface morphologies of carbon fibers were examined by Fourier transform infrared spectrometer, atomic force microscopy, and scanning electron microscopy. Results showed that a uniform and thick graphene oxide films were constructed on the surface of carbon fiber. Deposition density increased by introduction of pretreatment of the carbon fiber in the electrophoretic deposition process has been shown as a possible method. Dynamic contact angle analysis results indicated that the deposition of graphene oxide significantly improved surface free energy of carbon fiber by increasing surface area and polar groups. The introduction of graphene oxide in the carbon fiber-reinforced epoxy composites results in a 55.6% enhancement in the interfacial shear strength and confirms the remarkable improvement in the interfacial adhesion strength of the composites, and the fracture mechanism was also analyzed. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of carbon nanotubes coatings onto carbon fiber by oxidative treatments combined with electrophoretic deposition on interfacial properties of carbon fiber composite

To improve the interfacial performance of carbon fiber (CF) and epoxy resin, carbon nanotubes (CNTs) coatings were utilized to achieve this purpose through coating onto CF by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition (EPD) process. The influence of electrophoretically deposited CNTs coatings on the surface properties of CFs were investigated by Fourier transform infrared spectrometer, atomic force microscopy, scanning electron microscopy and dynamic contact angle analysis. The results indicated that the deposition of carbon nanotubes introduced some polar groups to carbon fiber surfaces, enhanced surface roughness and changed surface morphologies of carbon fibers. Surface wettability of carbon fibers may be significantly improved by increasing surface free energy of the fibers due to the deposition of CNTs. The thickness and density of the coatings increases with the introduction of pretreatment of the CF during the EPD process. Short beam shear test was performed to examine the effect of carbon fiber functionalization on mechanical properties of the carbon fiber/epoxy resin composites. The interfacial adhesion of CNTs/CF reinforced epoxy composites showed obvious enhancement of interlaminar shear strength by 60.2% and scanning electron microscope photographs showed that the failure mode of composites was changed after the carbon fibers were coated with CNTs.

Influence of deposited CNTs on the surface of carbon fiber by ultrasonically assisted electrophoretic deposition

The surface property of carbon fiber directly affects the interface performance between carbon fiber and matrix. To improve the surface property of carbon fiber, we proposed a simple method to prepare carbon nanotubes /carbon fiber hybrid fiber via ultrasonically assisted electrophoretic deposition (EPD). Surface morphologies and surface functional group of carbon fibers were examined by atomic force microscopy (AFM), scanning electron microscopy (SEM) and fourier transform infrared spectrometer (FTIR), respectively. The results show that the deposition of carbon nanotubes changed the surface morphologies of carbon fibers and introduced polar groups (C=O and C-O) to carbon fiber surface. Comparing the results with EPD-only, ultrasonically assisted EPD increased the uniformity of carbon nanotubes coatings whereas only sparse and not uniformly deposition formed without ultrasonic.

Influence of graphene oxide coatings on carbon fiber by ultrasonically assisted electrophoretic deposition on its composite interfacial property

Graphene oxide coatings were utilized to enhance the interfacial properties of carbon fibers. In this work, a facile route is proposed to prepare graphene oxide/carbon fiber hybrid fiber via ultrasonically assisted electrophoretic deposition (EPD) without complex chemical reactions and long processing time. Surface functional group, surface roughness and surface morphologies of carbon fibers were examined by Fourier transform infrared spectrometer (FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. Surface free energy of the fiber was characterized by dynamic contact angle analysis (DCAA). The results indicated that the deposition of graphene oxide introduced some polar groups to carbon fiber surfaces and changed the surface morphologies of carbon fibers. Surface wettability of carbon fibers may be significantly improved by increasing surface free energy of the fibers due to the deposition of graphene oxide. Comparing the results with EPD-only, ultrasonically assisted EPD increased the thickness and uniformity of graphene oxide coatings whereas only sparse deposition formed without ultrasonic. Short beam shear test was performed to examine the impact of carbon fiber functionalization on the mechanical properties of the carbon fiber/epoxy resin composites. An improvement of 55% from 36.7 to 56.9MPa in interlaminar shear strength confirms the remarkable improvement in the interfacial adhesion strength of the composites.

Properties of carbon fiber and composites modified with different-sized graphene oxide sheets

The graphene oxide (GO) sheets with different size distributions were effectively separated by a centrifugation method. The exfoliated single-layer structure and the size of GO sheets were verified by scanning electron microscopy (SEM), atomic force microscope (AFM), and metallurgical microscope, respectively. Two different-sized GO sheets water suspensions were obtained, which were then directly dispersed in carbon fiber (CF) sizing agent, respectively. The influences of the different-sized GO sheets on CF and CF composites were explored. The workability in later process of CF and CF surface morphology were characterized by abrasion resistance, fluffs and breakage, stiffness, and SEM. SEM micrographs demonstrated that a nonuniform distribution of the large-sized GO was lapped on CF whereas the small-sized GO was uniformly leaned on CF. The interlaminar shear strength of the small-sized GO/CF reinforced composite could reaches the maximum value. It indicated that the interfacial region between CF and polymer matrix could be enhanced by adjusting the size of GO sheets. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Atmospheric Plasma Treatment of Carbon Fibers for Enhancement of Their Adhesion Properties

Plasma processing of carbon fibers is aimed to provide better contact and adhesion between individual plies without decrease of the carbon fiber (CF) mechanical resistance. This work deals with surface modification of CFs by atmospheric pressure dielectric barrier discharge (DBD) in air. Scanning electron microscopy (SEM) of a single untreated fiber showed many thin tracks aligned along the fiber. This feature can be explained by the fiber manufacturing process. SEM of the treated samples revealed many small particles distributed over entire surface of the fiber. These particles are product of the fibers surface etching during the DBD treatment that removes the epoxy layer covering as-received samples. The alteration of CF surface morphology was also confirmed by the Atomic force microscopy (AFM), which indicated that the CF roughness increased as a result of the plasma treatment. Analysis of the surface chemical composition provided by X-ray photoelectron spectroscopy (XPS) showed that oxygen and nitrogen atoms are incorporated onto the surface. The polar oxygen radicals formed on the surface lead to increasing of the CF surface energy. Both, the increase of surface roughness and the surface oxidation contribute for enhancement of CF adhesion properties.

Preparation and Properties of Emulsion Type Sizing Agent for Carbon Fiber

The epoxy resin and polyalkylene glycol allyl glycidyl ether (AEPH) were used to prepare the emulsion type epoxy sizing agents for carbon fiber (CF) by phase inversion emulsification method. Effects of mass ratio of mixed emulsifiers and emulsifiers/resin (ωe/r) and shear rate on stability of emulsion were investigated by centrifugal sedimentation analysis. Scanning electron microscope (SEM) was used to analyze the surface morphology of carbon fiber. Results show that the optimal emulsion was obtained when mass ratio of polyoxyethylene octylphenol ether-10 (OP-10), polysorbate-80 (Tween-80) and sodium dodecyl benzene sulfonate (SDBS) was 65:25:10, ωe/rwas 9% and shear rate was 9000 r/min. The centrifugal sedimentation mass fraction of emulsion is 10.1%. SEM micrograph shows that the sizing agent forms a smooth film covering the carbon fibers.