• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1661-1664
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• 2010

The photocatalytic decomposition of toluene vapor by bare and $TiO_2$-coated carbon fibers was studied. Atomic layer deposition (ALD) was used to perform the $TiO_2$ coating. We show that, under our conditions, the photocatalytic activity of bare carbon fibers was comparable with that of $TiO_2$ films, which are known to be good photocatalysts. The origin of the high photocatalytic activity of bare carbon fibers is discussed.

• Composites Research
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• v.34 no.2
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• pp.82-87
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• 2021

The mechanical properties of carbon fiber-reinforced epoxy composites (CFRPs) are greatly dependent on the interfacial adhesion between the carbon fibers and the epoxy matrix. Introducing nanomaterial reinforcements into the interface is an effective approach to enhance the interfacial adhesion of CFRPs. The main purpose of this work was to introduce graphitic nanofiber (GNFs) between an epoxy matrix and carbon fibers to enhance interfacial properties. The composites were reinforced with various concentrations of GNFs. For all of the fabricated composites, the optimum GNF content was found to be 0.6 wt%, which enhanced the interlaminar shear strength (ILSS) and fracture toughness (KIC) by 101.9% and 33.2%, respectively, compared with those of neat composites. In particular, we observed a direct linear relationship between ILSS and KIC through surface free energy. The related reinforcing mechanisms were also analyzed and the enhancements in mechanical properties are mainly attributed to the interfacial interlocking effect. Such an effort could accelerate the conversion of composites into high performance materials and provide fundamental understanding toward realizing the theoretical limits of interfacial adhesion and mechanical properties.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1333-1339
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• 2023

To produce activated carbon fibers, the process is carried out through either physical activation method or chemical activation method. In this study, we present the results regarding the characteristics of activated carbon fibers manufactured under various conditions through the quantitative control of steam. The yield after activation indicates a decreasing trend with the increase in steam quantity and activation time. Additionally, specific surface area characteristics exhibit variations based on activation time and steam flow rate. The SEM analysis results reveal that higher steam flow rates lead to the presence of both mesopores and macropores on the surface of activated carbon fibers (ACF).

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.476-482
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• 2013

In this work, the effects of electrochemical oxidation of carbon fiber surfaces on mechanical interfacial properties of carbon fibers-reinforced polarized-polypropylene matrix composites were studied with various current densities during the treatments. Surface properties of the fibers before and after treatments were observed by SEM, AFM, XPS, and contact angle measurements. Mechanical interfacial properties of the composites were measured in terms of critical stress intensity factor ($K_{IC}$). From the results it was found that $O_{1s}$ peaks of the fiber surfaces were strengthened after electrochemical oxidation which led to the enhancement of surface free energy of the fiber, resulting in good mechanical performance of the composites. It can be concluded that electrochemical oxidation of the carbon fiber surfaces can control the interfacial adhesion between the carbon fibers and polarized-polypropylene in this composites system.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.363-369
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• 2013

In this work, the effects of ozone treatments on mechanical interfacial properties of carbon fibers-reinforced nylon-6 matrix composites were investigated. The surface properties of ozone treated carbon fibers were studied by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Mechanical interfacial properties of the composites were investigated using critical stress intensity factor ($K_{IC}$). The cross-section morphologies of ozone-treated carbon fiber/nylon-6 composites were observed by scanning electron microscope (SEM). As a result, $K_{IC}$ of the ozone-treated carbon fibers-reinforced composites showed higher values than those of as-received carbon fibers-reinforced composites due the enhanced $O_{1s}/C_{1s}$ ratio of the carbon fiber by the ozone treatments. This result concludes that the mechanical interfacial properties of nylon-6 matrix composites can be controlled by suitable ozone treatments on the carbon fibers.

• Carbon letters
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• v.1 no.2
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• pp.69-75
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• 2000

Naphtha cracking bottom oil was reformed with heat treatment and then spun at $310^{\circ}C$. These pitch-based carbon fibers were carbonized at $1000^{\circ}C$ after oxidation at $280^{\circ}C$, for 90 min. These fibers were chemically activated with molar ratio of KOH/CF (1 : 1) at different temperatures ($250{\sim}900^{\circ}C$) for 1 hr. The process of activation was characterized with DTA, TGA, BET surface area and pore size distribution. The activation of fibers by KOH was performed by several process. One is the reduction process that carbon fiber was reacted with $K_2O$ produced from dehydration process above $400^{\circ}C$. The other is the process that $K_2CO_3$ was directly reacted with carbon fiber. At $800^{\circ}C$, the activation was performed by catalyzed mechanism that $K_2O$ was obtained from the reaction of metal potassium with $CO_2$, then was changed to $K_2CO_3$. At $870^{\circ}C$, the activation was also observed that activation mechanism was promoted by metal catalyst with $CO_2$ from decomposition of $K_2CO_3$. The specific surface area of prepared activated carbon fibers was dependent on the activation mechanism. The specific surface area was in the range of $1519{\sim}2000\;cm^3/g$ and was the largest prepared at $870^{\circ}C$. The pores developed were mostly micropores which was very narrow and uniform. The total pore volume was $0.58{\sim}0.77\;cm^3/g$.

• Polymer(Korea)
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• v.27 no.1
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• pp.52-60
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• 2003

In this work, two types of Ni-plating, namely electrolytical and electroless Ni-platings on carbon fiber surfaces, were carried out to enhance the impact resistance of composites. And the comparison between electrolytical and electroless methods on their impact properties of composite system was studied. The surface properties of carbon fibers were characterized using XRD, SEM, and contact angle measurements. The impact behaviors were investigated using an Izod type impact tester. As experimental results, it was observed that electrolessly plated Ni layers had Ni-P alloys on carbon fiber surfaces as revealed by XRD, and electrolytically Ni-plated carbon fibers showed higher surface free energies than those of the electrolessly Ni-plated carbon fibers. In particular, the impact strengths of electrolessly Ni-plated carbon fibers-reinforced plastics were strongly increased. These results were probably due to the difference of wettabilities according to the different types of Ni-plating methods.

• Carbon letters
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• v.17 no.1
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• pp.79-84
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• 2016

• Carbon letters
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• v.12 no.4
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• pp.223-228
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• 2011

In this present work, the effect of additional heat-treatment (AHT) in the range from $1800^{\circ}C$ to $2400^{\circ}C$ on the chemical composition, morphology, microstructure, tensile properties, electrical resistivity, and thermal stability of commercial polyacrylonitrile (PAN)-based carbon fibers was explored by means of elemental analysis, electron microscopy, X-ray diffraction analysis, single fiber tensile testing, two-probe electrical resistivity testing, and thermogravimetric analysis (TGA). The characterization results were in agreement with each other. The results clearly demonstrated that AHTs up to $2400^{\circ}C$ played a significant role in further contributing not only to the enhancement of carbon content, fiber morphology, and tensile modulus, but also to the reduction of fiber diameter, inter-graphene layer distance, and electrical resistivity of "as-received" carbon fibers without AHT. The present study suggests that key properties of commercial PAN-based carbon fibers of an intermediate grade can be further improved by proprietarily adding heat-treatment without applying tension in a batch process.

• Carbon letters
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• v.8 no.2
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• pp.127-133
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• 2007

In this study, commercially available pitch-based carbon fibers of general grade were post-heat-treated using a boxtype high temperature furnace at $1800^{\circ}C$, $2000^{\circ}$, $2200^{\circ}C$, and $2400^{\circ}C$, respectively. The fundamental characteristics of each heat-treated carbon fibers were investigated in terms of chemical composition, morphology, thermal stability, X-ray diffraction, single filament tensile test, and electrical resistivity. The result showed that the fiber properties were significantly influenced by the post-heat-treatment, indicating the greater effect with increasing treatment temperature. The carbon contents, thermal stability, and tensile properties of the carbon fibers used here were further increased by the post-heat-treatment, whereas the d-spacing between graphene layers and the electrical resistivity were reduced with increasing post-heat-treatment temperature.