• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.193-197
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• 2014

The electrode for gas sensor was prepared by using pitch-based activated carbon fibers and polyvinyl alcohol (PVA) to investigate the toxic gas sensing characteristics. The physicochemical properties of activated carbon fibers electrode for gas sensor were analyzed with SEM and BET. Toxic gases sensing property of the electrode was also identified by different toxic gases such as $NH_3$, NO and $CO_2$. The specific surface area of activated carbon fibers electrode for gas sensor was decreased by 33% owing to PVA used as a binder compared with the activated carbon fibers. However, its pore size distribution of the ACF electrode was not greatly influenced by PVA. The activated carbon fibers electrode for gas sensor responded to toxic gases by electron hopping unlike semiconductor based gas sensors. In this study, activated carbon fibers electrode was decreased to 7.5% in resistance for the NH3 gas of the 100 ppm concentration and its $NH_3$ gas sensing property was confirmed the most excellent compared with other toxic gases.

• 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).

• Carbon letters
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• v.12 no.2
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• pp.70-80
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• 2011

Two pitches with different average molecular structures were electrospun and compared in terms of the properties of their fibers after oxidative stabilization, carbonization, and activation. The precursor with a higher molecular weight and greater content of aliphatic groups (Pitch A) resulted in better solubility and spinnability compared to that with a lower molecular weight and lower aliphatic group content (Pitch B). The electrical conductivity of the carbon fiber web from Pitch A of 67 S/cm was higher than that from Pitch B of 52 S/cm. The carbon fiber web based on Pitch A was activated more readily with lower activation energy, resulting in a higher specific surface area compared to the carbon fiber based on Pitch B (Pitch A, 2053 $m^2/g$; Pitch B, 1374 $m^2/g$).

• Composites Research
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• v.29 no.5
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• pp.256-261
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• 2016

In this work, we have prepared the filter papers with the pitch-based activated carbon fibers and the binder fibers using wet-laid process. The influence of the binder fiber on the porosity of the filter papers has been investigated by using nitrogen adsorption isotherms at 77 K and a scanning electron microscope (SEM). As a result, the specific surface area has increased with an decrease in the content of binder fiber. It has been shown that the optimum ratio of pitch-based activated carbon fibers and the binder fibers is 70:30, resulting in high porosity, excellent bonding strength, large specific surface area ($650.4m^2/g$) and high noxious gas removal efficiency (86.9%). In addition, it has been observed that the mean pore size distribution of the fiber papers has not been affected by the binder fiber.

• Carbon letters
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• v.3 no.2
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• pp.93-98
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• 2002

Short pitch fibers were prepared from petroleum based isotropic precursor pitch by melt-blown technology. The pitch fibers were stabilized in oxidizing condition, followed by steam activations at various conditions. The fiber surface and pore structures of the activated carbon fibers (ACFs) were respectively characterized by using SEM and applying BET theory from nitrogen adsorption at 77 K. The weight loss of the oxidized fiber was proportional to activation temperature and activation time, independently. The adsorption isotherms of the nitrogen on the ACFs were constructed and analyzed to be as Type I consisting of micropores mainly. The specific surface area of the ACFs proportionally increased with the weight loss at a given activation temperature. The specific surface area was ranged 850~1900 $m^2/g$ with pores of narrow distribution in sizes. The average pore size was ranged 5.8~14.1 ${\AA}$ with the larger value from the more severe activation condition.

• Carbon letters
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• v.5 no.2
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• pp.51-54
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• 2004

Isotropic pitch-based carbon fiber was isothermally activated in $CO_2$ atmosphere. Structural parameters of the isotropic carbon fibers and activated carbon fibers (ACFs) were evaluated by X-ray diffraction (XRD). The $d_{002}$ and La of the carbon fibers were measured to be 4.04 ${\AA}$ and 23.6 ${\AA}$ and those of ACFs were 4.29 ${\AA}$ and 22.7 ${\AA}$, respectively, representing less ordered through activation process. The pores in the ACFs were characterized by BET, and they showed super-high specific surface area of maximum value 3,495 $m^2/g$ from average pore size of 8.3 ${\AA}$ at 59% burn-off. It was recognized that 8-9 ${\AA}$ was optimum range of pore size for efficient creation of high specific surface area. The average size of the pores formed at higher temperature ($1100^{\circ}C$) was larger than that of the pores formed at lower temperature ($900^{\circ}C$).

• Proceedings of the Korean Fiber Society Conference
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• 1997.04a
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• pp.323-327
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• 1997

• Carbon letters
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• v.22
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• pp.96-100
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• 2017

• 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 $0.58{\sim}0.77\;cm^3/g$.

• Carbon letters
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• v.6 no.1
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• pp.1-5
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• 2005

Isotropic pitch based carbon fibers were exposed to isothermal oxidation in carbon dioxide gas to study the activation kinetics under the temperature of 800~$1100^{\circ}C$. The kinetic equation $f=1-{\exp}(-at^b)$ was introduced and the constant b was obtained in the range of 0.92~1.25. It was shown that the activated carbon fiber shows the highly specific surface area (SSA) when the constant b comes close to 1. The activation kinetics were evaluated by the reaction-controlling regime (RCR) according to changes of the apparent activation energy with changes of the conversion. It was observed that the activation energies increase from 47.6 to 51.2 kcal/mole with the conversion increasing from 0.2 to 0.8. It was found that the pores of the activated carbon fiber under the chemical reaction were developed well through the fiber.