• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.61-61
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• 2010

In the present work, we present the optimized the hybrid structures of carbon nanotubes (CNTs) and metal nanocomposites including Cu, Al, Co and Ni using the first principle calculations based on the density functional theory. Introduction of CNTs into a metal matrix has been considered to improve the mechanical properties of the metal matrix. However, the binding energy between metals and pristine CNTs wall is known to be so small that the interfacial slip between CNTs and the matrix occurs at a relatively low external stress. The application of defective or functionalized CNTs has thus attracted great attention to enhance the interfacial strength of CNT/metal nanocomposites. Herein, we design the various hybrid structures of the single wall CNT/metal complexes and characterize the interaction between single wall CNTs and various metals such as Cu, Al, Co or Ni. First, differences in the binding energies or electronic structures of the CNT/metal complexes with the topological defects, such as the Stone-Wales and vacancy, are compared. Second, the characteristics of functionalized CNTs with various surface functional groups, such as -O, -COOH, -OH interacting with metals are investigated.We found that the binding energy can be enhanced by the surface functional group including oxygen since the oxygen atom can mediate and reinforce the interaction between carbon and metal. The binding energy is also greatly increased when it is absorbed on the defects of CNTs. These results strongly support the recent experimental work which suggested the oxygen on the interface playing an important role in the excellent mechanical properties of the CNT-Cu composite[1].

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.202-202
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• 1999

The Polyethylene (PE), Polystyrene (PS) and Polytetrafluoroethylene (PTFE) surface modification was investigated by hydrogen io assisted reaction (H-IAR) in oxygen environment. The IAR is a kind of surface modification techniques using ion beam irradiation in reactive gas environment. The energy of hydrogen ion beam was fixed at 1keV, io dose was varied from 5$\times$1014 to 1$\times$1017 ions/$\textrm{cm}^2$, and amount of oxygen blowing gas was fixed 4ml/min. Wettability was measured by water contact angles measurement, and the surface functionality was analyzed by x-ray photoelectron spectroscopy. The contact angle of water on PE modified by argon ion beam only decrease from 95$^{\circ}$ to 52$^{\circ}$, and surface energy was not changed significantly. But, the contact angle using hydrogen ion beam with flowing 4ml/min oxygen stiffly decreased to 8$^{\circ}$ and surface energy to 65 ergs/cm. In case of PS, the contact angle and surface energy changes were similar results of PE, but the contact angle of PTEE samples decreased with ion dose up to 1$\times$1015 ions/$\textrm{cm}^2$, increased at higher dose, and finally increased to the extent that no wetting was appeared at 1$\times$1017 ions/$\textrm{cm}^2$. These results must be due to the hydrogen ion beam that cleans the surface removing the impurities on polymer surfaces, then hydrogen ion beam was activated with C-H bonding to make some functional groups in order to react with the oxygen gases. Finally, unstable polymer surface can be changed from hydrophobic to hydrophilic formation such as C-O and C=O that were confirmed by the XPS analysis, conclusionally, the ion assisted reaction is very effective tools to attach reactive ion species to form functional groups on C-C bond chains of PE, PS and PTFE.

• Carbon letters
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• v.3 no.2
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• pp.80-84
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• 2002

The surface treatment of C-type isotropic pitch-based carbon fiber was carried out by anodic oxidation in 5 wt% $NH_4NO_3$ electrolyte. The changes of fiber surface and carbon fiber/ABS resin composites were characterized by SEM, XPS and mechanical properties test. The oxygen functional groups on the surface, such as hydroxyl (-C-OH), carboxyl (-COOH) groups etc., increased after oxidation. Tensile strength, flexural strength and modulus of carbon fiber/ABS composites were also enhanced. However, the impact strength decreased with the improvement of the surface adhesion between CF and matrix.

• Carbon letters
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• v.4 no.1
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• pp.21-23
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• 2003

In this work, the effect of anodic oxidation treatment on Cr(VI) ion adsorption behaviors of activated carbon fibers (ACFs) was investigated. The aqueous solutions of 10 wt% $H_3PO_4$ and $NH_4OH$ were used for acidic and basic electrolytes, respectively. Surface characteristics and textural properties of ACFs were determined by XPS and $N_2$ adsorption at 77 K. The heavy metal adsorption of ACFs was conducted by ICP. As a result, the adsorption amount of the anodized ACFs was improved in order of B-ACFs > A-ACFs > pristine-ACFs. In case of the anodized treated ACFs, the specific surface area was decreased due to the pore blocking or pore destroying by acidic electrolyte. However, the anodic oxidation led to an increase of the Cr(VI) adsorption, which can be attributed to an increase of oxygen-containing functional groups, such as, carboxylic, lactonic, and phenolic groups. It was clearly found that the Cr(VI) adsorption was largely influenced by the surface functional groups, in spite of the reduced specific surface area of the ACFs.

• Journal of the Korean Electrochemical Society
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• v.9 no.1
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• pp.10-18
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• 2006

This article is concerned with the overview of the activated carbon fibers. Firstly, this review provides a comprehensive survey of the overall processes for the synthesis of the activated carbon fibers from the carbonaceous materials. Subsequently, the physicochemical properties such as pore structures and surface oxygen functional groups of the activated carbon fibers were discussed in detail. Finally, as electrochemical applications of the activated carbon fibers to electrode materials for electric double-layer capacitor (EDLC), the electrochemical characteristics of the activated carbon fiber electrodes and the various methods to improve the capacitance and rate capability were introduced. In particular, the effect of pore length distribution (PLD) on kinetics of double-layer charging/discharging was discussed based upon the experimental and theoretical results in our work. And then we discussed in detail the applications of the activated carbon fibers to adsorbent materials for purification of liquid and gas.

• Carbon letters
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• v.3 no.1
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• pp.17-24
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• 2002

The electrochemical behavior of the $LiCoO_2$ electrode, containing carbon black as a conductor, depends upon the nature and characteristics of carbon black. In this study, six different kinds of carbon blacks were employed to investigate the relationship between the properties of carbon blacks and electrochemical characteristics of the electrode. The larger amount of surface oxygen functional groups brought the lower electrical conductivity for the carbon blacks. The electrical conductivity of carbon blacks was closely related to the impurities such as ash and volatile content. The rate capability and cyclability of the electrode were improved with the higher conductivity of carbon blacks used. So, it can be concluded that high conductive carbon black plays an important role as a conductor for high rate of charge-discharge capability and initial efficiency.

• Carbon letters
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• v.11 no.2
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• pp.131-136
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• 2010

Propellant waste was impregnated on the surface of activated carbon fiber and heat-treated at different temperature to introduce newly developed functional groups on the ACF surface. Functional groups of nitrogen and oxygen such as pyridine, pyridone, pyrrol, lacton and carboxyl were newly introduced on the surface of modified activated carbon fiber. The porosity, specific surface area, and morphology of those modified ACFs were changed as increasing the heat-treated temperature from 200 to $500^{\circ}C$. The optimum heat-treatment temperature was suggested to $500^{\circ}C$, because lower temperature given rise to the decrease of specific surface area and higher temperature resulted in the decrease of weight loss. Propellant waste can be used as an useful surface modifier to porous carbons.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.319-324
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• 2016

In this study, pitch-based carbon fibers in the acid were radiated with an electron beam to modify their surface, and surface changes were investigated according to each treatment conditions. Nitric acid and hydrogen peroxide were used as a drenched acidic solution and an electron beam dose was set to 200 and 400 kGy. The use of nitric acid introduced more oxygen functional groups on carbon fiber surfaces than that of using hydrogen peroxide, and also introduced nitrogen functional groups into the carbon fiber surface. In addition, oxygen functional groups introduced on carbon fiber surface increased as the electron beam dose increased due to the fact that the oxidizing material can be easily formed by e-beam radiation in nitric acid than the hydrogen peroxide, and also the higher energy electron beam dose can help forming more oxidizing materials. Moreover, the generation of C=O functional groups was favorable when using nitric acid because oxidizing C-OH functional groups to the C=O functional groups mainly occurred by $NO_2$ radicals generated by the electron beam radiation in a nitric acid solution.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.23-28
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• 2024

Cesium is a potential toxic contaminant due to its high solubility, which allows it to easily penetrate the human body and potentially induce cancer or DNA mutations. In this study, oxygen functional groups were introduced on activated carbons (ACs) by ozone treatment to enhance the cesium adsorption capacity. As the ozone treatment time increased, the oxygen content on the ACs surface increased. Subsequently, the electrostatic interaction between ACs and cesium enhanced, resulting in higher cesium ion adsorption efficiency across all samples. In particular, the sample treated with ozone for 7 minutes at an internal ozone concentration of 50000 ppm had roughly 12% greater oxygen functional group content and the highest cesium removal effectiveness (97.6%). Meanwhile, samples treated for 5 minutes showed a 0.3% cesium removal rate difference compared to those treated for 7 minutes, which was caused by the surface chemical similarity of the two samples due to the reactive characteristics of ozone gas. However, the cesium adsorption performance of ozonated activated carbon seems to be mainly influenced by the amount of oxygen functional groups introduced to the surface, although the specific surface area and pore structure of the activated carbon are also important.

• Journal of the Korean Society of Tobacco Science
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• v.27 no.1 s.53
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• pp.59-67
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• 2005

Activated carbon fiber (ACF) was surface modified by nitric acid to improve the adsorption efficiency of the propylamine. The adsorption amount of propylamine of the modified ACF increased $17\%$ more than that of as-received ACF. Desorption of propylamine from the propylamine saturated ACF was occurred in two steps, the first step started arround $50^{\circ}C$ showing the desorption of physically adsorbed propylamine and the second step started at $200^{\circ}C$ showing the decomposition of chemically adsorbed propylamine. Total desorption amount of propylamine from the modified ACF was larger than that of the as-received ACF because of increased functional groups. The oxygen and nitrogen contents on the modified ACF increased by 1.5 and 3 times compared with the as-received ACF. A part of propylamine adsorbed on ACF formed pyridine-like or pyrrolic structures with 2 carbons exposed on the surface of the ACF. It was found that propylamine reacted with strong or weak acidic functional groups such as -COOH or -OH existed on ACF surface.