• The Korean Journal of Ceramics
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• v.3 no.1
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• pp.5-12
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• 1997

Charged carbon clusters which are formed by the gas activation are suggested to be responsible for the formation of the metastable diamond film. The number of carbon atoms in the cluster that can reverse the stability between diamond and graphite by the capillary effect increases sensitively with increasing the surface energy ratio of graphite to diamond. The gas activation process produces charges such as electrons and ions, which are energetically the strong heterogeneous nucleation sites for the supersaturated carbon vapor, leading to the formation of the charged clusters. Once the carbon clusters are charged, the surface energy of diamond can be reduced by the electrical double layer while that of graphite cannot because diamond is dielectric and graphite is conducting. The unusual phenomena observed in the chemical vapor deposition diamond process can be successfully approached by the charged cluster model. These phenomena include the diamond deposition with the simultaneous graphite etching, which is known as the thermodynamic paradox and the preferential formation of diamond on the convex edge, which is against the well-established concept of the heterogeneous nucleation.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.307-312
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• 2017

In this study, the electrochemical performance of surface modified carbon using the PFO (pyrolyzed fuel oil) was investigated by chemical activation with KOH and $K_2CO_3$. PFO was heat treated at $390{\sim}400^{\circ}C$ for 1~3h to prepared the pitch. Three carbon precursors (pitch) prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3h), 4001(at $400^{\circ}C$ for 1h) and 4002 (at $400^{\circ}C$ for 2h). Also, the effect of chemical activation catalysts and mixing time on the development of porosity during carbonization was investigated. The prepared carbon was analyzed by BET and FE-SEM. It was shown that chemical activation with KOH could be successfully used to develop carbon with specific surface area ($3.12m^2/g$) and mean pore size (22 nm). The electrochemical characteristics of modified carbon as the anode were investigated by constant current charge/discharge, cyclic voltammetry and electrochemical impedance tests. The coin cell using pitch (4002) modified by KOH has better initial capacity (318 mAh/g) than that of other pitch coin cells. Also, this prepared carbon anode appeared a high initial efficiency of 80% and the retention rate capability of 2C/0.1 C was 92%. It is found that modified carbon anode showed improved cycling and rate capacity performance.

• Carbon letters
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• v.4 no.4
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• pp.168-174
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• 2003

Silver nitrate ($AgNO_3$) powder was mixed into a reformed pitch precursor. Then, the silver-containing pitch was melt spun to form round and "C" shape fibers. A wire mesh was inserted prior to the nozzle to improve the spinnability of the silvercontaining precursor pitch. Silver particles in the carbon fibers (CFs) were detected by XRD and TEM. These tests showed that silver particles were uniformly distributed and the total amount of silver remained constant during stabilization and carbonization. Next, the silver-containing CFs were activated by steam diluted in nitrogen gas. Silver particles accelerated the activation rate, but the specific surface areas of the silver-containing ACFs were similar to those of non-silver containing ACFs at the same burn-off levels. The specific surface area of the C-shaped activated carbon fibers was larger than that of the round activated carbon fibers. The likely reason is that the surface area of a C-shaped CF is about two times larger than that of a round CF when equivalent cross-sectional areas are compared. A small amount of silver particles in the periphery of the CFs was removed during the activation, but the remainder of silver was stayed within the ACFs.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.98-100
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• 2003

The efficiency of the adsorption of adsorbents depends on both pore size and shape. In other to adsorb hydrated ion in application of electric double layer capacitor (EDLC), mesopore is necessary[1,2]. Tamai et al.[3] reported that an increased portion of mesopore was introduced through addition of metal or organometallic compound in the precursor and following activation of the carbon fibers with steam. (omitted)

• Journal of the Korean Society of Safety
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• v.10 no.2
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• pp.84-91
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• 1995

The characteristics of critical spontaneous ignition of granulated activated carbon were investigated In atmospheres of differing oxygen concentration. At the same concentration the larger vessels yielded the lower critical spontaneous ignition temperature. At the same vessel, as the concentration of oxygen was reduced, Ignition occurred later and at higher ambient temperature, and critical spontaneous ignition temperature increased. The apparent activation energy calculated from the Frank-Kamenetskii's ignition theory appeared to be the slight different value respectively and the mean apparent activation energy was 19850㎈/㏖.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.208-213
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• 2002

We present the temperature and excitation power density dependence of the photoluminescence from carbon-doped GaAs epilayers grown on GaAs (311)A substrate by atmospheric pressure metalorganic chemical vapor deposition. The measured temperature dependence of the PL peak energy is well expressed by an empirical formula proposed by Varshni. The thermal quenching mechanism of the intensity of 16 K luminescence peak at 1.480 eV is described with the dominant activation energy of 27$\pm$2 meV. The activation energy shows an evidence that the emission band involves the carbon acceptor in the recombination process.

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.157-162
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• 2018

In the study, herbaceous biomass waste including giant miscanthus, corn stalk, and wheat stalk were used to prepare commercially valuable activated carbons by KOH activation. The waste biomass predominantly consists of cellulose/hemicellulose and lignin, in which decomposition after carbonization and activation contributed to commercially valuable specific surface areas (>$2000m^2/g$) and specific capacitances (>120 F/g) that exceeded those of commercial activated carbon. The significant electrochemical performance of the herbaceous biomass-derived activated carbons indicated the feasibility of utilizing waste biomass to fabricate energy storage materials. Furthermore, with respect to both economic and environmental perspectives, it is advantageous to obtain activated carbon from herbaceous biomass waste given the ease of handling biomass and the low production cost of activated carbon.

• International Journal of Automotive Technology
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• v.7 no.3
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• pp.261-267
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• 2006

Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration. Carbon oxidation characteristics were investigated by temperature programmed oxidation(TPO) method as well as constant temperature oxidation(CTO) with a flow reactor including porous bed. The activation energy of carbon oxidation was increasing with temperature and had two different constant values in the early and the later stage of the oxidation process respectively in TPO experiment. Kinetic constants were derived and the reaction mechanisms were assumed from the experimental results and a simple reaction scheme was proposed, which approximately predicted the overall oxidation process in TPO as well as CTO.

• Carbon letters
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• v.16 no.2
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• pp.78-85
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• 2015

Activated carbons (ACs) were prepared by activation of coal tar pitch (CTP) in the range of $700^{\circ}C-1000^{\circ}C$ for 1-4 h using potassium hydroxide (KOH) powder as the activation agent. The optimal activation conditions were determined to be a CTP/KOH ratio of 1:4, activation temperature of $900^{\circ}C$, and activation time of 3 h. The obtained ACs showed increased pore size distribution in the range of 1 to 2 nm and the highest specific capacitance of 122 F/g in a two-electrode system with an organic electrolyte, as measured by a charge-discharge method in the voltage range of 0-2.7 V. In order to improve the performance of the electric double-layer capacitor electrode, various mixtures of CTP and petroleum pitch (PP) were activated at the optimal activation conditions previously determined for CTP. Although the specific capacitance of AC electrodes prepared from CTP only and the mixtures of CTP and PP was not significantly different at a current density of 1 A/g, the AC electrodes from CTP and PP mixtures showed outstanding specific capacitance at higher current rates. In particular, CTP-PP61 (6:1 mixture) had the highest specific capacitance of 132 F/g, and the specific capacitance remained above 90% at a high current density of 3 A/g. It was found that the high specific capacitance could be attributed to the increased micro-pore volume of ACs with pore sizes from 1 to 2 nm, and the high power density could be attributed to the increased meso-pore volume.

• Journal of the Korean GEO-environmental Society
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• v.9 no.3
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• pp.45-50
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• 2008

In this work, stainless steel mesh-supported activated carbons were prepared using phenolic resin and cellulose fiber. $ZnCl_2$ was used as a activation reagent in this work. $ZnCl_2$-chemical activation method has been proposed to produce highly porous activated carbons. The objectives of this work were to develop an optimal condition for manufacturing activated carbon assemblies screen from stainless steel mesh and phenolic resin. The iodine number was more increased over activation temperature of $450^{\circ}C$. Iodine number was 657 mg/g at activation temperature of $550^{\circ}C$, penolic resin concentration 20% and $ZnCl_2$ concentration 15%. Iodine number was 1359.4 mg/g when 10% cellulose added to these conditions.