• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.425-431
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• 2005

New type of supercapacitor using high surface area activated carbons mixed with high conductivity polypyrrole (Ppy) has been prepared in order to achieve low impedance and high energy density. Mixed carbons of BP-20 and MSP-20 were used as the active electrode material, and polypyrrole doped with 2-naphthalenesulfonic acid (2-NSA) and carbon black (Super P) as conducting agents were added to activated carbons in order to enhance good electric conductivity. Electrodes prepared with the activated electrode materials and the conducting agents were added to a solution of organic binder [P(VdF-co-HFP) / NMP]. The ratio of optimum electrode composition was 78 : 17 : 5 wt.％ of (MSP20 : BP-20=1 : 1), (Super P : Ppy=10 : 7) and P(VdF-co-HFP) respectively. The performance of unit cell with addition of 7 wt％ Ppy have shown specific capacitance of 28.02 F/g, DC-ESR of $1.34{\Omega}$, AC-ESR of $0.36{\Omega}$, specific energy of 19.87 Wh/kg and specific power of 9.77 kW/kg. With addition of Ppy, quick charge-discharge of unit cell was possible because of low ESR, low charge transfer resistance and quick reaction rate. And good stability up to 500 chargedischarge cycles were retained about 80％ of their original capacity. It was concluded that the specific capacitance originated highly from compound phenomena of the pseudocapacitance by oxidation-reduction of polypyrrole and the nonfaradaic capacitance by adsorption-desorption of activated carbons.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.308-312
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• 2013

Active carbons with high specific surface area and micro pore structure were prepared from the coconut shell char using the chemical activation method of NaOH. The preparation process has been optimized through the analysis of experimental variables such as activating chemical agents to char ratio and the flow rate of gas during carbonization. The active carbons with the surface area (2,481 $m^2/g$) and mean pore size (2.32 nm) were obtained by chemical activation with NaOH. The electrochemical performances of hybrid capacitor were investigated using $LiMn_2O_4$, $LiCoO_2$ as the positive electrode and prepared active carbon as the negative electrode. The electrochemical behaviors of hybrid capacitor using organic electrolytes ($LiPF_6$, $TEABF_4$) were characterized by constant current charge/discharge, cyclic voltammetry, cycle and leakage tests. The hybrid capacitor using $LiMn_2O_4$/AC electrodes had better capacitance than other hybrid systems and was able to deliver a specific energy as high as 131 Wh/kg at a specific power of 1,448 W/kg.

• Journal of the Korean Society of Tobacco Science
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• v.16 no.2
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• pp.181-190
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• 1994

Various active carbons were made from plant sources of coconut shell, pine tree, oak tree and lignite coal. Pore characteristics of these adsorbents were investigated. 1, With increasing activation time, specific surface area and pore volume increased, but the development of micropores was limited at a certain level. The average pore diameter, by BET, of coconut active carbon was 15.5-21.8$\AA$ and that of lignite carbon was 15.6-31.3$\AA$. The pore diameters of silica-gel, sepiolite and zeolite was 30.9$\AA$, 58.6$\AA$ and 55.7$\AA$, respectively. 2. The Horvath - Kawazoe micropore diameter of coconut shell active carbon was under 10.5$\AA$ and that of the other active carbon was under 20.9$\AA$ but silica-gel 33$\AA$, sepiolite 103 $\AA$ and zeolite was unexpectedly large to be 175$\AA$. From the difference between BET micropore diameter and Howath - Kawazoe diameter, it could be said that silica - gel has comparatively uniform pore diameter but sepiolite and zeolite have very uneven diameter. 3. Total pore volume of coconut shell active carbon was 0.27-1.04 cm3/g but that of the other active carbon, 0.23-0.62 cm3/g, was much lower than that of coconut shell active carbon. Hydrophilic adsorbent silica - gel and sepiolite showed big difference in specific surface area, but pore volumes of these were 0.47 and 0.56 cm3/g showing similar value and micropore volumes of these were, respectively, 0.06 cm3/g and 0.04 cm3/g. Total pore volume of zeolite was 0.1 cm3/g and that of micropore was only 0.02 cm3/g.

• Journal of Hydrogen and New Energy
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• v.22 no.4
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• pp.527-533
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• 2011

CNFs had been well addressed due to numerous promising applications in science and technology. Besides the same physicochemical properties of ordinary carbon materials such as active carbons and carbon black, they exhibit specific, e.g., tubular or fibrous structures, a large surface area, high electrical conductivity stability, as well as extremely high mechanical strengh and modulus, which make them a superior material for electrochemical capacitors. In this study, CNFs were pretreated by mechanical milling with different time in mortar and pestle. The milled CNFs were used as active material of electrode whose electrochemical property was tested to find physicochemical characterization variation. CNF electrode milled for 5 min has the highest electric capacitance. XPS spectrum were employed to explore changes in functional group induced from mechanical milling. Crystal size was calculated to analyze change of peak from different milling time by XRD. The CNF milled for 5 min has the largest crystal size and the highest electric capacitance.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.2
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• pp.184-191
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• 2007

Coal-, coconut- and wood-based activated carbons and anthracite were tested for an adsorption and biodegradation performances of nitrogenous chlorinated by-products such as chloropicrin, DCAN, DBAN and TCAN. In early stage of operations, an adsorption performance was a main mechanism for removal of nitrogenous chlorinated by-products, however as increasing populations of attached bacteria, the bacteria played a major role in removing nitrogenous chlorinated by-products in the activated carbon and anthracite biofilter. It was also investigated that the compounds were readily subjected to biodegrade. Whilst the coal- and coconut-based activated carbons were found most effective in adsorption of the compounds, the anthracite was worst in adsorption of the compounds. Highest populations and activity of attached bacteria were shown in the coal-based activated carbon. The populations and activity of attached bacteria decreased in the order: coconut-based activated carbon > wood-based activated carbon > anthracite. The attached bacteria were inhibited for removal of the compounds at temperatures below $10^{\circ}C$. The attached bacteria were more active at higher water temperatures$(20^{\circ}C\;<)$ but less active at love. water temperature$(10^{\circ}C\;>)$. The removal efficiencies of the compounds obtained using coal-, coconut- and wood-based activated carbons and anthracite were directly related to the water temperatures. In particular, water temperature was the most important factor for removal of the compounds in the anthracite biofilter because the removal of the compounds depended mainly on biodegradation. Therefore, the main removal mechanism of the compounds the main mechanism on the removal of the compounds using activated carbon was both adsorption and biodegradation by the attached bacteria. The observation suggests that using coal-based activated carbon is the best for removal of nitrogenous chlorinated by-products in the water treatment.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3183-3189
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• 2010

In order to increase the specific capacitance and energy density of supercapacitors, non-aqueous supercapacitors were prepared using lithium transition-metal oxides and activated carbons as active materials. The electrochemical properties were analyzed in terms of the content of lithium transition-metal oxides. The results of cyclic voltammetry and AC-impedance analyses showed that the pseudocapacitance may stem from the synergistic contributions of capacitive and faradic effects; the former is due to the electric double layer which is prepared in the interface of activated carbon and organic electrolyte, and the latter is due to the intercalation of lithium ($Li^+$) ions. The specific capacitance and energy density of a supercapacitor improved as the lithium transition-metal oxides content increased, showing 60% increase compared to those of supercapacitor using a pure activated carbon positive electrode.

• Carbon letters
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• v.8 no.4
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• pp.274-279
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• 2007

In order to understand the breakthrough behaviour of iodine vapours on impregnated carbon systems, an active carbon, 80 CTC grade, $12{\times}30$ BSS particle size and $1104\;m^2/g$ surface area, was impregnated with metal salts such Cu, Cr, Ag, Mo and Zn, and an organic compound Triethylene diamine (TEDA) to prepare different carbon systems such as whetlerite, whetlerite/TEDA, whetlerite/KI/KOH and ASZMT. The prepared adsorbents along with active carbon were characterized for surface area and pore volume by $N_2$ adsorption at liquid nitrogen temperature. These carbon systems were compared for their CT (concentration X time) values at 12.73 to 53.05 cm/sec space velocities and 2 to 5 cm carbon column bed heights. The carbon column of 5.0 cm bed height and 1.0 cm diameter was found to be providing protection against iodine vapours up to 5.5 h at 3.712 mg/L iodine vapour concentration and 12.73 cm/sec space velocity. The study clearly indicated the adsorption capacities of carbon systems to be directly proportional to their surface area values. Dead layer with all the prepared carbon systems was found to be less than 2.0 cm indicating it to be minimum bed height to have protection against $I_2$ vapours. Effect of carbon bed height and flow rate was also studied. The active carbon showed maximum protection at all bed heights and flow rates in comparison to all other impregnated carbon systems, showing that only physical adsorption is responsible for the removal of iodine vapours.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2961-2965
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• 2012

Mesoporous carbons with tailored pore size were prepared by using sucrose as the carbon source and silicas as the templates. The silica templates were obtained from a hydroxypropyl-${\beta}$-cyclodextrin-silica hybrids using ammonium perchlorate oxidation at different temperatures to remove the organic matter. The structures and surface chemistry properties of these carbon materials were characterized by $N_2$ adsorption, TEM, SEM and FTIR measurements. The catalytic performances of these carbon materials were investigated through the reduction of nitroaromatic using hydrazine hydrate as the reducing agent. Compared with other carbon materials, such as active carbon, and carbon materials from the silica templates obtained by using calcination to remove the organic matter, these carbon materials exhibited much higher catalytic activity, no obvious deactivation was observed after recycling the catalyst four times. Higher surface area and pore volume, and the presence of abundant surface oxygen-containing functional groups, which originate from the special preparation process of carbon material, are likely responsible for the high catalytic property of these mesoporous carbon materials.

• Journal of Environmental Science International
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• v.16 no.9
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• pp.1091-1098
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• 2007

Activated carbon was prepared from waste citrus peels by chemical activation with $ZnCl_2$. The optimal condition of carbonization was at $300^{\circ}C$ for 1.5 hr. Activation experiments with carbonized samples prepared at optimal carboniztion condition were carried out under various conditions such as activation temperature of 400 to $900^{\circ}C$, activation time of 0.5 to 2.0 hr, and $ZnCl_2$ ratio of 100 to 300%. In order to investigate the physical properties of the activated carbons prepared, iodine adsorptivities and specific surface areas were measured and their morphologies were observed from scanning electron microscopy. As $ZnCl_2$ ratio increased, activation yield decreased, while iodine adsorptivity and specific surface area increased. The optimal condition of activation was at 300% $ZnCl_2$ ratio and $300^{\circ}C$ for 1.5 hr, and then iodine adsorptivity and specific surface area was measured as about 862 mg/g and $756m^2/g$, respectively. SEM photography showed that the surface morphology was changed and many active pore were produced by chemical activation.

• Journal of ILASS-Korea
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• v.15 no.1
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• pp.31-37
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• 2010

The aim of this work is to investigate the spray and combustion characteristics of dimethyl-ether (DME) at various injection conditions. The spray characteristics such as spray tip penetration and spray cone angle were experimentally studied from the spray images which obtained from the spray visualization system. Combustion and emissions characteristics were numerically investigated by using KIVA-3V code coupled with Chemkin chemistry solver. From these results, it revealed that DME spray had a shorter spray tip penetration and wider spray cone angle than that of diesel spray due to the low density, low surface tension, and fast evaporation characteristics. At the constant heating value condition, DME fuel showed higher peak combustion pressure and earlier ignition timing, because of high cetane number and superior evaporation characteristics. In addition, the combustion of DME exhausted more $NO_x$ emission and lower HC emission due to the active combustion reaction in the combustion chamber. The result shows that DME had a little soot emission due to its molecular structure characteristics with no direct connection between carbons.