• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.164-166
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• 2002

Over the past two decades, the electrochemical supercapaictors are receiving growing attention due to their possible applications as power backup in electronic equipment and electrical vehicles. Both of amorphous cobalt oxide and manganese dioxide were prepared by sol-gel process reported in our previous work. Nano-structured supramolecular oligomer of 1,5-diamino anthraquinone(DAAQ) coated metal oxides were successfully prepared by electrochemical oxidation from an acidic non-aqueous medium. We established process parameters of the technique for the formation of nano-structured materials. Furthermore, improved the capacitive properties of the nano structured metal oxide electrodes using controlled solution chemistry. $CoO_2$ and $MnO_2$-based composite electrode showed relatively good electrochemical behaviors in acidic electrolyte system with respect to specific capacity and scan rate dependency

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.41-44
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• 2008

In this paper, the gas generator using hydrogen peroxide catalytic decomposition was designed for turbine generator operation. The gas generator used 90wt% rocket-grade of hydrogen peroxide and manganese dioxide as a catalyst. Turbine generators utilizing gas generators were investigated and the prestudy was prepared using automobile turbocharger instead of turbine generator.

• Journal of the Korean Chemical Society
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• v.26 no.3
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• pp.128-134
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• 1982

The electrical conductivity of n-type polycrystalline MnOx-Ti$O_2$ system containing 0.40, 0.80, and 1.60 mol % of manganese oxide has been measured from 100 to 400$^{\circ}$C and 1100 to 1300$^{\circ}$C under oxygen partial pressures of$10^{-8}\;to\;10^{-1}$ atm. Plots of log conductivity vs. reciprocals of absolute temperature at constant $Po_2$'s are found to be linear with an inflection, and the activation energies obtained from the slopes appear to be an enough average 0.18eV for the extrinsic and 3.70eV for the intrinsic. The log $\sigma$ vs. log $Po_2$ are found to be linear at $Po_2$'s of $10^{-8}\;to\;10^{-1}$atm. The conductivity dependences on $Po_2$at the two temperature regions are closely approximated by $\sigma{\propto}$Po_2$-1}6$ for the extrinsic and $${\sigma}{\propto}Po_2^{-1}4}$$ for the intrinsic, respectively. The predominant defects are believed to be Vo-2e' and $Ti^3$${\cdot}$interstitial at the extrinsic and intrinsic. From the interpretations of conductivity dependences on temperature and$Po_2$ , the conduction mechanisms and possible band models are proposed.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2349-2356
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• 2014

The recycling technology by the catalytic conversion is one of the most promising techniques for the $CO_2$ treatment of coal burning power plant flue gases. The conversion of $CO_2$ to valuable product of $CH_4$ can be used as a fuel to run the turbine for electricity generation. Through this technique, the amount of coal needed for the combustion in a gas turbine can be reduced as well as $CO_2$ emissions. Therefore, a series of catalysts based on cerium oxide doped with copper, nickel and manganese were prepared by impregnation method. From the characterization analysis, it showed that the prepared catalysts calcined at $400^{\circ}C$ were amorphous in structure with small particle size in the range below 100 nm. Meanwhile, the catalyst particles were aggregated and agglomerated with higher surface area of $286.70m^2g^{-1}$. By increasing the calcination temperature of catalysts to $1000^{\circ}C$, the particle sizes were getting bigger (> 100 nm) and having moderate crystallinity with lower surface area ($67.90m^2g^{-1}$). From the catalytic testing among all the prepared catalysts, Mn/Ce-75/$Al_2O_3$ calcined at $400^{\circ}C$ was assigned as the most potential catalyst which gave 49.05% and 56.79% $CO_2$ conversion at reaction temperature of $100^{\circ}C$ and $200^{\circ}C$, respectively.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.2
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• pp.135-144
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• 1999

The purposes of this study were to survey types of pretreatment methods adopted by industrial hygiene laboratories in Korea for extracting heavy metals in welding fume samples and to compare performances of two pretreatment methods, the acid extraction and the microwave digestion, in extracting heavy metals contained in the real workplace samples from various welding jobs including arc, argon, and carbon dioxide. A total of 25 analytical chemists in the industrial hygiene laboratories participating the quality control program directed by the Korea Industrial Safety Corporation were interviewed by telephone. For the purpose of comparing performance of extracting heavy metals from real workplace samples, a total of 53 welders from 21 workplaces located in Anyang, Uiwang, and Kunpo areas were sampled from the period of March 22, 1999 to April 20, 1999. It was found that the most frequently adopted method for samples from the quality control program was the acid extraction method(40%) followed by the NIOSH 7300 method(36%). The NIOSH method, however, was the dominant method(36%) for samples from workplace followed by the acid extraction method(28%). In this study, two extraction methods, the acid extraction and the microwave digestion, were compared in terms of recovery rate, accuracy, and precision for both manganese and chromium. Both methods produced comparable results for the samples prepared for the quality control program. In contrast, concentrations of two heavy metals determined from real workplace samples pretreated with the microwave digestion method were statis tically significantly higher, manganese(166%) and chromium (200%), than those of utilizing the acid extraction method. These findings were consistent regardless of types of welding techniques used. The results of this study clearly show the importance of verifying the analytical performances of extraction methods for heavy metals not only for the samples from the quality control program but also from the real world samples collected from welding jobs.

• Resources Recycling
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• v.26 no.4
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• pp.34-41
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• 2017

The effect of Mn(II) concentration on the anodic reactions occurring on a Pb-Ag electrode in sulfuric acid solutions has been studied by potentiostatic oxidation in the potential range of 1.8 to 2.0 V. High oxidation potentials and low initial concentrations of Mn(II) resulted in higher concentrations of soluble Mn(III) ions which were obtained from spectrophotometric analysis of the solution after oxidation. $MnO_2$ was deposited on the electrode by electrochemical oxidation of Mn(II) at 1.8 and 1.9 V, while it was formed by disproportionation of Mn(III) at 2.0 V. No $PbO_2$ was formed in the presence of Mn(II) during potentiostatic oxidation treatment for two hours at 1.8 V. Chemical reduction of $PbO_2$ with Mn(II) led to a decrease in the amount of $PbO_2$ as Mn(II) concentration increased at 1.9 and 2.0 V.

• Journal of the Korean Chemical Society
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• v.8 no.4
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• pp.188-191
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• 1964

A new gas-chromatographic method for determining carbon and hydrogen in organic compounds has been developed. After sample combustion was performed in a regular analytical combustion tube with an internal oxidant (a mixture of silver oxide and manganese dioxide) under a helium flow, the water produced was converted to acetylene by passing through a calcium carbide tube. The carbon dioxide and acetylene were trapped by a molecular sieve 5A column at room temperature. The trapped gases were released under programmed temperature raise up to $340^{\circ}C$ and the released gases were passed through a silica gel column. The adsorption of $CO_2$ and $C_2H_2$ in the molecular sieve 5A trapping column were found to be quantitative and the silica gel column showed an excellent resolution of $CO_2$ and $C_2H_2$ for analytical purpose. The analytical results for various known compounds based on the out-put of the thermal conductivity cell calibrated for the amounts of carbon and hydrogen contents in benzoic acid, showed average errors ${\pm}0.5%$ and ${\pm}0.33%$ for carbon and hydrogen, respectively.

• Journal of the Korean Applied Science and Technology
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• v.18 no.3
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• pp.174-179
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• 2001

The spinel $Fe_{3}O_{4}$ powders were synthesized using 0.2 $M-FeSO_4{\cdot}7H_{2}O$ and 0.5 M-NaOH by oxidation in air and the spinel $LiMn_{2}O_{4}$ powders were synthesized at 480 $^{\circ}C$ for 12 h in air by a sol-gel method using manganese acetate and lithium hydroxide as starting materials. The synthesized $LiMn_{2}O_{4}$ powders were mixed at portion of 5, 10, 15 and 20 wt% of $Fe_{3}O_{4}$ powders using a ball-mill. The mixed catalysts were dried at room temperature for 24 hrs. The mixed catalysts were reduced by hydrogen gas at 350 $^{\circ}C$ for 2 h. The carbon dioxide decomposition rates of the mixed catalysts were 90% in all the mixed catalysts but the decomposition rate of carbon dioxide was increased with adding $LiMn_{2}O_{4}$ powders to $Fe_{3}O_{4}$ powders.

• Journal of Soil and Groundwater Environment
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• v.10 no.4
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• pp.62-69
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• 2005

Removal of 4-chlorophenol (4CP) by natural manganese dioxide (NMD) catalyzed reaction was investigated in this study. Tests were also carried out to evaluate the effects of pH and natural organic matter (NOM) on the degradative oxidation of 4CP. Experimental results proved that NMD was effective for the removal of 4CP. Extensive kinetic analysis suggests that overall oxidation of 4CP by NMD is second-order reaction, the first-order with respect to 4CP, and the first-order with respect to NMD, respectively. Also, 4CP oxidation rates on the Mn-oxide surfaces were highly dependent upon experimental conditions such as pH, initial concentration of 4CP or NMD, and existence of humic acid. As pH increased above PZC of NMD, the reaction rate of 4CP was decreased, due to the low affinity of 4CP on NMD at high pH. At pH lower than PZC of NMD, reaction rate of 4CP was also decreased. It was considered that humic acid was involved in the oxidative coupling reaction of 4CP by NMD, resulting in the enhanced degradation rate of 4CP. This study proved that natural manganese oxide can be effectively applied for the removal of chlorophenols in aqueous phase.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2441-2444
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• 2003

This paper describes fabrication of a micro cell counter integrated with an oxygen micropump and Sephadex G-25 beads counting experiment. The device utilized a phototransistor, microwindow, and light source of microscope for beads detection. Microheater and microchannel were used for pumping and guiding of beads to the microwindow. Counting capability of the device was tested with a peristaltic pump and the measured signals (${\sim}10\;mV$) with oscilloscope showed peak shape when beads passed the microwindow. Pumping of beads by the oxygen micropump was carried out by heating paraffin, which enveloped manganese dioxide (catalyst), to trigger the decomposition of hydrogen peroxide into water and oxygen. It lasted for 5 min with $7\;{\mu}l$ of wt. 30 % hydrogen peroxide. Beads counting by oxygen micropump showed peaks ($2{\sim}20\;mV$) with $30\;{\mu}l$ of beads sample and the number of peaks by magnitude was acquired.