• Applied Biological Chemistry
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• v.40 no.5
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• pp.442-446
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• 1997

A new analytical method was developed by HPLC after supercritical fluid extraction and fluorogenic derivatization for the determination of quinclorac (3,7-dichloro-8-quinoline carboxylic acid) in soil. The graminicide quinclorac was extracted from soil by supercritical fluid extraction. Supercritical carbon dioxide at 7000 psi $(80^{\circ}C)$ modified with 30% of methanol extracted quinclorac from soil samples at the level of $0.1ng\;g^{-1}$ with 96% recovery. Extracted quinclorac was determined by HPLC as a fluorescent derivative. Derivatization was made with 4-bromomethyl-7-methoxycoumarin (4-Br-Mmc) using 18-crown-6-ether as a catalyst. The conversion was completed within 30 min and the limit of detection was 0.5 ppb to prove that the procedure could be used in the residue analysis of the pesticides containing carboxylic acid group.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.288-288
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• 2013

Lithium-ion battery (LIB) is one of the most important rechargeable battery and portable energy storage for the electric digital devices. In particular, study about the higher energy capacity and longer cycle life is intensively studied because of applications in mobile electronics and electric vehicles. Generally, the LIB's capacity can be improved by replacing anode materials with high capacitance. The graphite, common anode materials, has a good cyclability but shows limitations of capacity (~374 mAh/g). On the contrary, silicon (Si) and germanium(Ge), which is same group elements, are promising candidate for high-performance LIB electrodes because it has a higher theoretical specific capacity. (Si:4200 mAh/g, Ge:1600 mAh/g) However, it is well known that Si volume change by 400% upon full lithiation (lithium insertion into Si), which result in a mechanical pulverization and poor capacity retention during cycling. Therefore, variety of nanostructure group IV elements, including nanoparticles, nanowires, and hollow nanospheres, can be promising solution about the critical issues associated with the large volume change. However, the fundamental research about correlation between the composition and structure for LIB anode is not studied yet. Herein, we successfully synthesized various structure of nanowire such as Si-Ge, Ge-Carbon and Si-graphene core-shell types and analyzed the properties of LIB. Nanowires (NWs) were grown on stainless steel substrates using Au catalyst via VLS (Vapor Liquid Solid) mechanism. And, core-shell NWs were grown by VS (Vapor-Solid) process on the surface of NWs. In order to characterize it, we used FE-SEM, HR-TEM, and Raman spectroscopy. We measured battery property of various nanostructures for checking the capacity and cyclability by cell-tester.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.624-628
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• 1998

The aromatic organic solvents(BTX) were decomposed in the fixed bed reactor packed with a 0.5% $Pt/{\gamma}-Al_2O_3$ catalyst, then, supercritical carbon dioxide(SC-$CO_2$) was used as the reaction media. And the conversion was dependent on the inlet concentration of BTX and the molar density of SC-$CO_2$. The conversion of BTX was decreased with increasing of inlet concentration, and was increased with temperature and pressure. The maximum conversion of benzene was 98.5% at $300^{\circ}C$ and 204.1 atm, and that of toluene and xylene were 82.0 and 76.5%, respectively, at $350^{\circ}C$ and 204.1 atm. The intermediate products of partial oxidation were identified as benzaldehyde, phenol, benzenemethanol, and so on. The BTX can be effectively converted into harmless $CO_2$ and $H_2O$ at appropriate operating condition. Thus, the nontoxic recovery process was suggested as the removal method of BTX.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.130-137
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• 1997

Intumescent inorganic and organic coatings which dintr one from the other by the type of gas formers and the mechanisms of foam formation have been obtained and investigated. Inorganic intumescent coatings are the compositions based on water glass and mineral additives with different dispersity. Mineral additives contain adsorbed and absorbed water and carbonates which are destructed with the carbon dioxide and water evolution during the flame action on coating. The decreasing of mineral additives particle sizes under the mechanical milling with the fraction precipitation promotes the foam coke formation with less defects. Here the main structure of comparing compositions does not change. In organic coatings based on epoxy-polymers the polyammonium phosphate additive is used. It is the cabonization catalyst and the foam agent. The polyammonium phosphate of various dispersity employed is uniformly distributed on the polymeric matrix. The decreasing of the particle sizes leads to the increasing of the fire resistant properties of the intumescent coa-ting. The fire resistant analysis of the coating during more than an hour: the coating back side the temperature on plastic or wooden materials does not exceed 423K, and on metal-573K.

• Journal of Radiation Industry
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• v.6 no.1
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• pp.55-59
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• 2012

Polyacrylonitrile (PAN)-based carbon fibers have been widely used due to their unique chemical, electrical, and mechanical properties. Electron beam irradiation has been extensively employed as means of altering properties of polymeric materials. Electron beam irradiation can induce chemical reactions in materials without any catalyst. Electron beam irradiation may be useful in accelerating the thermal compression stabilization of PAN nanofibers. To investigate the irradiation effect on PAN fibers, PAN nanofibers were irradiated by electron beam at 1,000~5,000 kGy. Irradiated and non-irradiated PAN nanofibers were heated at 180 and $220^{\circ}C$ without applying pressure for 15 min. Then 1 metric ton has been applied for 5 min. SEM images have been found that the fiber kept its morphological behavior after the hot pressing up to electron beam irradiated 1,000 kGy. DSC thermograms showed that the peak temperatures of the exothermic reactions were found to decrease with increasing electron beam irradiation doses and temperature. FT-IR spectra have been found to decrease $C{\equiv}N$ stretch band with increasing the electron beam irradiation dose. These results indicate that the modification of PAN via reactions such as cyclization is significantly enhanced by electron beam irradiation and thermal compression technique.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.591-596
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• 2019

A recently developed propellant, ammonium dinitramide (ADN, $NH_4N(NO_2)_2$ is stable and safe at an ambient condition. However, it requires high purity for practical applications. A very little quantity of foreign impurities in ADN may cause clogging of thruster nozzles and catalyst poisoning for the use of a liquid propellant. Thus, several purification processes for precipitated ADN particles such as repetition extraction, activated carbon adsorption and low-temperature extraction were presented in this study. The purifying methods helped to improve the chemical purity as evaluated by FT-IR and UV-Vis spectroscopy in addition to ion chromatography (IC) analyses. Among the purification processes, adsorption was found to be the best, showing a final purity of 99.8% based on relative quantification by IC. Thermal analysis revealed an exothermic temperature of $148^{\circ}C$ for the synthesized liquid monopropellant, but rose to $188^{\circ}C$ when urea was added.

• Journal of Sensor Science and Technology
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• v.30 no.2
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• pp.94-98
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• 2021

In this study, pure and Co3O4/CoFe2O4-loaded Indium oxide (In2O3) nanofibers were synthesized by the electrospinning of an Indium/Polyvinylpyrrolidone precursor solution containing cobalt and iron bimetallic zeolitic imidazolate frameworks and subsequent heat treatment. The ethanol, toluene, p-xylene, benzene, carbon monodxide, and hydrogen gas sensing characteristics of the solution were measured at 250-400 ℃. 0.5 at%-Co3O4/CoFe2O4-loaded In2O3 nanofibers exhibited extreme response (resistance ratio - 1) to 5 ppm of ethanol (210.5) at 250 ℃ and excellent selectivity over the interfering gases. In contrast, pure In2O3 nanofibers exhibited relatively low responses to all the analyte gases and low selectivity above 250-400 ℃. The superior response and selectivity toward ethanol is explained by the catalytic roles of Co3O4 and CoFe2O4 in gas sensing reaction and the electronic sensitization induced by the formation of p (Co3O4/CoFe2O4)-n (In2O3) junctions.

• Membrane Journal
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• v.31 no.6
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• pp.393-403
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• 2021

Enzymes are important class of catalyst for biotransformation. Stability and reusability of enzymes during the catalysis process is a key issue. Activity of enzyme can be enhanced by its immobilization on a suitable substrate by creation of specific microenvironment. A variety of membranes has been used as substrate due to the biocompatibility and simpler method to tune hydrophilicity/hydrophobicity property of the membrane surface. In this review, polymer membranes including cellulose, polyacrylonitrile (PAN), polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF), polyethersulfone (PES) are introduced and discussed in detail. Biodegradation of organic contaminants by immobilized enzyme is an environmental friendly process to reduce the contamination of environment in pharmaceutical company and textile industries. The controlled hydrolysis of oil can be performed in enzyme immobilized membrane bioreactor (EMBR), resulting in reducing carbon emission and reduced environmental pollution. Bioethanol and biodiesel are considered alternative fossil fuels that can be prepared in EMBR.

• Journal of Soil and Groundwater Environment
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• v.27 no.1
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• pp.17-24
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• 2022

This work examined the effect of mixing transition metal-based additives [FeCl₃, Fe-containing paper mill sludge (PMS), CoCl₂·H₂O, ZrO₂, and α-Fe₂O₃] on the thermochemical conversion of coffee waste (CW) in carbon dioxide-assisted pyrolysis process. Compared to the generation amounts of syngas (0.7 mole% H₂ & 3.0 mole% CO) at 700℃ from single pyrolysis of CW, co-pyrolysis in the presence of Fe- or Zr-based additives resulted in the enhanced production of syngas, with the measured concentrations of H₂ and CO ranging 1.1-3.4 mole% and 4.6-13.2 mole% at the same temperature, respectively. In addition, α-Fe₂O₃ biochar possessed the adsorption capacity of As(V) (19.3 mg g^-1) comparable to that of ZrO₂-biochar (21.2 mg g^-1). In conclusion, solid-type Fe-based additive can be highly considered as an efficient catalyst to simultaneously produce syngas (H₂ & CO) as fuel energy resource and metal-biochar as sorbent.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.308-320
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• 2022

The high internal resistance (R_int) that develops across the sediment microbial fuel cells (SMFC) limits their power production (~4/10 mW m^-2) that can be recovered from an initial oil-contaminated sediment (OCS). In the anolyte, R_int is related to poor biodegradation activity, quality and quantity of contaminant content in the sediment and anode material. While on the catholyte, R_int depends on the properties of the catholyte, the oxygen reduction reaction (ORR), and the cathode material. In this work, the main factors limiting the power output of the SMFC have been minimized. The power output of the SMFC was increased (47 times from its initial value, ~4 mW m^-2) minimizing the SMFC R_int (28 times from its initial value, 5000 ohms), following the main modifications. Anolyte: the initial OCS was amended with several amounts of gasoline and kerosene. The best anaerobic microbial activity of indigenous populations was better adapted (without more culture media) to 3 g of kerosene. Catholyte: ORR was catalyzed in birnessite/carbon fabric (CF)-cathode at pH 2, 0.8M Na₂SO₄. At the class level, the main microbial groups (Gammaproteobacteria, Coriobacteriia, Actinobacteria, Alphaproteobacteria) with electroactive members were found at C-anode and were associated with the high-power densities obtained. Gasoline is more difficult to biodegrade than kerosene. However, in both cases, SMFC biodegradation activity and power output are increased when ORR is performed on birnessite/CF in 0.8 M Na₂SO₄ at pH 2. The work discussed here can focus on bioremediation (in heavy OCS) or energy production in future work.