• Journal of the Korean Chemical Society
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• v.18 no.2
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• pp.110-116
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• 1974

Reduction of chromate ion at the Pt-electrode was investigated in neutral unbuffered solutions, in buffered solutions of pH between 8 and 10, and in strongly alkaline medium. In buffered solutions of pH between 8 and 10, the number of electrons transfered in the reduction of chromate ion increased progressively with increasing pH. When chromate ion was reduced in 0.2 N sodium hydroxide medium the following mechanism was suggested: $CrO_4^=+H_2O+2e{\rightarrow}CrO_3^=+2OH^-,\;CrO_3^=3H_2O+e{\rightarrow}Cr(OH)_3+3OH^-$ When tetramethylammonium hydroxide (pH=13.5) was used as the supporting electrolyte, a second wave indicated strong adsorption. In unbuffered solutions of 0.1 N potassium chloride the linear sweep voltammogram consists of three or four distinct waves depending on the initial voltage and the voltage sweep rates, but the first wave was difficult to explain as a diffusion controlled wave.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.394.1-394.1
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• 2014

고효율 및 낮은 구동 전압을 가지는 유기 발광소자를 제작하기 위한 많은 연구가 진행되고 있다. 고효율 및 낮은 구동전압을 가지는 p-i-n 유기발광소자는 정공수송층에 p형 무기 도펀트를 도핑하고, 전자수송층에 n형 무기 도펀트를 사용하여 제작하지만, 무기 도펀트는 높은 온도에서 증착하기 때문에 챔버 내의 다른 유기 물질들이 함께 증착되거나 유기 박막에 손상을 가져올 수 있는 단점을 가지고 있기 때문에 유기물 n형 도펀트의 경우는 연구가 필요하다. 본 연구에서는 유기 p형 도펀트인 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile과 유기 n형 도펀트인 bis (ethylenedithio)-tetrahiafulene (BEDT-TTF)를 사용하여 p-i-n 구조의 유기 발광소자를 제작하였다. 유기 n형 도펀트인 BEDT-TTF는 전자수송층 사이에서 산화-환원 반응을 통해 많은 전자를 생성하게 되고, 증가한 전자들로 인해서 Al 음극전극과 전자수송층 사이의 에너지장벽이 낮추는 역할을 하게 된다. BEDT-TTF를 도핑하지 않은 유기 발광소자보다 BEDT-TTF를 도핑하였을 때, 100 cd/m2 일때 약 2.4 V 작동 전압의 감소를 관측할 수 있었다. 이 결과는 음극전극으로부터 발광층으로 전자의 주입이 원활하게 되고, 그 결과 낮은 구동전압 및 고효율을 가지는 p-i-n 유기 발광소자를 제작할 수 있다는 것을 보여준다.

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.13-17
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• 2003

Cryogel and aerogel Pt-Ru/C were synthesized by the sol-gel process for the electrooxidation of methanol. From XRD analysis, it was found that the catalysts had highly dispersed Pt-Ru alloys on carbon support although high temperature treatments have been conducted. Electrocatalytic activities of 3 type aerogel catalysts were investigated in half cell experiments by cyclic voltammetry. Among them, Phloroglucinol-Formaldehyde(PF) type catalyst shows the highest activity. From the results of deactivation test for each catalysts, the aerogel catalysts are found to have excellent durability compared with those prepared by colloidal method.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.16-21
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• 2016

Silicon/Carbon/CNT composites as anode materials for lithium-ion batteries were synthesized to overcome the large volume change during lithium alloying-de alloying process and low electrical conductivity. Silicon/Carbon/CNT composites were prepared by the fabrication processes including the synthesis of SBA-15, magnesiothermic reduction of SBA-15 to obtain Si/MgO by ball milling, carbonization of phenolic resin with CNT and HCl etching. The prepared Silicon/Carbon/CNT composites were analysed by XRD, SEM, BET and EDS. In this study, the electrochemical effect of CNT content to improve the capacity and cycle performance was investigated by charge/discharge, cycle, cyclic voltammetry and impedance tests. The coin cell using Silicon/Carbon/CNT composite (Si:CNT=93:7 in weight) in the electrolyte of $LiPF_6$ dissolved in organic solvents (EC:DMC:EMC=1:1:1 vol%) has better capacity (1718 mAh/g) than those of other composition coin cells. The cycle performance of coin cell was improved as CNT content was increased. It is found that the coin cell (Si:CNT=89:11 in weight) has best capacity retension (83%) after 2nd cycle.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.80-85
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• 2015

Silicon/carbon composites as anode materials for lithium-ion batteries were examined to find the cycle performance and capacity. Silicon/carbon composites were prepared by a two-step method, including the magnesiothermic reduction of SBA-15 (Santa Barbara Amorphous material No. 15) and carbonization of phenol resin. The electrochemical behaviors of lithium ion batteries were characterized by charge/discharge, cycle, cyclic voltammetry and impedance tests. The improved electrochemical performance attributed to the fact that silicon/carbon composites suppress the volume expansion of the silicon particles and enhance the conductivity of silicon/carbon composites (30 ohm) compared to that of using the pure silicon (235 ohm). The anode electrode of silicon/carbon composites showed the high capacity approaching 1,348 mAh/g and the capacity retention ratio of 76% after 50 cycles.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.303-308
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• 2018

Silicon/Carbon (Si/C) composite as anode materials for lithium-ion batteries was synthesized to find the effect of binders and an electrolyte additive. Si/C composites were prepared by two step method, including magnesiothermic reduction of SBA-15 (Santa Barbara Amorphous material No. 15) and carbonization of phenol resin. The electrochemical performances of Si/C composites were investigated by charge/discharge, cyclic voltammetry and impedance tests. The anode electrode of Si/C composite with PAA binder appeared better capacity (1,899 mAh/g) and the capacity retention ratio (92%) than that of other composition coin cells during 40 cycles. Then, Vinylene carbonate (VC) was tested as an electrolyte additive. The influence of this additive on the behavior of Si/C anodes was very positive (3,049 mAh/g), since the VC additive is formed passivation films on Si/C surfaces and suppresses irreversible changes.

• Journal of Soil and Groundwater Environment
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• v.7 no.3
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• pp.79-84
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• 2002

The optimal operation conditions, including voltage applied, reaction time, distance between electrodes. and electrode material. were investigated for the treatment of soil flushing effluent using electrofloatation. When 3V was applied for 1 hour, 88% oil-water separation efficiency was achieved. In case of 6V and above, 90% efficiencies were achieved. As reaction time and distance between electrodes were longer, separation efficiencies were higher and lower, respectively. Separation efficiencies for different anode materials were copper > aluminum > iron > titanium. It might result from the differences of their electrical conductivities.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.203-209
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• 2023

Cobalt sulfide nanocomposites were synthesized through a simple hydrothermal method as anode materials for sodium ion batteries (SIBs). In this work, a cobalt sulfide nanoparticle (CoS-NF) and a cobalt sulfide nanocomposite integrated with reduced graphene oxide (CoS@G-NC) were fabricated for electrochemical energy storage performance of battery. The as-prepared CoS@G-NC electrode exhibited reversible and stable cycle performance (62 % after 30 cycles at current density of 200 mA g^-1). The improved electrochemical property was attributed to the small grain growth and uniform distribution of cobalt sulfide during synthesis, which maximized the diffusion pathway for sodium ions and effectively suppressed the delamination and volume expansion of cobalt sulfide during the conversion reaction. The results provide promising anode materials for next-generation SIBs.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.230-237
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• 2017

In this study, electrochemical methods were used to determine the optimum protection potential of S355ML steel for the cathodic protection of offshore wind-turbine-tower substructures. The results of potentiodynamic polarization experiments indicated that the anodic polarization curve did not represent a passivation behavior, while under the cathodic polarization concentration, polarization was observed due to the reduction of dissolved oxygen, followed by activation polarization by hydrogen evolution as the potential shifted towards the active direction. The concentration polarization region was found to be located between approximately -0.72 V and -1.0 V, and this potential range is considered to be the potential range for cathodic protection using the impressed current cathodic protection method. The results of the potentiostatic experiments at various potentials revealed that varying current density tended to become stable with time. Surface characterization after the potentiostatic experiment for 1200 s, by using a scanning electron microscope and a 3D analysis microscope confirmed that corrosion damage occurred as a result of anodic dissolution under an anodic polarization potential range of 0 to -0.50 V, which corresponds to anodic polarization. Under potentials corresponding to cathodic polarization, however, a relatively intact surface was observed with the formation of calcareous deposits. As a result, the potential range between -0.8 V and -1.0 V, which corresponds to the concentration polarization region, was determined to be the optimum potential region for impressed current cathodic protection of S355ML steel.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.487-492
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• 2021

In this study, the electrochemical properties of pitch coated silicon sheets/graphite anode materials were investigated. Using NaCl as a template, silicon sheets were prepared through the stöber method and the magnesiothermic reduction methode. In order to synthesize the anode composite, the silicon sheets and graphite were combined with SDBS. The pitch coated silicon sheets/graphite was synthesized using THF as a solvent for the anode material composite. The physical properties of the prepared anode composites were analysed by XRD, SEM, EDS and TGA. The electrochemical performances of the prepared anode composites were performed by the current charge/discharge, rate performance, cyclic voltammetry and EIS tests in the electrolyte LiPF₆ dissolved solvents (EC:DMC:EMC=1:1:1 vol%). As the silicon composition of silicon sheets/graphite composite material increased, the discharge capacity also increased, but the cycle stability tended to decrease. The anode material of pitch coated silicon sheets/graphite composite (silicon sheets:graphite=3:7 weight ratio) showed the initial discharge capacity of 1228.8 mAh/g and the capacity retention ratio of 77% after 50 cycles. From these results, it was found that the cycle stability of pitch coated silicon sheets/graphite was improved.