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습식 분급으로 입도 조절된 서브 마이크론 크기의 Si 음극활물질의 전기화학적 특성 분석
나병기,서진성,김현수 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.1
In this study, the particle size of Si polycrystals was controlled through wet-sedimentation method, and changes in the capacity and cyclic characteristics of the Si anode material according to the particle size were observed. After wet-sedimentation of Si particles pulverized by a vibration mill, the non-uniform particle distribution of Si was uniformly controlled. The d50 of a sample in which Si was sedimented for 24 hours decreased to 0.50 μm. As a result of the electrochemical characteristic analysis, the Rct value representing the resistance in the electrode was significantly reduced due to the decrease in particle size. The unclassified Si sample exhibited a discharge capacity of 2,869 mAh/g in the first cycle, and decreased to 85.7 mAh/g after 100 cycles. The sample in which Si was classified for 24 hours showed a capacity of 3,394 mAh/g initially, and maintained a capacity of 1,726 mAh/g after 100 cycles. As the size of the Si particles decreased, the discharge capacity increased and the cycle life was also increased. 본 연구에서는 습식 분극을 통하여 Si 다결정의 입자 크기를 조절을 하였으며, 입자 크기에 따른 Si 음극활물질의용량 및 수명 특성 변화를 관찰하였다. 진동밀로 분쇄한 Si 입자를 습식법으로 분급한 시료의 입도를 분석한 결과 Si 의 불균일한 입자 분포가 균일하게 조절이 되었다. Si를 24시간 분급한 시료의 d50이 0.50 μm로 감소하였다. 전기화학적 특성 분석 결과, 입자 크기의 감소로 인하여 전극 내의 저항을 나타내는 Rct 값이 현저하게 줄어들었다. 분급하지 않은 Si 시료는 첫 사이클에서 2,869 mAh/g의 방전용량을 나타내었고, 100 사이클 후에는 85.7 mAh/g으로 방전용량이감소하였다. Si를 24시간 분급한 시료의 경우에 초기에는 3,394 mAh/g의 용량을 보였으며, 100사이클 후에는 1,726 mAh/g의 용량을 유지하였다. 결과적으로 Si 입자의 크기가 감소할수록 방전용량이 증가하였으며, 사이클 수명도 증가하였다.
Adsorption and desorption characteristics of CF4 on fixed bed column
나병기,Sung-Sup Suh,Neung Gyun Ahn 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.6
Adsorption and desorption characteristics of CF4, which is considered a significant global warming compound, were experimentally investigated. Dynamic behavior of feed gas mixture of CF4 and N2 was observed by breakthrough curve. Effects of CF4 concentrations in the feed gas were investigated, and three pressurization methods were compared. Desorption experiments were carried out using vacuum blowdown and purge. Desorption curves with various N2 flow rates, feed compositions, and purge time were obtained. The enrichment factor was high for low concentration of CF4. However, the time required for complete desorption was independent of CF4 concentration. In the operation of separate vacuum blowdown and purge steps, a short period of vacuum blowdown followed by the purge step was effective.
나병기,조병원,김다혜,이희우 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.6
Gel type electrolyte was formulated by blending of PEDGA and PAN. PEDGA is a UV curable polymer which forms a chemical crosslink by UV or heat. Gel type electrolyte is very stable in ionic conductivity and interfacial resistance for a long storage time. It has the advantage of manufacturing the battery in a continuous process because oligomer crosslinking occurs in few seconds without heating. Discharge capacity and cycle life were increased by using LiPF6/LiCF3SO3 mixed lithium salt and adding inorganic filler such as TiO2.
Reduction of COD and Color of Acid and Reactive Dyestuff Wastewater Using Ozone
나병기,최재욱,송형근,한춘,구기갑,Whun Lee 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.2
Wastewaters obtained from bromamine acid dye and reactive dye manufacturing were treated by ozone bubbling in a cylindrical batch reactor for the purpose of reducing COD to below 150 mg/L, which is the environmental discharge standard of the Republic of Korea. Remarkable COD reduction and decolorization were observed at pH over 11. High inlet gas flowrate and high concentration of ozone gave better results. Little precipitation was observed under the conditions of remarkable COD reduction. At pH of 11, 15 LPM of inlet gas flowrate and 89.3 g/Nm3 of ozone flowrate, the COD of bromamine acid dyestuff wastewater was reduced to 95 mg/L after 90 minutes, and the COD of reactive dyestuff wastewater was reduced to 120 mg/L after 120 minutes. Decolorization was completed after 30 minutes of reaction.
입자 크기 및 탄소 코팅에 따른 리튬이온배터리용 SiOx 음극활물질의 전기화학적 특성
나병기,박안나 한국화학공학회 2024 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.62 No.1
본 연구에서는 리튬이온배터리용 고용량 음극활물질인 실리콘의 부피팽창을 완화하고 사이클 안정성을 향상시키기위해 SiOx@C 복합소재를 제조하였다. Stӧber 법을 통해 입자 크기가 각각 100, 200, 500 nm인 SiO2를 합성하였고, 마그네슘 열환원을 통해 SiOx (0≤x≤2)를 제조하였다. 그 후 SiOx에 PVC를 탄화시켜 SiOx와 C의 비율에 따라 SiOx@C 음극활물질을 합성하였다. 제조된 SiOx와 SiOx@C 음극활물질의 물리적 특성은 XRD, SEM, TGA, 라만분광법, XPS, BET를 사용해 분석하였다. 그리고 사이클 테스트, 율속특성, CV, EIS 테스트를 통해 전기화학적 특성을 조사하였다. 입자 크기가 가장 작은 100 nm SiOx에 SiOx:C=70:30으로 탄소를 코팅하여 제조된 SiOx@C-7030은 100 사이클에서1055 mAh/g의 방전용량과 81.9%의 용량을 유지하여 가장 우수한 전기화학적 특성을 보여주었다. 이는 SiOx 음극활물질 입자의 크기를 줄이고, 탄소를 코팅하여 사이클 안정성을 향상시킬 수 있다는 것을 의미한다. In this study, the electrochemical properties of SiOx@C composite materials were prepared to alleviate volume expansion and cycle stability of silicon and to increase the capacity of anode material for LIBs. SiO2 particles of 100, 200, and 500 nm were synthesized by the Stӧber method, and reduced to SiOx (0≤x≤2) through the magnesiothermic reduction method. Then, SiOx@C anode materials were synthesized by carbonization of PVC on SiOx. The physical properties of prepared SiOx and SiOx@C anode materials were analyzed by XRD, SEM, TGA, Raman spectroscopy, XPS and BET. The electrochemical properties were investigated by cycling performance, rate performance, CV and EIS test. As a result, the SiOx@C-7030 manufactured by coating carbon at SiOx : C = 70 : 30 on a 100 nm SiOx with the smallest particle size showed the best electrochemical properties with a discharge capacity of 1055 mAh/g and a capacity retention rate of 81.9% at 100 cycles. It was confirmed that cycle stability was impoved by reducing particle size and carbon coating.
나병기 ( Byung Ki Na ),민경일 ( Kyong Il Min ),임의순 ( Eui Soon Yim ),정충섭 ( Chung Sub Jung ),김재곤 ( Jae Kon Kim ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.2
Gasoline generates organic acid and polymer (gum) by hydrocarbon oxidation depending on the storage environment such as temperature and exposure to sunlight, which can cause metal corrosion, rubber and resin degradation and vehicle malfunction caused by accumulation in fuel supply system. The gasoline which has not been used for a long time in bi-fuel (LPG-Gasoline) vehicle causes problems, and low octane number gasoline have evaporated into the field, but the exact cause has not been studied yet. In this study, we suggest a plan of quality management by investigating the gasoline oxidation behavior. In order to investigate the oxidation behavior of gasoline, changes of gasoline properties were analyzed at various storage conditions such as storage time, storage vessel type (vehicle fuel tank, PE vessel and Fe vessel) and storage circumstances (sunlight exposure and open system, etc.). Currently distributing gasoline and bioethanol blended fuel (blended 10%) were stored for 18 weeks in summer season. The sample stored in PE vessel was out of quality standard (octane number, vapor pressure, etc.) due to the evaporation of the high octane number and low boiling point components through the vessel cap and surface. Especially, the sunlight exposure sample stored in PE vessel showed rapid decrease of vapor pressure and increase of gum. Bioethanol blended fuel showed similar results as gasoline.
졸-겔법을 이용한 리튬이온전지용 SnOx-Al2O3 음극활물질의 제조
방종민, 나병기 충북대학교 산업과학기술연구소 2010 산업과학기술연구 논문집 Vol.24 No.1
SnO2,-Al2O3, cointrosite material was manufactured for an anode material of lithium ion battery. Sol gel synthesis was used to make unifromly mixed composite material . The particles were coated with carbon to increase the conductivity and the cycle characteristics . TGA, XRD, SEM, XPS was used to analyze crystal stnictures and surface properties. The material was pasted on the copper sheet and assembled to the coin cell. The charge/discharge properties and the cycle characteristics were analyzed by battery cycler.