• 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.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.263-266
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• 2013

It was investigated the electrochemical characteristics of the Ni-MH battery by hydrophilic process. For adopting the Ni-MH battery in water-electrolyte, polyolefin separator was processed the hydrophilic treatment. No treatment sample did not meet KS standard (KSC 8544) but hydrophilic treatment ones satisfied with the KS standard in electrochemical characteristics, such as discharge performance, retention capacity, and cycle performance. All hydrophilic treatment samples showed similar battery performances. Among them, sulfonation treatment sample exhibited the highest value in aspect of capacity retention rate (> 88%). Furthermore, fluoride treatment sample showed the best cycle performance during battery test. This sample maintained a good cycling performance until $1,480^{th}$ cycle, which was about 3 times as compared with that of KS standard (500 cycle).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.179-179
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• 2012

국내에는 나노 분말 제조를 위한 RF 열플라즈마 시스템 제조 기술이 확보되어 있지 않고, 또한 나노 파우더 제조를 위한 공정 기술 역시 외국 업체에 전적으로 의존하고 있다. 본 연구에서는 나노 분말 제조를 위한 RF 열 플라즈마 토치 시스템 개발과 고품질의 나노 파우더 합성 공정 기술을 확립하여 필요 기관에 제공하는데 있다. 80 kW RF Plasma torch system의 설계 및 제작을 위해 플라즈마 Simulator인 CFD-ACE+를 이용하여 플라즈마 토치 및 반응로 내의 온도 분포, 유체 유동, 열전달 등의 해석을 통해 플라즈마 토치 및 반응로의 반경 및 길이, 구조의 설계 값을 도출하여 반응로를 설계하여 RF 파워, RF 플라즈마 토치(Torch), 반응기(Reactor), 사이클론(Cyclone), 포집부(Collector), 열교환기 및 진공배기 시스템으로 구성하였다. Si 나노 소재의 경우, 이차전지 음극재에 적용이 가능한 대표적인 소재로서 높음 비용량과 충/방전시 부피팽창을 감소시킬 수 있어 이차전지의 고용량 구현을 위해서는 가장 중요한 소재중 하나로 많은 관심 재료로 평가 받고 있다. 따라서 본 연구에서는 상용화된 Si 원료 powder를 사용하여 고상 분체 공급 장치를 통하여 고온의 플라즈마를 통과시켜 기상화 및 결정화과정을 통해 Si 나노분말을 제조하였다. 공정 변수로서 공정압력 및 플라즈마 power, Gas의 변화량에 따른 나노 분말의 제조 특성에 대한 실험을 진행한 후 제조된 나노 분말을 비표면적측정(BET) 및 SEM 측정 결과 분석을 통하여 시스템 특성을 파악하였으며 제조된 Si 나노 파우더는 이차전지 음극재로서 770 mAh/g의 용량과 93%@50 cycle 수준의 유지율을 나타내었다.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.415-420
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• 2016

To enhance electrochemical performances of anode materials, the surface of coal tar pitch (CTP) was modified by incorporating heteroatoms through chemical treatment with phosphoric acid ($H_3PO_4$). The prepared anode materials with modified CTP was analyzed by XRD, FE-SEM and XPS. The electrochemical performances of modified CTP were investigated by constant current charge/discharge test, rate performance, cyclic voltammetry and impedance tests using the electrolyte of $LiPF_6$ dissolved in the mixed organic solvents (ethylene carbonate : dimethyl carbonate = 1 : 1 vol% + vinylene carbonate 3 wt%). The coin cell using modified CTP ($H_3PO_4/CTP$ = 3 : 100 in weight) has better initial capacity and initial efficiency (489 mAh/g, 82%) than those of other composition coin cells. Also, it was found that the capacity retention was 86% after 30 cycles and the rate capability was 87% at 2 C/0.1 C.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.2
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• pp.39-47
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• 2010

In Wireless Sensor Network, transmission errors are frequently occurred due to the node failure, battery discharge, and interference by objects. Although Directed Diffusion has been considered as a prominent Data-centric routing algorithm, it revealed some weaknesses at this kind of unexpected network errors. In order to address the problem, we proposed a radio-aware routing algorithm for improving reliability of Directed Diffusion in Wireless Sensor Networks. The proposed algorithm is aware of the network status based on the radio information of MAC and PHY layers using a cross-layer approach. The link quality and the node failure information from the acquired network status were used to decide an alternative path to provide a reliable data transmission in error-prone sensor networks. The proposed algorithm showed its effectiveness of the data delivery rate and data ratio with several simulations consisting of various error rates and the number of nodes.

• 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 the Korean Electrochemical Society
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• v.12 no.3
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• pp.239-244
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• 2009

This paper aims to report the effect of surface treatment on graphite and its effect on the improvement of $Al_2O_3$ and $nano-Li_4Ti_5O_{12}$. The structure and property of surface treatment on graphite were determined by scanning electron microscopy, transmission electron microscopy and electrochemical property and safety were determined by charge/discharge cycler, accelerating rate calorimeter. The composite with different metallic oxide exhibited the first efficiency of 82.5% and specific capacity of 350 mAh/g. Although the composite showed same efficiency and specific capacity at first cycle, surface treatment on graphite by $nano-Li_4Ti_5O_{12}$ exhibited a higher charge/discharge rate, cycle life and thermal stability.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.12
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• pp.13-19
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• 2004

We have been studied on the high concentration ozonized water production technology which substitute for the SPM wet cleaning solution process as the PR strip process after the photolithography process in the semiconductor and flat panel display manufacturing. In this work, we have developed the surface discharge type ozone generator which has the characteristics of the 12 ［wt%］ ozone concentration at the oxygen gas flow of 0.5［ℓ/min］ oxygen per cell and also developed the high efficiency ozone contactor for the mixing ozone gas with deionized water. As the production test results of the ozonized water, we obtained the ozonized water concentration above 80［ppm］ at the 10［wt%］ ozone gas concentration, and also had a good result of the PR strip rate of 147［nm/min］. at the 70［ppm］ ozonized water.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.313-317
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• 1995

최근 환경오염이 심각한 사회문제로 대두됨에 따라 환경오염원을 제거하기 위한 여러 가지의 집진장치가 개발되고 있는데 화력발전소에서는 건식정전집진장치(dry electrostatic precipitator)를 이용하고 있다. 건식정전집진장치는 햄머(hammer) 방식의 충격장치를 설치하여 집진극과 방전극에 충격을 가함으로써 충격력을 극대화시키고 높은 분진박리 효과를 꾀하고 있는데 환경오염원이 되고 있는 집진판의 분진의 분리율을 높이기 위해서는 집진판의 전체 영역에서 분진을 동일하게 떨어뜨릴 수 있는 충격장치가 설계되어야 하는데, 이를 위해서는 충격하중에 따른 집진판의 진동 형태를 정확하게 분석하여야 한다. 본 연구에서는 집진판의 충격하중에 따른 진동의 형태를 분석하기 위해 펄스 레이저를 이용한 2중 노출 홀로그래피 시스템을 구성하였다. 홀로그래픽 간섭계는 이미 오래 전에 개발된 레이저 응용 계측기법으로서 주로 정현적인 진동을 하는 진동체의 진동 현상을 연구하는 데에 많이 사용되어 왔는데 그 기술 개발은 상당한 수준에 있다. 그러나 종래의 기술들은 주로 헬륨-네온(He-Ne)레이저와 같은 연속 레이저(continuous wave laser)를 이용한 기술들인데 최근에는 루비(ruby) 레이저와 같은 펄스 레이저 (pulse laser)를 이용한 기술이 많이 응용되고 있다. 이 펄스 레이저 홀로그래픽 간섭계를 Gottenberg는 응력파에 의해서 발생된 변형을 측정하기 위해 사용하였고 Aprahamian등은 보(beam)와 평판의 굽힘파(bending wave)의 전파 특성 연구에 이용하였다. 그 실험적 결과는 수치적 해석 결과와 비교되어 매우 좋은 일치성을 보였는데 이러한 펄스 레이져 홀로그래픽 간섭계 기법의 주요 장점은 어떠한 특정한 순간에 관찰하고자 하는 시험편의 전체 영역의 파동 전파 형상을 관찰할 수 있다는 것이다. 따라서 본 연구에서는 펄스 레이저를 응용한 2중 노출 홀로그래피법(double exposure holography method)을 이용해서 집진판에 충격하중이 가해졌을 때 발생하는 진동이 발생과 전파 특성을 충격하중의 방향에 따라서 분석하였다.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.459-464
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• 2016

In this study, the electrochemical characteristics of porous silicon/carbon composite anode were investigated to improve the cycle stability and rate performance in lithium ion batteries. In this study, the effect of TEOS and $NH_3$ concentration, mixing speed and temperature on particle size of nano silica was investigated using $St{\ddot{o}}ber$ method. Nano porous Si/C composites were prepared by the fabrication processes including the synthesis of nano $SiO_2$, magnesiothermic reduction of nano $SiO_2$ to obtain nano porous Si by HCl etching, and carbonization of phenolic resin. Also the electrochemical performances of nano porous Si/C composites as the anode were performed by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of $LiPF_6$ dissolved inorganic solvents (EC:DMC:EMC=1:1:1vol%). It is found that the coin cell using nano porous Si/C composite has the capacity of 2,006 mAh/g and the capacity retention ratio was 55.4% after 40 cycle.