• 공업화학
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• 제2권3호
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• pp.253-261
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• 1991

폴리이미드의 전구체인 폴리아믹산을 benzophenone tetracarboxylic dianhydride (BTDA)와 4, 4'-diamino diphenyl methane (MDA) 혹은 MDA와 3, 3'-dimethyl benzidine (OTB)의 혼합디아민과 용액축중합반응에 의하여 합성하였다. 반응용매로는 m-cresol과 m-cresol/xylene의 혼합용매를 사용하였다. TGA 분석 결과 폴리이미드 필름은 초기분해 온도가 $540^{\circ}C-590^{\circ}C$의 범위로서 내열성이 우수하였다. DSC 분석으로 중합체의 유리전이온도는 $340^{\circ}$ 이상임을 확인하였다. 폴리이미드 필름은 양호한 기계적, 전기적 물성값을 갖는 시료에서 인장강도가 $16Kg/mm^2$ 이상이었고, 절연파괴전압이 200 KV/mm 정도였다. 대체로 MDA 만을 디아민으로 사용한 단일중합체보다 MDA/OTB 공중합체의 물성이 우수하였고, m-cresol에서 합성한 중합체보다 m-cresol/xylene 혼합용매계에서 합성한 중합체의 물성값이 우수하였다.

• 공업화학
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• 제26권2호
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• pp.121-127
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• 2015

전기화학적 양극산화 기법으로 제조한 타이타늄 나노튜브는 타이타늄 특유의 강한 화학내구성 및 나노튜브의 높은 종횡비로 인하여 넓은 범위에 응용된 소재이다. 전해질의 구성 성분과 종류, pH, 전압, 온도 그리고 양극산화 시간이 타이타늄 나노튜브의 성상을 결정짓는 요소들이며 도핑을 통해 촉매능을 부여할 수 있다. 비금속 및 금속 원소 모두 도핑 가능하며 도핑 방법 역시 다양하다. 도핑 방법에는 합금 양극산화, 열처리법, 함침법, 전기도금법 등 다양한 방법들이 이용되며 점차 간단하고 빠른 도핑 방법을 찾는 방향으로 연구가 진행되고 있다. 본 총설에서는 타이타늄 나노튜브의 생성 원리와 상용된 제법들에 관하여 기술하고 도핑과 그 응용 및 최근의 도핑 연구 동향을 다루도록 하겠다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.30.1-30.1
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• 2011

Silicon is one of useful materials in various industry such as semiconductor, solar cell, and secondary battery. The metallic silicon produces generally melting process for ingot type or chemical vapor deposition (CVD) for thin film type. However, these methods have disadvantages of high cost, complicated process, and consumption of much energy. Electrodeposition has been known as a powerful synthesis method for obtaining metallic species by relatively simple operation with current and voltage control. Unfortunately, the electrodeposition of the silicon is impossible in aqueous electrolyte solution due to its low oxidation-reduction equilibrium potential. Ionic liquids are simply defined as ionic melts with a melting point below $100^{\circ}C$. Characteristics of the ionic liquids are high ionic conductivities, low vapour pressures, chemical stability, and wide electrochemical windows. The ionic liquids enable the electrochemically active elements, such as silicon, titanium, and aluminum, to be reduced to their metallic states without vigorous hydrogen gas evolution. In this study, the electrodeposion of silicon has been investigated in ionic liquid of 1-butyl-3-methylpyrolidinium bis (trifluoromethylsulfonyl) imide ([bmpy]$Tf_2N$) saturated with $SiCl_4$ at room temperature. Also, the effect of electrode materials on the electrodeposition and morphological characteristics of the silicon electrodeposited were analyzed The silicon electrodeposited on gold substrate was composed of the metallic Si with single crystalline size between 100~200nm. The silicon content by XPS analysis was detected in 31.3 wt% and the others were oxygen, gold, and carbon. The oxygen was detected much in edge area of th electrode due to $SiO_2$ from a partial oxidation of the metallic Si.

• Transactions on Electrical and Electronic Materials
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• 제15권6호
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• pp.328-332
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• 2014

Thin film transistors (TFTs) with an amorphous silicon zinc tin oxide (a-2SZTO) channel layer have been fabricated using an RF magnetron sputtering system. The effect of the change of excitation electron on the variation of the total interfacial trap states of a-2SZTO systems was investigated depending on sputtering power, since the interfacial state could be changed by changing sputtering power. It is well known that Si can effectively reduce the generation of the oxygen vacancies. However, The a-2SZTO systems of ZTO doped with 2 wt% Si could be degraded because the Si peripheral electron belonging to a p-orbital affects the amorphous zinc tin oxide (a-ZTO) TFTs of the s-orbital overlap structure. We fabricated amorphous 2 wt% Si-doped ZnSnO (a-2SZTO) TFTs using an RF magnetron sputtering system. The a-2SZTO TFTs show an improvement of the electrical property with increasing power. The a-2SZTO TFTs fabricated at a power of 30 W showed many of the total interfacial trap states. The a-2SZTO TFTs at a power of 30 W showed poor electrical property. However, at 50 W power, the total interfacial trap states showed improvement. In addition, the improved total interfacial states affected the thermal stress of a-2SZTO TFTs. Therefore, a-2SZTO TFTs fabricated at 50 W power showed a relatively small shift of threshold voltage. Similarly, the activation energy of a-2SZTO TFTs fabricated at 50 W power exhibits a relatively large falling rate (0.0475 eV/V) with a relatively high activation energy, which means that the a-2SZTO TFTs fabricated at 50 W power has a relatively lower trap density than other power cases. As a result, the electrical characteristics of a-2SZTO TFTs fabricated at a sputtering power of 50 W are enhanced. The TFTs fabricated by rf sputter should be carefully optimized to provide better stability for a-2SZTO in terms of the sputtering power, which is closely related to the interfacial trap states.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.765-771
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• 2012

$SF_6$ gas has been used as arc quenching and insulating medium for high and extra high voltage switching devices due to its high dielectric strength, its excellent arc-quenching capabilities, its high chemical stability and non toxicity. Despite of its significant contributions, the gas was classified as one of the greenhouse gas in the Kyoto Protocol. Thus, many researches are conducted to find out the replacement materials and to develop the $SF_6$ gas useless electrical equipment. This paper describes experiments on the temperature change-related breakdown characteristics of $SF_6$ gas ($SF_6$) and $SF_6$ liquid ($LSF_6$) in a model GIS(Gas-Insulated Switchgear) chamber in order to show the possibility of more stable and safe usages of $SF_6$ gas. The breakdown characteristics are classified into three stages, namely the gas stage of $SF_6$ according to Paschen's law, the coexisting stage of $SF_6$ gas with liquid in considerable deviation at lower temperature, and the stage of $LSF_6$ and remaining air. The result shows that the ability of the $LSF_6$ insulation is higher than the high-pressurized $SF_6$. Moreover, it reveals that the breakdown characteristics of $LSF_6$ are produced by bubble-formed $LSF_6$ evaporation and bubbles caused by high electric emission and the corona. In addition, the property of dielectric breakdown of $LSF_6$ is determined by electrode form, electrode arrangement, bubble formation and movement, arc extinguishing capacity of the media, difficulty in corona formation, and the distance between electrodes. The bubble formation and flow separation phenomena were identified for $LSF_6$. It provides fundamental data not only for $SF_6$ gas useless equipment but also for electric insulation design of high-temperature superconductor and cryogenic equipment machinery, which will be developed in future studies.

• 환경위생공학
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• 제18권3호통권49호
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• pp.35-42
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• 2003

The electric resistance and constant current were investigated on the nickel-thallium-phosphorus alloy deposits by electroless-plating. The Ni-Tl-P alloy deposits were achieved with a bath using sodium hypophosphit as the reducing agent and sodium citrate as the comlexing agent. The basic plating solution is composed of 0.1M NiSO$_4$, 0.005${\sim}$0.0IM Tl$_2$S0$_4$, 0.1${\sim}$O.2M sodium hypophosphite and 0.02${\sim}$O.IM sodium citrate and the plating condition were pH 5${\sim}$6, temperrature 80$_4$90${\circ}$C. The results obtained are summarized as follows: 1) The crystal structure of deposit was amorphous structure as deposited state, became microcrystallized centering on Ni(111) plane by heat treatment at 200${\circ}$C, and grew as polycrystalline Ni, Ni$_3$P, Ni$_5$p$_2$,Tl, etc. by heat treatment higher than 350${\circ}$C. The grain size of plated deposits was grown up to 28.3~42.0nm by heat treatment for 1hour at 500${\circ}$C. 2) The electrical resistivity showed a comparatively high value of 192.5$_4$208.3 ${\mu}$${\Omega}$Cm and its thermal stability was great with resistivity value less than 0.22% in the thermal surroundings of 200${\circ}$C. 3) Ni-Tl-P alloy deposit showed such good constant current-making-effect in the variation of electric voltage, heat treatment temperature, and the composition of the deposit that it can be put to practical use as the matter of constant current device.

• Transactions on Electrical and Electronic Materials
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• 제12권5호
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• pp.213-217
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• 2011

The nonlinear electrical properties and degradation behavior against an impulse-current of 400 A in the ZnO-$Pr_6O_{11}$-CoO-$Cr_2O_3$-$Y_2O_3$-$Er_2O_3$ (ZPCCYE) varistors were investigated with different $Y_2O_3/Er_2O_3$ ratios. The $Y_2O_3/Er_2O_3$ mole ratio has a significant effect on nonlinear electrical properties and impulse degradation behavior of the ZPCCYE varistors. The varistors added with $Y_2O_3/Er_2O_3$ = 0.5/0.5 exhibited the best nonlinear properties with 39 in nonlinear coefficient (${\alpha}$) and the best clamp characteristics, in which the clamping voltage ratio (K) was in the range of K = 1.62-2.18 at an impulse-current of 1-50 A. The varistors added with $Y_2O_3/Er_2O_3$ = 0.25/0.5 exhibited the best electrical stability, with $%{\Delta}E_{1mA/cm^2}$=-5.6%, $%{\Delta}{\alpha}$ = 6.7%, and $%{\Delta}J_L$ = -14.6% against an impulse-current of 400 A. On the contrary, the varistors added with $Y_2O_3/Er_2O_3$ = 0.5/0.5 were destroyed applying an impulse-current of 400 A.

• 전기학회논문지P
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• 제58권3호
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• pp.357-361
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• 2009

This study performed analysis on the thermal pattern and current characteristics of an LED ((Light Emitting Diode) street lamp. It did this using a TVS (Thermal Video System) to analyze the LED street lamp's thermal pattern, and measured its characteristics using an oscilloscope. The ambient temperature and humidity during the experiment were maintained at $24{\pm}2[^{\circ}C]$ and 50~60[%]. The capacity of the LED street lamp was 120[W] and nine sets of modules were arranged at uniform intervals. On one module, 24 LED lamps were arranged in a radial pattern. The analysis of the thermal diffusion pattern at the front of the LED lamp showed that the maximum surface temperature was approximately $34[^{\circ}C]$. In addition, there was almost no change in the temperature of the upper cover, and the temperature at the side showed a uniform thermal diffusion pattern. The surface temperature of the converter converting AC to DC increased to approximately $46[^{\circ}C]$. The analysis results of the thermal characteristics of one LED indicated uniform thermal characteristics for an initial eight minutes. However, the temperature at the center of the LED increased to approximately $82[^{\circ}C]$ after 12 minutes had elapsed. It can be seen from this that the temperature at the center of the LED was higher than the allowable temperature, $70[^{\circ}C]$ of the insulating material for general electrical devices. Therefore, it is necessary to design a lamp in such a way that the plastic insulating material does not come into contact with or get close to the LED lamp. The voltage of the LED lamp converted by the AC/DC converter was measured at DC 27[V] and the current was DC 13[A]. Consequently, it can be seen that in order to secure an adequate light source, it is important to supply a stable current that was greater than the current of other light sources. Therefore, appropriate radiation of heat is required to secure the stability and reliability of the system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.221-221
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• 2013

Striving to replace the well known silicon nanocrystals embedded in oxides with solution-processable charge-trapping materials has been debated because of large scale and cost effective demands. Herein, a silicon quantum dot-polystyrene nanocomposite (SiQD-PS NC) was synthesized by postfunctionalization of hydrogen-terminated silicon quantum dots (H-SiQDs) with styrene using a thermally induced surface-initiated polymerization approach. The NC contains two miscible components: PS and SiQD@PS, which respectively are polystyrene and polystyrene chains-capped SiQDs. Spin-coated films of the nanocomposite on various substrate were thermally annealed at different temperatures and subsequently used to construct metal-insulator-semiconductor (MIS) devices and thin film field effect transistors (TFTs) having a structure p-$S^{++}$/$SiO_2$/NC/pentacene/Au source-drain. C-V curves obtained from the MIS devices exhibit a well-defined counterclockwise hysteresis with negative fat band shifts, which was stable over a wide range of curing temperature ($50{\sim}250^{\circ}C$. The positive charge trapping capability of the NC originates from the spherical potential well structure of the SiQD@PS component while the strong chemical bonding between SiQDs and polystyrene chains accounts for the thermal stability of the charge trapping property. The transfer curve of the transistor was controllably shifted to the negative direction by chaining applied gate voltage. Thereby, this newly synthesized and solution processable SiQD-PS nanocomposite is applicable as charge trapping materials for TFT based memory devices.

• 에너지공학
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• 제24권3호
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• pp.6-12
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• 2015

자동차, 조선, 발전설비 및 산업기계 등 거의 전 산업분야의 제품 생산단계에 용접기술이 사용되고 있다. 본 연구에서는 구조용 금속제품 제조공장에서 많이 사용되어지는 PLC $CO_2$ 자동용접 시스템의 설계 및 구현에 관해 조사하였다. 이를 위해 시스템의 구동부 지지대에 대해 구조해석을 수행하였으며 전력절약형 시스템의 구현을 위해 자동전압조정기의 사양선택, 시스템의 상호인터페이스 및 회로도 설계를 고안하였다. 그 결과 용접 구동부 지지대의 설계가 안전함을 확인하였으며, 또한 PLC $CO_2$ 자동용접 시스템은 다품종 소량 생산형 구조물 제조공장의 용접자동화에 적합하며 생산성 향상, 품질안정 및 전력 절약에 기여할 수 있음을 확인하였다.