• 한국세라믹학회지
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• 제37권2호
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• pp.128-133
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• 2000

In this work, soft carbons produced by pyrolysis of petroleum and coal-tar pitch were used as the negative electrode for Li-ion batteries. We studeid the charge/discharge capacity and the interfacial reaction of these electrodes by constructing a half cell. Charge/discharge property was studied by a constant-current step and the interfacial reaction between the electrolyte and the surface of a carbon electrode was studied by the cyclic voltammetry. The initial charge/discharge capacity for the coal-tar pitch carbon increased exceedingly with the heat treatment temperature. On hte other hand, the capacity of the petroleum pitch carbon increased with temperature up to 1000$^{\circ}C$, thereafter decreased continuously. While the charge capacity decreased with the cycle number, the reversibility increased above 90%. In addition, the thermal stability and crystallization of petroleum and coal-tar pitches were analyzed by TGA and XRD, respectively.

• 한국응용과학기술학회지
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• 제32권4호
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• pp.718-723
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• 2015

For the fabrication of the Si negative electrode in Li-ion batteries (LIBs) containing the cross-linking polymer binder, in this work, the urethane acrylate (UA) oligomer was synthesized via a simple synthetic process. The cross-linked poly(urethane acrylate) (CPUA)/carbone black (CB)/Si composite (CPUA/CB/Si composite) was fabricated through reactions between their reactive vinyl segments in the UA oligomer. Interestingly, the CPUA/CB/Si composite showed better cycle performance than the poly(vinylidene fluoride) (PVdF)/CB/Si composite (PVdF/CB/Si composite) and the polyurethane (PU)/CB/Si composite (PU/CB/Si composite). The CPUA/CB/Si composite had the best lithiation of about $2586mAh\;g^{-1}$. The UA oligomer showed a good compatibility with the electrode materials and current collector after and before a curing process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 제6회 학술대회 논문집 일렉트렛트 및 응용기술연구회
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• pp.27-30
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• 2004

Different types of hybrid negative materials on pitch based carbon and natural graphite for lithium ion batteries were studied. Two types of active materials were prepared, that is, pitch based graphite carbon, and pitch based carbon impregnating natural graphite. The specific capacity, capacity recovery in high temperature condition, and other electrochemical properties were achieved for these materials. We found that addition of natural graphite type to the pitch based carbon can significant1y improve the specific capacity and interfacial resistance. However, use of natural graphite will cause a serious capacity loss in the high temperature condition owing to its increasing interface resistance. The specific capacity ranged from 321 to 348 mAh/g and the maximum specific capacity was obtained in the case of pitch based carbon impregnating natural graphite.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.561-565
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• 2008

Generally, reaction wheels or thrusters are used for attitude control of a satellite. There is a potential method for the attitude control utilizing the plasma flow on the Low Earth Orbit. In the present study, experiments which simulate attitude control of a Low Earth Orbit Satellite using the ionosphere were conducted. In this experiment, a plasma flow was generated by a steady-state Hall type accelerator. However it is known that the Hall type accelerator, which is used as plasma source, produces a torque around its axis called "swirl torque". This torque would affect the attitude control in the above-mentioned experiments. First of all, we conducted the measurement of the swirl torque. Secondly, experiments using a satellite model with negative electrodes were conducted. The negative electrodes generated torque around the axis, and controlled the attitude of the satellite model by changing the applied voltage.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.129-133
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• 2007

Focused Ion Beam(FIB) systems is a useful tool for the fabrication of micro-nano scale structures. In this study, the effects of FIB etching on the Au microstructure are systematically investigated. As the fabrication parameters, ion dose, dwell time and beam overlap ratio are studied. First, the increases of Ga ion dose makes the milling yield higher and the sidewall of milling profile steeper. Dwell time is found to have little effects on the milling profile due to the relatively large milling area of $1\times1{\mu}m^2$ used in this study. However, beam overlap significantly affects not only milling rate but also milling profile. As the beam overlap ratio changes from positive to negative, the development of regular cross-stripe patterns at the bottom with low milling rate is observed.

• 한국세라믹학회지
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• 제55권4호
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• pp.307-324
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• 2018

Rechargeable lithium-ion batteries (LIBs) have been rapidly expanding from IT based applications to uses in electric vehicles (EVs), smart grids, and energy storage systems (ESSs), all of which require low cost, high energy density and high power density. The increasing demand for LIBs has resulted in increasing price of the lithium source, which is a major obstacle to wider application. To date, the possible depletion of lithium resources has become relevant, giving rise to the interest in Na-ion batteries (NIBs) as promising alternatives to LIBs. A lot of transition metal compounds based on conversion-alloying reaction have been extensively investigated to meet the requirement for the anodes with high energy density and long life-time. In-depth understanding the electrochemical reaction mechanisms for the transition metal compounds makes it promising negative anode for NIBs and provides feasible strategy for low cost and large-scale energy storage system in the near future.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.113-115
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• 1994

We considered the ion and photo-induced properties as a function of wavelength by exposing the light over the band gap of a-Ag/a-$Se_{75}$$Ge_{25}$ and the low-energy defocused $Ga^{+}$ ion beam on Ag/a-$Se_{75}$$Ge_{25}$ thin film. This film acts as a negative resist for photo or ion beam lithography. We observed that the absorbance coefficient decreased with increasing the photo-exposing time and exposing the ion beam. The bandgap shifts toward longer wavelength called a "darkening effect" are observed in the films exposed to both photons and ions. We suggest that a primary step in the Ag layer and a secondary step is in a-$Se_{75}$$Ge_{25}$ film layer.

• 한국전기전자재료학회논문지
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• 제21권8호
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• pp.687-694
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• 2008

This paper is focused on the improvement of MOS device reliability related to deuterium process. The injection of deuterium into the gate oxide film was achieved through two kind of method, high-pressure annealing and low-energy implantation at the back-end of line, for the purpose of the passivation of dangling bonds at $SiO_2/Si$ interface. Experimental results are presented for the degradation of 3-nm-thick gate oxide ($SiO_2$) under both negative-bias temperature instability (NBTI) and hot-carrier injection (HCI) stresses using P and NMOSFETs. Annealing process was rather difficult to control the concentration of deuterium. Because when the concentration of deuterium is redundant in gate oxide excess traps are generated and degrades the performance, we found annealing process did not show the improved characteristics in device reliability, compared to conventional process. However, deuterium ion implantation at the back-end process was effective method for the fabrication of the deuterated gate oxide. Device parameter variations under the electrical stresses depend on the deuterium concentration and are improved by low-energy deuterium implantation, compared to conventional process. Our result suggests the novel method to incorporate deuterium in the MOS structure for the reliability.

• 분석과학
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• 제6권1호
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• pp.77-82
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• 1993

음이온 화학적 이온화 질량분석법은 아미노산 분석에 있어서 sensitivity를 향상시킬 수 있는 좋은 방법이 될 수 있다. 강한 전자 포획성 분자들에 대해서 이 방법은 femtomole에서 attomole($10^{18}$)까지 측정한계가 내려가는 것이 보고되고 있다. 이 논문에서는 아미노산을 전자 포획성 물질인 dinitro-phenyl(DNP) 유도체를 만들어 음이온 화학적 이온화 질량 분석법으로 스펙트럼을 얻어 이를 전자 이온화법으로 얻은 질량 스펙트럼과 비교하였다. 그 결과 음이온 질량분석법의 경우 이온화 과정의 선택성 때문에 background noise가 훨씬 줄어들어 깨끗한 스펙트럼이 얻어졌다.

• Journal of Electrical Engineering and Technology
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• 제1권4호
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• pp.520-527
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• 2006

The electrical discharge and operational characteristics of needle and wire-cylinder corona charger based on current measurements for positive and negative coronas were evaluated and compared. A semi-empirical method was used to determine the ion concentrations in the charging zone and at the outlet of both chargers. Results from experimental investigation revealed that magnitudes of the charging current from the wire-cylinder charger were approximately 3.5 and 2 times smaller than those from the needle charger for the positive and negative coronas, respectively. The ion number concentrations at the outlet for positive corona of both chargers were higher than fur negative corona at the same voltage. Flow and electric fields in the charging zone of both chargers were also analyzed via numerical computation. Strong electric field strength zone was identified and led to high charging and particle deposition. Effect of particle deposition on the evolution of discharge current was presented. It was shown that ions loss inside the wire-cylinder charger was higher than the needle charger The particle deposited on the corona electrodes and on the grounded cylinder caused a great reduction in charging efficiency of both chargers.