• Korean Chemical Engineering Research
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• 제54권5호
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• pp.593-597
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• 2016

고분자전해질 연료전지에서 전해질막의 이온전도도에 미치는 상대습도, 전류밀도, 온도의 영향에 대해 연구하였다. 전해질막의 물의 함량과 물의 이동은 이온전도도에 많은 영향을 미친다. 전기삼투와 역확산만으로 물 이동을 모사하고 해석하였다. 이온전도도는 셀 밖에서 측정 장비로 막 상태에서 그리고 막전극합체로 구동상에서 측정되었다. 상대습도 증가에 따라 막 내 물 함량이 증가하였고 물 함량 증가에 따라 이온전도도도 상승하였다. 전류밀도 증가에 따라 전기삼투와 역확산에 의한 물의 양이 증가해 물 함량이 선형적으로 증가하였고 그 결과 전류밀도 증가에 따라 이온전도도가 선형적으로 상승하였다. 온도가 $50^{\circ}C$에서 $80^{\circ}C$C로 증가함에 따라 이온전도도는 약 40% 증가하였다.

• 한국재료학회지
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• 제31권2호
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• pp.68-74
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• 2021

Zinc-ion Batteris (ZIBs) are recently being considered as energy storage devices due to their high specific capacity and high safety, and the abundance of zinc sources. Especially, ZIBs can overcome the drawbacks of conventional lithium ion batteris (LIBs), such as cost and safety issues. However, in spite of their advantages, the cathode materials under development are required to improve performance of ZIBs, because the capacity and cycling stability of ZIBs are mainly influenced by the cathode materials. To design optimized cathode materials for high performance ZIBs, a novel manganese oxide (MnO2) coated graphite sheet is suggested herein with improved zinc-ion diffusion capability thanks to the uniformly decorated MnO2 on the graphite sheet surface. Especially, to optimize MnO2 on the graphite sheet surface, amounts of percursors are regulated. The optimized MnO2 coated graphite sheet shows a superior zinc-ion diffusion ability and good electrochemical performance, including high specific capacity of 330.8 mAh g-1 at current density of 0.1 A g-1, high-rate performance with 109.4 mAh g-1 at a current density of 2.0 A g-1, and remarkable cycling stability (82.2 % after 200 cycles at a current density of 1.0 A g-1). The excellent electrochemical performance is due to the uniformly decorated MnO2 on the graphite sheet surface, which leads to excellent zinc-ion diffusion ability. Thus, our study can provide a promising strategy for high performance next-generation ZIBs in the near future.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.159-160
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• 2012

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.193-193
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• 2011

Strong adhesion of a silicon carbide (SiC) coating to a WC-Co substrate was achieved through an ion beam mixing technique and the corrosion resistance of the SiC coated WC-Co was investigated by means of a potentiodynamic electrochemical test. In a 1 M NaOH solution, the corrosion current density of SiC-coated WC-Co after heat treatment at 500$^{\circ}C$ was about 50 times lower than that for the as-received WC-Co. In addition, the corrosion resistance systematically increases with increasing the SiC coating thickness. On the other hand, for a 0.5 M H2SO4 solution, the corrosion current density for SiC-coated WC-Co was about 3 times lower than that for the as-received WC-Co. We discuss the physical reasons for the changes in the corrosion current density with the different electrolytes.

• Journal of Power Electronics
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• 제13권1호
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• pp.31-39
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• 2013

The conventional non-isolated boost converter has some drawbacks such as poor dynamic performance and a discontinuous output current, which make it unsuitable for battery charging applications. In spite of its compactness and lightness, it is not preferred as a charger of portable electronic devices. In this paper, a non-isolated boost converter topology for Li-ion batteries suitable for fuel cell powered laptop computers is proposed and analyzed. The proposed converter has an additional inductor at the output to make a continuous output current. This feature makes it suitable for charger applications by eliminating the disadvantages of the conventional non-isolated boost converter mentioned above. A prototype of the proposed converter is built for the Li-ion battery charger of a laptop computer to prove the validity and advantages of the proposed topology.

• Bulletin of the Korean Chemical Society
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• 제24권7호
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• pp.937-942
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• 2003

The relaxation phenomena of ionic currents through the charged membrane under the constant applied potentials has been studied. The formulation was obtained for the non stationary current by assuming that the ion mobility is independent of concentration and the potential gradient is a constant within membrane, and it was applied to the experimental results with the sulfonated polystyrene collodion base membrane. It has been shown that the initial ion distributions in the membrane play a predominant role in the relaxation phenomena.

• Journal of Power Electronics
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• 제16권1호
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• pp.268-276
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• 2016

A hybrid sinusoidal-pulse current (HSPC) charging method for the Li-ion batteries in electric vehicle applications is proposed in this paper. The HSPC charging method is based on the Li-ion battery ac-impedance spectrum analysis, while taking into account the high power requirement and system integration. The proposed HSPC method overcomes the power limitation in the sinusoidal ripple current (SRC) charging method. The charger shares the power devices in the motor inverter for hardware cost saving. Phase shifting in multiple pulse currents is employed to generate a high frequency multilevel charging current. Simulation and experimental results show that the proposed HSPC method improves the charger efficiency related to the hardware and the battery energy transfer efficiency.

• 전기화학회지
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• 제24권4호
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• pp.93-99
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• 2021

스트레처블 에너지 저장 장치 경량화를 위해 금속 집전체를 대체할 경량 물질 개발에 대한 관심이 높아지고 있다. 본 연구에서는 전도성 고분자인 PEDOT:PSS를 전기방사법으로 제조한 나노 섬유를 리튬이온전지용 집전체로 사용하였다. 나노 섬유는 도펀트인 DMSO를 사용해 향상된 전기 전도성을 나타냈으며, 신축성 평가결과로 부터 30% 이상의 신축률을 보여주었다. 또한, 나노 섬유 집전체를 사용함으로써 액체 전해질의 침투가 용이하며, 나노 섬유 네트워크를 통해 전자전도성을 높이는 효과를 나타났었다. DMSO 도핑 PEDOT:PSS@PAM 나노 섬유 필름 집전체를 사용한 리튬이온전지는 135mAh g^-1의 높은 방전용량을 보여주었으며, 1000 사이클 이후 73.5%의 높은 용량 유지율을 나타내었다. 따라서, 전도성 나노 섬유의 우수한 전기화학적 안정성과 기계적 특성은 신축성 에너지 저장 장치의 경량 집전체로서의 활용이 가능함을 보여주었다.

• 대한수의학회지
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• 제38권2호
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• pp.280-289
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• 1998

Voltage-sensitive ion channels contribute to establishment of the cell excitablity and the generation of the cellular function. At hamster oocytes in the primitive stage during developing process, an inward current elicited by voltage pulses was found to be carried mainly by $Ca^{2+}$. Even at present, $Ca^{2+}$ channels serve as the most probable route to pass this inward current but there is no evidence of the presence of this channels in eggs. To date, both the characteristic properties and the physiological role in the early stage of development remain unclear. Here we examined the characteristic properties of the inward current and changes in this currents at unfertilized oocytes, fertilized zygotes and two-cell embryos using whole-cell voltage clamp technique. The inward current carried reportedly by $Ca^{2+}$ was remained following removing external $Ca^{2+}$ but completely abolished by further replacement of impermeants such as tetramethylammonium ion ($TMA^+$) or $choline^+$ instead of $[Na^+]_0$. Tetrodotoxin did not affect on this inward current remained at $[Ca^{2+}]_0$-free condition. Removal of $Na^+$ ion out of the experimental solution clearly decreased the current. After adding 2mM $Ca^{2+}$ to the $Na^+$-free media, the inward current was restored. Interestingly, this current carried by either $Ca^{2+}$ or $Na^+$ was decreased by the reduction of intracellular $Cl^-$ concentration, or by $Cl^-$ channel blockers such as niflumic acid, DIDS and SITS. When $Cl^-$ concentration was lowered without changes in other ionic components, this inward current was reduced. At fertilized oocytes and two-cell embryos, the inward current carried by $Ca^{2+}$ and $Na^+$ was severely reduced. Also $Cl^-$ component could not be observed. From these results, the inward current is composed of $Ca^{2+}$, $Na^+$ and $Cl^-$ component, suggesting that the channel carrying this inward current is not selective specifically to $Ca^{2+}$. During early stage of development, the voltage-sensitive ion current seems not to contribute essentially to the cell cleavage and differentiation. The loss of $Cl^-$ component after fertilization suggests that $Cl^-$ may play a role in maintaining the viability of unfertilized ova.

• Journal of Electrical Engineering and Technology
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• 제6권4호
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• pp.556-562
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• 2011

In the present study, a simple corona-wire charger for unipolar diffusion charging of aerosol particles is designed, constructed, and characterized. Experimental characterizations of the electrostatic discharge in terms of current-voltage relationships of positive and negative coronas of the corona-wire charger are also presented and discussed. The charging current and ion concentration in the charging zone increased monotonically with corona voltage. The negative corona showed higher current than the positive corona. At the same corona voltages, the current in the discharge zone is about 600 times larger than the charging current. The ion number concentrations ranged within approximately $5.0{\times}10^{10}$ to $1.24{\times}10^{16}$ and $4.5{\times}10^{12}$ to $2{\times}10^{16}$ ions/$m^3$ in the discharge and charging zones, respectively. A numerical model is used to predict the behavior of the electric potential lines. Numerical results of ion penetration through the inner electrode are in good agreement with the experimental results.