• 한국재료학회지
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• 제33권12호
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• pp.530-536
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• 2023

The theoretical capacity of silicon-based anode materials is more than 10 times higher than the capacity of graphite, so silicon can be used as an alternative to graphite anode materials. However, silicon has a much higher contraction and expansion rate due to lithiation of the anode material during the charge and discharge processes, compared to graphite anode materials, resulting in the pulverization of silicon particles during repeated charge and discharge. To compensate for the above issues, there is a growing interest in SiO_x materials with a silica or carbon coating to minimize the expansion of the silicon. In this study, spherical silica (SiO₂) was synthesized using TEOS as a starting material for the fabrication of such SiO_x through heating in a reduction atmosphere. SiO_x powder was produced by adding PVA as a carbon source and inducing the reduction of silica by the carbothermal reduction method. The ratio of TEOS to distilled water, the stirring time, and the amount of PVA added were adjusted to induce size and morphology, resulting in uniform nanosized spherical silica particles. For the reduction of the spherical monodisperse silica particles, a nitrogen gas atmosphere mixed with 5 % hydrogen was applied, and oxygen atoms in the silica were selectively removed by the carbothermal reduction method. The produced SiO_x powder was characterized by FE-SEM to examine the morphology and size changes of the particles, and XPS and FT-IR were used to examine the x value (O/Si ratio) of the synthesized SiO_x.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.3025-3032
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• 2012

Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a two step polymerization method. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were prepared with a wet-type beadsmill method. A polymer, which is easily removable by a thermal treatment (intermediate polymer) was polymerized on the outer surfaces of Si-CNT nanocomposites. Subsequently, another polymer, which can be carbonized by thermal heating (carbon precursor polymer) was incorporated onto the surfaces of pre-existing polymer layer. In this way, polymer precursor spheres containing Si-CNT nanohybrids were produced using a two step polymerization. The intermediate polymer must disappear during carbonization resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests.

• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.636-643
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• 2006

Si-C materials were synthesized by the heating the mixture of silicon and polyvinylidene fluoride (PVDF). The electrochemical properties of the Si-C materials as the high capacitive anode materials of lithium secondary batteries were evaluated by the galvanostatic charge-discharge test through 2032 type $Si-C{\mid}Li$ coin cells. Charge-discharge tests were performed at C/10 hour rate(C = 372 mAh/g). Initial discharge and charge capacities of $Si-C{\mid}Li$ cell using a Si-C material derived from PVDF(20wt.%) were found to be 1,830 and 526 mAh/g respectively. The initial discharge-charge characteristics of the developed Si-C electrode were analyzed by the electrochemical galvanostatic test adopting the capacity limited charge cut-off condition(GISOC). The range of reversible specific capacity IIE(intercalation efficiency at initial discharge-charge) and IICs(surface irreversible specific capacity) were 216 mAh/g, 68 % and 31 mAh/g, respectively.

• International Journal of Safety
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• 제11권2호
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• pp.5-9
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• 2012

The discharge properties of super high-pressure mercury lamp are due to resistance heating for energy input, and results in temperature increase. The cooling equilibrium state is reached by the heat conduction, convection and radiation. In order to predict the fluid flow and heat transfer in and around the mercury lamp accurately, its visualization is of utmost importance. Such visualization is carried out by CFD program in this study. We focus on Anode shape to calculate four cases, namely AA, AB, AC and AD separately, and compare the temperature distribution and velocity vector in each case to predict cooling capacity and fluid flow properties. It can be concluded that the shape of anode plays an important role that affects the fluid flow and heat transfer in a mercury lamp.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2396-2400
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• 2007

Transparent In-doped (1 at.%) zinc oxide (IZO) thin films are deposited by pulsed DC magnetron sputtering with H2 mixed Ar atmosphere on glass substrate without any heating process. Even at room temperature, highly c-axis oriented IZO thin films were grown in perpendicular to the substrate. The hydrogenated IZO (IZO:H) film isolated in H2 atmosphere for 30 min exhibited an average optical transmittance higher than 85% and low electrical resistivity of less than 2.7 × 10?3 Ω·cm. These values are comparable with those of commercially available ITO. Each of the IZO films was used as an anode contact to fabricate organic light-emitting diodes (OLEDs) and the device performances studied. At the current density of 1 × 103 A/m2, the OLEDs with IZO:H (H2) anode show excellent efficiency (11 V drive voltage) and a good brightness (8000 cd/m2) of the light emitted from the devices, which are as good as the control device built on a commercial ITO anode.

• 공업화학
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• 제35권1호
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• pp.37-41
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• 2024

열대성 과일로 널리 재배되고 있는 코코넛(coconut)의 독특한 껍질(shell)은 과육 섭취 후 얻어지는 부산물로 활용 가치가 클 것으로 기대된다. 이 코코넛 껍질을 전도성 고분자와 혼합하여 복합소재를 간단한 방식으로 제조하고 섭씨 600도 정도의 상대적 저온에서 탄화하여 수득되는 소재의 전기화학적 특성 및 활용 가능성을 고찰하였다. 먼저, 외형적 요소를 주사전자현미경(scanning electron microscope, SEM)으로 관찰하였다. 탄소의 미세구조를 라만(Raman) 분광 분석을 통하여 추론하였다. 전기전도 가능성을 간단한 옴의 관계(Ohmic relation)를 통하여 확인하였다. 나아가, 탄화된 재료가 리튬 이차 전지의 음극(anode) 소재로 활용될 수 있는지 여부를 반쪽 전지(half-cell) 충방전(charge/discharge) 테스트를 통해 살펴보았으며, 최대 충전 용량은 약 750 mAh로 높게 나타났으나, 충전이 진행됨에 따라 빠른 감소를 보였다. 본 연구는 향후 목질계 폐기물의 활용에 대한 중요한 정보를 제공할 것이다.

• 약학회지
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• 제37권1호
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• pp.76-83
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• 1993

The changes in discharge current, emission and/or oscillation frequency of the electric oscillation of a glow discharge are the potential sensitive measure of the concentration of an impurity in the argon plasma supporting gas. A single jet enhanced glow discharge has been interfaced with the gas chromatograph via 1/8" O.D. tube with a heating pad to study the changes in discharge current. To investigate the optimum operating conditions of the glow discharge system as detector for gas chromatography, pressure, gas flow rate, discharge current, distance between the anode and the cathode have been studied.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.350-351
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• 2005

The electrochemical behavior of Si-C material synthesized by heating the mixture of silicon and polyvinylidene fluoride (PVDF). Coin cells of the type 2025 were made using the synthesized material and the electrochemical studies were performed. Si-C/Li cells were made by using the developed Si-C material. Charge/discharge test was performed at 0.1C hour rate. Initial charge and discharge capacities at Si-C material derived from 20 wt.% of PVDF was found to be 1,830 and 526 mAh/g respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216 mAh/g at Si-C material derived from 20 wt.% of PVDF, IIE, intercalation efficiency at initial charge/discharge, was 68 %. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm*g.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.82.2-82.2
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• 2011

A channel design which is closely related with the mass transport overpotential is one of the most important procedures to optimize the whole fuel cell performance. In this study, three dimensional results of a numerical study for gas distribution in channels of a molten carbonate fuel cell (MCFC) unit cell for a 1kW class stack was presented. The relationship between the fuel and air distribution in the anode and cathode channels of the unit cell and the electric performance was observed. A charge balance model in the electrodes and the electrolyte coupled with a heat transfer model and a fluid flow model in the porous electrodes and the channels was solved for the mass, momentum, energy, species and charge conservation. The electronic and ionic charge balance in the anode and cathode current feeders, the electrolyte and GDEs were solved for using Ohm's law, while Butler-Volmer charge transfer kinetics described the charge transfer current density. The material transport was described by the diffusion and convection equations and Navier-Stokes equations govern the flow in the open channel. It was assumed that heat is produced by the electrochemical reactions and joule heating due to the electrical currents.

• 분석과학
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• 제8권4호
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• pp.583-590
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• 1995

Pitch-based mesophase carbon fibers prepared at different temperatures were heat-treated at temperatures lower than those of the preparation and the electrochemical Li doping/undoping characteristics were evaluated in relation to the data of IR, mass, etc. Presence of surface hydroxyls were confirmed by FTIR for lower temperature sample which showed poor anode characteristics. Upon oxidative heating, removal of surface hydroxyls took place, resulting in a remarkable improvement of the electrode characteristics. At the same time, surface roughening took place, which was confirmed by SEM and double layer capacity measurements. In situ mass spectra obesrved during the heat-treatments showed gas evolution of $H_2O$, CO, $CO_2$, $C_2H_4$, and/or $H_2$ depending on the conditions. These data together with those of weight loss and conductivity provided us a valuable information in regard to the evaluation of the electrochemical characteristics.