• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.78-83
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• 2014

In this research, we evaluated the performance and characteristics of carbon supported PtM (M = Ni and Y) alloy catalysts (PtM/Cs) synthesized by a modified polyol method. With the PtM/Cs employed as a catalyst for the oxygen reduction reaction (ORR) of cathodes in proton exchange membrane fuel cells (PEMFCs), their catalytic and ORR activities and electrical performance were investigated and compared with those of commercial Pt/C. Their particle sizes, particle distributions and electrochemically active surface areas (EAS) were measured by TEM and cyclic voltammetry (CV), while their ORR activity and electrical performance were explored using linear sweeping voltammetries with rotating disk electrodes and rotating ring-disk electrodes as well as PEMFC single cell tests. TEM and CV measurements show that PtM/Cs have the compatible particle size and EAS with Pt/C. When it comes to ORR activity, PtM/C showed the equivalent or better half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production(%) to or than commerical Pt/C. Based on results gained by the three electrode tests, when the PEMFC single cell tests were carried out, the current density measured at 0.6 V and maximum power density of PEMFC single cell adopting PtM/C catalysts were better than those adopting Pt/C catalyst. It is therefore concluded that PtM/C catalysts synthesized by modified polyol can result in the equivalent or better ORR catalytic capability and PEMFC performance to or than commercial Pt/C catalyst.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.30-37
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• 1989

The PIN type a-SiC:H/a-Si:H heterojunction solar cells were fabricated by using the rf glow discharge decomposition of $SiH_4$ mixed with $CH_4,B_2,H_6\;and\;PH_3.$ The efficiency of the solar cell of the $SnO_2/ITO$ was higher than that of ITO transparent oxide layer by 1.5%. The P layer was prepared with the thickness of $100{\AA}$ and $CH_4/SiH_4$ ration of 5. The I layer has been deposited on the P layer and it is not pure intrinsic but near N type. So $SiH_4$ mixed with $B_2H_6$ of 0.3ppm was used to change this N type nature to intrinsic having the thickness of 5000${\AA}$. And consecutively, the N layer was deposited with t ethickness of $400{\AA}$ using $SiH_4/PH_3$ mixtures. The solar cell demonstrated 0.94V of $V_{oc'}$ 14.6mA/cm of $J_{sc}$ and 58.2% of FF, resulting the efficiency of 8.0%. To minimize loss by the reflection of light, $MgF_2$ layer was coated on the lgass and the efficiency was improved by 0.5%. Therefore, the solar cell indicated overall efficiency of 8.5%.

• Korean Journal of Materials Research
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• v.27 no.10
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• pp.518-523
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• 2017

In commercial solar cells, the pattern of the front electrode is critical to effectively assemble the photo generated current. The power loss in solar cells caused by the front electrode was categorized as four types. First, losses due to the metallic resistance of the electrode. Second, losses due to the contact resistance of the electrode and emitter. Third, losses due to the emitter resistance when current flows through the emitter. Fourth, losses due to the shading effect of the front metal electrode, which has a high reflectance. In this paper, optimizing the number of finger on a $4{\times}4$ solar cell is demonstrated with known theory. We compared the short circuit current density and fill factor to evaluate the power loss from the front metal contact calculation result. By experiment, the short circuit current density($J_{sc}$), taken in each pattern as 37.61, 37.53, and $37.38mA/cm^2$ decreased as the number of fingers increased. The fill factor(FF), measured in each pattern as 0.7745, 0.7782 and 0.7843 increased as number of fingers increased. The results suggested that the efficiency(Eff) was measured in each pattern as 17.51, 17.81, and 17.84 %. Throughout this study, the short-circuit current densities($J_{sc}$) and fill factor(FF) varied according to the number of fingers in the front metal pattern. The effects on the efficiency of the two factors were also investigated.

• Journal of the Korean Vacuum Society
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• v.11 no.3
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• pp.183-188
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• 2002

In the present study AI$(CH_3)_3)$films were deposited by the ALD technique using trimethylaluminum(TMA) and ozone to improve the quality of the AI$(CH_3)_3)$ films, since the $OH^-$ radicals existing in the AI$(CH_3)_3)$ films deposited using TMA and $H_2O$ degrade the physical and the dielectric properties of the AI$(CH_3)_3)$ film. The XPS analysis results indicate that the $OH^-$ radical concentration in the AI$(CH_3)_3)$film deposited using $O_3$is lower than that using $H_2O$. The etch rate of the AI$(CH_3)_3)$film deposited using $O_3$is also lower than that using $H_2O$, suggesting that the chemical inertness of the former is better than the latter. The MIS capacitor fabricated with the TiN conductor and the $Al_2$O$_3$dielectrics formed using $O_3$offers lower leakage current, better insulating property and smaller flat band voltage shift $({\Delta}V_{FB})$.

• Journal of the Korean Vacuum Society
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• v.9 no.4
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• pp.315-320
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• 2000

We have investigated the crystal structure and electrical properties of Pt/SBT/$ZrO_2$/Si (MFIS) and Pt/SBT/Si (MFS) structures for the gate oxide of ferroelectric memory. XRD spectra and SEM showed that the SBT film of SBT/$ZrO_2$/Si structure had larger grain than that of SBT/Si structure. $ZrO_2$ film between SBT film and Si substrate is confirmed as a good candidate for a diffusion barrier by the analysis of AES. The remanent polarization decreased and coercive voltage increased in Pt/SBT/$ZrO_2$/Pt/$SiO_2$/Si structure. This effect may increase memory window of MFIS structure directly related to the coercive voltage. From the capacitance-volt-age characteristics, the memory windows of Pt/SBT (210 nm)/$ZrO_2$ (28 nm)/Si structure were in the range of 1~l.5 V at the applied voltage of 4~6 V. The current densities of Pt/SBT/ZrO$_2$/Si with as -deposited Pt electrode and annealed at $800^{\circ}C$ in $O_2$ambient were $8\times10^{-8} A/\textrm{cm}^2$ and $4\times10^{-8}A/\textrm{cm}^2$ , respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.559-559
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• 2013

KSTAR (Korea Superconducting Tokamak Advanced Research) 장치는 차세대 에너지원 중의 하나인 핵융합로를 위한 과학기술 기반을 마련하기 위해 개발된 중형급 토카막 실험장치로서 토카막 운전 영역의 확장과 안정성 확보, 정상상태 운전 도달을 위한 방법 연구, 최적화된 플라즈마 상태와 연속 운전 실현 등을 주요 목표로 하고 있다. 이를 위해 핵융합 반응에 의한 점화조건과 가까운 상태로 플라즈마를 가열해주어야 하며, 토카막 장치의 저항가열 이외에도 외부에서 추가 가열이 반드시 필요하다. 중성 입자빔 입사 장치는 현재 토카막에서 사용되고 있는 가열장치 중 가장 신뢰성있는 추가 가열 장치라 할 수 있으며 한국 원자력연구원에서는 1997년부터 KSTAR 토카막 실험 장치에 사용될 중성 입자빔 입사 장치를 개발해왔었다. 중성빔 입사 장치는 크게 이온원, 진공함, 열량계, 진공 펌프, 중성화 장치, 이온덤프와 전자석으로 이루어져 있으며, 이중 이온원은 중성빔의 성능을 좌우하는 핵심적인 장치라 할 수 있다. 최근 한국원자력연구원에서는 2 MW 중성 입자빔 입사장치용 이온원 개발을 완료하여 KSTAR 토카막 장치에 설치하였으며, 2013년 현재 KSTAR에는 총 두 개의 이온원이 장착되어 최대 약 3 MW 이상의 중수소 중성 입자빔을 입사하여 KSTAR 토카막 실험의 H-mode 달성과 운전 시나리오 연구에 많은 기여를 하고 있다. 한국원자력연구원에서 최초로 개발된 이온원은 미국 TFTR 장치에서 사용되었던 US LPIS (Long Pulse Ion Source)를 기본으로 하여 국내 개발을 수행하였다. 이 온원은 크게 플라즈마를 발생시키는 플라즈마 발생부와 발생된 이온을 인출 및 가속시키는 가속부로 구성되는데, 개발과정에서 가장 먼저 KSTAR의 장주기 운전에 적합하도록 플라즈마 방전부와 가속부의 냉각회로를 요구되는 열부하에 맞게 설계 수정하였다. 그 후 플라즈마 방전부는 방전 시간과 안정성, 플라즈마 밀도의 균일도, 정격 운전, 방전 효율 등을 고려하여 수정 보완하며 개발을 진행하여왔다. 가속부의 경우 국내 제작기술의 한계를 극복하기 위해 빔 인출그리드를 TFTR의 US LPIS 모델의 슬릿형 그리드 타입에서 원형 인출구 타입으로 변경하였으며, 이후 가속 전극의 고전압 내전력 문제, 빔 인출 전류와 전력, 인출 빔의 광학적 질(quality), 빔 인출 시간 동안의 안정성 등을 위해 그리드의 크기와 간격, 모양 등을 변경하여 개발을 수 행하여 왔다. 이 논문은 한국원자력연구원에서 개발이 진행되어 왔던 이온원들을 시간적으로 되짚어 보면서 현재까지의 성과와 문제점, 그리고 앞으로의 개발 방향에 대해 논의하고자 한다.

• Korean Journal of Materials Research
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• v.11 no.5
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• pp.339-344
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• 2001

An all solid-state thin film supercapacitor (TFSC) with Co$_3$O$_4$/LiPON/Co$_3$O$_4$ structure was fabricated on Pt/Ti/Si substrate using Co$_3$O$_4$ thin film electrode. Each Co$_3$O$_4$ film was grown by reactive dc reactive magnetron sputtering with increasing $O_2$/[Ar+O$_2$] ratio. Amorphous LiPON electrolyte film was deposited on Co$_3$O$_4$/Pt/Ti/Si in pure nitrogen ambient by using reactive rf magnetron sputtering. The electrochemical behavior of the Co$_3$O$_4$/LiPON/Co$_3$O$_4$ multi-layer structures exhibits a behavior of a bulk-type supercapacitor, even though much lower capacity (from 5 to 25 mF/$\textrm{cm}^2$-$\mu\textrm{m}$) than that of the bulk one. It was found that the TFSC showed a fairly constant discharge capacity with a constant current of 50 $\mu\textrm{A}/\textrm{cm}^2$ at the cut-off voltage 0-2V during 400 cycles. It is shown that the electrochemical behavior of the Co$_3$O$_4$/LiPON/Co$_3$O$_4$ TFSC is dependent upon the sputtering gas ratio. The capacity dependency of electrode films on different gas ratios was explained by different structural, electrical, and surfacical properties.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.727-731
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• 2008

Mesoporous Pt-Au alloy films were successfully fabricated on ITO-coated glass by electrodeposition method using tri-blockcopolymer (P123) as a templating agent. The electrolyte consisted of 10 mM hydrogen hexachloroplatinate ($H_2PtCl_6$), 10 mM hydrogen tetrachloroaurate ($HAuCl_4$), and proper amount of P123. For comparison, control samples were electrodeposited without $HAuCl_4$ and P123. Film composition was determined by EDS(Energy Dispersive X-ray Spectroscopy), and the mesoporous structure was confirmed by TEM(Transmission Electron Microscopy). SEM(Scanning Electron Microscopy) was utilized to examine surface morphology, and it was observed that the addition of P123 affected the particle growth, resulting in the significant change of surface morphology. Methanol oxidation and CO oxidation were carried out to investigate electrocatalytic activities of synthesized samples. It was observed that the catalytic activity was strongly dependent on the film compositions. Compared with nonporous electrode prepared without P123 templating, mesoporous films prepared with P123 templating showed much higher catalytic activities and stability for both methanol oxidation and CO oxidation. These enhanced electrocatalytic activities were due to the high surface area and facilitated charge transfer of mesoporous films.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.861-867
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• 2019

$Li_4Ti_5O_{12}$ is a promising next-generation anode material for lithium-ion batteries due to excellent cycle life, low irreversible capacity, and little volume expansion during charge-discharge process. However, it has poor charge capacity at high current density due to its low electrical conductivity. To improve this weakness, porous $Li_4Ti_5O_{12}$ was synthesized by sol-gel method with P123 as chelating agent. The physical characteristics of as-prepared sample was investigated by XRD, SEM, and BET analysis, and electrochemical properties were characterized by cycle performance test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS). $Li_4Ti_5O_{12}$ synthesized by 0.01mol ratio of P123/Ti showed most unified particle size, high specific surface area, and relatively high porosity. EIS analysis showed that depressed semicircle size was remarkably reduced, which suggested resistance value in electrode was decreased. Capacity in rate performance showed 178 mAh/g at 0.2C, 170 mAh/g at 0.5C, 110 mA/h at 5C, and 90 mAh/g at 10C. Capacity retention also showed 99% after rate performance.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.574-581
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• 2022

Nanofibers comprising reduced graphene oxide (rGO) and Mo₂C/Mo₂N nanoparticles (Mo₂C/Mo₂N rGO NFs) were prepared for a functional interlayer of Li-S batteries (LSBs). The well-dispersed Mo₂C and Mo₂N nanoparticles in the nanofiber structure served as active polar sites for efficient immobilization of dissolved lithium polysulfide. The rGO nanosheets in the structure also provide conductive channels for fast ion/electron transport during charging-discharging and ensured reuse of lithium polysulfide during redox reactions through a fast charge transfer process. As a result, the cell assembled with Mo₂C/Mo₂N rGO NFs-coated separator and pure sulfur electrode (70 wt% of sulfur content and 2.1 mg cm^-2 of sulfur loading) showed a stable discharge capacity of 476 mA h g^-1 after 400 charge-discharge cycles at 0.1 C. Furthermore, it exhibited a discharge capacity of 574 mA h g^-1 even at a high current density of 1.0 C. Therefore, we believe that the proposed unique nanostructure synthesis strategy could provide new insights into the development of sustainable and highly conductive polar materials as functional interlayers for high performance LSBs.