• 한국세라믹학회지
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• 제56권1호
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• pp.65-70
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• 2019

Simple fabrication of a powdered Ge-reduced graphene oxide (Ge-rGO) composite via spray pyrolysis and reduction is introduced herein. Successful incorporation of the rGO nanosheets with Ge hindered the aggregation of Ge and conferred enhanced structural stability to the composite by alleviating the mechanical stress associated with drastic volume changes during repeated cycling. The Li-ion storage performance of Ge-rGO was compared with that of powdered Ge metal. The reversible discharge capacity of Ge-rGO at the $200^{th}$ cycle was $748mA\;h\;g^{-1}$ at a current density of $1.0A\;g^{-1}$ and Ge-rGO showed a capacity of $375mA\;h\;g^{-1}$ even at a high current density of $5.0A\;g^{-1}$. The excellent performance of Ge-rGO is attributed to the structural robustness, enhanced electrical conductivity, and formation of open channels between the rGO nanosheets, which facilitated electrolyte penetration for improved Li-ion diffusion.

• 전기화학회지
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• 제11권4호
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• pp.297-303
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• 2008

구연산과 에틸렌 글리콜이 함유된 분무용액으로부터 분무열분해 공정에 의해 미세한 $LiNiO_2$ 분말들을 합성하였다. 마이크론 크기를 가지는 구형 형상 및 다공성의 전구체 분말들은 $800^{\circ}C$에서의 후열처리 후에 마이크론 크기 및 균일한 형태를 가지는 $LiNiO_2$ 분말로 전환되었다. 분무용액에 첨가된 구연산 및 에틸렌 글리콜의 농도가 0에서 1 M 까지 증가할 때 $LiNiO_2$ 분말들의 초기 방전 용량은 199 mAh/g 에서 171 mAh/g 까지 감소하였다. 구연산과 에틸렌 글리콜을 함 유한 분무용액으로부터 합성된 $LiNiO_2$ 분말은 리튬의 첨가량이 양론비보다 6 mol% 과량일 때 198 mAh/g의 최대 초기 방전 용량을 가졌다. 미세한 $LiNiO_2$ 분말은 0.1 C 의 전류 밀도하에서 30회 충방전 후에 방전 용량이 198 mAh/g 에서 163 mAh/g 으로 감소하였다.

• 한국통신학회논문지
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• 제40권5호
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• pp.974-980
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• 2015

해양환경 하에서 강재에 대한 방식 목적으로 Al-3%Mg 용사선재를 이용하여 아크 용사코팅을 실시하였다. 그리고 Al-3%Mg 용사코팅 층의 내식성을 개선하기 위하여 유/무기 복합 세라믹 후처리를 실시하였다. 후처리 적용에 따른 용사코팅 층의 다양한 전기화학적 실험 결과, 양극분극과 음극분극 실험 시 모든 전위구간에서 후처리 적용 시 전류밀도가 작게 나타나 내식성 개선이 확인되었다. 그리고 후처리된 용사코팅 층의 표면에서 관찰된 마이크로 크랙의 영향으로 자연전위 계측 시 심한 전위변동이 나타났으며, 양극분극 실험 시에는 후처리 층의 탈리손상이 용이하게 발생하였다. 그럼에도 불구하고 타펠분석을 기반으로 외부 환경차단 효과를 나타내는 코팅 효율이 92.11%로 산출되어 Al-3%Mg 용사코팅 층의 내식성이 향상되었다.

• 한국결정성장학회지
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• 제29권6호
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• pp.359-364
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• 2019

서스펜션 플라즈마 스프레이 법은 미세한 분말을 용사 공정에 적용함으로써 전통적인 플라즈마 스프레이 법의 단점을 극복하고자 개발된 코팅법이다. 본 연구에서는 고밀도의 Y₂O₃ 코팅막을 제조하기 위해 서스펜션 플라즈마 스프레이법을 이용하여 플라즈마 건의 전류량과 총 가스 유량을 공정변수로 하여 코팅막을 제조하였으며, 그에 따른 코팅막 특성에 대한 연구를 하였다. 코팅막의 미세구조 및 물리적 특성 평가 결과 플라즈마 건 전류량 200 A, 총 가스 유량 220 L/min의 조건에서 층상 결함 없이 0.2 vol%의 매우 낮은 기공률을 갖는 고밀도의 Y₂O₃ 코팅막을 제조할 수 있었다.

• 한국표면공학회지
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• 제27권1호
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• pp.12-18
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• 1994

The plasma spray process was used to deposit coatings of $ZrO_2$-8wt%Y2O3 powders on mild steel sub-strate, and the characteristics of as-deposited and heat treated coatings have been investigated. Particulary, the variations of porosity, wear resistance, thermal barrier and thermal shock resistance in $ZrO_2$-8wt% $Y_2O_3$coatings after heat treatment under vacuum circumstance have been investigated. The porosity of the coating layer was increased with increased spray distance. In the case of the arc current of 450A and at the spray distance of 50mm, it was obtained the lowest amount of porosity. After heat treatment, the amount of porosity was found to be decreased, and the wear resistance, microhardness and thermal shock resistance were im-proved. However, the thermal barrier was decreased.

• Current Photovoltaic Research
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• 제3권2호
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• pp.61-64
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• 2015

In solar industry, numerous researchers reported about cold spray method among various electrode formation technic, but there are no known a bonding mechanism of metal powder. In this study, a cross-section of copper electrode formed by cold spray method was observed and heterogeneous phase between silicon substrate and copper electrode was analyzed using morphology observation technic. SEM and TEM analysis were performed to analyze a crystallinity and distribution shape of heterogeneous copper phase. Molecular dynamics simulation was performed to calculate glass transition temperature of copper metal. In the result, amorphous copper phase was observed near interface between silicon substrate and metal electrode. The results of the molecular dynamics simulation show that an amorphous copper phase could be formed at a temperature below the melting point of copper because cold spraying resulted in a lower glass transition temperature.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.16-22
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• 2004

Dimethyl Ether (DME) has been considered as one of the most attractive alternative fuels for a compression ignition engine. The major advantage of DME-fuelled engine is a great potential for soot-free combustion without sacrificing an inherent high thermal efficiency of diesel engine, despite a necessity for modification of the conventional fuel injection system. An experimental study on DME and conventional diesel sprays was conducted by employing a common-rail type fuel injection system with a 5-holes sac type nozzle, including a constant volume vessel pressurized with nitrogen gas. The injection rates of DME and diesel fuel were recorded with the Bosch type injection rate meter. The injection delay of DME was shorter than that of diesel fuel. The measured injection rates of DME and diesel fuel were correlated with spray penetrations. The prediction method of spray penetration was established using the injection rates, which was verified with the Dent's penetration model and found to agree well for DME case.

• 전기학회논문지
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• 제60권1호
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• pp.85-92
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• 2011

Main characteristic in railroad is the guided movement of the wheel by the track through a metal-to-metal contact, conferring to the rail vehicle a single degree of freedom. There are defects such as head check, shelling, corrugation, squats etc in surface of the rail by interface between the wheel and rail. These defects bring about reducing the life-cycle of rails and track components and increasing noises. In case of bad conditions, it is possible to happen to full-scale accident such as derailment. Recently, the track capacity has been increased for increasing speed and operation efficiency. So, maintenance and indirect cost have been increased. Currently, a coating method of rail construction is proposed by using the ceramics in Korea. Rails are used as the earth in electrical railroad systems. Currently traction return current is flowed through wheels of trains. In case of rails coated, problems are caused in the contact power between wheel and coating material of spray. In this paper, electric model is presented in the AT feeding method. In case of rails coated, electric model is presented. Also, standard resistance of the ceramic is demonstrated by contact power between wheel and coating material of spray.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2011년도 춘계학술대회 및 Fine pattern PCB 표면 처리 기술 워크샵
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• pp.196-197
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• 2011

Rudder, one of the most important component in the marine vessel, is now being decreased life time to serve due to cavitation erosion, vortex current, high flow speed suffer from ship speed going up dramatically. In this study, 10 kinds of thermal spray coating materials(2 of Zn alloy series, 3 of Al alloy series, 3 of Cu alloy series, 2 of STS alloy series) are chosen to apply on specimens and analyze micro structure, metallic composition, properties(porosity, oxidation) by using visual observation, XRD, EDX etc.. Additionally, to refine the characteristic of corrosion endurance for thermal spray coating layer, compared with thermal spray process and 5 kinds of heavy duty painting and AC paint (Anti-Corrosion Paint). Based on above mentioned experimental results, a priority of all coated specimens on corrosion-erosion endurances finalized and summarized there by desirable composition and process of thermal sprayed material properly.

• Journal of Biosystems Engineering
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• 제29권1호
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• pp.21-28
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• 2004

Spraying is one of the most efficient methods for pesticide and insecticide control. Generally, orchard sprayers(aircarrier sprayer) are used for such applications. However, when an orchard sprayer is used, only 20% of total amount of spray deposits on the target. The rest of spray are not only wasted but are also potential sources of environmental pollution. The research far the development of electrostatic spraying system for orchard sprayer was conducted to develop the new pesticide application technology for the reduction of environmental pollution and f3r the production of safe agricultural products. The spray characteristics for nozzles with the different charging methods were tested and the effect of electrostatic charge was analyzed, in the laboratory experiments. The results of this study indicate that the capacitive type of electrostatic spraying nozzle exhibits a large current deposition of water sprays on the sample target. The covering area ratio by conventional spraying system was 10.2%, while that of electrostatic sprays with pulse induction charging method gave the increased covering area ratio by 4.3 times.