• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2573-2576
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• 2013

Rate capability and cyclability of $LiMn_2O_4$ should be improved in order to use it as a cathode material of lithium-ion batteries for hybrid-electric-vehicles (HEV). To enhance the rate capability and cyclability of $LiMn_2O_4$, it was coated with $MnV_2O_6$ by a sol-gel method. A $V_2O_5$ sol was prepared by a melt-quenching method and the $LiMn_2O_4$ coated with the sol was heat-treated to obtain the $MnV_2O_6$ coating layer. Crystal structure and morphology of the samples were examined by X-ray diffraction, SEM and TEM. The electrochemical performances, including cyclability at $60^{\circ}C$, and rate capability of the bare and the coated $LiMn_2O_4$ were measured and compared. Overall, $MnV_2O_6$ coating on $LiMn_2O_4$ improves the cyclability at high temperature and rate capability at room temperature at the cost of discharge capacity. The improvement in cyclability at high temperature and the enhanced rate capability is believed to come from the reduced contact between the electrode, and electrolyte and higher electric conductivity of the coating layer. However, a dramatic decrease in discharge capacity would make it impractical to increase the coating amount above 3 wt %.

• 한국전기전자재료학회논문지
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• 제27권8호
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• pp.528-534
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• 2014

Thermal batteries are primary reserve batteries that use inorganic salt as electrolytes which are inactive at room temperature. The two principal heat sources that have been used in thermal batteries are heat paper and heat pellets. As soon as the heat paper, which is ignited by the initiator, in turn ignites the heat pellets, all the solid electrolytes are melted into excellent ionic conductors. However, the high combustion temperature by heat papers in thermal batteries causes thermal decomposition at the cathode, eventually leading to a thermal runaway. In this paper, we have attempted to prepare $Zr/BaCrO_4$ heat papers coated with KCl molten salt. We have also investigated the effect of a molten salt coating on the heat papers through the thermal characteristics such as calorimetric value, combustion temperature and burning rate. The calorimetric value and combustion temperature of heat papers were reduced with an increase in the molten salt coating. As a result, the molten salt coating on heat papers greatly reduced risk of a thermal runaway and improved the stability of thermal batteries.

• Journal of Electrochemical Science and Technology
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• 제10권2호
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• pp.196-205
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• 2019

Ni-rich layered oxides $Li(Ni_xCo_yMn_z)O_2$ (x + y + z = 1) have been extensively studied in recent times owing to their high capacity and low cost and can possibly replace $LiCoO_2$ in the near future. However, these layered oxides suffer from problems related to the capacity fading, thermal stability, and safety at high voltages. In this study, we use surface coating as a strategy to improve the thermal stability at higher voltages. The uniform and conformal $Al_2O_3$ coating on prefabricated electrodes using atomic layer deposition significantly prevented surface degradation over prolonged cycling. Initial capacity of 190, 199, 188 and $166mAh\;g^{-1}$ is obtained for pristine, 2, 5 and 10 cycles of ALD coated samples at 0.2C and maintains 145, 158, 151 and $130mAh\;g^{-1}$ for high current rate of 2C in room temperature. The two-cycle $Al_2O_3$ modified cathode retained 75% of its capacity after 500 cycles at 5C with 0.05% capacity decay per cycle, compared with 46.5% retention for a pristine electrode, at an elevated temperature. Despite the insulating nature of the $Al_2O_3$ coating, a thin layer is sufficient to improve the capacity retention at a high temperature. The $Al_2O_3$ coating can prevent the detrimental surface reactions at a high temperature. Thus, the morphology of the active material is well-maintained even after extensive cycling, whereas the bare electrode undergoes severe degradation.

• 한국표면공학회지
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• 제5권3호
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• pp.77-85
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• 1972

A method of preparation of synthetic ignorgaic coating on copper (patina) has been presented . An Eh--pH diagram was constructed for the present Cu-H2O-SO$_4$ system using the most recently available thermodynamic data. In the path of the patination at room temperature the general behaviour of copper in acidic copper sulfate solutions with potassium chlorate as an oxidizing agent appeared to follow those predictable in this Eh-pH diagram. In the presence 0.05 molar cupric sulfate at a temperature of about 28$^{\circ}C$ a green brochantite (CuSO$_4$$.$3Cu(OH)$_2$) layer was formed on copper sheet in 20 days. In a solution having an initial pH of 3.5 the development of a brochantite coating has been observed to take place in two stages. In the first, a layer of cuprous oxide formed on the copper at a relatively rapid rate. In the ensuing step the outer layer of cuptrite was oxidized at much slower rate to form brochantite. The syntetic coatings appeared to consist of crystal-lites of brochanitite growing perpendicular to the cuprose oxide surface. The outer tips of the -crystallites were reasily broken off and gave to the layer a rather chalky character. Underneath, at the brochantite Cu$_2$O interface, however, the green layers were firmely attached. The effect of reagent concentration , solution agitation , and moderate temperature increase were investigated to improve the quality of coating. So also in a qualitative way were the effect of light.

• 한국태양에너지학회 논문집
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• 제36권5호
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• pp.1-8
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• 2016

In this paper, we evaluated the effect of a silica-based Anti-Reflection(AR) coating for PV modules. The coating technique can be easily applied to large-scale PV modules at room temperature with improvements of the optical properties that is qualified by the optical transmission measurements on the coated cover glass of the modules. The power improvement of the large-scale PV modules shows the increasing about 2.4% at standard condition of the coating technique on average. To improve the AR coating effect of the PV modules, we have characterized the individual PV modules by the measurements of DC power output, modified performance ratio(PRm) and the regression. The results show that the significant improvements of the AR coating effect are 6.4%, 5.5% and 4.5% of increasing of the performances by using the measurements of DC power output, modified performance ratio(PRm) and the regression, respectively.

• Tribology and Lubricants
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• 제15권1호
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• pp.39-45
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• 1999

The wear behavior of $Al_2$O$_3$-40%TiO$_2$deposited on casted aluminum alloy (ASTM A356) by APS (Air Plasma Spray) against SiC ball has been investigated in this work. Wear tests were carried out at room temperature. The friction coefficient of $Al_2$O$_3$-40%TiO$_2$coating is lower than that of pure $Al_2$O$_3$coating(APS). $Al_2$O$_3$-40%TiO$_2$coating indicated the existence of the optimal coating thickness. It is found that voids and pores of coating surface resulted in the generation of cracks, and the cohesive of splats and the porosity of surface play a role in wear characteristics. It is suggested that the mismatch of thermal expansion of substrate and coating play an important role in wear performance. Tension and compression under thermo-mechanical stress may be occurred by the mismatch between thermal expansion of substrate and coating. The crack propagation above interface is observed in SEM.

• 한국안전학회지
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• 제18권3호
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• pp.14-21
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• 2003

This study deals with the influence of ceramic coating on characteristics of friction and abrasion of aluminum allot(7075 T6) used in mechanical casting. In this research, frictional wear characteristic of ceramic coating materials such as $A1_2O_3$, $Si_3N_4$, SiC was investigated using aluminum alloy(7075 T6) and stainless 403 cast iron under room temperature and normal air pressure. The coating layer was observed using SEM. The conclusions are as follows: 1) Friction coefficients of $A1_2O_3$, SiC and $Si_3N_4$ are obtained 0.63 0.56 and 0.54 respectively. 2) Abrasion resistance of stainless 403 cast iron with $Si_3N_4$ is the best among the ceramic coating materials. 3) Abrasion mechanism of aluminum alloy(7075 T6) coaled with ceramic material and stainless 403 cast iron is caused by brittle fracture. 4) Coating the ceramic material on the aluminum alloy(7075 T6) can effectively increase the antiwear, impact properties, and corrosion resistance.

• 한국식품영양과학회지
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• 제44권2호
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• pp.260-267
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• 2015

본 연구에서는 장용성 연질캡슐 코팅가소제로서 PEG(polyethylene glycol)의 활용가능성에 대하여 알아보고자 PEG의 분자량 및 첨가 농도에 따른 코팅 품질을 확인하였으며, 기존에 보고된 가소제인 AMG(acetylated monoglyceride)와 triacetin을 사용하여 코팅된 장용성 연질캡슐의 품질 특성을 비교하였다. PEG 분자량(400, 4,000, 6,000)에 따른 코팅 품질에는 큰 차이가 없었으나 PEG 첨가 농도의 경우 고형분 대비 5% PEG를 사용한 코팅에서는 연질캡슐 피막 접착부에서 코팅 필름 갈라짐이 발생하였으며, PEG 첨가량이 낮을수록 인공장액에서의 붕해시간이 연장되고 백색도가 증가하는 결과를 나타내었다. 용출시험에서 용출의 초기 구간(30~90분)에서는 PEG의 용출 속도가 상대적으로 빠른 모습을 나타내었으며, PEG, AMG 및 triacetin 간의 유의적 차이가 일부 시점에서 관찰되었으나 전체적인 용출 양상은 큰 차이를 보이지 않았다. 또한 PEG 코팅에 비해 AMG와 triacetin 코팅의 경우 백색도가 유의적으로 높았고 가속조건인 고온다습한 환경에서 2개월간 보관 후에 코팅 필름이 갈라졌으며, 붕해시험에서 부적합한 결과를 확인하였다. 결론적으로 우수한 물리 화학적 특성으로 의약품 등에 널리 사용되는 첨가제인 PEG는 장용성 연질캡슐 코팅 가소제로서 활용가능성이 충분하다고 판단하였다.

• Tribology and Lubricants
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• 제26권3호
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• pp.162-166
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• 2010

The purpose of this study is to show the friction and wear characteristics on the vapor deposited Tiseries coating layers on the SCM415 steel. In this research, frictional wear characteristic of coating materials such as TiN, TiCN, TiAlN was investigated under room temperature, normal air pressure and dry lubricating condition. Therefore this study carried out research on the friction coefficient, micro hardness(Hv), roughness, SEM on the vapor deposited coating layers on the SCM415 steel.

• KSTLE International Journal
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• 제6권2호
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• pp.45-50
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• 2005

Plasma ceramic spray that is applied on a machine part under severe work conditions has been investigated for tribological behavior. The application of ceramic coatings by plasma spray has become essential in tribosystems to produce wear resistance and long life in severe conditions. The purpose of this study was to investigate the wear characteristics of $8\%Y_{2}O_3-ZrO_2$ coating, in view of the effect of post-spay heat treatment. The plasma-sprayed $8\%Y_{2}O_3-ZrO_2$ coating was studied to know the relationship between phase transformations and wear behavior related to post-spray heat treatment. Wear test was carried out with ball on disk type on normal loads of 50N,70N and 90N under room temperature. The phase transformation of phase and the value of residual stress were measured by X-ray diffraction method(XRD). Tribological characteristics and wear mechanisms of coatings were observed by SEM. The tribological wear performance was discussed in the focusing of residual stress. Consequently, post-spray heat treatment plays an important role in decreasing residual stress. Residual stress in the coating system has a significant influence on the wear mechanism of coating.