• 한국초전도ㆍ저온공학회논문지
• /
• 제11권1호
• /
• pp.1-4
• /
• 2009

Mechanical and electrical properties of silver stabilizer layer of coated conductor, which as prepared with nano silver paste as starting materials, have been investigated, Nano silver paste was coated on a YBCO film by dip coating process at a diping speed of 20m/min. Coated film was dried in air and heat treated at $400{\sim}700^{\circ}C$ in an oxygen atmosphere. Adhesion strength between YBCO and silver layer was measured by a tape est(ASTM D 3359). Hardness and electrical conductivity of the samples were measured by pencil hardness test (ASTM D 3363) and volume resistance test by LORESTA-GP (MITSHUBISHD, respectively. The sample heat-treated at $500^{\circ}C$ showed poor adhesion 1B, but samples heat treated at higher than $600^{\circ}C$ showed enhanced adhesion of 5B. The silver layer heat-treated at $700^{\circ}C$ showed the high hardness value larger than 9 H, low volume resistance, surface resistance value as well as superior current carrying capacity compared to sputtered silver. SEM observations showed that a dense silver layer was formed with a thickness of about $2{\mu}m$. Dip coated silver layer prepared by using nano silver paste showed superior electrical and mechanical characteristics.

• 동력기계공학회지
• /
• 제19권6호
• /
• pp.12-18
• /
• 2015

Austenitic stainless steels generally experience the occurrence of chromium-depleted zones at the boundaries, known as sensitization, caused by the carbide precipitation that takes place due to a welding process or heat treatment. Normally, the depleted zones become the focus of the intense corrosion. In this study, the Cr-free organic/inorganic hybrid solution was developed, and the artificially degraded STS316S and STS347H with the solution-coating investigated the corrosion resistance by salt spray test. Both the OIBD-1 and OIBD-2 solutions improved the corrosion resistance of STS310S and STS347H. The corrosion resistance with the OIBD-1 solution was better than that of OIBD-2 solution. Additionally, Both solutions have been proven excellence in adhesion ability, boiling water resistance and flexibility. However, a problem of rubbing after the boiling was found out to be overcome.

• 한국표면공학회지
• /
• 제32권1호
• /
• pp.31-42
• /
• 1999

The effect was investigated that aluminium in the zinc bath has on the coating adhesion of Hot-rolled Galvanized Iron(HGI) manufactured without pickling process. It is thought that the coating adhesion of HGI manufactured without pickling process is good due to the fact that increasing aluminium content in the zinc bath makes zinc and aluminium diffuse to the cracks or pores in the scale formed through the reduction heat treatment, and Fe-Zn-Al compound with good ductility is formed in the scale layer and plays a role of anchor between zinc coating and substrate. It is possible that HGI with the good coating adhesion was produced without pickling treatment in the zinc bath with more that 3wt% of Al content even at the $550^{\circ}C$ of conventional reduction heating temperature. In creasing the temperature of heating section and aluminium content in the zinc bath prevents the Zn-Fe alloy. The corrosion resistance of HGI manufactured without pickling process is excellent because of the mixed reaction of zinc sacrifice and aluminium passivity film.

• 한국재료학회지
• /
• 제7권1호
• /
• pp.76-80
• /
• 1997

용융탄산염 연료전지 분리판의 wet-seal부의 내식성 향상을 위한 NiAl 피복공정이 조사되었다. AlSl 316 스테인레스강위에 Ni과 Al를 순차적으로 피복한 후, $800^{\circ}C$에서 3시간 열처리하여 NiAl상이 형성됨을 확인할 수 있었다. NiAl상이 피복된 스테인레스강은 $650^{\circ}C$, 용융탄산염($62^{m}/_{o}Li_2CO_3-38^{m}/_{o}/K_{2}CO_{3}$)내에서 침지시험을 통해 내식성이 평가되었는데, AISI 316 스테인레스강에 비해 우수한 내식성을 보였다. 이는 표면에 치밀하게 형성된 AI 산화물층에 의한 것으로 판단되었다.

• 한국재료학회지
• /
• 제19권12호
• /
• pp.649-656
• /
• 2009

Inorganic oxide colloids dispersed in alcohol were applied to a stainless steel substrate to produce oxide coatings for the purpose of minimizing emissive thermal transfer. The microstructure, roughness, infrared emissive energy, and surface heat loss of the coated substrate were observed with a variation of the nano oxide sol and coating method. It was found that the indium tin oxide, antimony tin oxide, magnesium oxide, silica, titania sol coatings may reduce surface heat loss of the stainless steel at 300${\circ}C$. It was possible to suppress thermal oxidation of the substrate with the oxide sol coatings during an accelerated thermal durability test at 600${\circ}C$. The silica sol coating was most effective to suppress thermal oxidation at 600${\circ}C$, so that it is useful to prevent the increase of radiative surface heat loss as a heating element. Therefore, the inorganic oxide sol coatings may be applied to improve energy efficiency of the substrate as the heating element.

• 한국산학기술학회논문지
• /
• 제11권2호
• /
• pp.608-613
• /
• 2010

본 연구는 건축용 바닥재로 널리 이용되는 PVC 상재의 표면을 열에 의한 손상으로부터 보호하기 위하여 기존에 사용하는 광경화형 우레탄-아크릴 수지에 내열성(anti-cigar burning)을 향상시킨 광경화형 수성도료 개발에 관한 것이다. PVC 바닥상재용으로 사용되는 내열기능성이 없는 우레탄-아크릴 수지에 인계화합물을 주원료로 합성한 내열재, 구아니딘을 주원료로 합성한 내열재, 일시적 방염제로 사용되는 제 2인산암모늄을 수지의 양 대비 함량(wt%)을 10, 20, 30%로 변화하여 첨가한 후 배합하여 수지의 내열성을 향상시킨 코팅액을 제조하였다. 제조한 코팅액은 코팅층의 두께조절이 가능한 Bar-coating을 사용하여 PVC 바닥상재에 코팅한 후, 내열성, 부착력, 내화학성, 코팅두께 등의 코팅층 표면물성을 평가하였다. 연구결과, 수지에 인계화합물을 주원료로 합성한 내열재 30%를 혼합하여 제조한 코팅액을 Bar-coater No.12로 코팅한 코팅표면이 열에 의한 손상이 가장 적고, 부착력 100%, 내화학성 양호로 가장 좋은 물성을 보였다. 전반적으로 내열재 함량이 높고, 코팅 두께가 두꺼울수록 내열성이 우수한 것으로 나타났다.

• Advances in materials Research
• /
• 제8권4호
• /
• pp.275-293
• /
• 2019

The engine parts material used in gas turbines (GTs) should be resistant to high-temperature variations. Thermal barrier coatings (TBCs) for gas turbine blades are found to have a significant effect on prolonging the life cycle of turbine blades by providing additional heat resistance. This work is to study the performance of TBCs on the high-temperature environment of the turbine blades. It is understood that this coating will increase the lifecycles of blade parts and decrease maintainence and repair costs. Experiments were performed on the gas turbine blade to see the effect of TBCs in different combinations of materials through the air plasma method. Three-layered coatings using materials INCONEL 718 as base coating, NiCoCrAIY as middle coating, and La₂Ce₂O₇ as the top coating was applied. Finite element analysis was performed using a two-dimensional method to optimize the suitable formulation of coatings on the blade. Temperature distributions for different combinations of coatings layers with different materials and thickness were studied. Additionally, three-dimensional thermal stress analysis was performed on the blade with a commercial code. Results on the effect of TBCs shows a significant improvement in thermal resistance compared to the uncoated gas turbine blade.

• 한국응용과학기술학회지
• /
• 제30권4호
• /
• pp.672-678
• /
• 2013

Although the basalt fiber has superior fire-resistance and chemical resistance, it has many disadvantages in its applications. Generally, the tensile and loop strengths of basalt fiber were decreased with generated frictional heat during industial appplications. To solve this problem, polytetrafluoroethylene (PTFE) coating system was introduced and a sutable coating condition was evaluated. The basalt fiber was pre-treated with triethoxytrifluoropropylsilane (TMTFPS) at various pHs and then coated with PTFE dispersions with penetrating agent sodium bis(2-ethylhexyl)sulfo succinate (DOS-Na) to increase the tensile and loop strengths as well as to reduce the fibril during working. A universial testing machine (Instron Model 3366) was used to measure tensile and loop strengths. When the PTFE dispersion with 0.25 wt% of DOS-Na was coated on the surface of basalt fiber after pre-treating with 5 wt% of PTFE, the highest tensile and loop strengths were reached to 3.5 gf/D and 2.4 gf/D, respectively.

• 한국재료학회지
• /
• 제27권9호
• /
• pp.471-476
• /
• 2017

In order to improve the high temperature oxidation resistance and lifespan of mat type porous carbon insulation, SiC was coated on carbon insulation by solution coating using polycarbosilane solution, curing in an oxidizing atmosphere at $200^{\circ}C$, and pyrolysis at temperatures up to $1200^{\circ}C$. The SiOC phase formed during the pyrolysis process was converted into SiC crystals as the heat treatment temperature increased, and a SiC coating with a thickness of 10-15 nm was formed at $1600^{\circ}C$. The SiC coated specimen showed a weight reduction of 8.6 % when it was kept in an atmospheric environment of $700^{\circ}C$ for 1 hour. On the other hand, the thermal conductivity was 0.17 W/mK, and no difference between states before and after coating was observed at all.

• 연구논문집
• /
• 통권25호
• /
• pp.193-205
• /
• 1995

Plasma 용사 코팅 기술은 전자산업과 정보산업의 기초인 Micro 반도체 산업의 기능성 목적으로 응용되고 있으며, 항공기 등의 첨단산업에서 디젤엔진이나 가스터빈 등 응용 범위를 점차 확대하고 있는 실정이다. 또한 첨단요소 부품에 적용하여 내마모성, 내열성, 내피로성, 내부식성 등을 부여하고 있다. 기능성 부품에 후처리하여 제품의 부가가치를 향상시킬 수 있어, Plasma 용사 코팅기술의 중요성은 날로 증대되고 있는 실정이다. 본 연구에서는 Plasma 용사 기술을 이용하여 코팅을 형성 내마모시험을 통해 국내 첨단요소 부품에 기능성 부여과 낙후된 용사 기술을 향상시키는 데 있다.