• 한국재료학회지
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• 제14권6호
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• pp.443-450
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• 2004

Parylene polymer thin film shows excellent homogeneous coverage chracteristics when it was deposited onto very complex three dimensional solid matters, such as deep hole and micro crack. The parylene deposition process can be conducted at room temperature although most of chemical vapor deposition processes request relatively high processing temperature. Therefore, the parylene coating process does not induce any thermal problems. Parylene thin film is transparent and has extremly high chemical stability. For example, it shows high chemical stability with high reactive chemical solutions such as strong acid, strong alkali and acetone. The bio-stability of this material gives good chances to use for a packaging of biomedical devices and electronic devices such as display. In this review article, principle of deposition process, properties and application fields of parylene polymer thin film are introduced.

• Journal of Welding and Joining
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• 제13권2호
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• pp.132-138
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• 1995

Rene80 superalloy was liquid phase diffusion bonded by using boron(B) as an insert material, where B has high diffusivity and higher melting point as an insert material. Bonding procedure and bonding mechanism of Rene80/B/Rene80 joint were investigated. As results, liquid metal was produced by solid state reaction between base metal and insert material on bonding zone. The liquid metal was produced preferentially at the grain boundary. Except for production of liquid metal, other bonding procedure was nearly same as TLP(Transient Liquid Phase) bonding. Bonding time, however, was reduced compared to prior result of TLP bonding. By bonding S.4ks at l453K, Ren80/B/Rene80 joint was isothermally solidified and homogenized where thickness of insert material was 7.5.mu.m.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2008년도 추계학술발표논문집
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• pp.107-122
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• 2008

종이의 도공액이 고농도화 됨에 따라 도공액의 유동학적 특성에 대한 연구가 더욱 더 중요시 되고 있다. 기존의 합성 증점제의 경우는 단순히 증점 보수제의 기능을 가지고 있으므로 고농도/고속 도공시 블레이드하에서 점탄성적인 성질 중 팽윤에 의한 탄성의 성질이 더 강하게 남아있게 되어 다양한 도공 트러블의 원인이 될 수 있다. 최근에는 이러한 단점을 개선하기 위한 표면 흡착형 유동성 조절제가 소개되고 있다. 따라서 본 연구에서는 알카리 팽윤형 합성 증점제와 표면 흡착형 유동성 개량제로 업계에 알려진 2종의 유동성 조절제가 고농도 도공액의 점탄성적인 유동특성에 미치는 영향성을 검토하였고, PDA(Penetration Dynamic Analyzer) 모듈을 이용하여 원지에 흡수되는 흡수 거동을 관찰하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2007년도 추계학술대회 논문집
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• pp.75-76
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• 2007

ZnS:Cu,Cl phosphor was coated by solid-gel reaction with $SiO_2$ outside layer. The effect of $Cu^{2+}$-doping concentration has been investigated on the luminescence characteristics of ZnS:Cu,Cl blue-green phosphors for inorganic electro luminescent device. Also, SiO2 coated layers' effect on luminescence characteristics. Evaluation of luminescence characteristics dependent on the synthesis conditions is important to get high-performance phosphors properties. EL and PL properties such as luminescence intensity and chromaticity of ZnS:Cu,Cl phosphors synthesized with different concentration of activator, $Cu^{2+}$, were analysed separately

• 센서학회지
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• 제15권2호
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• pp.148-152
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• 2006

This paper describes the fabrication of SiCN microstructures for super-high temperature MEMS using photopolymerization of pre-ceramic polymer. In this work, polysilazane liquide as a precursor was deposited on Si wafers by spin coating, microstructured and solidificated by UV lithography, and removed from the substrate. The resulting solid polymer microstructures were cross-linked under HIP process and pyrolyzed to form a ceramic of withstanding over $1400^{\circ}C$. Finally, the fabricated SiCN microstructures were annealed at $1400^{\circ}C$ in a nitrogen atmosphere. Mechanical characteristics of the SiCN microstructure with different fabrication process conditions were evaluated. The elastic modules, hardness and tensile strength of the SiC microstructure implemented under optimum process condtions are 94.5 GPa, 10.5 GPa and 11.7 N/min, respectively. Consequently, the SiCN microstructure proposed in this work is very suitable for super-high temperature MEMS application due to very simple fabrication process and the potential possiblity of sophisticated mulitlayer or 3D microstructures as well as its good mechanical properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.392-393
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• 2006

This paper describes the fabrication of SiCN microstructures for super-high temperature MEMS using photopolymerization of pre-ceramic polymer. In this work. polysilazane liquide as a precursor was deposited on Si wafers by spin coating. microstructured and solidificated by UV lithography. and removed from the substrate. The resulting solid polymer microstructures were cross-linked under HIP process and pyrolyzed to form a ceramic of withstanding over $1400^{\circ}C$. Finally, the fabricated SiCN microstructures were annealed at $1400^{\circ}C$ in a nitrogen atmosphere. Mechanical characteristics of the SiCN microstructure with different fabrication process conditions were evaluated. The elastic modules. hardness and tensile strength of the SiC microstructure implemented under optimum process conditions are 94.5 GPa, 10.5 GPa and 11.7 N/min, respectively. Consequently, the SiCN microstructure proposed in this work is very suitable for super-high temperature MEMS application due to very simple fabrication process and the potential possiblity of sophisticated multlayer or 3D microstructures as well as its good mechanical properties.

• 한국재료학회지
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• 제29권11호
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• pp.684-689
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• 2019

Single crystals, which have complexed composition, are fabricated by solid state grain growth. However, it is hard to achieve stable properties in a single crystal due to trapped pores. Aerosol deposition (AD) is suitable for fabrication of single crystals with stable properties because this process can make a high density coating layer. Because of their unique features (nano sized grains, stress inner site), it is hard to fabricate single crystals, and so studies of grain growth behavior of AD film are essential. In this study, a $BaTiO_3$ coating layer with ${\sim}9{\mu}m$ thickness is fabricated using an aerosol deposition method on (100) and (110) cut $SrTiO_3$ single crystal substrates, which are adopted as seeds for grain growth. Each specimen is heat-treated at various conditions (900, 1,100, and $1,300^{\circ}C$ for 5 h). $BaTiO_3$ layer shows different growth behavior and X-ray diffraction depending on cutting direction of $SrTiO_3$ seed. Rectangular pillars at $SrTiO_3$ (100) and laminating thin plates at $SrTiO_3$ (110), respectively, are observed.

• 한국재료학회지
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• 제20권7호
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• pp.356-363
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• 2010

For this paper, we investigated the area specific resistance (ASR) of commercially available ferritic stainless steels with different chemical compositions for use as solid oxide fuel cells (SOFC) interconnect. After 430h of oxidation, the STS446M alloy demonstrated excellent oxidation resistance and low ASR, of approximately 40 $m{\Omega}cm^2$, of the thermally grown oxide scale, compared to those of other stainless steels. The reason for the low ASR is that the contact resistance between the Pt paste and the oxide scale is reduced due to the plate-like shape of the $Cr_2O_3$(s). However, the acceptable ASR level is considered to be below 100 $m{\Omega}cm^2$ after 40,000 h of use. To further improve the electrical conductivity of the thermally grown oxide on stainless steels, the Co layer was deposited on the stainless steel by means of an electroless deposition method; it was then thermally oxidized to obtain the $Co_3O_4$ layer, which is a highly conductive layer. With the increase of the Co coating thickness, the ASR value decreased. For Co deposited STS444 with 2 ${\mu}m$hickness, the measured ASR at $800^{\circ}$ after 300 h oxidation is around 10 $m{\Omega}cm^2$, which is lower than that of the STS446M, which alloy has a lower ASR value than that of the non-coated STS. The reason for this improved high temperature conductivity seems to be that the Mn is efficiently diffused into the coating layer, which diffusion formed the highly conductive (Mn,Co)$_3O_4$ spinel phases and the thickness of the $Cr_2O_3$(S), which is the rate controlling layer of the electrical conductivity in the SOFC environment and is very thin

• 한국결정성장학회지
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• 제31권6호
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• pp.282-286
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• 2021

Laser-carburized TiZrN 코팅의 침탄 공정에서 탄소 페이스트 두께에 따른 탄소의 침투 깊이 및 압축잔류응력 변화를 탄소 포텐셜 측면으로 비교·고찰하였다. 스크린 프린팅과 스핀 코팅 방법을 이용하여 각각 1.1 mm와 0.4 mm의 두께로 탄소 페이스트를 도포하고, 동일한 레이저 조사 조건에서 레이저 침탄을 실시하였다. 탄소 페이스트가 두꺼워질수록 침탄된 TiZrN 시료의 회절 패턴이 더 저각으로 이동하였으며, 고용체 강화 및 격자 왜곡의 심화를 나타내었다. TEM을 이용한 미세구조 분석에서도 두꺼운 페이스트로부터 침탄된 TiZrN 내 결정질 결함이 증가하고 높은 탄소 농도를 보였으며, 이는 페이스트 두께가 두꺼워질수록 탄소 포텐셜도 높아짐을 의미하였다. XPS depth profile 분석에서도 두꺼운 페이스트를 통해 침탄된 TiZrN 시료에서 높은 탄소 농도 및 탄화물 형성을 보이면서, 탄소 페이스트 두께 조절에 의해 침탄에서 표면 탄소농도와 탄소 포텐셜 증가가 일어남을 나타내었다. 아울러, 탄소 농도의 증가는 표면의 압축잔류응력 증가(3.67 GPa에서 4.58 GPa로)에 기여하였음을 확인하였다.

• 공업화학
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• 제7권5호
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• pp.902-912
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• 1996

여러 가지의 고체산 촉매에 의한 1-펜텐의 골격이성화 반응에서 반응활성, 선택도, 반응메카니즘 및 촉매의 산의 세기와 촉매활성과의 관계를 연구하였다. 여러 가지의 고체산 촉매중에서 천연제올라이트가 가장 높은 활성을 보여주었고, 불소나 황산으로 처리된 ${\eta}$-알루미나는 변형되지 않은 경우에 비해 활성이 크게 증가하였다. 한편 반응온도가 증가할수록 이소펜텐의 수율이 증가하였고, 접촉시간의 증가에 따라 이소펜텐의 수율이 증가하였다. 그러나 높은 반응온도와 아주 긴 접촉시간에서는 크래킹 반응의 생성물이 증가하였다. 금속이온으로 치환된 천연제올라이트에서의 활성은 감소하였고, 이것은 금속이온의 polarizing power와 관계가 있는 것으로 나타났다. 암모니아 승온탈착실험 결과에 의하면 촉매의 활성은 촉매의 산의 세기와 밀접한 관계가 있는 것으로 나타났다.