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Nb seeding이 Ag 박막 성장모드에 미치는 영향에 대한 열역학적인 고찰
변응선(Eungsun Byon),김동호(Dong-Ho Kim),전상조(Sang-Jo Jeon) 한국표면공학회 2007 한국표면공학회지 Vol.40 No.1
For low-emissivity application on window glass, coalescence of thin film silver islands is crucial for high transmittance in the visible and high reflectance in the infrared. It is well known that the underlayer affects the growth mode. In this work, the effect of the underlayer on the growth of silver films deposited by filtered cathodic vacuum arc is discussed. While a nominal 0.1 nm niobium underlayer has promoted the coalescence of silver islands, a 0.2 nm layer did not show these features. From a thermodynamic approach, Nb seeding less one monolayer is considered to reduce the surface energy between the silver atoms and Nb/TiO2 surface, resulting the change of its growth from 3D islands to 2D-layer modes. If the seed layer exceeds one monolayer, however, a rougher surface is formed because the surface energy of Nb itself is superior to that of Nb-TiO2. The onset of silver layer on the roughened Nb surface is required more silver.
열처리 조건에 따른 무전해 Ni/전해 Cr 이중도금의 계면반응 및 균열성장거동 분석
손기락,최명희,이규환,변응선,이병호,박영배,Son, Kirak,Choi, Myung-Hee,Lee, Kyu Hawn,Byon, Eungsun,Rhee, Byong-Ho,Park, Young-Bae 한국마이크로전자및패키징학회 2016 마이크로전자 및 패키징학회지 Vol.23 No.3
무전해 Ni/전해Cr이중도금 구조에서 무전해 Ni의 결정화 열처리 조건이 Cr도금의 균열성장 및 Ni/Cr계면반응에 미치는 영향을 분석하였다. 비정질 무전해 Ni/전해 Cr 도금 후 $750^{\circ}C$에서 6시간 동안 1회 열처리한 시편을1단계 열처리 조건으로 정했다. 또한, 무전해 Ni도금 후 동일 열처리를 통해 결정화 시킨 후, 전해 Cr도금 후 한번 더 동일조건 열처리한 경우를 2단계 열처리 조건으로 정하여 상호 비교하였다. 두 가지 열처리 조건 모두에서 공통적으로 Ni/Cr계면에서 상호확산에 의한 Ni-Cr고용체band layer가 관찰되었다. 1단계 열처리 조건의 경우 Cr도금에 관통균열이 발생하였으며, 2단계 열처리 조건의 경우 Cr도금에 표면 미소균열만 형성되고 관통균열은 거의 발생하지 않았다. 이는 무전해 Ni도금 직후 열처리에 의해 Ni-P비정질 구조에서 Ni, $Ni_3P$상으로 결정화되면서 급격한 체적 감소가 발생하여 Cr층의 잔류응력 완화에 영향을 끼쳐서, 상부 전해 Cr도금의 관통균열 형성에 영향을 미치는 것으로 판단된다. This study investigated the effect of heat treatment conditions not only on the Cr surface crack propagation behaviors but also on the Ni/Cr interfacial reaction characteristics in electroless Ni/electroplated Cr double coating layers on Cu substrate. Clear band layer of Ni-Cr solid solutions were developed at Ni/Cr interface after heat treatment at $750^{\circ}C$ for 6 h. Channeling cracks formed in Cr layer after 1 step heat treatment, that is, heat treatment after Ni/Cr plating, while little channeling cracks formed after 2 step heat treatment, that is, same heat treatments after Ni and Cr plating, respectively, due to residual stress relaxation due to crystallization of Ni layer before Cr plating.
서스펜션 진공 플라즈마 용사법을 통한 YSZ 코팅의 형성
유연우(Yeon Woo Yoo),변응선(Eungsun Byon) 한국표면공학회 2017 한국표면공학회지 Vol.50 No.6
As increasing thermal efficiency of the gas turbine, the performance improvement of thermal barrier coatings is also becoming important. Ytrria stabilized zirconia(YSZ) is the most popular materials for ceramic top coating because of its low thermal conductivity. In order to enhance the performance of thermal barrier coatings for hot sections in the gas turbine, suspension plasma spraying was developed in order to feed nano-sized powders. YSZ coatings formed by suspension plasma spraying showed better performance than YSZ coatings due to its exclusive microstructure. In this research, two YSZ coatings were deposited by suspension vacuum plasma spraying at 400 mbar and 250 mbar. Microstructures of YSZ coatings were analyzed by scanning electron image(SEM) on each spraying conditions, respectively. Crystalline structure transformation was not detected by X-ray diffraction. Thermal conductivity of suspension vacuum plasma sprayed YSZ coatings were measured by laser flash analysis. Thermal conductivity of suspension vacuum plasma sprayed YSZ coatings containing horizontally oriented nano-sized pores and vertical cracks showed 0.6-1.0 W/m·K, similar to thermal conductivity of YSZ coatings formed by atmospheric plasma spraying.
펄스형 진공 아크법에 의한 ZnO 박막의 상온합성 및 이의 전기적 특성에 미치는 산소분압비의 영향
신민근(Min-Geun Shin),변응선(Eungsun Byon),이성훈(Sunghun Lee),김도근(Do-Geun Kim),전상조(Sang-Jo Jeon),구본흔(Bon Heun Koo) 한국표면공학회 2005 한국표면공학회지 Vol.38 No.5
Highly c-axis oriented Zinc oxide (ZnO) films were successfully deposited at room temperature by oxygen ion-assisted pulsed filtered vacuum arc. The effect of oxygen gas ratio (O₂/O₂+Ar) on the preferred orientation, surface morphology and resistivity of the ZnO films were investigated. Highly crystalline ZnO films with (002) orientation were obtained at over 13% of oxygen gas ratio. Increasing oxygen gas ratio up to 80% was found to improve crystallinity of the films. From hall measurements, it was found that the film has n-type characteristic and carrier concentration and its mobility were closely related with oxygen gas ratio. Minimal resistivity of 3.6×10<SUP>-3</SUP> Ωㆍ㎝ was obtained in the range of 20% to 40% of oxygen gas ratio.
실링재 및 실링방법이 HVOF 용사된 CrC-NiCr 코팅의 내식성에 미치는 영향
정영훈(Younghun Jeong),남욱희(Uk-Hee Nam),변응선(Eungsun Byon),강태일(Tae-il Kang),강정윤(Chung-Yun Kang) 한국표면공학회 2014 한국표면공학회지 Vol.47 No.6
Effects of sealant and sealing procedure on corrosion resistance of high velocity oxy-fuel (HVOF) sprayed coatings were studied. HVOF-sprayed CrC-20NiCr coatings were sealed using three commercial sealants based on phenolics and epoxy. Penetration depth of sealants, measured by fluorescent microscope technique, was between 19 μm and 340 μm depending on sealant, sealing condition or sealing procedure. It was found that sealing on rotation status was more effective than that on stationary specimen due to the Coriolis effect of fluid in pores of the coating. From the CASS results, corrosion resistance of properly sealed CrC-20NiCr coatings was equal to that of hexa-valent chromium plating.
ZnO 박막의 전기적 구조적 특성에 미치는 수소 분압비의 영향
이성훈(Sunghun Lee),신민근(Min-Geun Shin),변응선(Eungsun Byon),김도근(Do-Geun Kim),전상조(Sang-Jo Jeon),구본혼(Bon Heun Koo) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.6
Effect of hydrogen partial pressure ratio on the structural and electrical properties of highly c-axis oriented ZnO films deposited by oxygen ion-assisted pulsed filtered vacuum arc at a room temperature was investigated. The hydrogen partial pressure ratio were 1.4%~9.8% at 40% oxygen pressure ratio. The conductivity of ZnO:H films was increased from 1.4% up to 4.2% due to relatively high carrier mobility caused by improvement of crystallinity. While the conductivity of ZnO:H films were decreased over than 4.2% and (0002) orientation was also deteriorated. The lowest resistivity of ZnO:H films was 2.5 × 10?³ Ωㆍ㎝ at 4.2% of hydrogen pressure ratio. Transmittance of ZnO:H films in visible range was 85% which is lower than that of undoped ZnO films because of declined preferred orientation.
열처리 시간에 따른 Ni-P/Cr 이중 도금 층의 계면 거동에 관한 연구
최명희(Myung-Hee Choi),박영배(Young-Bae Park),이병호(Byong-ho Rhee),변응선(Eungsun Byon),이규환(Kyu Hwan Lee) 한국표면공학회 2015 한국표면공학회지 Vol.48 No.6
The thermal barrier coating (TBC) for inner wall of liquid-fuel rocket combustor consists of NiCrAlY as bonding layer and ZrO₂ as a top layer. In most case, the plasma spray coating is used for TBC process and this process has inherent possibility of cracking due to large difference in thermal expansion coefficients among bonding layer, top layer and metal substrate. In this paper, we suggest crack-free TBC process by using a precise electrodeposition technique. Electrodeposited Ni-P/Cr double layer has similar thermal expansion coefficient to the Cu alloy substrate resulting in superior thermal barrier performance and high temperature oxidation resistance. We studied the effects of phosphorous concentrations (2.12 wt%, 6.97 wt%, and 10.53 wt%) on the annealing behavior (750℃) of Ni-P samples and Cr double layered electrodeposits. Annealing temperature was simulated by combustion test condition. Also, we conducted SEM/EDS and XRD analysis for Ni-P/Cr samples. The results showed that the band layers between Ni-P and Cr are Ni and Cr, and has no formed with heat treatment. These band layers were solid solution of Cr and Ni which is formed by interdiffusion of both alloy elements. In addition, the P was not found in it. The thickness of band layer was increased with increasing annealing time. We expected that the band layer can improve the adhesion between Cr and Ni-P.