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Effect of Post-N+Implantation on the Microstructure of the Interfacial Non-Cubic BN Layers
Byon, Eungsun,Lee, Sunghun,Kim, Jongkuk,Lee, Gunhwan,Han, Seunghee,Lee, Eungjik,Yoon, Jae-Hong,Lee, Sang-Ro 대한금속학회 2002 METALS AND MATERIALS International Vol.8 No.1
Plasma source ion implantation has been applied as a post treatment in order to modify the interfacial sp^2 bonded layer of the cubic BN (cBN) films. The effect of ion irradiation on the microstructure of the noncubic BN layer was investigated. From HRTEM observation, the thickness of the BN layer of the representative sample was about 100 nm including 15 nm of initially grown non-cubic layer at the interface between a substrate and the cubic layer. At optimal plasma source implantation conditions, an acceleration voltage of 50 keV and an ion dose of 2×10 exp(16) ions/㎠, the microstructure of the interfacial non-cubic BN layer was changed. It was noticed that the ion irradiation caused the recrystallization of the amorphous phase and transformed the small crystallites into another phase. The micro-hardness of the complex consisting of a hard and soft layer increased as a result of phase transformations. This was caused by atomic displacements in the initially grown amorphous and hexagonal layers. The atomic displacements calculated by the TAMIX code were in the range of 0.31∼0.52 nm per atom within 70∼100 nm in depth.
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.
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.