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배문기 ( Mun Ki Bae ),김태규 ( Tae Gyu Kim ) 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.2
The crystal grains of polycrystalline diamond vary depending on deposition conditions and growth thickness. The diamond thin film deposited by the CVD method has a very rough growth surface. On average, the surface roughness of a diamond thin film deposited by CVD is in the range of 1-100 um. However, the high surface roughness of diamond is unsuitable for application in industrial applications, so the surface roughness must be lowered. As the surface roughness decreases, the scattering of incident light is reduced, the heat conduction is improved, the mechanical surface friction coefficient can be lowered, and the transmittance can also be improved. In addition, diamond-coated cutting tools have the advantage of enabling ultra-precise machining. In this study, the surface roughness of diamond was improved by thermal diffusion reaction between diamond carbon atoms and ferrous metals at high temperature for diamond thin films deposited by MPCVD. (Received March 4, 2021; Revised March 15, 2021; Accepted March 19, 2021)
표면개질에 의한 헤테로에피텍시 단결정 다이아몬드의 결정성 향상
배문기 ( Mun Ki Bae ),김민수 ( Min Su Kim ),김성우 ( Seong Woo Kim ),윤수종 ( Su Jong Yoon ),김태규 ( Tae Gyu Kim ) 한국열처리공학회 2020 熱處理工學會誌 Vol.33 No.3
Recently, many studies on growth of single crystal diamond using MPECVD have been conducted. The heteroepitaxial method is one of the methods for growing diamonds on a large-area substrate, and research on synthesis of single crystal diamonds using SrTiO<sub>3</sub>, MgO, and sapphire substrates has been attempted. In addition, research is being conducted to reduce the internal stress generated during diamond growth and to improve the crystallinity of the diamond. The compressive stress generated therein causes peeling and bowing from the substrate. This study aimed to synthesize heteroepitaxial single crystal diamonds with high crystallinity by surface modification. A diamond thin film was first grown on a sapphire/Ir substrate by MPECVD, and then etched with H<sub>2</sub> gas to modified the morphology and roughness of the surface. A secondary diamond layer was grown on the surface, and the internal stress, crystallinity of the diamond were investigated. As a result, the fabrication of single crystal diamonds with improved crystallinity was confirmed. (Received May 10, 2020; Revised May 15, 2020; Accepted May 22, 2020)
HFCVD에 의한 증착압력 변화에 따른 Single Crystal Diamond 합성
김민수 ( Min Su Kim ),배문기 ( Mun Ki Bae ),김성우 ( Seong-woo Kim ),김태규 ( Tae Gyu Kim ) 한국열처리공학회 2020 熱處理工學會誌 Vol.33 No.1
Single crystal diamonds are in great demand in such fields as mechanical, electronic applications and optoelectronics. Large area single crystal diamonds are attracting attention in future industries for mass production and low cost. In this study, hot filament CVD (HFCVD) is used to grow large area single crystal diamond. However, the growth rate of large area single crystal diamond using HFCVD is known to be very low. The goal of this study is to use single crystal diamond substrates in HFCVD with methane-hydrogen gas mixtures to increase the growth rate of single crystal diamond and to optimize the conditions by analysing the effects of deposition conditions for high quality crystallinity. The deposition pressure, the ratio of CH<sub>4</sub> / H<sub>2</sub> gas, the substrate temperature and the distance between the filament and the substrate were optimized. The sample used a 4×4 (mm<sup>2</sup>) size single crystal diamond substrate (100), the CH<sub>4</sub> / H<sub>2</sub> gas ratio was fixed at 5%, the substrate temperature was synthesized to about 1000℃. At this time, the deposition pressure was changed to three types of 50, 75, 85 Torr and deposited. Finally, optimization was investigated under pressure conditions to analyse the growth rate and quality of single crystal diamond. (Received January 8, 2020; Revised January 17, 2020; Accepted January 22, 2020)
임호기 ( Ho Gi Lim ),배문기 ( Mun Ki Bae ),김태규 ( Tae Gyu Kim ) 한국열처리공학회 2016 熱處理工學會誌 Vol.29 No.6
High temperature alloy steel such as Ni-Cr-Mo-V material has excellent properties of high strength and high heating resistance. It has been used for several military weapon components such as gun barrel of a warship, turbine rotor and turbine disk for nuclear power plant. Being curious about this material required excellent wear resistance and durability in extreme environmental conditions. A dry wear test at the ambient air and Ar gas conditions in the room temperature were performed in this study. What`s more a lubricant wear test at different temperature was conducted. In addition that DLC was coated on Ni-Cr-Mo-V alloy steel substrate with a thickness of 3 μm, a property of it was compare with lubricant conditions. All the coefficient of friction and wear volume, comparing with DLC coated specimens. The test parameters were selected as follows: 10 N for normal load; 80 rpm for sliding wear speed; and 300 m for the sliding wear distance. (Received October 7, 2016; Revised October 21, 2016; Accepted November 4, 2016)