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육방정 질화붕소 나노입자 합성 및 열전도성 복합체 응용
정재용,김양도,신평우,김영국,Jung, Jae-Yong,Kim, Yang-Do,Shin, Pyung-Woo,Kim, Young-Kuk 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.6
Much attention has been paid to thermally conductive materials for efficient heat dissipation of electronic devices to maintain their functionality and to support lifetime span. Hexagonal boron nitride (h-BN), which has a high thermal conductivity, is one of the most suitable materials for thermally conductive composites. In this study, we synthesize h-BN nanocrystals by pyrolysis of cost-effective precursors, boric acid, and melamine. Through pyrolysis at $900^{\circ}C$ and subsequent annealing at $1500^{\circ}C$, h-BN nanoparticles with diameters of ~80 nm are synthesized. We demonstrate that the addition of small amounts of Eu-containing salts during the preparation of melamine borate precursors significantly enhanced the crystallinity of h-BN. In particular, addition of Eu assists the growth of h-BN nanoplatelets with diameters up to ~200 nm. Polymer composites containing both spherical $Al_2O_3$ (70 vol%) and Eu-doped h-BN nanoparticles (4 vol%) show an enhanced thermal conductivity (${\lambda}{\sim}1.72W/mK$), which is larger than the thermal conductivity of polymer composites containing spherical $Al_2O_3$ (70 vol%) as the sole fillers (${\lambda}{\sim}1.48W/mK$).
BCl<sub>3</sub>-H<sub>2</sub>-Ar 분위기를 이용한 2단계 플라즈마 보로나이징 특성
남기석,이구현,신평우,송요승,김배연,이득용,Nam, Kee-Seok,Lee, Gu-Hyun,Shin, Pyung-Woo,Song, Yo-Seung,Kim, Bae-Yeon,Lee, Deuk-Yong 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.6
A two-step plasma-assisted boronizing process was carried out on the AISI 1045 steel substrate to reduce the pore density introduced by a conventional single plasma boronizing process. The specimens were plasma boronized for 1 h at $650^{\circ}C$ and subsequently far 7 h at $800^{\circ}C$ in an atmosphere of $BCl_3-H_2-Ar$. The boride layer thickness was parabolic in boronizing time, a high HV reading of 1540 was found up to the boride layer thickness of $25{\mu}m$. It was found that the morphology of the boride layer prepared by the two-step boronizing process was changed from a columnar to a tooth-like structure and the pores in the borided steel were eliminated completely in comparison to those synthesized by the conventional single boronizing process, implying that it is highly applicable for enhancing the dense and compact coating properties of the low-alloy steel.
고 안정성 전구체를 사용한 InP/ZnS 반도체 나노입자 합성 및 발광 특성 향상
이은진,문종우,김양도,신평우,김영국,Lee, Eun-Jin,Moon, Jong-Woo,Kim, Yang-Do,Shin, Pyung-Woo,Kim, Young-Kuk 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.6
We report a synthesis of non-toxic InP nanocrystals using non-pyrolytic precursors instead of pyrolytic and unstable tris(trimethylsilyl)phosphine, a popular precursor for synthesis of InP nanocrystals. In this study, InP nanocrystals are successfully synthesized using hexaethyl phosphorous triamide (HPT) and the synthesized InP nanocrystals showed a broad and weak photoluminescence (PL) spectrum. As synthesized InP nanocrystals are subjected to further surface modification process to enhance their stability and photoluminescence. Surface modification of InP nanocrystals is done at $230^{\circ}C$ using 1-dodecanethiol, zinc acetate and fatty acid as sources of ZnS shell. After surface modification, the synthesized InP/ZnS nanocrystals show intense PL spectra centered at the emission wavelength 612 nm through 633 nm. The synthesized InP/ZnS core/shell structure is confirmed with X-ray diffraction (XRD) and Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP-AES). After surface modification, InP/ZnS nanocrystals having narrow particle size distribution are observed by Field Emission Transmission Electron Microscope (FE-TEM). In contrast to uncapped InP nanocrystals, InP/ZnS nanocrystals treated with a newly developed surface modified procedure show highly enhanced PL spectra with quantum yield of 47%.
이동균(Dong kyun Lee),박상우(Sang woo Park),신평우(Pyung woo Shin),이건엽(Gunyub Lee),문형석(Hyung Suk Mun) 한국철도학회 2018 한국철도학회 학술발표대회논문집 Vol.2018 No.5
철도차량은 육상을 이용하여 짧은 시간에 많은 화물을 수송할 수 있는 에너지 효율이 우수한 친환경적인 녹색수송 수단으로 전 세계의 수요가 급증하고 있으며 남북철도 연결과 함께 유라시아로 연결하는 대륙철도로의 진출을 추진하고 있다. 하지만, 남북 인접지역의 화물열차에는 서로 다른 제동장치를 사용하고 있어 인접지역의 제동장치 특성을 분석하고 혼합편성 상호운영을 위한 국내 제동장치의 방향을 소개하고자 한다. Railway vehicles are eco-friendly green transportation vehicles with excellent energy efficiency that can transport large quantities of cargo in a short time with using land, and it is increasing rapidly as the demand for in the world. It is promoting the entry of the continental railway linking to Eurasia with connecting to the South & North Korea Railway. However, since different brake control unit is used for the freight train in the South-North region, the characteristics of the brake control unit in the South-North region is analyzed and the directions of the domestic brake control unit for mixing and interoperability are introduced.
스크랩 불순물이 Zr 합금의 미세조직 및 기계적 특성에 미치는 영향
정구범 ( Gu Beom Jeong ),김인원 ( In Won Kim ),송재숙 ( Jae Sook Song ),신평우 ( Pyung Woo Shin ),홍순익 ( Sun Ig Hong ) 한국주조공학회 2016 한국주조공학회지 Vol.36 No.3
In this study, the effect of scrap ratio on the mechanical properties of Zr alloys was studied. Oxygen content in the ingot cake increased rapidly with increasing fraction of scrap, which can be attributed to the surface oxide of scrap including small pieces of turning, chips, etc. Iron content did not increase much with the increasing addition of scrap, suggesting scrap materials was well reserved in the iron-free container. As-cast structure of Zr alloy with the scrap: sponge ratio displayed plate/or needle α phase and no appreciable change of the cast structure was observed with change of scrap fraction. The strength increases with increasing fraction of scrap, which can be attributed to the increase of oxygen content. The ductility decreased slightly with increase of scrap fraction. Dislocation-oxygen interaction is known to increase the strength at the expense of ductility. Ingot cake with intentionally added Fe2O3 exhibited the drastic decrease of the formability, even exhibited the brittle fracture behavior during rolling. The oxidation resistance, however, increased with the increase of scrap fraction because of high oxygen content, which may prevent more penetration and diffusion of oxygen into matrix.
박윤서(Park, Yun-Seo),최두석(Choi, Doo-Seuk),이주형(Lee, Ju-Hyung),신평우(Shin, Pyung-Woo),박성영(Park, Sung-Young) 한국산학기술학회 2012 한국산학기술학회논문지 Vol.13 No.3
본 연구에서는 유동해석과 실험을 통하여 소형엔진 흡기포트의 성능 최적화를 수행하였다. 포트각, 플랜지면 적 및 포트형상은 흡기포트의 성능을 결정하는 중요한 설계인자이다. 특히 가공곡률이 공기유량계수에 매우 중요한 영향을 미치는 핵심인자임을 확인하였다. 포트각과 플랜지면적이 증가하면, 흡기포트내의 압력분포와 압력기울기가 개선되어 공기유량계수가 개선되었다. 유동해석 결과는 플로우박스 실험결과 대비 최대 8% 오차를 보였으나, 설계 변수에 따른 공기유량계수 경향을 우수하게 반영하였다. 최적의 설계변수를 적용한 흡기포트 모델은 양산모델 대비 약 4.5% 개선된 공기유량계수 성능을 나타내었다. Performance optimization of a small engine intake port has been studied through computational and experimental approach. Port angle, flange area and port shape are very important design parameters affecting performance of an intake port. Especially, radius of curvature of intake port inner surface has major effect on the flow coefficient of an intake port. As increasing port angle and flange area, flow coefficient is increased because pressure distribution and pressure gradient in the intake port are improved. Even though computational results over-predict maximum 8% compared with experimental result, they describe the tendency of flow coefficient according to the design parameters. Optimized intake port shows about 4.5% improved flow performance.