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용탕단조에 의한 Al2O3-SiO2 단섬유 및 SiC whisker 강화 알루미늄 합금기 복합재료의 제조
홍성길,윤중렬,최정철 ( Sung Kil Hong,Jung Yul Yun,Jung Chul Choi ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.1
N/A SiC whisker and Al₂O₃-SiO₂short fiber reinforced AC8A, AC8B and AC8B(J) matrix composites were fabricated by squeeze casting method. Preform deformation, change of reinforcement volume-fraction and formation of macro-segregation in two composites were investigated by using micro Vickers hardness test, analysis of macro and micro structures with OM, SEM and EDAX. Al₂O₃,-SiO₂short fiber preform manufactured with 5% SiO₂binder in this study was considerably deformed and cracked, nevertheless, the short fibers were distributed homogeneously in the composites. In SiC whisker reinforced composites, on the other hand, preform deforming and cracking were not occurred, however, macro segregation zone formed along the infiltration routes by interface reaction during infiltration of molten metal into the preform was observed at center-low area in the composites. The decrease of hardness in the macro segregation zone resulted from the depletion of Si and Mg atoms.
Rheo-Compocasting 법으로 제조한 Mg / SiCp 복합재료의 조직 및 경도 특성에 미치는 Zn , Zr 첨가의 영향
홍성길,최정철 ( Sung Kil Hong,Jung Chul Choe ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.6
N/A SiC particles reinforced Mg-Zr, Mg-Zn and Mg-Zn-Zr composites were manufactured by Rheocompocasting method. Effects of Zn, Zr addition on microstructures and hardness were investigated by using the micro Vickers hardness tester, the optical and scanning electron microscopy. By the Zr addition to the pureMg/SiC_p composites, SiC particles become more homogeneously dispersed and grain refined so that the micro hardness of the composite increased. In case of Zn addition, although grain refinement and homogeneous dispersion effects of SiC particles were not obtained, hardness was more increased than the only Zr added composite by the formation of many Mg-Zn intermetallic compounds at grain boundary. In the Mg-Zn-Zr/SiC_p composite, the highest value of hardness was obtained by triple effects such as grain refining, dispersion hardening of SiC particles and Mg-Zn compounds.
Economic Valuation of an Urban Green Space Using Double-Bounded Dichotomous Choice CVM
홍성권,김재현,조현길,Hong, Sung-Kwon,Kim, Jae-Hyun,Jo, Hyun-Kil Korean Institute of Landscape Architecture 2005 韓國造景學會誌 Vol.32 No.6
본 연구는 서울시 도시녹지를 1평을 늘리는 것에 대한 시민들의 지불의사금액(WTP)을 이단계 이선 가상가치법으로 계산함으로써 도시녹지의 경제적 가치를 평가하고, WTP에 영향을 미치는 변수들의 종류와 영향력 정도를 밝히기 위해 수행되었다. 지불도구는 기금이었으며, 'fat-tail problem'없이 WTP를 계산하기 위해 생존분석을 사용하였다. 분석 결과, 서울시민들은 생활녹지 1평을 늘리는데 약 23,400원을 기부할 용의가 있었다. WTP에 영향을 주는 변수는 자연환경태도(NEP), 구조적 제한요소, 소득 및 환경보전을 위해 편리함을 양보할 의사이었다. 본 연구의 결과는 도시녹지의 개발 또는 보존과 관련된 정부의 의사결정이나 도시녹지 관련 예산 확충을 요구할 수 있는 기본 자료로 활용할 수 있을 것이다.
SiCp / Al-4wt%Cu 복합재료의 조직과 고온시효경화거동에 미치는 Ti 첨가의 영향
홍성길,최정철 ( Sung Kil Hong,Jung Chul Choe ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.1
N/A SiC particle reinforced Al-4wt%Cu-Xwt%Ti(X=0, 0.15, 0.3) composites(V_f=5%) were fabricated by using of rheo-compocasting method. Effects of Ti addition on the dispersion behavior of SiC particle, grain refinement and age hardening behavior at 300℃, 400℃ in SiC_p/Al-Cu composites were investigated with use of optical, scanning electron microscopy, DSC and Rockwell hardness tester. SiC_p in as-cast composites was dispersed at grain boundary and redispersed along the movement of grain boundary by grain coarsening during aging treatment at 300 and 400℃. Effects of grain refining and increase of hardness by Ti addition were not obtained scarcely in the SiC_p reinforced composite compared with the matrix alloys. The 0.15wt%Ti added composite indicated good age hardening behavior at 300℃ and 400℃ compared with the other composites.
Ar-H<sub>2</sub>플라즈마 건식제련과 마이크로웨이브침출을 통한 지르콘샌드로부터 고순도 지르코니아 분리
이정한,홍성길,Lee, Jeong-Han,Hong, Sung-Kil 한국자원리싸이클링학회 2016 資源 리싸이클링 Vol.25 No.3
In this study, zircon sand is separated into zirconia and silica by using the Ar-$H_2$ arc plasma refining. And then silica is removed from it by the microwave leaching method to produce a high pure zirconia. Plasma melting consist of two sequential processes; reduction process with Ar gas only followed by refining process with Ar-$H_2$ gas. After cooling in chamber. The solid phase obtained at $240^{\circ}C$ were found to be composed of 20% sulfuric acid solution. The solution was used as a leaching solution with microwave irradiation to obtain a high purity zirconia. 본 연구에서는, 아크 플라즈마 정련을 이용하여 지르콘샌드($ZrSiO_4$)를 지르코니아($ZrO_2$)와 실리카($SiO_2$)로 분리하였다. 실리카를 마이크로웨이브 침출을 통해 제거하고 고순도의 지르코니아를 얻었다. 플라즈마 퓨전은 두 가지 공정을 순차적으로 진행하였다. Ar 100% 분위기에서 환원 공정을 거친 후, Ar-$H_2$ 혼합 가스를 통해 정련과정을 거쳤다. 진공 챔버 내에서 냉각 후 지르코니아와 실리카로 이루어진 고상을 얻었다. 마이크로웨이브 침출을 위해 $240^{\circ}C$, 20% 황산용액을 사용하였다. 분석 결과 고순도(98.6%)의 지르코니아를 얻을 수 있었다.
Al 합금과 STD61강의 소착에 미치는 첨가원소 Fe, Mn의 영향
김유미,홍성길,최세원,김영찬,강창석,Kim, Yu-Mi,Hong, Sung-Kil,Choi, Se-Weon,Kim, Young-Chan,Kang, Chang-Seog 한국재료학회 2012 한국재료학회지 Vol.22 No.4
Recently, various attempts to produce a heat sink made of Al 6xxx alloys have been carried out using die-casting. In order to apply die-casting, the Al alloys should be verified for die-soldering ability with die steel. It is generally well known that both Fe and Mn contents have effects on decreasing die soldering, especially with aluminum alloys containing substantial amounts of Si. However, die soldering has not been widely studied for the low Si aluminum (1.0~2.0wt%) alloys. Therefore, in this study, an investigation was performed to consider how the soldering phenomena were affected by Fe and Mn contents in low Si aluminum alloys. Each aluminum alloy was melted and held at $680^{\circ}C$. Then, STD61 substrate was dipped for 2 hr in the melt. The specimens, which were air cooled, were observed using a scanning electron microscope and were line analyzed by an electron probe micro analyzer. The SEM results of the dipping soldering test showed an Al-Fe inter-metallic layer in the microstructure. With increasing Fe content up to 0.35%, the Al-Fe inter-metallic layer became thicker. In Al-1.0%Si alloy, the additional content of Mn also increased the thickness of the inter-metallic layer compared to that in the alloy without Mn. In addition, EPMA analysis showed that Al-Fe inter-metallic compounds such as $Al_2Fe$, $Al_3Fe$, and $Al_5Fe_2$ formed in the die soldering layers.