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고온용 SiC<SUB>f</SUB>/SiC 복합재료개발 기술과 활용방향
윤한기(Han Ki Yoon),이영주(Young Ju Lee),박이현(Yi Hyun Park) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.11
The development of the first wall whose major function is to withstand high neutron and heat fluxes is a critical path to fusion power. The materials database and the fabrication technology are being developed for design, construction and safety operation of the fusion reactor. The first wall was designed to consist of the plasma facing armor, the heat sink layer and the supporting plates. and Porous materials are of significant interest due to their wide applications in catalysis, separation, lightweight structural materials. In this study, the characteristics of the sintering process of SiC ceramic, SiCf/SiC composite and porous Cf/SiC composite have been introduced order to study of the fusion blanket materials and heat-exchange pannel.
고온선박엔진용 MoSi₂ 금속간화합물의 경도와 방전가공특성
윤한기(HAN-KI YOON),이상필(SANG-PILL LEE) 한국해양공학회 2002 韓國海洋工學會誌 Vol.16 No.6
This paper describes the machining characteristics of the MoSi₂-based composites through the process of electric discharge drilling with various tubular electrodes. In addition to hardness characteristics, microstructures of Nb/MoSi₂ laminate composites were evaluated from the variation of fabricating conditions, such as preparation temperature, applied pressure, and pressure holding time. MoSi₂-based composites have been developed in new materials for jet engines of supersonic-speed airplanes and gas turbines for high-temperature generators. These high performance engines may require new hard materials with high strength and high temperature-resistance. Also, with the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material. The tool electrode is almost non-unloaded, because there is no direct contact between the tool electrode and the work piece. By combining a non-conducting ceramic with more conducting ceramic, it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and MoSi₂ powder was an excellent strategy to improve hardness characteristics of monolithic MoSi₂. However, interfacial reaction products, like (Nb, Mo)SiO₂ and Nb₂Si₃ formed at the interface of Nb/MoSi₂, and increased with fabricating temperature. MoSi₂ composites, with which a hole drilling was not possible through the conventional machining process, enhanced the capacity of ED-drilling by adding NbSi₂, relative to that of SiC or ZrO₂ reinforcements.
윤한기(Han Ki Yoon),이진경(Jin Kyung Lee),오정석(jung Seok Oh),손수정(Soo Jung Shon),H. Takanashi 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.5
This work is to scope potentiality of solid state bonding for SiC and W and to define key mechanism to make high temperature components satisfy their requirements. The preliminary result indicated the potential of the method as fabrication process of SiC and W high temperature system component. In this study, we investigate the microstructure mechanism, two types of reaction layer between W and SiC of interphase structure.
Inject ion-molded Bamboo/PBS 복합재료의 섬유길이에 따른 기계적 특성
윤한기(Han-Ki Yoon),이연희(Yeon-Hee Lee),Hitoshi Takagi,Kazuya Ohkita 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In this paper we studied the effects of fiber length on mechanical properties of injection-molded bamboo/PBS composites. We carried out tensile test and Izod tests for evaluating the mechanical properties of bamboo/PBS composites. The fiber length of the composites consisted of the range from -75㎛, +75㎛ to -180㎛, +180㎛ to -250㎛, and +250㎛ to -500㎛. Also we examined fracture surface of the bamboo/PBS composites by SEM. The results of evaluated tensile strength of the composites with bamboo fiber ranging from +75㎛ to -180㎛ and from +180㎛ to -250㎛ were higher than those ranging from -75㎛ and from +250㎛ to -500㎛. Izod impact strength of the bamboo/PBS composites decreased in the case of the composites with shorter fiber length. In particular, the shortest fiber length in range of -75㎛, we observed sharply dropped strength. The fracture surface of the bamboo/PBS composites showed the formation of pull-out fibers.
윤한기(Han-Ki Yoon),이종호(Jong-Ho Lee),유덕생(Duck-Seng Ryu),최석인(Seok-In Choi) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
Painted coating is a work to cover the surface of the blocks from the interior and exterior. It is used for raising qualities and values of automobiles. This process makes protection and elegance to the material surfaces. A lot of researches about the composition of aluminum or plastic and the process of making steel sheet materials of automobiles were studied. However painted coating studies were insufficient. It is important that researching about characteristics of the roughness and critical scratch load by the effect of painted coating because the roughness was expected to cause a low effect to the painted coating. In this study, the characteristics of painted coating on polished aluminum sheets with different conditions were investigated to develop the work condition and process of painted coating on aluminum sheet in automobile manufacture line. The results showed the roughness after final painted coating was similar to the first roughness of sheet. The high surface roughness and force of the specimen polished by sandpapers was obtained.
자동차용 경량화 AI/CFRP 하이브리드 복합재료의 굽힘강도 특성
윤한기(Han-Ki Yoon),이경봉(Kyung-Bong Lee) 한국자동차공학회 2002 한국자동차공학회 지부 학술대회 논문집 Vol.2002 No.3
Al/CFRP Hybrid composites by using automobile were made with alternating Al7075 sheets and CFRP preparers by autoclave co-curing process. There are many factors influencing the performances of the laminate. We made it changing volume fraction and fiber orientation of CFRP. In this paper, 3-point bending test was conducted to investigate the influence of volume fraction and fiber orientation of CFRP on Bending strength characteristics.<br/>
SiC-SiC세라믹스 동종재 접합재의 전단강도 특성 평가
윤한기(Han Ki Yoon),정헌채(Hun Chea Jung),T.Hinoki,A.Kohyama 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.5
SiC-SiC복합재료는 뛰어난 고온특성, 내산화성 및 크립(creep)에 대한 저항성이 우수하고 또한 중성자에 의한 조사 손상이 다른 세라믹스에 비해서 적게 받는다는 장점으로 인하여 핵융합로의 블랑켓(blanket), 제1벽(first-wall) 및 다이버터(di-vertor) 등의 후보재료로 적용이 기대되고 있다. SiC-SiC복합재료 특성이 저하되는 것이므로 이들 재료의 전단강도 특성 평가는 매우 중요하다. 본 연구에서는 SiC제조특성과 소결온도에 대한 전단강도 특성의 평가한다. In this study, joining methods with SiC powder as the joining adhesives were studied in order to avoid the residual stresses coming from CTE (Coefficient of Thermal Expansion) mismatch between substrate and joining layer. The shear strength and microstructure of joined material between Sic substrates are investigated. The commercial Hexoloy-SA (Saint-Gobain Ceramics, USA) used in this work as substrate material. The fine β-SiC nano-powder which the average particle size is below 30 nm, Al₂O₃, Y₂O₃, and SiO₂ were used as joining adhesives. The specimens were joined with 20MPa and 1400-1900℃ by hot pressing in argon atmosphere. The shear test was performed to investigate the bonding strength. The cross-section of the joint was characterized by using an optical microscope and scanning electron microscopy(SEM).