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고온, 고압에서의 요오드 치환 Polycarbosilane의 합성 및 특성
변지철,라케쉬 산다난드 샤르비드레,김윤호,박승민,고명석,민효진,이나영,류재경,김택남,Byen, Ji Cheol,Sharbidre, Rakesh Sadanand,Kim, Yoon Ho,Park, Seung Min,Ko, Myeong Seok,Min, Hyo Jin,Lee, Na young,Ryu, Jae-Kyung,Kim, Taik-Nam 한국재료학회 2020 한국재료학회지 Vol.30 No.9
SiC is a material with excellent strength, heat resistance, and corrosion resistance. It is generally used as a material for SiC invertors, semiconductor susceptors, edge rings, MOCVD susceptors, and mechanical bearings. Recently, SiC single crystals for LED are expected to be a new market application. In addition, SiC is also used as a heating element applied directly to electrical energy. Research in this study has focused on the manufacture of heating elements that can raise the temperature in a short time by irradiating SiC-I<sub>2</sub> with microwaves with polarization difference, instead of applying electric energy directly to increase the convenience and efficiency. In this experiment, Polydimethylsilane (PDMS) with 1,2 wt% of iodine is synthesized under high temperature and pressure using an autoclave. The synthesized Polycarbosilane (PCS) is heat treated in an argon gas atmosphere after curing process. The experimental results obtain resonance peaks using FT-IR and UV-Visible, and the crystal structure is measured by XRD. Also, the heat-generating characteristics are determined in the frequency band of 2.45 GHz after heat treatment in an air atmosphere furnace.
570MPa급 용접구조용강 다층 용접금속의 강도 및 충격인성에 미치는 입열 및 패스간 온도의 영향
변지철,방국수,장웅성,박철규,정우현,Byun, Ji-Chul,Bang, Kook-Soo,Chang, Woong-Sung,Park, Chul-Gyu,Chung, Woo-Hyun 대한용접접합학회 2006 대한용접·접합학회지 Vol.24 No.1
570MPa grade weldable steels were gas metal arc welded with various heat inputs and interpass temperatures using flux cored wires. Effects of heat input and interpass temperature on the strength and impact toughness of weld metal were investigated in terms of microstructural change, recovery of alloying elements, and the amount of reheated weld metal. Increase of heat input and interpass temperature resulted in decrease of weld metal strength. This is because of the small amount of acicular ferrite, large columnar size and low recovery of alloying elements such as manganese and silicon. In addition to the microstructural change, weld metal toughness was also influenced by the deposition sequence. It increased with an increase of the amount of reheated weld metal.
수열합성 반응에 의한 3mol % 지르코니아 세라믹의 Fe2+, Fe3+, Er3+치환에 따른 상변태와 물성 변화
변지철, 이현철, 김택남, 류재경 배재대학교 공학연구소 2017 공학논문집 Vol.19 No.1
Zirconia is a heat-resistant material with a high melting temperature(2700℃) and has low thermal conductivity and excellent corrosion resistance. However, application has been limited due to brittleness, which is a disadvantage of ceramic materials. As a way to improve this, the addition of Y3+ improves the strength by phase transformation, which can improve the brittle problem, which is a disadvantage of ceramic. Many studies have been conducted on the addition of Y3+ after the addition has been found to be more efficient than the other additives. In this experiment, have studied the additives that replace this Y3+. Expeiments on the possibility of replacing Y3+ by adding an alternative additive considering Zr-sol(Fe2+, Fe3+, Er3+) in consideration of Atomic size, Crystal ionic raddi and Effective Ionic raddi. ZOC(ZrOCl2*8H2O) was dissolved in distilled water and synthesized by hydrothermal synthesis at 160℃ for 24hours. The formed Zr-sol was separated into a supernatant and precipitate. The supernatant was washed with distilled water, and the presence of chloride ion was confirmed using AgNO3. And add to the cleaned Zr-sol an additive that is believed to be a substitute for Y3+. The prepared Zirconia was calcined at 900℃ for 2hours, and the crystal phase was analyzed by XRD similar that of YSZ. The calcined powder was uniaxial pressed and sintered at 1500℃ for 2hours. The sintered specimens were first measured for specific gravity. And the particle size distribution, EDAX and FESEM were measured. 지르코니아는 고온에선 용융하는 (2700℃) 낮은 열전도율과 부식저항이 우수한 세라믹이다. 이에 우수한 파괴인성을 주기 위해 3 mol % Y를 첨가하게 되고, 상온에서 정방정 상으로 존재함으로써 파괴인성이 증가한 것으로 알려져 있다. 따라서 본 실험에서는 Y와 유효 원자 반경이 유사한 Er3+ (89pm)를 첨가함으로써, 과연 어떤 변화가 나타나는지를 알아보았다. 또한 원자가가 유사한 Fe3+와 Fe2+ 를 첨가하여 물성변화와 상변화를 조사하였다. 연구결과 이온 반경이 Y와 유사한 Er3+에서는 완전한 정방정상과 밀도, 투광율 (일부 파장은 제외)을 나타내었으나, 이온 반경이 약1/2 인 Fe2+, Fe3+를 첨가한 경우에는 단사정과 비정질 그리고, 650nm이하의 파장에서는 거의 투광하지 않는 현상을 보였다.