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김성훈,김경훈,도환수,박주석,김경자,심광보,Kim, Seong-Hoon,Kim, Kyung-Hun,Dow, Hwan-Soo,Park, Joo-Seok,Kim, Kyung-Ja,Shim, Kwang-Bo 한국결정성장학회 2016 韓國結晶成長學會誌 Vol.26 No.2
본 연구에서는 열간가압소결법으로 SiC를 소결하여 균열자기치유 특성을 분석하였다. SiC는 $Al_2O_3$와 $Y_2O_3$를 소결조제로 $1950^{\circ}C$, 50 MPa, 아르곤(Ar) 분위기에서 소결하였다. 소결된 시편을 $3{\times}4{\times}40mm$, 절단 및 가공하고, Vickers 경도기를 이용하여 49.6 N으로 예비균열을 생성하였다. $1200{\sim}1400^{\circ}C$, 1~10시간 산화분위기에서 열처리한 후 XRD, SEM, 3점 굽힘강도를 측정하였다. $1300^{\circ}C$ 1시간에서 741 MPa, 5시간에서 770 MPa로 가장 우수한 균열자기치유 효과를 나타내는 것으로 분석되었다. In this study, it was investigated that characteristic of crack-self-healing of hot-pressed SiC. SiC ceramics was sintered with $Al_2O_3$ and $Y_2O_3$ sintering additive by hot press. Sintering was performed in hot-press furnace in flowing argon (Ar), holding for 3 hr under $1950^{\circ}C$ and 50 MPa. The sintered SiC was machined into 3-point bending strength specimen of $3{\times}4{\times}40mm$, and introduced pre-crack by Vickers indentation at 49.6 N. Specimens were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), 3-point bending strength after heat treatment at $1200{\sim}1400^{\circ}C$ for 1~10 hr. The best crack-self-healing ability was achieved 770 MPa 3-point bending strength by heat treatment at $1300^{\circ}C$ for 5 hr.
성에 제거용 대면적 투명 히터를 위한 환원된 산화 그래핀 연구
조승근,문해인,김영원,도환수,이정우 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.8
Transparent heaters are promising devices because of their versatile applications in vehicles, smart windows, and sensors, etc. Indium tin oxide is widely used for transparent heater materials due to its high electronic conductivity and visible light transmittance. However, the cost of indium is too high, and its fabrication needs sophisticated processes, so that many studies have focused on alternative materials which are inexpensive and easy-to-synthesize. Graphene is a two-dimensional material in which carbon atoms bond to form a hexagonal structure, and it can be an alternative material due to its superior electronic/ thermal conductivity and cost-effectiveness. Here, we chemically treated graphite to synthesize large-sized graphene oxide (LGO), and coated it on a glass substrate, followed by reduction using hydrogen iodide for large-sized reduced graphene oxide (LrGO) on glass. From surface characterizations, we confirmed that the lateral size of the LGO was over 50 μm and the LGO sheets were uniformly coated on the glass, which minimized intersheet contact resistance. Structural characterizations demonstrated that the LGO sheets were reduced to LrGO and the LrGO sheets coated on the glass showed a transmittance of 76.2 % at 550 nm with a sheet resistance of 0.98 kΩ. Finally, the temperature of the substrate increased up to 30 oC when 30 V of voltage was applied for 5 min, and the frost on the glass surface vanished within 1 min.
상압소결 질화알루미늄의 소결 첨가제 변화에 따른 열적 및 기계적 특성
황진욱,문소윤,남상용,도환수,Hwang, Jin Uk,Mun, So Youn,Nam, Sang Yong,Dow, Hwan Soo 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.5
Aluminum nitride (AlN) has excellent electrical insulation property, high thermal conductivity, and a low thermal expansion coefficient; therefore, it is widely used as a heat sink, heat-conductive filler, and heat dissipation substrate. However, it is well known that the AlN-based materials have disadvantages such as low sinterability and poor mechanical properties. In this study, the effects of addition of various amounts (1-6 wt.%) of sintering additives $Y_2O_3$ and $Sm_2O_3$ on the thermal and mechanical properties of AlN samples pressureless sintered at $1850^{\circ}C$ in an $N_2$ atmosphere for a holding time of 2 h are examined. All AlN samples exhibit relative densities of more than 97%. It showed that the higher thermal conductivity as the $Y_2O_3$ content increased than the $Sm_2O_3$ additive, whereas all AlN samples exhibited higher mechanical properties as $Sm_2O_3$ content increased. The formation of secondary phases by reaction of $Y_2O_3$, $Sm_2O_3$ with oxygen from AlN lattice influenced the thermal and mechanical properties of AlN samples due to the reaction of the oxygen contents in AlN lattice.