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다층원소박판에서 $TiAl_3$의 고온자전합성에 미치는 승온속도의 영향
김연욱,김병관,남태운,허보영,김영직,Kim, Yeon-Uk,Kim, Byeong-Gwan,Nam, Tae-Un,Heo, Bo-Yeong,Kim, Yeong-Jik 한국재료학회 1998 한국재료학회지 Vol.8 No.11
Ti 과 AI의 고순도 원소 박판을 이용하여 열간프레스장치에서 고온자전합성법으로 TiAI계 금속간화합물을 제조하였다. 원소 박판에서 $TiAl_3$ 금속간화합물을 제조하는 데 승온속도, 압력, 온도 등의 변수가 고온자전합성에 영향을 미치는 중요한 인자다. 특히 승온속도는 반응합성온도를 결정하는 인자로서 본 실험에서 DTA 분석을 이용하여 공정변수를 결정하였다. DTA 분석결과에 따르면, Ti와 AI의 계면에서 반응합성은 AI의 용융점 이하와 이상의 온도에서 두 번 발생함을 알 수 있다. 또한 승온속도가 증가할수록 두 반응합성온도는 증가하였다. 10층의 Ti 박판과 9층의 AI 박판을 $20^{\circ}C$/min의 승온속도로 고온자전합성시킨 후, $810^{\circ}C$와 240MPa의 압력에서 4시간 동안 열처리한 결과 $700\mu\textrm{m}$ 두께의 TiAI계 금속간화합물 판재를 제조하였으며, XRD 회절과 SEM으로 확인하였다. Titanium aluminide intermetallic compound was formed from high purity elemental Ti and A1 foils by selfpropagating, high-temperature synthesis(SHS1 in hot press. Formation of $TiAl_3$ intermetallics at the interface between Ti and Al foil was observed to be controlled by temperature, pressure and heating rate. Especially, the heating rate is the most important role to form intermetallic compound by SHS reaction. According to DTA experiment, the SHS reactions appeared at two different temperatures below and above the melting point of Al. It was also observed that both SHS reaction temperatures increased with increasing the heating rate. After the SHS reaction of alternatively layered 10 Ti and 9 A1 foils at the heating rate of $20^{\circ}C$/min, the $700\mu\textrm{m}$ thick titanium aluminide sheet was formed by heat treatment at $810^{\circ}C$ for 4hours.
급냉응고된 Mg-Zn합금의 응고조직에 미치는 Al첨가의 영향
김연욱,허보영,Kim, Yeon-Uk,Heo, Bo-Yeong 한국재료학회 1997 한국재료학회지 Vol.7 No.6
Melt-overflow 급냉응고장치를 이용하여 두께 약 300$\mu\textrm{m}$, 폭 10mm의 Mg-Zn합급 스트립을 연속적으로 제조하였다. 또한 알루미늄을 첨가하여, 첨가원소에 따른 결정립미세화와 기계적강도에 미치는 영향을 조사하였다. 스트립의 미세응고조직은 전자현미경(TEM, SEM)과 image analyzer를 이용하여 분석하였으며, 경도시험으로 기계적특성을 평가하였다. Mg-5wt%Zn합금 스트립의 경도는 결정립크기의 제곱근에 반비례하여 급냉응고에 의한 결정립미세화 효과로 같은 조성의 일반주조 합금보다 2배 이상의 높은 경도값을 가지며, 알루미늄을 첨가함으로서 2배 정도의 결정립미세화 효과를 얻어 경도가 더욱 증가하였다. 결정입계를 따라 생성된 금속간화합물은 마그네슘화합금의 입계부식을 방지하여 우수한 내식성을 갖는다. 따라서 적절한 합금설계와 급냉응고법을 적용시키면 마그네슘합금의 취약성을 보완하며 경량성의 장점을 최대한 활용할 수 있다.
Yeon Uk Kim(김연욱),Jae Jun Lee(이재준),Pyeong An Kim(김평안),Jae Hun Yang(양재훈),Ui Yeon Nam(남의연),Yu Mi Woo(우유미),Jung Hwan Park(박정환) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The optogenetic brain stimulation system has attracted significant attention, as it can provide powerful solutions for continuous and real-time monitoring of various neurological diseases such as stroke, epilepsy, and dementia. A number of research groups have developed diverse optogenetic modulating systems, however, the limited lifespan of traditional batteries requires periodic (every 7 years) replacement surgery for optogenetic treatment. Herein, we demonstrated a selfpowered optogenetic brain stimulation system by scavenging wasted magnetic energy and operating flexible micro lightemitting diodes (f-μLEDs). Through the flash-induced stamping technology, a micro/nanostructured surface was formed on the triboelectric Nylon film, which was applied for outstanding performance magneto-mechano-triboelectric nanogenerator (MMTENG). The flash-treated MMTENG generated an open-circuit voltage of 870 V and a short-circuit current of 145 μA under a 7 Oe magnetic field, which was successfully operating an f-μLED array. The developed optogenetic brain stimulation system was smoothly inserted under the skull of the mouse without fatal damage of brain tissues.
Ui Yeon Nam(남의연),Yu Mi Woo(우유미),Yeon Uk Kim(김연욱),Jae Hun Yang(양재훈),Pyeong An Kim(김평안),Jae Jun Lee(이재준),Jung Hwan Park(박정환) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Herein, a outstanding performance Cu nanowires with sheet resistance of 17Ω sq<SUP>-1</SUP> and transmittance of 88% was fabricated by flash-induced plasmonic nanowelding process. The high-intensity flashlight (in the region of visible wavelength) significantly enhanced plasmonic welding of Cu NW intersections without any oxidation. Simultaneously, near-infrared (NIR) spectrum of flash light interlocked the interface between polyethylene terephthalate substrate and Cu NWs. To investigate the adhesion enhacement of interlocked Cu NWs, we conducted a quantitative peel test. the measured NW interfacial fracture force increased by 208% compared to that of a pristine Cu NW electrode. To demonstrate versatile uses of flash-induced Cu NW conductors, transparent resistive memory devices and touch screen panel were successfully fabricated on plastics by employing the flash-welded excellent performance Cu NW network.
Pyeong An Kim(김평안),Yeon Uk Kim(김연욱),Ui Yeon Nam(남의연),Jae Hun Yang(양재훈),Yu Mi Woo(우유미),Jae Jun Lee(이재준),Hyeryeon Seo(서혜련),Jung Hwan Park(박정환) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
One-dimensional metallic nanowires (NWs) have been studied for flexible transparent conductors to replace indium tin oxide due to their brittleness and high costs. Flash-induced heating methods have received attention as a new technique for next-generation flexible electrodes, because of their advantages such as fast processing, large area processability, and compatibility with roll-to-roll manufacturing. Herein we report flexible AgNWs conductors with outstanding optoelectronic properties and robust adhesion on flexible substrates. Localized photothermic energy could occur at the junctions of AgNWs by flash light, resulting in an entirely welded AgNW network. At the same time, the interface of AgNWs and underlying PET film could be melted by the near-infrared (NIR) spectrum of flashlight, which increased the adhesion of the AgNWs by 310 %. To confirm the practical uses of our technique, we successfully fabricated a high-quality transparent energy harvester by using flash-welded AgNW network.