Waseda University · 공학
Akihiko Hirata 교수의 연구실은 금속 유리와 비정질 산화규소와 같은 비정질 금속 및 산화물 재료의 나노구조와 원자적 순서를 고해상도 전자현미경 및 광학 기반 분석 기법을 통해 규명하는 데 주력하고 있습니다. 특히 앵스트로 범위의 전자 회절을 활용한 국소적 icosahedral 구조의 직접 관측을 통해 비정질 금속 유리의 기하학적 불안정성과 구조적 과도성을 규명하고 있으며, 이는 비정질 재료의 상전이 및 거동 이해에 기여합니다. 또한 밀리미터파 광전자 기반 무선 송신 기술을 통한 고속 무선 통신 시스템의 개발도 함께 진행하고 있습니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
Icosahedral order has been suggested as the prevalent atomic motif of supercooled liquids and metallic glasses for more than half a century, because the icosahedron is highly close-packed but is difficult to grow, owing to structure frustration and the lack of translational periodicity. By means of angstrom-beam electron diffraction of single icosahedra, we report experimental observation of local icosahedral order in metallic glasses. All the detected icosahedra were found to be distorted with
We present a wireless link system that uses millimeter-wave (MMW) photonic techniques. The photonic transmitter in the wireless link consists of an optical 120-GHz MMW generator, an optical modulator, and a high-power photonic MMW emitter. A uni-traveling carrier photodiode (UTC-PD) was used as the photonic emitter in order to eliminate electronic MMW amplifiers. We evaluated the dependence of UTC-PD output power on its transit-time limited bandwidth and its CR-time constant limited bandwidth, a
Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous s
