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레이저 표면열처리가 Zircaloy-4 합금의 산화에 미치는 영향
한정호,임갑순,석호천,정용환,이덕현 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.8
The effect of heat treatment on the oxidation behavior of Zircaloy-4 plates was investigated in 400 to 600℃ steam for alpha-annealed, beta-quenched, and laser surface beta-treated samples. It was observed that the laser treatment resulted in the formation of surface layer of 40∼50㎛ thick beta-treated structure on the mass of alpha-annealed plates, and the microstructure of laser treated layer was much finer than those of alpha-annealed and beta-quenched samples. The corrosion resistance of laser treated Zircaloy was found to be superior to other two samples in a1l the temperatures. At 600 ℃, the corrosion rate was changed from cubic (W=kt^(1/3)) to linear rate(W=kt) after about 7 hour exposures. The marked improvement in corrosion resistance of laser treated samplers is thought to be due to the change of the second phase particle distribution. The coarse and discrete particles in the alpha-annealed structure changed to the fine and chain-like particles in the laser heat treated samples. In this study, the structure of oxide layer was observed to be only one type of monoclinic ZrO₂.
Site-Specific Magnetic Assembly of Nanowires for Sensor Arrays Fabrication
Rheem, Y.,Hangarter, C.M.,Eui-Hyeok Yang,Deok-Yong Park,Myung, N.V.,Bongyoung Yoo IEEE 2008 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol.7 No.3
<P>The effect of variation in local magnetic field on magnetic assembly of 30 and 200 nm diameter Ni nanowires synthesized by template directed electrodeposition was investigated with different materials (Ni-Ni and Ni-Au) and shapes of electrodes. Ni-Au paired electrodes improved confinement of the assembled Ni nanowires across the electrode gap because of the narrower distribution of magnetic field around the gap between the two electrodes. Simulation results indicated a local magnetic field strength at the electrode tip increased by a factor of 2.5 with the use of a needle-shape electrode as compared to rectangular- shape electrode. The resistance of nanowire interconnects increased as the applied voltage was raised, and under the same applied voltage, the increase in resistance is further enhanced at lower temperatures because of higher current density.</P>
Y. W. Rheem,C. G. Kim,C. O. Kim,Y. Choi 한국자기학회 2001 Journal of Magnetics Vol.6 No.3
Microstructure modifications are investigated for annealed Co-based amorphous ribbon in vacuum and open air. X-ray diffraction (XRD) spectra for annealed sample in vacuum indicate atomic arrangements with initial nucleation of hcp-Co crystallite at 380 ℃ annealing temperautre. However, the XRD spectra in samples with long annealing times of t_α ≥ 300 min demonstrate sharp and good developed surface crystalline hcp-, fcc- Co and Co₂Si phases. The giant magnetoimpedance (GMI) profile at 0.1 ㎒ displaying one-peak behavior in vacuum annealed samples at T = 380 ℃, irrespective of annealing time t_α from 20 to 480 mim. For the annealed samples in an open air, the GMI profile shows two-peaks for t_α = 20 min annealed sample. However, one of peaks disappears and an asymmetric GMI profile exhibits a drastic step-like change near zero field for t_α ≥ 300 min. Such asymmetric GMI characteristics is related to the surface microstructures of fcc-Co, hcp-Co and Co₂Si crystalline phases.
I-V characteristics of a vertical single Ni nanowire by voltage-applied atomic force microscopy
D.S. Choi,유봉영,Y. Rheem,김영근,N.V. Myung 한국물리학회 2010 Current Applied Physics Vol.10 No.4
We report the measurement of the electrical resistivity of a vertical single Ni nanowire. A vertical array of Ni nanowires was fabricated on a Si substrate by electrodeposition using a nanoporous alumina template. The Ni nanowires possessed a face-centered-cubic polycrystalline structure. A voltage-applied atomic force microscope was used to make a nanometer-scale point contact on top of the vertical grown single Ni nanowire. The measured resistance was 1.1 MΩ for a nanowire with length of 3 ㎛ and diameter of 20 nm.