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허진희,Youngmok Rhyim 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.9
In this study, we designed and fabricated a poly-Si-based solar cell device by using conventional Si processes. The electrical properties, such as the open-circuit voltage (V<sub>oc</sub>), the short-circuit current (I<sub>sc</sub>), the fill factor, the external quantum efficiency (EQE) and the efficiency of prepared solar cell devices, were characterized with a standardized measurement system. Also, the correlation between the photoinduced current and the variation of the defect density was then investigated for various locations by using a photoconductive atomic force microscopy (PC-AFM) system. We verified that in a high-defect-density region such as a grain boundary, a triple junction or a crack, photoinduced carriers easily recombined and induced a decrease in the diffusion length and a low level of photoinduced current. Moreover, we suggest a very effective method to reduce the contact resistance between the cantilever tip and the sample surface, which can disturb the flow of photoinduced current.
Characterization of zirconium hydrides in Zircaloy-4 cladding with respect to cooling rate
Kim, Sung-Dae,Rhyim, Youngmok,Kim, Ju-Seong,Yoon, Jonghun Elsevier 2015 Journal of nuclear materials Vol.465 No.-
<P><B>Abstract</B></P> <P>In order to characterize the habit planes and crystallographic relation between the α-matrix and various kinds of Zr hydrides, three different Zr hydrides including δ-hydride, γ-hydride, and surface hydride are produced by controlling the cooling rate from 0.5 to 300 °C/min. Analysis of SAED patterns and TEM images of the Zr hydrides demonstrates representative habit planes and crystallographic relation according to the hydride morphologies. The macroscopic δ-hydride has two kinds of habit planes such as <SUB> { 10 1 ¯ 7 } α </SUB> and <SUB> { 0002 } α </SUB> , while microscopic δ-hydride has the habit plane of <SUB> { 0002 } α </SUB> at the cooling rate of 0.5–10 °C/min. The microscopic γ-hydride has the major habit plane of <SUB> { 10 1 ¯ 7 } α </SUB> at the cooling rate of 300 °C/min in which the crystallographic relation between the γ-hydride and the α-Zr matrix as <SUB> ( 11 1 ¯ ) γ </SUB> ‖ <SUB> ( 01 1 ¯ 1 ) α </SUB> ; <SUB> ( 111 ) γ </SUB> ‖ <SUB> ( 0001 ) α </SUB> ; <SUB> [ 1 1 ¯ 0 ] γ </SUB> ‖ <SUB> [ 11 2 ¯ 0 ] α </SUB> .</P>
탄화온도 및 재담금 처리에 따른 중공형 탄소다공체의 기공구조 및 특성
이은주,이창우,김양도,임영목,Yi, Eunju,Lee, Changwoo,Kim, Yangdo,Rhyim, Youngmok 한국재료학회 2013 한국재료학회지 Vol.23 No.1
Today, the modification of carbon foam for high performance remains a major issue in the environment and energy industries. One promising way to solve this problem is the optimization of the pore structure for desired properties as well as for efficient performance. In this study, using a sol-gel process followed by carbonization in an inert atmosphere, hollow spherical carbon foam was prepared using resorcinol and formaldehyde precursors catalyzed by 4-aminobenzoic acid; the effect of carbonization temperature and re-immersion treatment on the pore structure and characteristics of the hollow spherical carbon foam was investigated. As the carbonization temperature increased, the porosity and average pore diameter were found to decrease but the compression strength and electrical conductivity dramatically increased in the temperature range of this study ($700^{\circ}C$ to $850^{\circ}C$). The significant differences of X-ray diffraction patterns obtained from the carbon foams carbonized under different temperatures implied that the degree of crystallinity greatly affects the characteristics of the carbon form. Also, the number of re-impregnations of carbon form in the resorcinol-formaldehyde resin was varied from 1 to 10 times, followed by re-carbonization at $800^{\circ}C$ for 2 hours under argon gas flow. As the number of re-immersion treatments increased, the porosity decreased while the compression strength improved by about four times when re-impregnation was repeated 10 times. These results imply the possibility of customizing the characteristics of carbon foam by controlling the carbonization and re-immersion conditions.