http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Lee, Hyun-Kwuon Materials Research Society of Korea 2013 한국재료학회지 Vol.23 No.10
The milling and particulate characteristics of Al alloy-$Al_2O_3$ powder mixtures for a reaction-bonded $Al_2O_3$ (RBAO) process were studied. A commercially available prealloyed Al powder with Zn, Mg, Cu and Cr alloying elements (7475 series) was mixed with a calcined sinter-active $Al_2O_3$ powder and then milled in centrifugal milling equipment for ~48 hrs. The Al alloy-$Al_2O_3$ powder mixtures after milling were characterized and evaluated in various ways to reveal their particulate characteristics during milling. The milling efficiency of the Al alloy increased with a longer milling time. Comminution of the Al alloy particles started with its elongation, showing a high aspect ratio. With a longer milling time, the elongated Al alloy particle changed in terms of its shape and size, becoming equiaxially fine particles. Regardless of the milling efficiency of the Al alloy particles, all of the Al alloy particles repeatedly experienced strong plastic deformation during milling, giving rise to higher density of surface defects, such as microcracks, and leading to higher residual microstress within the Al alloy particles. The chemical reactions, oxidation behavior and hydration behavior of the Al alloy particles and the hydrolysis characteristics of their reaction with the environment were also observed during the milling process and during the subsequent powder handling steps.
Reaction-Bonded Al<sub>2</sub>O<sub>3</sub> Ceramics Using Oxidation of Al Alloy Powder
Lee, Hyun-Kwuon Materials Research Society of Korea 2014 한국재료학회지 Vol.24 No.5
Fabrication of reaction-bonded $Al_2O_3$ (RBAO) ceramics using Al-Zn-Mg alloy powder was studied in order to improve traditional RBAO ceramic processing using Al powder. The influence on reaction-bonding and microstructure, as well as on physical and mechanical properties, of the particulate characteristics of the $Al_2O_3$-Al alloy powder mixtures after milling, was revealed. Variation of the particulate characteristics of this $Al_2O_3$-Al alloy powder mixture with milling time was reported previously. To start, the $Al_2O_3$-Al alloy powder mixture was milled, reaction-bonded, post-sintered, and characterized. During reaction-bonding of the $Al_2O_3$-Al alloy powder mixture compacts, oxidation of the Al alloy took place in two stages, that is, there was solid- and liquid-state oxidation of the Al alloy. The solid-state oxidation exhibited strong dependence on the density of surface defects on the Al-alloy particles formed during milling. Higher milling efficiency resulted in less participation of the Al alloy in reaction-bonding. This was because of its consumption by chemical reactions during milling, and subsequent powder handling, and could be rather harmful in the case of over-milling. In contrast to very little dependence of oxidation of the Al alloy on its particle size after milling, the relative density, microstructure, and flexural strength were strongly dependent on particle size after milling (i.e., on milling efficiency). The relative density and 4-point flexural strength of the RBAO ceramics in this study were ~98% and ~365 MPa, respectively, after post-sintering at $1,600^{\circ}C$.
Lee, Hyun-Kwuon Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.5
The effect of Al content on the processing of reaction-bonded $Al_2O_3$ (RBAO) ceramics using 40v/o ~ 80v/o Al-Zn-Mg alloy powder was studied in order to improve traditional RBAO ceramic processes that use ~ 40v/o pure Al powder. The influence of high Al content in starting $Al_2O_3$-Al alloy powder mixtures on its particulate characteristics, reaction-bonding, microstructure, physical and mechanical properties was revealed. Starting $Al_2O_3$-Al alloy powder mixtures with 40v/o ~ 80v/o Al alloy powder were milled, reaction-bonded, post-sintered, and characterized. With an increasing Al alloy content, the milling efficiency of Al alloy powder was lowered, resulting in a larger particle size after milling. However, in spite of the larger particle size of Al alloy powder, the oxidation, i.e., reaction-bonding, of the Al alloy was successfully completed via solid and liquid state oxidation, in which the activation energy of the oxidation was nearly the same regardless of Al alloy content. After reaction-bonding and post-sintering at $1600^{\circ}C$, RBAO ceramics from 80v/o Al alloy content showed a relative density of ~97% and a flexural strength of 251 MPa compared to ~ 96% and 353 MPa for RBAO ceramics from 40v/o Al alloy content, respectively. The lower flexural strength at 80v/o Al alloy content was due to the weak spinel phase that formed from Zn, Mg alloying elements in Al.
이상진,조경식,Hyun-Kwuon Lee 한양대학교 세라믹연구소 2005 Journal of Ceramic Processing Research Vol.6 No.1
Multi-component ceramic composites consisting of two, three and four phases, based on duplex microstructures of zirconia and alumina, were fabricated by a polymer complexation route employing polyethylene glycol (PEG) as a polymeric carrier. The polymer complexation route showed an unique exothermic reaction involving expansion of the powder structure and it provided highly sinterable powder by a simple ball milling process. In this study, the microstructures and flexural strengths of the multi-component (Al2O3-ZrO2-CeO2-SrO) ceramic composites were examined on the processing variations of the forming and sintering for close to nano-structures. A composite having four phases showed grain growth retardation and the microstructure and final phases were largely dependant on the sintering conditions. Needle-like grains from the addition of SrO improved the flexural strength of the multiphase composites.
기계적 합금화 및 스파크 플라즈마 소결에 의해 제조된 Al-Fe-X계 합금의 열적 안정성: II. Al-Fe-Cr and Al-Fe-Mo
이현권,이상우,조경식,Lee, Hyun-Kwuon,Lee, Sang-Woo,Cho, Kyeong-Sik 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.1
Mechanical alloying using high-energy ball mill and subsequent spark plasma sintering (SPS) process was applied to Al-Fe-Cr and Al-Fe-Mo powder mixture to investigate effects of Cr and Mo addition on thermal stability of Al-Fe, and thereby to enhance its thermal stability up to $500^{\circC}$. Various analytical techniques including micro-Vickers hardness test, SEM, TEM, X-ray diffractometry and corrosion test were carried out. It was found that addition of Cr and Mo to Al-Fe system played a role of grain growth inhibitor of matrix Al and some precipitates such as $Al_3Fe$ during SPS and subsequent heat treatment. The inhibition of grain growth resulted in increased Vickers hardness and thermal stability up to $500^{\circC}$ comparing to those of Al-Fe alloy system.
A New Lodging Tolerant and High-Yielding Glutinous Rice Cultivar "Dongjinchalbyeo"
Mun Sik Shin,Hyun Tak Shin,Jae Kil Lee,Kyu Seong Lee,Bo Kyeong Kim,Jae Kwuon Ko,Tae Hwan Noh,Ki Yong Ha,Young Doo Kim,Bo Kap Yang,Yang Ho Oh,Chong Seok Kim,Seung Yeob LeeHyun 한국육종학회 2003 한국육종학회지 Vol.35 No.4
“Dongjinchalbyeo” is a new japonica glutinous rice cultivar developed from a cross between Milyang95 and SR11155-4-2/Toyonishiki by the rice breeding team of the National Honam Agricultural Experiment Station (NHAES), RDA, in 1998. This cultivar has a sho
이현권,조경식,김미영,Lee, Hyun-Kwuon,Cho, Kyeong-Sik,Kim, Mi-Young 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.4
Need for plasma resistant ceramic materials has been continuously increased in semiconductor and display industry requiring plasma processing to realize ultra fine circuit process. Among promising candidates, alumina ceramics have still some advantages with respect to its economic aspect. In this study, fabrication of plasma resistant alumina ceramics was tried, and its processing optimization was also aimed. Careful processing control and thereby uniform microstructure of $Al_2O_3$ gave rise to enhanced plasma resistance, even comparable to market-governing commercial $Al_2O_3$. A further study is needed concerning ${\beta}-Al_2O_3$ materials system, presumably playing a decisive role in decreasing plasma resistance of $Al_2O_3$ ceramics.
Kim, Hyung-Joon,Lee, Hyun-Kwuon,Park, Jeong-Hyun The Korean Ceramic Society 2004 한국세라믹학회지 Vol.41 No.4
SrA1$_2$O$_4$를 착체중합법으로 합성하는 과정에 있어서 결정의 성장 거동을 연구하였다. 전구체를 900∼100$0^{\circ}C$의 온도범위에서 0∼10시간동안 열처리하였으며, XRD와 TEM을 이용하여 분석하였다 Scherrer's equation을 이용하여 결정자의 크기를 측정하였으며, 그 변화양상을 관찰하였다. 결정자의 크기는 초기 급격한 증가이후 시간의 제곱근에 따라 증가하였으며, 900, 980,그리고 100$0^{\circ}C$의 온도에서 10시간 열처리 이후에 32, 45, 그리고 59nm로 성장하였다. 결정성장속도는 열처리 온도가 증가함에 따라 4.5, 9.4, 그리고 18.6nm/h$^{1}$2/이였다. SrA1$_2$O$_4$was prepared by polymerized complex method and crystalline growth was investigated. Precursors was annealed at temperatures form 900 to 100$0^{\circ}C$, for different time(between 0 and 10 h), and that was determined by Transmittance Electron Microscopy (TEM) and X-Ray Diffractometer (XRD). Crystalline size was calculated by Scherrer's equation and its variation was studied. It increased rapidly in the primary stage and then slowly as a function of square root of time. so, It was grown to 32, 45 and 59nm after heating treatment at 900, 980, and 100$0^{\circ}C$ for 10 h respectively. Cstalline growth rates were 4.5, 9.6, and 18.6 nm/h$^{1}$2/ as a addition of heating temperature.
기계적 합금화 및 스파크 플라즈마 소결에 의해 제조된 Al-Fe-X계 합금의 열적 안정성: I. Al-Fe
이현권,이상우,조경식,Lee, Hyun-Kwuon,Lee, Sang-Woo,Cho, Kyeong-Sik 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.1
Mechanical alloying using high-energy ball mill and subsequent spark plasma sintering (SPS) process was applied to understand mechanical alloying processing of Al-Fe alloy system. The thermal stability of mechanically alloyed Al-Fe alloy was intended to be enhanced by SPS process. Various analytical techniques including particle size analysis, density measurement, micro-Vickers hardness test, SEM, TEM, and X-ray diffractometry were adopted to find optimum processing conditions for mechanical alloying and subsequent SPS and to estimate thermal stability of the prepared alloy. It was found from the treatment of mechanically alloyed Al-8wt.%Fe powder mixture that needle-shaped $Al_3Fe$ precipitates was formed in the Al-Fe matrix, and the alloy compact showed enhanced densification and reached its full density with little loss of its fine microstructure. After heat treatment at $500^{\circC}$, it was also shown that the thermal stability of Al-8wt.%Fe alloy fabricated in the present study was enhanced, which was due to its fine microstructure developed by fast densification of SPS.