Cu - Ti 계 합금의 스피노달 분해

주웅길(Woong Kil Choo),유장용(Jang Yong Yoo) 대한금속재료학회(구 대한금속학회) 1988 상변태 심포지엄 Vol.1 No.-

흑연이 분산된 알루미늄- 실리콘 합금의 마모특성

주웅길,홍주화 대한금속재료학회(대한금속학회) 1979 대한금속·재료학회지 Vol.17 No.6

알루미늄 합금의 마모 성질에 미치는 흑연과 실리콘의 영향을 조사하였다. 합금 LM 30와 이것에서 실리콘을 감소시킨 실험 합금의 용탕에 동으로 도금된 흑연입자를 vortex방법으로 분산시켰다. 흑연량이 5Wt.%까지는 합금의 내마모성은 증가하였고, 하중이 증가할수록 마모량은 증가하는데 흑연이 많을수록 내마모성의 증가가 현저하였다. 분산된 흑연이 마찰시 윤활제 역활을 하여 내마모성이 증가된 것으로 생각된다. 마찰속도가 1m/s일때에 마모량은 최대로 되며 실리콘 양이 증가함에 따라서 마모량이 증가하는데 마모 미립자에 의한 연삭마모가 되어서 경도가 큰 과공정합금의 내마모성이 작은 것으로 생각된다. 속도가 증가하면 (8m/s)전체적으로 마모량이 감소하고, 실리콘이 증가할수록 마모량이 감소되는데, 응착마모 기구가 지배한다고 생각된다. The effect of silicon addition and graphite dispersion in cast aluminum alloys on the wear characteristics was investigated. The graphite particles were initially coated with copper by cementation process, and then dispersed into the alloy melt by vortex method. The wear rate was measured on pin-on-disk type wear test machine without any lubricant. The wear rate decreased as the graphite content increased. At the higher contact pressure the increase in wear resistance of graphite dispersed aluminum alloy became more apparent. At the sliding speed near 1m/sec, high wear rate due to the abrasive wear mechanism was observed. At the higher sliding speed than 8m/sec lower friction and wear rate were observed. The reduced friction and wear rate were attributed to adhesive surface wear mechanism. The reduction of wear by graphite dispersion was more effective at the slow sliding speed less than 1m/sec.

임파결절 천자법의 진단적 가치에 관한 검토

고윤웅 ( Yun Woong Ko ),이주형 ( Choo Hyung Lee ),채응석 ( Eung Suk Chai ),한지숙 ( Jee Sook Hahn ),박호길 ( Ho Kil Park ),김경석 ( Kyung Suk Kim ) 대한내과학회 1974 대한내과학회지 Vol.17 No.11

BaTiO3 의 유전특성에 대한 Nb5+ 이온의 첨가효과

황인철,주웅길,이문호 한국화학공학회 1979 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.17 No.5

BaTiO₃의 소결밀도 및 유전특성에 소결온도와 Nb^(5+) 이온의 첨가가 미치는 영향을 고찰하였다. BaTiO₃의 유전상수 및 그 온도 특성은 Nb^(5+) 이온의 첨가량, 소결온도, 소결후 냉각속도에 따라서 변하였다. 이 결과는 grain size 및 내부응력과 밀접한 관련이 있다고 판단되며, 내부응력모델과 일치하였다. 약 0.5mole% 이하의 Nb^(5+) 이온을 첨가하였을 때는 소결능이 감소하는 경향을 나타냈으나, 그 이상을 첨가하였을 때는 소결능이 증가하였다. The effect of sintering temperature and Nb^(5+) ion addition on the sintered density and the dielectric properties of BaTiO₃ has been investigated. The dielectric constant and its temperature dependence of BaTiO₃ varied with the concentration of the Nb^(5+) ion, the sintering temperature, and the cooling rate after the sintering. Their variation was intimately related with the grain size and the internal stress, which coincided with the internal stress model. Below the concentration of about 0.5 mole% Nb^(5+) ion the sinterability was reduced, butt above that concentration it was raised.

7050 알루미늄 합금의 기계적 성질에 미치는 가공열처리의 영향

김준동,주웅길 대한금속재료학회(대한금속학회) 1980 대한금속·재료학회지 Vol.18 No.5

본 연구에서는 지금까지 알려진 ITMT (Intermediate Thermomechanical Treatment)의 두 방법인 FA-ITMT와 ISML-ITMT를 7050 알루미늄 합금에 적용함으로써 나타나는 미세조직 및 기계적 성질을 종래의 열처리 방법과 비교하였으며, 또한 FA-ITMT 과정중 고온 가공 온도와 가공도를 변화시켜, 이에 따른 기계적 성질을 조사하였다. 본 실험에 의하면 재래식 처리(CP)에 비하여 FA-ITMT와 ISML-ITMT process에 의하면 훨씬 더 미세한 재결정구조를 형성하나, AR (as-recrystallized) 처리재에서는 기계적 성질의 향상을 이루지 못했다. 반면에 AR+HR (as-recrystallized plus hot rolled) 처리재는 재래식 처리재에 비하여 연신율 및 파괴인성의 향상을 보였다. 이와같은 향상은 L-T방향에 비하여 T-L방향에서 더 현저하며, 이는 CP 처리재에 형성된 highly elongated grain에 기인한다. 한편 FA-ITMT시 7050 알루미늄 합금의 파괴인성은 고온가공온도가 증가함에 따라 증가하나, 470℃와 430℃의 경우에는 40%의 가공도에서 파괴인성의 최저치를 보였다. Effects of two intermediate thermomechanical treatments, which are FA-ITMT and ISML-ITMT on mechanical properties and microstructures of 7050 aluminum alloy were studied. The mechanical properties were investigated as function of deformation temperature and degree of deformation during final deformation step of FA-ITMT. The ITMT treated specimens were examined either in the as-recrystallized(AR) condition or in AR plus hot deformed condition (AR+HR). The results showed that fine grained microstructures can be obtained in 7050 aluminum alloy through the FA-ITMT and ISML-ITMT. However, the mechanical properties of ITMT AR treated specimen were inferior to those of conventionally processed specimen. Elongation and fracture toughness of AR+HR treated specimen were superior to those of conventionally processed specimen especially in the T-L direction. Fracture toughness increased as hot deformation temperature increased during FA-ITMT, and it also increased as the degree of hot deformation increased at 390℃. When the degree of hot deformation at 430℃ and 470℃ respectively was 40%, the fracture toughness showed the peak value.

복합주조법에 의한 Al2O3 및 SiC 입자를 함유한 알루미늄 합금 복합재의 제조와 기계적 성질에 관한 연구

한관희,주웅길,구양모 대한금속재료학회(대한금속학회) 1980 대한금속·재료학회지 Vol.18 No.1

복합주조법을 이용하여 0.3㎛에서 53㎛까지의 크기를 갖는 Al₂O₃, SiC 분말을 1 또는 3 w/o함유하는 알루미늄합금 기지의 복합재료를 제조하였다. 주조복합재내의 비금속 분말은 균일하게 분포되었다. 이 주조복합재괴는 열간단조와 압연으로써 두께 6㎛정도의 후판가공이 가능하였으며, 열간가공중에 기지합금내에 균일하게 분포되어 있던 비금속 분말은 가공방향으로 재배열하였다. 상온 및 250℃에서의 인장시험 결과 0.3㎛, 1㎛ Al₂O₃를 포함한 시편에서는 항복 및 인장강도가 모두 증가된 반면에 38㎛, 53㎛ SiC를 함유한 시편의 경우에는 단지 고온인장강도만이 기지합금에 비하여 증가되었다. 특히, 상온에서의 항복강도와 고온인장강도의 증가가 주목할 만 하였다. Aluminum alloy matrix composites containing 1 or 3 w/o of Al₂O₃ and SiC particles range in size from 0.3㎛ to 53㎛ were prepared by "Compocasting process." The non-metallic particles were uniformly distributed in the cast composites. The cast composite ingots can be fabricated to thick plate with 6㎜ thickness by hot forging and rolling, and the non-metallic particles initially uniformly distributed in matrix alloy were aligned along the working direction. Tensile tests conducted at room temperature and 250℃ show that in samples with 0.3㎛, l㎛ Al₂O₃ both yield and tensile strengths have increased, but in samples with 38㎛, 58㎛ SiC only high temperature tensile strength has increased over those of matrix alloy. Especially, the increase of room temperature yield strength and high temperature UTS was noticeable.

쪽 니람의 DNCB 유발 생쥐의 아토피 피부염에 미치는 효과

추한나,박은혜,정종길,백윤웅,김정상,Choo, Han-Na,Park, Eun-Hye,Jeong, Jong-Kil,Paek, Yun-Woong,Kim, Jeong-Sang 대한한의학방제학회 2014 大韓韓醫學方劑學會誌 Vol.22 No.1

Objectives : The purpose of this study was to investigate the effects of Polygonum tinctoria Niram(PTN) on atopic dermatitis(AD) in hairless mice induced by 2,4-dinitrochlorobenzene(DNCB). Method : They were divided into four group, Nor, Con, 1X and 5X, for evaluating the change of appearance of skin surface, skin hydration, thickness of epidermis and mast cell numbers during 30 days. Results : PTN suppressed symptoms of AD in appearance of skin and increased skin hydration for 1X and 5X. In histopathological examination, 1X and 5X significantly reduced the thickness of epidermis and number of mast cell in dermis. These results suggested that the PTN improved the AD-like symptoms of hairless Mice.

The Effect of Stoichiometric La$_{1/2}$Sr$_{1/2}$CoO$_3$ as Sputtered Bottom Electrode on SiO$_2$/Si(100)

Jai-Hyun Kim,Kyoung Shin Koh,Woong Kil Choo 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

In this study, we have investigated the ferroelectric and electrical properties of PZT 40/60 lms on bottom La1=2Sr1=2CoO3(LSCO) electrode. Also, to investigate LSCO as the bottom electrode, this LSCO thin lm was sputtered on SiO2/Si(100) wafer with several LSCO target compositions. As excess Co or Sr is added to the LSCO target, the resistivity of the LSCO thin lm has achieved the minimum value with the 5 at% Co and Sr excess target. For the ferroelectric properties, this particular capacitor with the aforementioned electrode shows better properties than others with the LSCO bottom electrodes deposited with dierent LSCO target compositions.4

BaTiO₃세라믹 커패시터의 시효현상

이문호(Moon Ho Lee),주웅길(Woong Kil Choo) 대한전기학회 1979 전기의 세계 Vol.28 No.5

Phase Transition of Fe and Nb-Substitued Pb(Mg1/2W1/2)O3 Ceramics

Jai-Hyun Kim,Kyoung Shin Koh,Woong Kil Choo 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

The crystal structure and dielectric properties of (1-x)Pb(Mg1=2W1=2)O3-xPb(Fe1=2Nb1=2)O3 (PMW1..xPFNx)(0.0 x 0.26) solid solution have been studied by X-Ray diraction and dielectric property measurements. On increasing PFN substitutions up to x = 0.14, the crystal structure changes from the cubic to the orthorhombic through a sharp phase transition of the paraelectric(PE)-antiferroelectric(AFE) type that is independent of applied frequency. However, on further increasing PFN substitution(0.16 x 0.26), the dielectric constant curve as a function of temperature becomes gradually broader and the apparent transition becomes frequencydependent while the low temperature phase crystal structure changes from the orthorhombic to the pseudocubic.