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- 저자 : 이건배 ( Kon Bae Lee ) (검색결과 7 건)
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윤상원,서종현,안재평,성태연,이건배,Yoon, Sang-Won,Seo, Jong-Hyun,Ahn, Jae-Pyoung,Seong, Tae-Yeon,Lee, Kon-Bae 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.2
The combination of focused ion beam (FIB) and 4 point probe nanomanipulator could make various nano manufacturing and electrical measurements possible. In this study, we manufactured individual ZnO nanowire devices and measured those electrical properties. In addition, tensile experiments of metallic Au and Pd nanowires was performed by the same directional alignment of two nanomanipulators and a nanowire. It was confirmed from I-V curves that Ohmic contact is formed between electrodes and nanomanipulators, which is able to directly measure the electrical properties of a nanowire itself. In the mechanical tensile test, Au and Pd nanowires showed a totally different fracture behavior except the realignment from <110> to <002>. The deformation until the fracture was governed by twin for Au and by slip for Pd nanowires, respectively. The crystallographic relationship and fracture mechanism was discussed by TEM observations. FIB와 나노메니퓰레이터를 이용한 다양한 nano manufacturing을 통해 단일 나노선 소자제작 및 평가가 가능하였으며 또한 나노물질 자체의 전기적, 기계적 특성 평가를 수행할 수 있었다. 나노메니퓰레이터를 나노선에 직접 접촉시켜 전기적 특성을 평가하는 기술은 STA 등과 함께 사용될 때 높은 신뢰도를 갖는 신호를 얻을 수 있었다. 특히, 이를 이용한 나노 소재 특성 평가기술은 소자제작 시간을 단축시킬 수 있고 패턴닝으로부터 화학적 오염을 줄일 수 있는 장점을 갖고 있었다. 또한 FIB와 나노메니퓰레이터를 적절히 이용하면 나노인장시험기로서 활용이 가능하였으며 나노선의 기계적 특성을 본격적으로 평가할 수 있었다. 본 연구의 나노인장시험으로부터 얻은 인장실험 및 TEM분석으로부터 Au 및 Pd 나노선의 인장 및 파괴거동을 직접적으로 관찰할 수 있었다. Au 나노선은 인장초기에 {111}<112> 쌍정이 생성되고 나노선의 직경이 감소하다가 더 이상 인장응력을 수용할 수 없게되면 <110> 축으로부터 <002> 방향으로 재배열하는 방식으로 네킹이 형성되며 최종적으로 결정축 재배열 이후에는 슬립에 의한 파괴가 진행된다. Pd 나노선의 경우에는 Au와는 전혀 다른 파괴거동을 보였다. 먼저 네킹없이 <002> 축으로의 재배열 현상이 관찰되며 이후 cross-slip에 의한 변형을 하였다. 두 나노선 모두 인장 응력이 가해지면 네킹 부분을 중심으로 한 부분에서만 변형이 일어나며 다른 부분에서는 아무런 변형을 찾아 볼 수 없었다.
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권훈,이건배,양형렬 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.7
In the 4Mo, 6W and 2Mo-3W steels the secondary hardening and fracture behaviors were studied. The alloying elements in these steels contributed to the secondary hardening by forming the fine carbides of the M₂C type. Mo had a strong effect on secondary hardening while W had a very weak effect on it but delayed the overaging. The MoW steel exhibited both the moderately strong hardening by the Mo-addition and considerable resistance to overaging by the W-addition. However, severe intergranular embrittlement for the Mo and MoW steels and the reduction in upper shelf energy for the W steel were observed in spite of thee decrease in hardness during overaging.
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권훈,이건배,양형렬 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.9
In alloy systems of the WCr and MoCr steels, which contains both the W or Mo, M₂C type carbide forming elements, and the Cr, the secondary hardening and fracture behavior were studied. The extent of secondary hardening was very weakened and the secondary hardening temperature range was lowered in the MoCr steel, as compared to the ternary Mo steels. Furthermore, the secondary hardening did not occur in the WCr steel. Because the Cr addition stabilizes the cementite of M₃C type, the effective precipitation of fine M₂C carbides cannot be achieved. In the WCr steel the coarse cementite is retained at higher temperatures probably due to the additive stabilizing effect of the W. Although the Cr addition has no merit in the secondary hardening itself, however, it eliminated the secondary hardening embrittlement, which was observed in the Mo and W steels in the absence of Cr.
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Co-Cr 함유 W 및 Mo 강의 이차경화 및 파괴거동
권훈,이건배,양형렬 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.9
In alloy systems of the WCrCo and MoCrCo steels, the secondary hardening and fracture behavior were studied. The decrease in hardness was very small up to 500℃ tempering temperature before the Co addition led to the clear secondary hardening at 550℃. Also, the peak hardness was higher than the as-quenched hardness. Since the Co addition may increase the driving force for formation of the M₂C type carbides and inhibit the softening by delaying the recovery of the dislocation structure, a substantial secondary hardening can be produced by the fine precipitation of M₂C type carbides from such a dislocation structure. The Co addition may degrade the impact toughness by means of the lowering of intrinsic toughness of matrix, the precipitation hardening of M₂C type carbides and the retention of coarse cementite. In the WCrCo steel, the lower hardeness and the higher impact toughness at relatively high test temperatures may result from the less dense precipitation of M₂C type carbides.
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김광훈,권훈,최창기,이건배 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.7
Secondary hardening embrittlement (SHE) in the 6W-3Ni(WN3) and 6W-6Ni(WN6) steels isothermally aged in the range, 550-650℃, was studied to analyze the effects of isothermal aging conditions, which cause variations in carbide morphology, impurity segregation, and hardening or softening of matrix, on the impact toughness and fracture behavior. In underaged conditions, the impact toughness reached the upper shelf energy (USE) levels with increasing test temperature, and mainly ductile dimples were observed on the fracture surfaces. In overaged conditions, on the other hand, the impact toughness was not recovered but remained at the low levels, 2-5 J, even at 250℃, and the fracture surfaces showed intergranular mode. In peak-aged conditions, the impact toughness reached USE levels and fracture surfaces were mostly represented by dimples, similar to those of underaged conditions. However, their USE levels were lower than those of underaged conditions by 10-15 J, or the impact toughness was not recovered and the fracture surfaces exhibited the intergranular mode, similar to those of overaged conditions. In underaged and peak-aged conditions showing the recovery of impact toughness, the relatively easy occurrence of transgranular dimples in the USE regime was caused by the coarse cementite and the intrinsic hardening with fine W_2C precipitation. In contrast, in overaged and peak-aged conditions showing no recovery of impact toughness, the easy occurrence of intergranular fracture is believed to be caused by the impurity segregation at the grain boundaries.
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