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김길무,조만형 대한금속재료학회(대한금속학회) 1972 대한금속·재료학회지 Vol.10 No.4
황산제일철(FeSO₄)의 해리에 대한 반응의 기구와 해리를 촉진시키기 위하여 환원제로서 첨가하는 탄소의 조성에 대하여 연구를 하였다. 황산제일철의 해리 반응은 황산제이철(Fe₂(SO₄)₃)의 형성을 동반하였으며 이로 인하여 황산제일철의 해리는 지연된다. 황산제일철의 해리를 촉진시키기 위하여 황산제이철의 형성을 억제하고, 또한 배소물로 얻어지는 Fe₂O₃의 촉매작용으로 인한 SO₂가 SO₃로의 산화도 억제하여야 한다. 이때 해리를 촉진시키기 위한 탄소의 양은 중성 분위기에서 전체 시료의 6%가 필요하며 시료의 가열은 빠를 수록 좋다. FeSO₄·7H₂O 에서 결정수를 탈수시키고 산화제일철을 960℃에서 배소시킨다면 총 2250.8 ㎉/㎏·Fe₂O₃의 열량이 소요될 것이다. When the dissociation of ferrous sulfate(FeSO₄) takes place, the reaction mechanism and the composition of carbon that is used as reduction agent for accelerating dissociation were studied. The formation of ferric sulfate(Fe₂(SO₄)₃) occurs in the process of the dissociation of ferrous sulfate. The formation of ferric sulfate always delays the dissociation of ferrous sulfate. The formation of ferric sulfate and the oxidation of SO₂ through the catalytic action of Fe₂O₃ must be avoided to increase the dissociation rate. At this time the ratio of carbon required to prevent this formation is 6% of the sample under the inert condition and the sooner the sample is heated, the better. For the dehydration of FeSO₄·7H₂O and the roasting of FeSO₄ about 2250.8(㎉/㎏·Fe₂O₃) is required at 960℃.
NiCoCrAlY 및 NiAl bond coat를 사용한 단열피복코팅의 파괴거동
김길무,구성모,Meier, G. H.,Pettit, F. S. 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.10
The effect of thermal cycling on the degradation of thermal barrier coatings has been studied. A Ni-based superalloy substrate was coated with an Al-rich NiAI or NiCoCrAlY bond coat and yttria stabilized zirconia. These specimens were exposed to two types of thermal cyclings, namely, 10 minute thermal cycling and 1 hour thermal cycling, at 1100℃ in the air. The TBC system with NiCoCrA1Y bond coat showed a longer life time in 10 minute thermal cycling compared to that with NiAI, while the TBC system with NiAl showed a longer life time in 1 hour thermal cycling compared to that with NiCoCrAlY. These degradation behaviors will be discussed in detail. (Received June 15, 2004)
Ni 기 및 Fe 기 합금의 고온 산화 및 탄화반응 (1)
김길무 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.12
The alloys Ni-30Cr, Fe-18Cr-6Al-1Hf and Ni-20Si were studied in oxidizing(air) and carburizing(CH₄/H₂) atmospheres at 950℃ to characterize their behavior. The carburization of Fe-18Cr-6A1-1Hf and Ni-20Si at 950℃ was negligible, due to rapid formation of oxide scales because the dissociation pressures of Al₂O₃ and SiO₂ scales are very low. The carburization of Vi-30Cr at 950℃ did not produce a continuous carbide layer, but discrete, globular carbides(Cr_7C₃) on the surface along with internal carbides(Cr₂3C_6)
반도체용 Contact Metal 의 열화에 관한 연구
김길무,공창식 한국부식학회 1991 Corrosion Science and Technology Vol.20 No.3
In order to investigate degradation of contact metals which is critical to the time to failure of devices, various Al-Cu-Si alloys were chosen, exposed to H₂, N₂, O₂ atmospheres at 550℃ and examined by conventional optical, scanning electron, transmission electron microscope and X-ray diffractometer. Also, the effects of moisture and Cl to these atmospheres were studied. Alloys consisted of fcc Al matrix and tetragonal Al₂ Cu precipitates. No degradation was observed by SEM when alloys were exposed to O₂ gas, but a considerable amount of degradation was observed when exposed to N₂ + H₂ atmosphere. Thin films of Al oxide, which were continuous and seemingly protective, formed when exposed to O₂ atmosphere. But continuous films were not found when exposed to N₂ + H₂ gases. The addition of water vapor to these gases enhanced degradation. This was due to the aqueous galvanic corrosion around Al₂Cu precipitates. The effect of addition of Cl to these gases was to accelerate degradation.
Mn-Mo-Ni 저합금강의 인성과 강도에 미치는 2 상영역 열처리와 템퍼링 조건의 영향
홍준화,김길무,오용준,안연상,김홍덕 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.3
The effect of intercritical heat treatment (IHT) and tempering conditions on impact toughness and strength in a Mn-Mo-Ni low alloy pressure vessel steel (SA508 Gr.3 steel) has been investigated. The optimum condition of the IHT for toughness improvement was developed. The application of IHT resulted in the increase of ductility and upper shelf energy and in the decrease of strength and ductile-to-brittle transition temperature (DBTT). The modification of tempering conditions reduced the loss of strength resulting from the IHT and maximized toughness improvement. The beneficial effects from the IHT were consistently maintained in spite of the changes of heating and cooling rates. Additionally, the cause of the increase in toughness was investigated in relation to the microstructural change. The IHT produces a composite structure of hard martensite and soft tempered bainite. Tempering following IHT results in spheroidization of carbides and finer effective grain size, which enhance resistance to the brittle fracture.