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超急冷 Ni_60B_40 合金의 構造 및 熱的 安定性에 관한 硏究(Ⅰ)
具滋洛,吳明錫,林榮彦,조성석 충남대학교 공업교육연구소 1981 論文集 Vol.4 No.2
The phase transformation and structure of rapidly quenched Ni_60B_40 alloy has been studied by x-ray diffraction and electrical resistivity measurements. The first step in the transformation of rapidly quenched Ni_60B_40 alloy was found to be Am+O-Ni_4B_3+m-Ni_4B_3 → O-Ni_4B_3+m-Ni_4B_3. The mechanism of transformation has been determined by the initially present microcrystallites in the amorphous matrix. The diffusional growth has three steps of growth of a disc with constant thickness, thickening of a disc and growth in axial direction only. The activation energy for crystallization is 43㎉/mole in the first step, 57㎉/mole in the second step and 55㎉/mole in the third step.
구자명 ( Jar Myung Koo ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.2
Effect of rapidly solidfid 6.5wt%Si-Fe alloy annealed in the sulfur atmosphere were studied. The ribbons Which were showed with random structure at the received state, were developed into(110) texture in the heat treatment of the vacuum atmosphere, into (100)texture in the sulfur atmosphere. After the ribbon was continuously annealed in the vacuum atmosphere for 3 min. at 1100℃, and sulfur atmosphere for 1hr at 1175℃, grain size of (100)plane was grew to 4-8㎜ and the coercive force was decreased to 2-4A/m remarkably.
고 Cr 주철을 (鑄鐵) 용접시킨 Hood Spring 강의 내마멸성에 (耐磨滅性) 관한 연구
구자명(Jar Myung Koo) 대한공업교육학회 1985 대한공업교육학회지 Vol.10 No.2
Toughness and wear resistance have been studied about the four domestic products, Japanese ones, England ones and Hood Spring steel welded 36% Cr Cast iron. It turned out as follows ; 1) The domestic products and Japanese ones had been similar to the hardness and the structure of tempered Martensite, but the England products had the structure of (pearlite + Ferrite) which its hardness was decreased markedly. The Hood Spring steel welded 36% Cr Cast iron had the best hardness in all ones and the structure of it was the (Fe·Cr)_7C₃, (Fe·Cr)_(23)C_6 and eutectic carbide. 2) In the result of wear test, the Japanese products was 1.6 times than domestic ones. The Hood Spring steel welded 36% Cr Cast iron was superier to the Japanese ones, the England ones turned out of low grade.
조성석,구자명,김학동 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.9
The magnetic properties and the structure of high silicon steel sheets (3wt%-6.5wt%Si) prepared by the twin roller-quenching method were investigated. The columnar grains about 5-7㎛ in diameter were observed in the as-prepared sheets and the columnar grains grew from the surface to the center part of the sheet. In the as-prepared sheet, the coercive force was 1.05 Oe for the 6.5 wt%Si-Fe sheet, and the average mag netic iron loss W_(15/50) and W_(10/50) of the sheets having the coercive force of 1.05 Oe was 1.50 W/㎏ and 0.46W/㎏ respectively.
급냉 고규소 강판의 자기적 특성에 미치는 열처리의 영향
조성석,구자명 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.10
The magnetic properties and the grain structure of 6.5 wt%Si-Fe alloy made by the twin roller method were measured after the various annealing temperature. When the annealing temperature was around 700℃, the primary recrystallization was formed near the middle part of the sheet thickness and the grain size increased with increasing temperature. When the sheets were annealed at 1200℃, the grains with the (100) planes were paralled to the sheet surface, The magnetic properties are improved by furnace cooling after annealing at 1200℃ for 1hr at the air pressure of 10^(-4) Torr.
쌍롤법으로 제조한 고규소강판의 자기적 특성에 미치는 Si 함량의 영향
조성석,천병선,구자명 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.2
The magnetic properties and microstructures of 0.3㎜ thick high Si-Fe alloys sheets made by the twin roll process were studied after annealing the sheets at 1100℃ for 60 minutes in the vacuum atmosphere of 10^(-4) Torr. The microstructure of 6.5 wt%Si-Fe alloy showed the DO₃precipitates in the B₂matrix. When the specimens were heated at a constant rate of 2℃/min, the electrical resistivities of 3, 4, 5 and 6wt%Si alloys increased in the temperature range between 330℃ and 750℃ in comparison to those of the as quenched state. On the contrary, the resistivity of 6.5 wt%Si alloy decreased in the temperature range between 350℃ and 550℃. The coercive force was 0.51 Oe for the 6.5 wt%Si-Fe alloy and the AC core loss W_(15/50) and W_(10/50) were 0.69 w/㎏ and 0.30w/㎏ respectively.
가스분무공정을 이용한 (AgSbTe<sub>2</sub>)<sub>15</sub>(GeTe)<sub>85</sub> 열전분말의 제조 및 특성평가
김효섭,이진규,구자명,천병선,홍순직,Kim, Hyo-Seob,Lee, Jin-Kyu,Koo, Jar-Myung,Chun, Byong-Sun,Hong, Soon-Jik 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.5
In this study, p-type $(AgSbTe_2)_{15}(GeTe)_{85}$: TAGS-85 compound powders were prepared by gas atomization process, and then their microstructures and mechanical properties were investigated. The fabricated powders were of spherical shape, had clean surface, and illustrated fine microstructure and homogeneous $AgSbTe_2$ + GeTe solid solution. Powder X-ray diffraction results revealed that the crystal structure of the TAGS-85 sample was single rhombohedral GeTe phase, which with a space group $R_{3m}$. The grain size of the powder particles increased while the micro Vickers hardness decreased with increasing annealing temperature within the range of 573 K and 723 K due to grain growth and loss of Te. In addition, the crystal structure of the powder went through a phase transformation from rhombohedral ($R_{3m}$) at low-temperature to cubic ($F_{m-3m}$) at high-temperature with increasing annealing temperature. The micro Vickers hardness of the as-atomized powder was around 165 Hv, while it decreased gradually to 130 Hv after annealing at 673K, which is still higher than most other fabrication processes.
Kim, Chan-Mi,Dharmaiah, Peyala,Kim, Hyo-Seob,Koo, Jar-Myung,Yoon, Jae-Sik,Hong, Hyun-Seon,Hong, Soon-Jik PAS 2017 ARCHIVES OF METALLURGY Vol.62 No.2
<P>The objective of this particular study was to recover valuable metals from waste plasma display panels using high energy ball milling with subsequent acid dissolution. Dissolution of milled (PDP) powder was studied in HCl, HNO3, and H2SO4 acidic solutions. The effects of dissolution acid, temperature, time, and PDP scrap powder to acid ratio on the leaching process were investigated and the most favorable conditions were found: (1) valuable metals (In, Ag, Mg) were recovered from PDP powder in a mixture of concentrated hydrochloric acid (HCl: H2O = 50:50); (2) the optimal dissolution temperature and time for the valuable metals were found to be 60 degrees C and 30 min, respectively; (3) the ideal PDP scrap powder to acid solution ratio was found to be 1:10. The proposed method was applied to the recovery of magnesium, silver, and indium with satisfactory results.</P>