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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.
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.
W-M(M=Cu, Sn, Ni)계 고밀도 복합재료 제조에 관한 기초연구(I)
장탁순,홍준희,이태행,구자명,송창빈,Jang, Tak-Soon,Hong, Jun-Hee,Lee, Tae-Haeng,Koo, Jar-Myung,Song, Chang-Bin 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.4
For the purpose of obtaining basic information on the development of lead-free materials, a high density composites (a) W-Cu, (b) W-Sn (c)W-Cu-Sn and (d) W-Cu-Ni were fabricated by the P/M method. The particle size of used metal powders were under 325 mesh, inner size of compaction mould was $\phi8$ mm, and compaction pressure was 400 MPa. A High density composite samples were sintered at a temperature between $140^{\circ}C$ and $1050^{\circ}C$ for 1 hour under Ar atmosphere. The microstructure, phase transformation and physical properties of the sintered samples were investigated. As the results, the highest relative density of 95.86% (10.87 g/$cm^3$) was obtained particularly in the sintered W-Cu-Sn ternary system sample sintered at 450 for 1hr. And, Rockwell hardness (HRB) of 70.0 was obtained in this system.
폐실리콘의 고에너지 밀링 과정에서 초기 입자 크기가 분말의 미세화에 미치는 효과
송준우,김효섭,김성신,구자명,홍순직,Song, Joon-Woo,Kim, Hyo-Seob,Kim, Sung-Shin,Koo, Jar-Myung,Hong, Soon-Jik 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.3
In this research, the optimal manufacturing conditions of fine Si powders from Si scrap were investigated as a function of different initial powder size using the high-energy ball milling equipment, which produces the fine powder by means of an ultra high-energy within a short duration. The morphological change of the powders according to the milling time was observed by Scanning electron microscopy (SEM). With the increasing milling time, the size of Si powder was decreased. In addition, more energy and stress for milling were required with the decreasing initial powder size. The refinement of Si scrap was rapidly carried out at 10min ball milling time. However, the refined powder started to agglomerate at 30 min milling time, while the powder size became uniform at 60 min milling time.
자기펄스 성형법에 의한 TiO<sub>2</sub> 나노 분말의 치밀화
김효섭,이정구,이창규,구자명,홍순직,Kim, Hyo-Seob,Lee, Jeong-Goo,Rhee, Chang-Kyu,Koo, Jar-Myung,Hong, Soon-Jik 한국재료학회 2008 한국재료학회지 Vol.18 No.8
In this research, fine-structure TiO2 bulks were fabricated in a combined application of magnetic pulsed compaction (MPC) and subsequent sintering and their densification behavior was investigated. The obtained density of $TiO_2$ bulk prepared via the combined processes increased as the MPC pressure increased from 0.3 to 0.7 GPa. Relatively higher density (88%) in the MPCed specimen at 0.7 GPa was attributed to the decrease of the inter-particle distance of the pre-compacted component. High pressure and rapid compaction using magnetic pulsed compaction reduced the shrinkage rate (about 10% in this case) of the sintered bulks compared to general processing (about 20%). The mixing conditions of PVA, water, and $TiO_2$ nano powder for the compaction of $TiO_2$ nano powder did not affect the density and shrinkage of the sintered bulks due to the high pressure of the MPC.
밀링조건이 사용 후 PDP패널의 유가금속 용출효율에 미치는 영향
김효섭,김찬미,이철희,이성규,홍현선,구자명,홍순직,Kim, Hyo-Seob,Kim, Chan-Mi,Lee, Chul-Hee,Lee, Sung-Kyu,Hong, Hyun-Seon,Koo, Jar-Myung,Hong, Soon-Jik 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.2
In this study, the microstructure and valuable metals dissolution properties of PDP waste panel powders were investigated as a function of milling parameters such as ball diameter size, milling time, and rotational speed during high-energy milling process. The complete refinement of powder could achieved at the ball diameter size of 5 mm due to sufficient impact energy and the number of collisions. With increasing milling time, the average particle size was rapidly decreased until the first 30 seconds, then decreased gradually about $3{\mu}m$ at 3 minutes and finally, increased with presence of agglomerated particles of $35{\mu}m$ at 5 minutes. Although there was no significant difference on the size of the particle according to the rotational speed from 900 to 1,100 rpm, the total valuable metals dissolution amount was most excellent at 1,100 rpm. As a result, the best milling conditions for maximum dissolving amount of valuable metals (Mg: 375 ppm, Ag 135 ppm, In: 17 ppm) in this research were achieved with 5 mm of ball diameter size, 3min of milling time, and 1,100 rpm of rotational speed.
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.
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.