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초미세 결정립을 가지는 몰리브덴의 제조 및 기계적 특성
김세훈,서영익,김대건,석명진,김영도,Kim, Se-Hoon,Seo, Young-Ik,Kim, Dae-Gun,Suk, Myung-Jin,Kim, Young-Do 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.3
Mo nanopowder was synthesized by ball-milling and subsequent hydrogen-reduction of $MoO_3$ powder. To fabricate ultra fine grained molybdenum, two-step sintering and spark plasma sintering process were employed. The grain size of specimen by two-step sintering and spark plasma sintering was around $0.6\;{\mu}m$ and $0.4\;{\mu}m$, respectively. Mechanical properties of ultra fine grained Mo with relative density of above 90% were significantly improved at room and high temperatures comparing to commercial bulk Mo of 99% relative density. This result was mainly explained by the grain size refinement due to diffusion-controlled sintering.
귀밑샘의 기무라병의 세침흡인 세포학적 소견 -세포학적 검사로 예측할 수 없었던 1예 보고-
김세훈,김혜령,김성은,양우익,이광길,홍순원,Kim, Se-Hoon,Kim, Hae-Ryoung,Kim, Sung-Eun,Yang, Woo-Ick,Lee, Kwang-Gil,Hong, Soon-Won 대한세포병리학회 2003 대한세포병리학회지 Vol.14 No.2
Kimura's disease is a chronic inflammatory disorder of unknown cause and is most prevalent among Asians. The cytologic findings of Kimura's disease are significant numbers of eosinophils in a background of lymphoid cells, occasional fragments of collagenous tissue, proliferation oi vessels, and Warthin-Finkeldey polykaryocytes. Among these features, the most important cytologic feature of Kimura's disease is a significant numbers of eosinophils. We experienced a case of Kimura's disease in the parotid gland which we fatted to recognize on cytology due to the apparent paucity of eosinophils. On careful retrograde reviewing of the cytologic findings, a few scattered leukocytes, previously interpreted as polymorphous leukocytes, had bilobed nuclei and coarse green but granular cytoplasm on Papanicolaou preparation. These leukocytes showed obvious orange-red intracyloplasmic granules as in eosionophils on Giemsa stain. The paucity of eosinophils may be due to the thick fibrosis around lymphoid follicles or any technical error during aspiration. Whereas the Warthin-Finkeldey type giant cell is not a sensitive cytologic marker of Kimura's disease, it may be a helpful cytologic feature. To reach a correct cytologic diagnosis of Kimura's disease, It is important to keep in mind that searching for Warthin-Finkeldey type giant cells and evaluation of Giemsa stain for detection of eosinophils would be helpful.
(Nd, Dy)-Fe-B 분말의 소결특성 및 상변화 연구
김세훈,김진우,김영도,Kim, Se-Hoon,Kim, Jin-Woo,Kim, Young-Do 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2
In this study, the sintering behavior of (Nd, Dy)-Fe-B powder which fabricated by strip-casting was investigated with various sintering temperatures and holding times. The relative density over 99% could be obtained by both sintering at $1070^{\circ}C$ for 1h and sintering at $970^{\circ}C$ for 20h. The grain growth was observed in sintered specimen at $1050^{\circ}C$ compared to one at $970^{\circ}C$. The isothermal sintering process below $1000^{\circ}C$ led to suppress grain growth showing the improved magnetic properties. The phase transformation of Nd-rich was confirmed by X-ray diffraction pattern.
반복 열처리한 Nd-Fe-B 소결 자석의 미세구조 제어 및 자성특성 평가
김세훈,김훈섭,김동환,김영도,Kim, Se-Hoon,Kim, Hoon-Sup,Kim, Dong-Hwan,Kim, Young-Do 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.6
Sintered Nd-Fe-B magnets have been widely used due to their excellent magnetic properties, especially for driving motors of hybrid and electric vehicles. The microstructure of Nd-Fe-B magnets strongly affects their magnetic properties, in particular the coercivity. Therefore, a post-sintering process like heat-treatment is required for improving the magnetic properties of Nd-Fe-B sintered magnets. In this study, cyclic heat treatment was performed at temperatures between $350^{\circ}C$ and $450^{\circ}C$ up to 16 cycles in order to control microstructures such as size and shape of the Nd-rich phase without grain growth of the $Nd_{2}Fe_{14}B$ phase. The 2 cycles specimen at this temperature range showed more homogeneous microstructure which leads to higher coercivity of 35 kOe than as-sintered one.
진공사출금형용 STS316L 금속 다공체 제조 및 기계적 특성
김세훈,김상민,노상호,김진평,신재혁,성시영,진광진,김태안,Kim, Se Hoon,Kim, Sang Min,Noh, Sang Ho,Kim, Jin Pyeong,Shin, Jae Hyuck,Sung, Si-Young,Jin, Jin Kwang,Kim, Taean 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.3
In this study, porous stainless steel (STS316L) sintered body was fabricated by powder metallurgy method and its properties such as porosity, compressive yield strength, hardness, and permeability were evaluated. 67.5Fe-17Cr- 13Ni-2.5Mo (wt%) powder was produced by a water atomization. The atomized powder was classified into size with under $45{\mu}m$ and over $180{\mu}m$, and then they were compacted with various pressures and sintered at $1210^{\circ}C$ for 1 h in a vacuum atmosphere. The porosities of sintered bodies could be obtained in range of 20~53% by controlling the compaction pressure. Compressive yield strength and hardness were achieved up to 268 MPa and 94 Shore D, respectively. Air permeability was obtained up to $79l/min{\cdot}cm^2$. As a result, mechanical properties and air permeability of the optimized porous body having a porosity of 25~40% were very superior to that of Al alloy.
김세훈,조태선,박민서,김영도,Kim, Se-Hoon,Jo, Tae-Sun,Park, Min-Suh,Kim, Young-Do 한국분말야금학회 2007 한국분말재료학회지 (KPMI) Vol.14 No.5
In recent years, a rapid increase in demands for the soft magnetic composite parts has been created and it has been tried to improve their properties by various processing methods, alloying elements and compaction parameters. Warm compaction method has been used for the reduction of residual stress, the improvement of magnetic properties and the higher densities. In this work, the effects of warm compaction and polymer binder on magnetic properties of Fe powder core were investigated. The sintering powder, Fe oxide, was ball-milled for 30n hours. And then ball-milled Fe oxide powder was reduced through hydrogen reduction process. The hydrogen reduced Fe powder and polymer binder were mixed by 3-D turbular mixer. And then the mixed powder was warm-compacted. The magnetic properties such as core loss and permeability were measured by B-H curve analyzer.
김세훈,석명진,김영도,Kim, Se-Hoon,Suk, Myung-Jin,Kim, Young-Do 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.4
3-D shape soft magnetic composite parts can be formed by general compaction method of powder metallurgy. In this study, the results on the high density nanostructured Fe-Si/Fe composite prepared by a warm compaction method were presented. Ball-milled Fe-25 wt.%Si powder, pure Fe powder and Si-polymer were mixed and then the powder mixture was compacted at various temperatures and pressures. Pore free density of samples up to 95% theoretical value has been obtained. The warm compacted sample prepared at 650 MPa and 240$^{\circ}C$ had highest compaction properties in comparison with other compacts prepared at 300, 400 MPa and room temperature and 120$^{\circ}C$. The magnetic properties such as core loss, magnetization saturation and coercivity were measured by B-H curve analyzer and vibration sample magnetometer.
김세훈,이영중,이제성,김영도,Kim, Se-Hoon,Lee, Young-Jung,Lee, Jea-Sung,Kim, Young-Do 한국분말야금학회 2007 한국분말재료학회지 (KPMI) Vol.14 No.3
Various approaches have been proposed to increase the green density. Warm compaction method has been used for the reduction of residual stress, the improvement of magnetic properties and the higher densities. In this work, the effect of warm compaction on green density of Fe powder was investigated. After ball-milling of Fe oxide powder for 30 hours, Fe oxide powder was reduced through the hydrogen reduction process. The pure Fe powder and polymer binder were mixed by 3-D tubular mixer. And then the mixed powder was warm-compacted with various compaction pressure and binder contents. The green density of specimen was added polyvinyl binder was higher than any other specimens.