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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.
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.
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.
(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.
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.
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.
당뇨 환자에서 경막외 농양과의 감별을 요한 원발성 척추 경막외 임파종 - 증례보고 -
김세훈,임동준,조태형,정용구,이훈갑,이기찬,서중근,Kim, Se Hoon,Lim, Dong Jun,Cho, Tai Hyoung,Chung, Yong Gu,Lee, Hoon Kap,Lee, Ki Chan,Suh, Jung Keun The Korean Neurosurgical Society 2001 Journal of Korean neurosurgical society Vol.30 No.3
척추 경막외 임파종은 전체 임파종의 7%정도를 차지하며, 가장 흔한 증상으로 척수 압박 증세를 유발하는 것으로 알려져 있다. 그 중에서도 원발성 척추 경막외 임파종, 즉 다른 장기의 침범 소견 없이 척추에만 국한되어 나타난 임파종은, 당뇨병 환자에서 급성 척수 압박 증상으로 나타났을 때, 척추 경막외 농양과의 감별을 요한다. 저자들은 48세의 여자 당뇨 환자에서 흉추부의 통증으로 내원 1개월 전까지 여러 차례 침술치료를 받고 난 후 통증이 악화되고 급성 하반신 부전마비와 배뇨 장애 및 감염 징후가 있어 본원에 내원하여, 병력과 제반 검사상 수술전에 척추 경막외 농양으로 진단되었던 원발성 척추 경막외 임파종 1례를 수술 치험하고 보고하는 바이다. Primary spinal epidural lymphoma(SEL), i.e. occurring in the absence of any detectable extraspinal lymphoproliferative disorder, is an unusual cause of spinal cord compression. The authors report a 48-year-old, diabetic woman presented with back pain followed by acute paraparesis and voiding difficulty. She had been treated with acupunctures on her back before admission, and complete blood count showed leukocytosis with neutrophilia and increased erythrocyte sedimentation rate(ESR). Thoracic spine magnetic resonance imaging(MRI) revealed an epidural mass extending from T5 to T8 with compression of the spinal cord. Emergency decompressive laminectomy was performed with a tentative diagnosis of spinal epidural abscess, but a B-cell lymphoma was final pathologic diagnosis. Further staging showed no other sites of lymphoma, and the spinal lesion was treated by chemotherapy and radiotherapy. The authors stress that primary SEL can mimic spinal epidural abscess(SEA) in the diabetic patient and should be a diagnostic consideration in patients with a syndrome of acute spinal cord compression manifested by a prodrome of back pain and neuroimaging consistent with an epidural compressive lesion, especially in a diabetic.