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김선이,김미래,손근용,박원욱,Kim, Sun-I,Kim, Mi-Rae,Sohn, Keun-Yong,Park, Won-Wook 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.4
The electromagnetic wave absorption sheets were fabricated by mixing of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHz$\sim$10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHz$\sim$1 GHz.
Fe계 나노결정립 분말 시트에 첨가된 CNT의 볼밀 공정에 따른 전자파 흡수 특성 변화
김선이,김미래,손근용,박원욱,Kim, Sun-I,Kim, Mi-Rae,Sohn, Keun-Yong,Park, Won-Wook 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.6
Electromagnetic wave energies are consumed in the form of thermal energy, which is mainly caused by magnetic loss, dielectric loss and conductive loss. In this study, CNT was added to the nanocrystalline soft magnetic materials inducing a high magnetic loss, in order to improve the dielectric loss of the EM wave absorption sheet. Generally, the aspect ratio and the dispersion state of CNT can be changed by the pre-ball milling process, which affects the absorbing properties. After the various ball-milling processes, 1wt% of CNTs were mixed with the nanocrystalline $Fe_{73}Si_{16}B_7Nb_{3}Cu_1$ base powder, and then further processed to make EM absorption sheets. As a result, the addition of CNT to Fe-based nanocrystalline materials improved the absorption properties. However, the increase of ball-milling time for more than 1h was not desirable for the powder mixture, because the ballmilling caused the shortening of CNT length and the agglomeration of the CNT flakes.
리튬이차전지용 다공성 Si-Ge-Al계 음극활물질의 전기화학적 특성
조충래,김명근,손근용,박원욱,Cho, Chung Rae,Kim, Myeong Geun,Sohn, Keun Yong,Park, Won-Wook 한국분말야금학회 2017 한국분말재료학회지 (KPMI) Vol.24 No.1
Silicon alloys are considered promising anode active materials to replace Li-ion batteries by graphite powder, because they have a relatively high capacity of up to 4200 mAh/g, and are environmentally friendly and inexpensive ECO-materials. However, its poor charge/discharge properties, induced by cracking during cycles, constitute their most serious problem as anode electrode. In order to solve these problems, Si-Ge-Al alloys with porous structure are designed as anode alloy powders, to improve cycling stability. The alloys are melt-spun to obtain the rapidly solidified ribbons, and then ball-milled to make fine powders. The powders are etched using 1 M HCl solution, which gives the powders a porous structure by removing the element Al. Subsequently, in this study, the microstructures and the characteristics of the etched powders are evaluated for application as anode materials. As a result, the etched porous powder shows better electrochemical properties than as-milled Si-Ge-Al powder.
유럽지역의 마그네슘 합금의 자동차 부품적용 현황과 전망
강민철(Min Cheol Kang),손근용(Keun Yong Sohn) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Magnesium alloys have recently been considered as candidate materials for many automotive components in Europe and North America because of their high specific strength and stiffness with good damping capacity. With the growing environmental reinforcements, the magnesium alloys consumption in automobiles is projected to grow in next decade. Currently, many automobile makers in Europe including Volks Wagen and BMW use magnesium alloys for powertrain components, chassis, and suspension parts. In this paper, the applications of magnesium alloys to automobiles, the prospects of their consumption, and the demand and suppy of magnesium ingots in Europe have been reviewed.<br/>
김현식 ( Hyun Sik Kim ),예대희 ( Dea Hee Ye ),강민철 ( Min Cheol Kang ),손근용 ( Keun Yong Sohn ),정해용 ( Hae Yong Jeong ) 한국주조공학회 2014 한국주조공학회지 Vol.34 No.1
Magnesium and its alloys are being applied to various kinds of industrial fields, especially their use on automotive parts and electronic part. These parts are manufactured mainly through die casting process and magnesium ingots are used as raw materials. In the case that ingot quality is not secured, massive casting defects can occur and some manufactures can be damaged by the defects. This study is to evaluate ingots` cleanliness of magnesium alloys. It includes composition analysis by spectrometer, measurement of inclusion contents by SEM, brightness test on fractured surface and etc. Especially, the brightness test is a very easy and quick evaluation method. The brightness becomes low when the amount of oxides or inclusions on the surface increases. The brightness test data have been compared with those obtained from other methods for measuring the mount of impurities, which showed good relationship between the brightness and the others. Thus, the brightness test could be a promising method to measure the cleanliness of magnesium alloys.
퍼멀로이 분말이 혼합된 철계 나노결정립 분말코어의 성형밀도와 연자성 특성에 관한 연구
신정훈 ( Jeong Hoon Shin ),정영목 ( Young Mok Jeong ),손근용 ( Keun Yong Sohn ),박원욱 ( Won-wook Park ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.9
Abstract: In this paper, the soft magnetic properties and compaction density of Fe-Si-B-Nb-Cu nanocrystalline powder cores, mixed with two kinds of permalloy powders (Ni<sub>70</sub>Fe<sub>30</sub> or Ni<sub>50</sub>Fe<sub>50</sub>), have been closely studied. Permalloy powders having an average diameter of 4 μm were added in the range of 5 to 15 wt%, and the powder composite was mixed with 1~2 wt% of water glass diluted with DI water. The powder cores were compacted in toroidal form at a pressure of about 35 tons, and then heat treated at 510 ~ 570 ℃ for 1 h. The magnetic properties of the soft magnetic composites (SMCs) were measured with a B-H analyzer and the microstructure was observed with FE-SEM. As a result, it was determined that the compaction density of the powder core increased with the increasing content of the mixed permalloy powder, which distinctly improved the composite`s magnetic properties, including initial permeability and core loss. (Received December 30, 2016; Accepted May 12, 2017)
순철분말을 혼합한 철계 비정질분말 코어의 성형성과 자기적특성 연구
윤성춘 ( Sung Choon Yoon ),문선규 ( Sun Gyu Moon ),손근용 ( Keun Yong Sohn ),박원욱 ( Won Wook Park ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.8
The effects of densification on the magnetic properties were studied in Fe-based amorphous powder cores mixed with pure iron powder. To normalize the effect of powder size on magnetic properties, the rapidly solidified amorphous powders were sieved and classified. The amorphous powders of .150 to +270 mesh were mixed with the pure iron powder of 3 μm in diameter up to 20 wt%. The powder composites were mixed with 2 wt% water glass diluted by DI Water at a ratio of 1:2. For the consolidation, the powder composites were compacted into a cylindrical die with lubricant to form toroidal cores, which were subsequently heat-treated at 430-460 ℃ for 10 minutes. The soft magnetic properties of the powder cores were investigated using a B-H curve analyzer and a flux meter at the frequency range of 10-100 kHz. The microstructure of the mixed powders and the compacted cores were observed using FE-SEM. It was notable that the density of the powder composites increased with an increase of the pure iron powders. As a result, the permeability and the core loss of the composite cores (especially, mixed with ~10 wt% pure iron powders) were greatly improved over those of conventional amorphous powder cores.
저합금강의 이중 오스테나이징 템퍼링에서 냉각 속도에 따른 미세조직 및 기계적 특성 변화
김경후 ( Gyeong-hoo Kim ),장재호 ( Jae-ho Jang ),김성환 ( Sung-hwan Kim ),김병준 ( Byung-jun Kim ),손근용 ( Keun-yong Sohn ),남대근 ( Dae-geun Nam ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.8
Spent nuclear fuel is stored and transported in cask bodies, but they become embrittled with the passage of time resulting in lattice defects due to neutron irradiation. Cask bodies made by the quenching and tempering (QT) treatment are not safe and are hard to store because of embrittlement caused by high levels of radiation and heat over long periods. Recently, it was shown that the double austenitizing tempering (DAT) treatment resulted in a significant improvement in strength and toughness as a result of austenite grain refinement. In this study, we evaluated the effects of DAT treatment for improving the mechanical properties of low alloy steel. We also investigated the effects of cooling rate on the DAT treatment. It was found that the charpy impact properties of the alloy were improved by the DAT treatment, which used water cooling comparing, compared to the QT heat treated specimen. As a result of microstructure analysis, it was determined that the grain size and carbide morphology were affected by mechanical properties such as the tensile, hardness and impact property. (Received January 20, 2017; Accepted March 24, 2017)
마그네슘용탕의 니켈 함량에 미치는 알루미늄, 망간 및 지르코늄의 영향
정대영 ( Dae Yeong Jeong ),문영훈 ( Young Hoon Moon ),문병기 ( Byoung Gi Moon ),박원욱 ( Won Wook Park ),손근용 ( Keun Yong Sohn ) 한국주조공학회 2015 한국주조공학회지 Vol.35 No.1
Variations of nickel contents and microstructures in molten magnesium alloys on the addition of aluminum, zirconium, and manganese have been investigated. Specimens were prepared by melting under SF6 and CO2 atmosphere and casting into a disc of 29 mm diameter with 7~10 mm thickness from the melt acquired at the top of crucible. Before casting, the molten metal was stirred for 3 minutes after each addition of alloying elements and maintained for 30 minutes for settling down. Results showed that zirconium did not significantly affect the content of nickel while aluminum remarkably reduced it by forming Al3Ni2 phase. When manganese are added to Mg-1wt%Ni alloy along with aluminum, both elements remarkably reduced the content of nickel. The addition of 1.5 wt% manganese to Mg-1wt%Ni alloy containing aluminum further reduced the content of nickel by more than 30%, during which an additional intermetallic phase Al10Mn3Ni was precipitated in the molten magnesium.