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가스분무한 Al-Si-Fe 합금분말 압출재의 기계적 성질
나형용,최이식 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.4
Al-(20,30wt%)Si-(3,5,8wt%)Fe alloy powders were consolidated by hot extrusion and the change powder microstructure during extrusion was investigated. The effects of Fe addition to Al-Si alloy on the mechanical properties, wear and heat resistance of extruded bars were examined, too. During extrusion of Al-Si-Fe alloy powders, primary Si is broken into fragments from 10∼20 ㎛ size to size less than 10 ㎛ and intermetallic compound from 20∼50 ㎛ size to size less than 5 ㎛. The intermetallic compound in matrix is broken finely, too. Additionally, during extrusion metastable δ phase(Al₄FeSi₂) intermetallic compound disappears and the equilibrium β phase(Al_5FeSi) is formed. Al-Si-Fe alloys showed better mechanical properties, wear and heat resistance than Al-Si binary alloys, resulting from the composite like hardening and matrix hardening by finely distributed primary and eutectic intermetallic compound. Especially, Al-20Si-8Fe alloy showed best physical properties in this work
나형용,최이식 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.2
In this study Al-(20,30wt%)Si-(3,5,8wt%)Fe alloy powders were manufactured by gas atomization and the characteristics of alloy powders were investigated. In rapidly solidified Al-Si-Fe alloy powders, primary δ phase (Al₄FeSi₂) with 20∼50 ㎛ in size is observed with primary Si. And the matrix of the powders consists of ternary eutectic of α-Al, Si and intermetallic compound. This intermetallic compound is found in the intercellular regions of α-Al in very small alloy powders, too. When Al-Si-Fe alloy powders are heat treated, the metastable δ phase disappears and equilibrium β phase(A1_5FeSi) is formed and residual Si precipitates around intermetallic compound. It is expected that the materials formed of Al-Si-Fe alloy powders will show better wear resistance, heat resistance and mechanical properties than Al-Si binary alloys due to finely distributed primary and eutectic intermetallic compounds.
과공정 Al-Si-(Fe) 합금의 마멸특성에 미치는 정출상의 영향
김원태,나형용,최이식,서해영 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.11
It was known that the wear characteristics of hypereutectic Al-Si alloys are mainly affected by the size and the volume fraction of primary Si phases. However, the effects of the size and the volume fraction of primary Si phases on the wear characteristics was not yet clear. Thus these were investigated in this study, and the effect of Fe addition on the wear characteristics was also studied. The wear test was carried out with variations of load (30∼2OON) and sliding speed (0.2, 1, 2m/s) at a constant sliding distance(2000m) on a pin-on-disk type wear testing machine. As a result, the Al-20Si-5Fe alloy, which had the primary phases of medium size(20∼30㎛), had the highest wear-transition-load(200N at sliding speed of 1m/s). The reason was related to MML (Mechanically Mixed Layer). MML, which was formed on alloy's worn surface, had the higher hardness than the matrix and played a role as solid-lubricants. Therefore it seemed that the MML protected the matrix from contacting with counterface and held back the thermal softening of matrix by inhibiting the temperature rising of the surface. The MML of Al-20Si-5Fe, which had primary phases of 20∼30㎛, had the highest hardness and inhibited most effectively the temperature rising of the surface.
Si-FeSi2/C Nanocomposite Anode Materials Produced by Two-Stage High-Energy Mechanical Milling
양윤모,Chadrasekhar Loka,김동필,주신용,문성환,최이식,박정한,이기선 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.3
High capacity retention Silicon-based nanocomposite anode materials have been extensively explored for use inlithium-ion rechargeable batteries. Here we report the preparation of Si-FeSi2/C nanocomposite through scalable atwo-stage high-energy mechanical milling process, in which nano-scale Si-FeSi2 powders are besieged by thecarbon (graphite/amorphous phase) layer; and investigation of their structure, morphology and electrochemicalperformance. Raman analysis revealed that the carbon layer structure comprised of graphitic and amorphous phaserather than a single amorphous phase. Anodes fabricated with the Si-FeSi2/C showed excellent electrochemicalbehavior such as a first discharge capacity of 1082 mAh g-1and a high capacity retention until the 30thcycle. Aremarkable coulombic efficiency of 99.5% was achieved within a few cycles. Differential capacity plots of the Si-FeSi2/C anodes revealed a stable lithium reaction with Si for lithiation/delithiation. The enhanced electrochemicalproperties of the Si-FeSi2/C nanocomposite are mainly attributed to the nano-size Si and stable solid electrolyteinterface formation and highly conductive path driven by the carbon layer.
다공성 흑연 소재를 이용한 바나듐 도핑된 반절연 SiC 단결정 성장의 특성 연구
이동훈,김황주,김영곤,최수훈,박미선,장연숙,이원재,정광희,김태희,최이식,Lee, Dong-Hun,Kim, Hwang-Ju,Kim, Young-Gon,Choi, Su-Hun,Park, Mi-Seon,Jang, Yeon-Suk,Lee, Won-Jae,Jung, Kwang-Hee,Kim, Tae-Hee,Choi, Yi-Sik 한국결정성장학회 2016 한국결정성장학회지 Vol.26 No.6
본 연구에서는 다공성 흑연 캡슐에 Vanadium carbide(VC) 분말을 채워 성장시킨 방법과 SiC 분말과 VC 분말을 혼합하여 다공성 흑연판을 그 위에 덮은 후 성장시키는 방법으로 진행하였으며, 성장된 결정들은 여러 분석방법을 사용하여 각각의 특성들을 관찰하였다. 반절연 SiC 성장은 6H-SiC 종자 결정을 사용하여 PVT(Physical Vapor Transport)법으로 성장을 진행하였다. 반절연으로 성장된 SiC 결정은 XRD를 이용하여 6H-SiC인 것을 확인하였으며, SIMS 분석결과 바나듐 도핑 농도가 바나듐 용해의 한계값 보다 높을 경우 석출물이 발생되며, 결정 품질 저하의 원인이 됨을 확인할 수 있었다. Vanadium-doped SiC crystals have been grown by using a porous graphite inner crucible filled with vanadium carbide (VC) and by using a porous graphite plate and SiC + VC powders, respectively. Semi-insulating SiC crystals were grown onto the 6H-SiC seed crystals by PVT (Physical Vapor Transport) method. The grown crystals were indicated to be 6H-SiC polytype by XRD. As result of SIMS analysis, vanadium-rich precipitates were observed when the vanadium concentration was relatively higher than the maximum solubility of vanadium ($3-5{\times}10^{17}cm^{-3}$) in vanadium-doped SiC crystals, which resulted in degradation of crystal quality.