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연속주조법에 의한 Al-11.3wt%Si 합금의 미세조직 변화에 미치는 Ti 및 Sr 의 영향
정찬회,김명한,조형호 ( Chan Hoi Jung,Myung Han Kim,Hyung Ho Jo ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.5
N/A The horizontal continuous casting process with the heated mold has been applied to study the effect of grain refiner or modifier such as Ti or Sr, respectively, in Al-11.3wt%Si alloy. The results represented that the addition of 0.02%Sr or 0.2∼0.4%Ti promoted the directionality of primary α dendrite, whereas the addition of 0.6%Ti suppressed the directionality. Also, the addition of 0.02%Sr suppressed the occurrence of feathery grains, while the addition of 0.2%Ti promoted the occurrence of feathery grain. The addition of Ti over 0.4% suppressed the occurrence of feathery grain, resulting from the in creasing grain-refining effect. The addition of Ti also increased the coarsening effect of eutectic silicon phase in Al-11.3%Si alloy.
RF 스퍼터링으로 증착된 하이드록시아파타이트 박막의 열처리 특성
정찬회,이준희,신윤학,김명한,최석환,김승언,Jung, Chan-Hoi,Lee, Jun-Hee,Shin, Youn-Hak,Kim, Myung-Han,Choi, Sock-Hwan,Kim, Seung-Eon 한국재료학회 2006 한국재료학회지 Vol.16 No.4
RF sputtering process was applied to produce thin hydroxyapatite(HAp) films on Ti-6Al-4V alloy substrates. The effects of different heat treatment conditions on the hardness between HAp thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the Ti-6Al-4V alloy substrates were heat treated for 1h at $850^{\circ}C\;under\;3.0{\times}10^{-3}torr$, and after deposition, the HAp thin films were heat treated for 1h at $400^{\circ}C,\;600^{\circ}C\;and\;800^{\circ}C$ under the atmosphere, and analyzed FESEM-EDX, FTIR, XRD, nano-indentor, micro-vickers hardness, respectively. Experimental results represented that the surface defects of thin films decreased by relaxation of internal stress and control of substrate structure followed by heat treatment of substrates before the deposition, and the HAp thin films on the heat-treated substrates had higher hardness than none heattreated substrates before the deposition, and the hardness properties of HAp thin films and Ti-6Al-4V alloy substrates appeared independent behavior, and the hardness of HAp thin films decreased by formation of $VTiO_3(OH),\;{\theta}-Al_{0.32}V_2O_5,\;Al_{0.33}V_2O_5$.
정찬회,김순국,이준희,정세진,김익수,Jung, Chan-Hoi,Kim, Soon-Kook,Lee, Jun-Hee,Jeong, Se-Jin,Kim, Ik-Soo 한국재료학회 2007 한국재료학회지 Vol.17 No.1
The effects of immersion time in the liquid nitrogen and deformation-induced martensitic transformation on the behavior of austenite stainless steels used for the hydrogen storage tank of auto-mobile at cryogenic temperature were investigated. With increasing of immersion time in the liquid nitrogen, the tensile strength of all austenite stainless steels at cryogenic temperature was increased because the martensite transformation of unstable austenite. The restraint of crack generation ana transmission also increased the tensile strength by the active ${\alpha}'$ transformation. The elongation decreasing of 321 steel is not the mechanical deformation of austenite phase but the stress induced martensite phase during the tensile test.
RF 스퍼터링으로 증착된 하이드록시아파타이트 박막의 ESCA 분석
정찬회,이준희,김순국,김명한,유재근,김승언,Jung, Chan-Hoi,Lee, Jun-Hee,Kim, Soon-Kook,Kim, Myung-Han,Yu, Jae-Keun,Kim, Seung-Eon 한국재료학회 2006 한국재료학회지 Vol.16 No.4
RF sputtering process was applied to produce thin hydroxyapatite(HAp) films on Ti-6Al-4V alloy substrates. The effects of different heat treatment conditions on the chemical composites between HAp thin films and Ti-6Al-4V alloy substrates were studied. After deposition, the HAp thin films were heat treated for 1h at $400^{\circ}C,\;600^{\circ}C\;and\;800^{\circ}C$ under the atmosphere, and analyzed O/M, FESEM-EDX and ESCA, respectively. Experimental results represented that interface of HAp thin films and Ti-6Al-4V alloy substrates was composed Ti-OH, TiO, TiN, $Al_2O_3,\;V_2O_3,\;VO_2$. pyrophosphate and decreased carbide followed by the increase of heat treatment temperature.
정찬회,김순국,이준희,이해우,장창우,Jung, Chan-Hoi,Kim, Soon-Kook,Lee, Jun-Hee,Lee, Hae-Woo,Jang, Chang-Woo 한국재료학회 2007 한국재료학회지 Vol.17 No.4
The effects of immersion time in the liquid nitrogen on the behavior of aluminum alloys used for the hydrogen storage tank of auto-mobile at cryogenic temperature were investigated. With increasing immersion time in the liquid nitrogen, the elongation of AI 5083 alloy at cryogenic temperature decreased because of non-uniform fracture of precipitates on the grain boundary, and the serration also occurred because of discontinuous slip due to rapid decreasing of the specific heat. The mechanical properties of AI 6061 alloy at cryogenic temperature were characterized by uniformed yield strength, tensile strength and elongation regardless of the immersion time in the liquid nitrogen. These mechanical properties of aluminum alloys at cryogenic temperature were interpreted by the strength of grain boundary and the slip deformation behavior.
RF 스퍼터링용 Hydroxyapatite 타겟의 제조 및 Hydroxyapatite/Ti-6Al-4V 합금 박막의 특성(I)
정찬회,김명한,Jung, Chan-Hoi,Kim, Myung-Han 한국재료학회 2003 한국재료학회지 Vol.13 No.4
RF sputtering process was applied to produce thin hydroxyapatite[HA, Ca10($PO_4$)$_{6}$ $ (OH)_2$films on Ti-6Al-4V alloy substrates. To make a 101.6 mm dia.${\times}$5 mm HA target, the commercial HA powder was first calcinated for 3h at $200^{\circ}C$. A certain amount of the calcinated HA powder was pressed under a pressure of 20,000 psi by the cold isostatic press(CIP) and the pressed HA target was sintered for 6 h at $1,200^{\circ}C$. The effects of different heat treating conditions on the bonding strength between HA thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the alloy substrates were annealed for 1 h at $850^{\circ}C$ under $3.0${\times}$10^{-3}$ Xtorr, and after deposition, the hydroxyapatite/Ti-6Al-4V alloy thin films were annealed for 1 h at 400, 600 and $800^{\circ}C$ under the atmosphere, respectively. Experimental results represented that the HA thin films on the annealed substrates had higher hardness than non-heat treated substrates before the deposition.
카운터 기반 디지털 보상 기법을 이용한 위상 고정 루프
정찬회(Chan-Hui Jeong),Ammar Abdullah,이관주(Kwan-Joo Lee),김훈기(Hoon-Ki Kim),김수원(Soo-Won Kim) 대한전기학회 2011 전기학회논문지 Vol.60 No.2
A digital technique is adopted to calibrate the current mismatch of the charge pump (CP) in phase-locked loops. A 2 ㎓ charge pump PLL (CPPLL) is used to justify the proposed calibration technique. The proposed digital calibration technique is implemented simply using a counter. The proposed calibration technique reduces the calibration time by up to a maximum of 50% compared other with techniques. Also by using a dual-mode CP, good current matching characteristics can be achieved to compensate 0.5㎂ current mismatch in CP. It was designed in a standard 0.13㎛ CMOS technology. The maximum calibration time is 33.6μs and the average power is 18.38㎽ with 1.5V power supply and effective area is 0.1804㎟.
김순국,장창우,이준희,정찬회,서용권,강충길,Kim, Soon-Kook,Jang, Chang-Woo,Lee, Jun-Hee,Jung, Chan-Hoi,Seo, Yong-Gwon,Kang, Choong-Gil 한국재료학회 2006 한국재료학회지 Vol.16 No.8
In recent years, Magnesium (Mg) and its alloys have become a center of special interest in the automobile industry. Due to their high specific mechanical properties, they offer a significant weight saving potential in modern vehicle constructions. Most Mg alloys show very good machinability and processability, and even the most complicated die-casting parts can be easily produced. The die casting process is a fast production method capable of a high degree of automation for which certain Mg alloys are ideally suited. In this study, step-dies and flowability tests for AM50 were performed by die-casting process according to various combination of casting pressure and plunger velocity. We were discussed to velocity effect of forming conditions followed by results of microstructure, FESEM-EDX, hardness and tensile strength. Experimental results represented that the conditions of complete filling measured die-casting pressure 400 bar, 1st plunger velocity 1.0 m/s and 2nd plunger velocity 6.0 m/s. The increasing of 2nd plunger velocity 4.0 to 7.0 m/s decreased average grain size of $\alpha$ phase and pore. It was due to rapid filling of molten metal, increasing of cooling rate and pressure followed by increased 2nd plunger velocity. The pressure should maintain until complete solidification to make castings of good quality, however, the cracks were appeared at pressure 800bar over.
이온빔에 의한 Cu/Polyimide 표면개질에 따른 접착력향상에 관한 연구
신윤학,추준식,이승우,정찬회,김명한,Shin Youn-Hak,Chu Jun-Sick,Lee Seoung-Woo,Jung Chan-Hoi,Kim Myung-Han 한국재료학회 2005 한국재료학회지 Vol.15 No.1
In microelectronics packaging, the reliability of the metal/polymer interfaces is an important issue because the adhesion strength between dissimilar materials is often inherently poor. The modification of polymer sufaces by ion beam irradiation and rf plasma are commonly used to enhance the adhesion strength of the interface. T-peel strengths were measured using a Cu/polyimide system under varying $Ar^+$ ion beam irradiation pretreatment conditions. The measured T-peel strength showed reversed camel back shape regarding the fixed metal-layer thickness, which was quite different from the results of the $90^{\circ}$ peel test. The elementary analysis suggests that the variation of the T-peel strength is a combined outcome of the plastic bending work of the metal and polymer strips. The results indicate that the peel strength increases with $Ar^+$ ion beam irradiation energy at the fixed metal-layer thickness.