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지창욱,김성훈,이재호,김양도,Ji, Chang-Wook,Kim, Seong-Hun,Lee, Jae-Ho,Kim, Yang-Do 한국재료학회 2009 한국재료학회지 Vol.19 No.11
Electrochemical deposition characteristics of CdSe nanorods were investigated for hybrid solar cell applications. CdSe nanorods were fabricated by electrochemical method in $CdSO_4$ and $H_2SeO_3$ dissolved aqueous solution using an anodic aluminum oxide (AAO) template. Uniformity of CdSe nanorods was dependent on the diameter and the height of holes in AAO. The current density, current mode, bath composition and temperature were controlled to obtain a 1:1 atomic composition of CdSe. CdSe nanorods deposited by direct-current method showed better uniformity compared to those deposited by purse-current and/or purse-reverse current methods due to the bottom-up filling characteristics. $H_2SeO_3$ concentration showed more significant effects on pH of solution and stoichiometry of deposits compared to that of $CdSO_4$. A 1:1 stoichiometry of uniform CdSe nanorods was obtained from 0.25M $CdSO_4-5$ mM $H_2SeO_3$ electrolytes with a direct current of 10 $mA/cm^2$ at room temperature. X-ray diffraction and electron diffraction pattern investigations demonstrate that CdSe nanorods are a uniform cubic CdSe crystal.
고융점 금속의 미소형상 정밀주조를 위한 탄소몰드의 적용성에 관한 연구
지창욱,이은주,김양도,임영목,Ji, Chang-Wook,Yi, Eun-Ju,Kim, Yang-Do,Rhyim, Young-Mok 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.2
Carbon material shows relatively high strength at high temperature in vacuum atmosphere and can be easily removed as CO or $CO_2$ gas in oxidation atmosphere. Using these characteristics, we have investigated the applicability of carbon mold for precision casting of high melting point metal such as nickel. Disc shape carbon mold with cylindrical pores was prepared and Ni-base super alloy (CM247LC) was used as casting material. The effects of electroless Nickel plating on wettability and cast parameters such as temperature and pressure on castability were investigated. Furthermore, the proper condition for removal of carbon mold by evaporation in oxidation atmosphere was also examined. The SEM observation of the interface between carbon mold and casting materials (CM247LC), which was infiltrated at temperature up to $1600^{\circ}C$, revealed that there was no particular product at the interface. Carbon mold was effectively eliminated by exposure in oxygen rich atmosphere at $705^{\circ}C$ for 3 hours and oxidation of casting materials was restrained during raising and lowering the temperature by using inert gas. It means that the carbon can be applicable to precision casting as mold material.
Al-Si 도금된 핫스탬핑 보론강의 저항 점용접시 도금층 용융거동 및 너겟 성장에 관한 연구
지창욱 ( Chang Wook Ji ),최일동 ( Il Dong Choi ),김양도 ( Yang Do Kim ),박영도 ( Yeong Do Park ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.11
The effect of coating melting behavior on nugget growth during resistance spot welding of hot- stamped boron steels was evaluated. A comparative analysis of the dynamic resistance for bare hot stamped and Al-Si coated hot stamped boron steels was carried out. The dynamic resistance curve of Al-Si coated hot stamped boron steel was higher than bare hot stamped boron steel during the whole stages of weld time. Higher α-peak and β-peak for Al-Si coated hot stamped boron steel resulted in larger nugget size at higher than 4.0 kA weld current owing to non-linear layer structure of alloyed coating, which appears to restrict the current passage through the faying interface. In the case of Al-Si coated hot-stamped boron steel, most of the Al-Fe intermetallic coatings are expected to be pushed away while in the liquid state at the faying interface. The pressure build up during the early stage of weld pushes the liquid Al-Fe intermetallic coating towards the edge of the faying interface. The continuous liquid state of Al-Fe intermetallic through the faying interface ensures the large contact area for the current passage to enlarge the nugget diameter. (Received June 1, 2014)
TMCP강의 용접 공정별 입열량에 따른 용접부 물성 평가 및 비교
최철영,지창욱,김형찬,남대근,김정돈,김순국,박영도,Choi, Chul Young,Ji, Chang Wook,Kim, Hyoung Chan,Nam, Dae-Geun,Kim, Joungdon,Kim, Soon Kook,Park, Yeong-Do 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.1
This paper has an aim to evaluate microstructure and fracture toughness of TMCP steel weldment applied for off-shore wind tower with the focus on the effect of heat input on the weldment with various welding processes; FCAW(13kJ/cm and 30kJ/cm), SAW(62kJ/cm), and EGW(177kJ/cm). Based on experimental results developed from this study, it was found that the impact toughness of top side for TMCP steel weldments with heat input up to 62 kJ/cm satisfied the required minimum value except the EGW(177kJ/cm). The heat input and microstructure are the main factors of impact toughness. The heat input of 13kJ/cm on back side with low heat input increased the amount of grain boundary ferrite which has low impact toughness, and heat input of 177kJ/cm on top side is significant enough to produce the austenite grain growth. The compositions and sizes of inclusions which are the dominant factors for the formation of acicular ferrite were analyzed by OM and EDS. As the heat input increased, the inclusions also grew and a nucleation site decreased. The size of nonmetallic inclusions and the crack width was nearly similar, therefore the inclusions were related with the crack propagation.