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알칼리 용액이 수소배관으로 사용되는 Stainless steel에 미치는 영향 분석
변창섭,최진영,임수곤,황갑진,신훈규 한국수소및신에너지학회 2012 한국수소 및 신에너지학회논문집 Vol.23 No.3
This study was performed to observe the change of stainless steel pipe interacting with alkaline solution. We used STS316L and STS304 as samples which were soaked in alkaline solution. We measured the samples by use of FE-SEM, EDX, SIMS to observe the surface and depth profile of both samples. The result showed that the precipitate appeared on the surface of both samples from 5 days. but the precipitate was confirmed to be decreased as time passes. but the quantitative change of precipitates at both samples was different as time passed. The EDX showed that the precipitate is Potassium from solution of Electrolysis. The result also showed that the primary elements of stainless steel pipeline and of Alkaline Solution were changed. The change of primary elements was severe between 5 days to 16 days and was stable around 40 days at both samples. The reaction of STS316L with alkaline solution was lower than STS304. We hoped that this study would be the foundation of developing the electrode of the alkaline hydrogen generator.
기계적 합금화과정에서의 in situ 열분석에 의한 Ti-50.0~66.7at%Si 분말의 합성거동
변창섭,이상호,이원희,현창용,김동관,Byun Chang Sop,Lee Sang Ho,Lee Wonhee,Hyun Chang Yong,Kim Dong Kwan 한국재료학회 2004 한국재료학회지 Vol.14 No.5
Mechanical alloying (MA) of Ti-50.0~66.7at%Si powders was carried out in a high-energy ball mill, and in situ thermal analysis was also made during MA. In order to classify the synthesis behavior of the powders with respect to at%Si, the synthesis behavior during MA was investigated by in situ thermal analysis and X-ray diffraction (XRD). In situ thermal analysis curves and XRD patterns of Ti-50.0~59.6at%Si powders showed that there were exothermic peaks during MA, indicating TiSi, $TiS_2$, and $Ti_{5}$ $Si_4$ phase formation by a rapid exothermic reaction of self-propagating high-temperature synthesis (SHS). Those of Ti-59.8~66.7 at%Si powders, however, showed that there were no peaks during MA, indicating any Ti silicide was not synthesised until MA 240 min. For Ti-50.0~59.6at%Si powders, the critical milling times for SHS increased from 34.5 min to 89.5 min and the temperature rise, $\Delta$T (=peak temperature-onset temperature) decreased form $26.2^{\circ}C$ to $17.1^{\circ}C$ as at%Si increased. The critical composition of Si for SHS reaction was found to be 59.6at% and the critical value of the negative heat of formation of Ti-59.6at%Si to be -1.48 kJ/g.
변창섭,임수곤,김수곤,신훈규,Byun, Chang-Sub,Lim, Soo-Gon,Kim, Su-Kon,Shin, Hoon-Kyu 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.7
We investigated the variation of anion exchange membrane of hydrogen generator of alkaline electrolysis. We detected the variation of elements and change of anion exchange membrane using EDS and FE-SEM. We detected two different sites of membrane because of different structure of membrane. $Sp_1$ shows that the distribution ratio of C, O, Al is 98% very higher than $Sp_2$ of 78%. Especially, the main elements of STS316 which is P, S, Fe, Ni were more detected at $Sp_2$ than $Sp_1$. We think that this result depends on the structure of membrane. This also affect the resistance, lifetime of membrane and decrease the efficiency of hydrogen production. We hope that this article is a foundation of developing of hydrogen production technology.
전기방전에 의한 Ti rod의 열처리 및 표면개질 특성에 관한 연구
변창섭,오낙현,안영배,천연욱,김영훈,조유정,이충민,이원희,Byun, C.S.,Oh, N.H.,An, Y.B.,Cheon, Y.W.,Kim, Y.H.,Cho, Y.J.,Lee, C.M.,Lee, W.H. 한국재료학회 2006 한국재료학회지 Vol.16 No.3
Single pulse of 2.0 to 3.5 kJ from $150{\mu}F$ capacitor was applied to the cp Ti rod for its surface modification and heat treatment. Under the conditions of using 2.0 and 2.5 kJ of input energy, no phase transformation has been occurred. However, the hardness and tensile strength decreased and the elongation increased after a discharge due to a slight grain growth. By using more than 3.0 kJ of input energy, the electro discharge made a phase transformation and the hardness at the edge of the cross section increased significantly. The Ti rod before a discharge was lightly oxidized and was primarily in the form of $TiO_2$. However, the surface of the Ti rod has been instantaneously modified by a discharge into the main form of TiN from $TiO_2$. Therefore, the electro discharge can modify its surface chemistry in times as short as $200{\mu}sec$ by manipulating the input energy, capacitance, and discharging environment.
정전기분사 증착법을 이용한 Hydroxyapatite (HA) 코팅에 관한 연구
변창섭,이원희,오낙현,김영훈,천연욱,이상호 한국생체재료학회 2005 생체재료학회지 Vol.9 No.3
Coatings of hydroxyapatite (HA) on titanium substrate have been conducted by electrostatic spray deposition (EDS). Electrostatic spray deposited HA films on Ti were heat-treated (400~900) and their physical characteristics were investigated by Scanning Electronic Microscopy (SEM), X-ray Diffractometer (XRD), and X-ray Photoelectronic Spectroscopy (XPS). The precursor of solution for the HA coating by ESD was prepared by mixing of nano-sized HA powder with ethyl alcohol. As-deposited HA films were consisted of HA particles which were distributed uniformly on the Ti substrate, showing a porous structure. By heat treatment (400~900oC), less porous and crystalline HA films were formed on Ti substrate. Major surface elements on the heat treated HA samples were Ca and P in the form of HA. It is concluded that EDS can be applied to the formation of uniform and crystalline HA films on Ti substrate.
기계적 합금화시 $Ti_3Si$ 및 $TiSi_2$ 합성에 미치는 분말 혼합도의 영향
변창섭 한국분말야금학회 1999 한국분말재료학회지 (KPMI) Vol.6 No.1
Different sizes of Si powder and milling medium materials (steel and partially stabilized zirconia (PSZ)) were used to synthesize $Ti_3Si$ and $TiSi_2$ by mechanical aollying (MA) of Ti-25.0.at.%Si and Ti-66.7at.% Si powder mixtures. the formation of each titanium silicide did not occur even after 360 min of MA of as-re-ceived Si and Ti powder mixtures due to the lack of homogeneity. $Ti_3Si$, however, was synthesized after 240 min of MA of Ti and 60 min-premilled Si powder mixture. ${\alpha}-TiSi_2$ and $TiSi_2$ were produced by jar milling of Ti and 60 min-premilled Si powder mixture for 48 hr and high -energy PSZ ball-milling in a steel vial for 360 min. The formation of each titanium silicide was characterized by a slow reaction rate as the reactants and product(s) coexisted for a certain period of time. The formation of $Ti_3Si$ and $TiSi_2$ and the reaction rates appeared to be influenced by the Si particle size, the homogeneity of the powder mixtures and the milling medium materials.
알칼리 전해액의 상호작용에 의한 Stainless Steel 주성분의 변화 분석
변창섭,임수곤,김수곤,최호상,신훈규,Byun, Chang-Sub,Lim, Soo-Gon,Kim, Su-Kon,Choi, Ho-Sang,Shin, Hoon-Kyu 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.7
In this paper, We studied the change of surface and variation of elements on both electrodes of hydrogen generator of alkaline electrolysis in use of FE-SEM and SIMS. We used the stainless steel 316(600 ${\mu}m$) as electrode in condition of 25%KOH, $60^{\circ}C$ Temperature. The results show that the intensity of elements (C, Si, P, S, Ti, Cr, Mn, Fe, Ni, Mo) of Positive Electrode are decreased as much as about $10^1{\sim}10^3 $than the original electrode. Thickness of Positive Electrode is decreased about 40 ${\mu}m$ after chemical reaction. The negative electrode, however, shows a slight variation in the intensity of elements (C, Si, P, Fe, Ni, Mn, Mo) but Change of thickness and surface' shape of electrode show nothing after chemical reaction. The change in thickness and variation of Stainless Steel 316 cause the lifetime of electrode to be shorted. We also observed hydrogen, oxygen, potassium in both electrodes. Especially, The potassium is increased in proportional with depth of positive electrode. this means the concentration of alkali solutions is changed. and so we have to supply alkaline solution to generator in order to produce same quantity of hydrogen gas continuously. we hope that this study gives a foundation to develop the electrode for hydrogen generator of alkaline electrolysis.
기계적 합금화에 의한 Ni Silicide 분말의 합성
변창섭 한국분말야금학회 1999 한국분말재료학회지 (KPMI) Vol.6 No.2
Nickel silicides ($Ni_5$Si$_2$, Ni$_2$Si and NiSi) have been synthesized by mechanical alloying (MA) of Ni-27.9at.9at%Si, Ni-33.3at% and Ni-50.0at% powder mixtures, respectively. From in situ thermal analysis, eash citical milling period for the formation of the three phases was observed to be 40.2, 34.9 and 57.5 min, at which there was a rapid increase in temperature. This indicates that rapid, self-propagating high-temperature synthesis (SHS) reactions were observed to produce the three phases during room-temperature high-energy ball milling of elemental powders. Each Ni silicide, Ni and Si, however, coexisted for an extended milling time even after the critical milling period. The powders mechanically alloyed after the critical period showed the rapid increase in microhardness. The Hv values were found to be higher than 1000kgf/mm$^2$. The formation of nickel silicides by mechanical alloying and the relevant reaction rates appeared to be influenced by the critical milling period and the heat of formation of the products involved ($Ni_5$Si$_2$$\rightarrow$-43.1kJ/mol.at., Ni$_2$Si$\rightarrow$-47.6kJ/mol.at., NiSi$\rightarrow$-42.4kJ/mol.at).