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EPMA를 이용한 침탄강의 정확하고 신뢰성 있는 탄소농도 측정을 위한 분석조건 최적화
권기훈,박현준,최병호,이영국,문경일 한국재료학회 2023 한국재료학회지 Vol.33 No.3
The carbon concentration in the carburized steels was measured by electron probe microanalysis (EPMA) for a range of soluted carbon content in austenite from 0.1 to 1.2 wt%. This study demonstrates the problems in carbon quantitative analysis using the existing calibration curve derived from pure iron (0.008 wt%C) and graphite (99.98 wt%C) as standard specimens. In order to derive an improved calibration curve, carbon homogenization treatment was performed to produce a uniform Kα intensity in selected standard samples (AISI 8620, AISI 4140, AISI 1065, AISI 52100 steel). The trend of detection intensity was identified according to the analysis condition, such as accelerating voltage (10, 15, 30 keV), and beam current (20, 50 nA). The appropriate analysis conditions (15 keV, 20 nA) were derived. When the carbon concentration depth profile of the carburized specimen was measured for a short carburizing time using the improved calibration curve, it proved to be a more reliable and accurate analysis method compared to the conventional analysis method.
AISI 4115 강의 진공 침탄 시 아세틸렌 유량에 따른 침탄 거동
권기훈,문경일,이영국,정민수 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.9
The vacuum carburizing behavior of AISI 4115 steel according to acetylene flow rates (1, 5, 10, 20, 30, 40, and 50 sccm) and temperatures (900, 950, and 1000 oC) was quantitatively investigated through microstructure, carbon concentration and hardness analyses. As the acetylene flow rate increased, the penetration rate of carbon into the surface of the samples (surface-carbon flux) increased, resulting in an increase in the solute carbon concentration at the surface up to the solubility of carbon in austenite. At the same time, the amount of carbon diffusion into the interior of the specimen and overall carburizing depth increased. When the carbon concentration in the surface of the carburized specimen exceeded the solubility of carbon in the austenite above a certain flow rate, cementite precipitated in the austenite grain boundaries. Accordingly, the surface hardness decreased and the amount of carbon diffusion into the specimen became constant as the solute carbon concentration in the austenite matrix at the surface of the specimen became constant. As a result, the overall solute carbon concentration and the effective case depth no longer increased. Meanwhile, the tendency of vacuum carburizing behavior according to temperature was the same, but as temperature increased, the surface-carbon flux and rate of carbon diffusion into the interior of the sample increased, resulting in increased carburizing depth. The appropriate flow rates (10, 20, and 30 sccm) and the corresponding surface-carbon fluxes (62.3, 135.7, and 216.7 g/m2h) were derived according to carburizing temperatures (900, 950, and 1000 oC), respectively.
혼합고분자처리에 의한 골판지 원지 및 골판지의 물성변화
권기훈,임부국,박성배,양재경,장준복,이종윤 한국펄프종이공학회 1999 펄프.종이기술 Vol.31 No.4
This study was performed to investigated the application of mixed resins for corrugated container board. The corrugated container board yields a sandwich structure in which a linerboard material is glued to a corrugated medium . Now, manufacturing corrugated container boards don't provide sufficient strength, and result in box failure during shipping . Therefore improvement of box strength is necessary . In this study, we intend to improve box strength by improving corrugated medium strength with mixed resins and to find the optimum treatment condition of this resins. First, we tried to mixed resins as Starch+CMC, Starch_Irea, CMC+Urea, Second, investigated to applicability of this resins for corrugated medium , and the third, measured tensile index, burst index, and edgewise compression index on liner, medium paper, and single faced corrugated container board. In this test results, we obtained that the improvement ratios of tensile index in liner and medium paper were approximately 80-185%, 60-118% , respectively. The respecting improvement ratios of edgewise compression index of single faced corrugated container board was approximately 91-124%, relatively. In addition, we concluded that optimum condition in mixing ratio was 1 :3 with CMC + Urea and the ap[plication amounts was 9% on materials. Fro manufacture of corrugated container board, optimum condition in mixing ratio was 1 : 3 with 5% CMC +Urea , because of considering to improvement of strength on cost.
Oxidative Methane Conversion to Ethane on Oxidized Pd/CeO<sub>2</sub> Catalysts at Low Temperature
권기훈,신동재,한정우,이현주 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
Methane upgrading into more valuable chemicals has received enormous attention. In this work, we show oxidative methane conversion to ethane using gaseous O<sub>2</sub> at low temperatures (< 400℃) and atmospheric pressure in a continuous reactor. A highly oxidized Pd deposited on ceria could produce ethane with the productivity as high as 0.84 mmol/g<sub>cat</sub>/h. The Pd-O-Pd sites, not Pd-O-Ce, were the active sites for selective ethane production at low temperatures. Density functional theory (DFT) calculations identified that Pd-O-Pd sites are energetically more advantageous for C-C coupling, while Pd-O-Ce prefers CH<sub>4</sub> dehydrogenation. The ceria helped Pd maintain oxidic state in reductive CH<sub>4</sub> flow. This work can give new insight for methane upgrading into C2 species.