http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
개별검색 DB통합검색이 안되는 DB는 DB아이콘을 클릭하여 이용하실 수 있습니다.
통계정보 및 조사
예술 / 패션
<해외전자자료 이용권한 안내>
- 이용 대상 : RISS의 모든 해외전자자료는 교수, 강사, 대학(원)생, 연구원, 대학직원에 한하여(로그인 필수) 이용 가능
- 구독대학 소속 이용자: RISS 해외전자자료 통합검색 및 등록된 대학IP 대역 내에서 24시간 무료 이용
- 미구독대학 소속 이용자: RISS 해외전자자료 통합검색을 통한 오후 4시~익일 오전 9시 무료 이용
※ 단, EBSCO ASC/BSC(오후 5시~익일 오전 9시 무료 이용)
The effect of the carbon element on the sulfidation rate of Fe-Al alloys was investigated at the temperature ranging from 500 to 800℃ under 1 atmospheric pressure of SO₂ gas. The sultidation rate of the alloys containing 0.1, 0.3, 0.5, 0.7 and 0.9 Wt%C was determined using a thermal balance. The structure and composition of reaction product of alloys were identified by the means of analytical instruments, S.E.M., E.D.S., W.D.S., A.E.S. and X-ray diffractometer. The adherence and stability of the products were discussed in terms of the analytical results and thermodynamical data. The rate is dependent on the temperature and the carbon content of the alloys. The sulfidation process obeys a parabolic rate law in the temperature region of 500℃ and 650℃. At the temperature of 800℃, the rate is initially parabolic and gradually becomes linear. The addition of 0.1 and 0.3 Wt.% carbon into the alloy increases the sulfidation rate. However, the carbon content above 0.3 Wt.% decreases the sulfidation rate. An increase in the reaction rate results mainly from the poor adherence and cracks of the scale from the growth stress in the scale and the evolution of CO gas between the scale and alloy. The scales consisted of several layers of FeO, Fe₃O₄, Fe₂O₃, FeAl₂2O₄ and Al₂S₃, Al₂O₃.
The oxidation rate of chromium carbide has been measured continuously using thermogravimetric analysis at different oxygen pressures ranging from 1.33×10^(-2) to 2.67×10^(-1)Pa O₂ at 1000- 1300℃. The oxidation of pure chromium has also been studied between 1000-1300℃ under 6.67×10^(-2)Pa O₂ and compared with that of chromium carbide. The oxidation of chromium carbide showed a linear behavior which was different from that, of chromium. The oxidation rate of chromium carbide increased with increasing temperature and oxygen pressure was lower than of pure chormium. Above 1200℃, the volatile oxide was formed and evaporated causing a weight loss. The compositions and morphorlogy of the oxide were studied with X-ray diffractometer and scanning electron microscope, respectively.
Carburization rate of pure chromium(over 99.99%) has been measured using thermogravimetric analysis method. The specimens were fabricated by sintering it in argon atmosphere in disc shape with diameter of 10mm and thickness of 3mm. Experiment was conducted controlling acxtylene gas to flow into the reaction tube in the pressure of 1.07×10^(-2) -5.33×10^(-2)Pa. Reaction products were identified with the aid of X-ray diffraction method, and the morphology change at the specimen surface observed with a scanning electron microscope. The weight gain versus time showed a tendency to follow linear behavior in the initial stage of carburizaton, but after 30 to 40 minutes it changed to following parabolic behavior, which indicates the reaction mechanism in the initial of carburization is different from that in the later stage of carburization. Apparent activation energy for the initial carburization stage found to be 26.4KJ/mole, while the value for the alter stage representing parabolic behavior to be 75.8KJ%mole.
Oxidation of WC powder compacts with 96, 88, 80 and 70% theoretical density has been studied at 1300 to 2100˚K and 6.67×10^(-4)∼ 6.67×10^(-3) mbar O₂. At the above conditions the oxidation behavior of WC is linear and very similar to that of W₂C. The oxidation rate increases with increasing porosity, and its increasing rate corresponds to the change of the surface area. A metallic surface layer was built up on the samples by the competitive reaction of the decaburization of WC and tungsten oxide evaporation.
The high temperature sulfidation reaction of Fe-Swt% Si alloys containing 0.5, 0.7, 1.0, 1.7wt% C was investigated in 1 atm SO₂ gas pressure at temperature ranging from 650℃ to 800℃. The sulfidation rate of the alloys was determined by thermogravimetric analysis. The structure and the composition of the reaction products were identified by the aid of SEM, EDS, AES analysis and X-ray diffraction technique. The scales formed on the alloy surface consisted of two types of layers: the outer Layers (FeO, Fe₃O₄, Fe₂O₃) and the inner layers (FeS, SiO₂). The overall reaction process obeyed a parabolic rate law over the temperature range 650-800℃, in which the reaction rate increased with increasing in the temperature. The activation energies for the sulfidation reaction of Fe-5Si, Fe-5Si-0.7C and Fe-5Si-1.7C were 41.2, 59.3, 96.6 KJ/mol, respectively. The addition of carbon in the Fe-Si alloy retarded the sulfidation reaction by forming the dense outer oxide layer and the thick inner SiO₂ layer. However, the influence of the carbon on the sulfidation rate was not remarkable above 800℃.
The oxidation rates of chromium carbide have been measured at 900 to 1300℃ and oxygen pressures between 2×10^(-2), 8×10^(-2) Pa using thermogravimetric analysis method. Oxidation behavior of chromium carbide apperareti to change very sensitively with both temperature and oxygen pressure. In case with the oxygen pressure lower than 8×10^(-2) Pa, the weight gain in the speciment due to the formation of chromium oxide occurred linearly with time at the every temperature studied, but when the oxygen pressure was increased up to 8×10^(-2)Pa, the weight gain behavior versus time showed entirely different tendency. That is, in the temperature range of 900℃ to 1000℃ weigh gain occurred, however in the range of 1000℃ to 1300℃ weight lost was observed. The reason for the observed linear kinetics could be inferred as follows. As the oxidation of carbide proceeded carbon monoxide would build up at interface of the chromium oxide and carbide. If the equilibrium pressure of carbon monoxide at the interface exceeds the gas pressure at the outer specimen surface, the oxide scale formed on it might be cracked exposing new carbide sites on which oxidation could occur successively. Through a thermodynamic consideration it was judged that the above deduction was reasonable. On the other hand, the weight lost mentioned above was explained that it could occur mainly due to the further oxidation of Cr₂O₃ to the volatile Cr₂O₃ at the corresponding experimental conditions. Weigh loss phenomenon mentioned before which was observed in the oxidation of chromium carbide was also clearfield by X ray diffraction method and SEM. That is, at 900℃ stable oxide of chromium, (Cr₂O₃, was identified easily on the specimen surface. However, at 1300℃, only a few amount of this stable oxide could be found on to specimen surface, indicating Cr₂O₃ had been evaporated to CrO₃ gas.