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(CFM)Ni_4.5Fe_0.25Cu_0.25의 水素貯藏特性에 미치는 熱싸이클의 影響
金大龍 경북대학교 산업기술연구소 1989 産業技術硏究誌 Vol.17 No.-
It is well known that hydrogen storage alloys were intrinsically degraded during a large number of cycles of hydriding and dehydriding. In this work, the effect of thermal cycles on the hydrogen storage characteristics of (CFM)Ni_4.5Fe_0.25Cu_0.25(CFM=cerium free mischmetal) was studied at a constant pressure by means of high pressure sievert apparatus and cyclic heating system. The hydrogen absorption capacity was decreased with increasing of the number of cycles and upper cycling temperature. Losses in capacity during the thermal cycles were not recovered by heat treatment. Even though applied pressure of the cycles was lower than the equilibrium pressure, capacity losses were also observed and hysteresis factor, especially absorption equilibrium plateau pressure was drastically increased. These results are explained by annealing effect, micro-phase separation and structure reordering during the thermally induced hydriding and dehydriding cycles.
김대용,김찬중,이재명 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.7
In order to develope a high capacity hydrogen-absorbing alloys for Ni-MH secondary battery, charge and discharge characteristic, of Ti-based and Zr-based Laves phase alloys were investigated. Ti-based Laves phase alloys showed low discharge capacity because of their poor electrode catalysis and lower hydrogen diffusivity in the alloys. However, some Ti-based alloys revealed relatively high discharge capacities up to 200mAh/g indicating possibility to use as electrode materials by a modification of alloys. Zr-based alloys showed higher discharge capacities and better electrode characteristics than Ti-based alloys. In the Zr-based alloys. Zr_(0.4)Ti_(0.6)Mn_(0.4)V_(0.6)Ni_(0.8)Fe)(0.2) electrode exhibited remarkably improved discharge capacity of 385mAh/g, in the case of slow charge and discharge. However in order to use this alloy for MH electrode, it is necessary further improvement of charge and discharge rate capability and cycle life.
한계전류형 YSZ 산소센서의 산소감응 특성에 미치는 고체전해질 결정성 및 확산장벽 두께의 영향
박동원,김대용,이동림 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.3
The limiting current type oxygen sensor is known for excellent characteristics at the low temperatures and throughout the wide oxygen concentration range. In this study, 3 ㏖% Y₂O₃ doped poly-crystal and 15 ㏖% Y₂O₃ doped single-crystal zirconia were used as the solid electrolyte of limiting current type oxygen sensors. The limiting current of the sensor using polycrystalline YSZ was observed over the oxygen concentration range of up to 62.5% and at a temperature range of 560℃∼720℃ in O₂-N₂ mixtures. The sensor using single crystal-YSZ had lower operating voltage than the sensor with polycrystalline YSZ probably due to its low electrolytic resistance.
熔融 Cd 中 Zn 과 Cu, Ag, In, Bi, Pb 및 Sn의 相互作用係數
尹秉河,金大龍 慶北大學校 1982 論文集 Vol.34 No.-
Zinc activities in dilute Cd-Zn and Cd-Zn-X(where, X; Cu, Ag, In, Bi, Pb and Sn)molten alloys have been measured in the temperature range of 450 to 570℃, using an e.m.f. measuring technique. The concentration cell utilized was pure Zn(1)|[ZnCl_2 (in fused KCl+LiCl eutectic electrolyte)]|[Cd-Zn or Cd-Zn-X(1)] The activities of zinc deviated positively from the Raoult's law. The activity coefficients of zinc in the ternary systems were decreased with increasing Cu and Ag, but increased with increasing In, Bi, Pb and Sn. The interaction parameters of the zinc-zinc and zinc-third element were found to be a linear functions of the reciprocal absolute temperature and were expressed by the following relations. ε^Zn_Zn = -930.7/T-6.4074 ε^Cu_Zn = -4070/T-4.3644 ε^Ag_Zn = -7261/T-5.1039 ε^In_Zn = -9769/T+3.5979 ε^Bi_Zn = 1585.6/T+3.1725 ε^Pb_Zn = -8410/T+2.0508 ε^Sn_Zn = 984/T-0.1943
Type 409 스테인리스 강의 입계부식 예민화 거동에 관한 연구
최병진,조미자,김대용 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.7
The sensitization behaviors to intergranular attack of Type 409 stainless steel have determined by chemical etching and double loop EPR test. The results of chemical etching test and double loop EPR test agreed well with each other. The degree of sensitizaton for specimens after heat-treatment at 1100℃ and 600℃ was significantly high. Then, T-T-S diagram of these annealed alloys is represented by two step "C" shape curve. Precipitates of severly sensitized specimens in grain boundries were identified as Ti(C, N) by EDS analysis. It is suggested that sensitization behavior of Type 409 stainless steel is influenced by micro-galvanic corrosion due to concentrated Ti(C, N) precipitates in grain boundaries, besides by chromium depletion. Especially, it was found that high temperature sensitization produced more Ti(C, N) precipitates than low temperature sensitization