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Mg_51Zn_20의 수소 화합물 형성·분해 반응에 관한 연구
宋明燁 전북대학교 전자산업개발연구소 1990 전자산업연구 Vol.1 No.-
In order to increase the hydriding and dehydriding rates of magnesium which has excellent hydrogen-storage properties, and intermetallic compound of magnesium with zinc, Mg_51Zn_20, is prepared. For the hydriding and dehydriding reactions is used a volumetric apparatus for high pressure, which is designed for hydriding and dehydriding under constant hydrogen pressures. In the early cycles of hydriding reaction Mg_51Zn_20 is decomposed into Mg, MgZn and Mg_2Zn_3, the Mg being hydrided. During subsequent cycles only the magnesium is hydrided and dehydri-ded. In the initial stage of hydriding reaction the nucleation controls the hydriding rates and then the diffusion of hydrogen atoms through growing hydriede layer controls them. Dehydriding rates are controlled by the nucleation of Mg-H solid solution. In addition are studied activation process, equilibrium plateau pressures and microstructures of hydrided samples.
( Myoung Youp Song ),( Young Jun Kwak ),( Seong Ho Lee ),( Hye Ryoung Park ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.12
Ni and LiBH4 with a high hydrogen-storage capacity of 18.4 wt% were added to MgH2. A sample with a composition of 86 wt% MgH2-10 wt% Ni-4 wt% LiBH4 (named MgH2-10Ni-4LiBH4) was prepared by milling under H2 (reaction-involved milling, RIM), and its hydriding and dehydriding properties were then examined. The activation of MgH2-10Ni-4LiBH4 for hydriding and dehydriding reactions was not required. The as-milled sample absorbed 2.54 wt% H for 5 min, 3.72 wt% H for 10 min, 4.90 wt% H for 20 min, and 4.90 wt% H for 60 min at 623 K under 12 bar H2, absorbing nearly 5 wt% H for 60 min. The as-milled sample desorbed 2.86 wt% H for 5 min, 4.78 wt% H for 15 min, and 4.94 wt% H for 60 min at 623 K under 1.0 bar H2. The inverse dependence of the hydriding rate on temperature is due to a decrease in the driving force for the hydriding reaction (the difference between applied hydrogen pressure and equilibrium plateau pressure) as the temperature increases.
Comparison of Hydrogen Storage Properties of Pure MgH2 and Pure Mg
( Myoung Youp Song ),( Young Jun Kwak ),( Seong Ho Lee ),( Hye Ryoung Park ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.9
At the first cycle (n=1), pure MgH2 absorbed hydrogen extremely slowly at 593 K under 12 bar H2, absorbing 0.04 wt% H for 60 min. Activation of the pure MgH2 was completed after five hydriding- dehydriding cycles. At the 6th cycle, the pure MgH2 absorbed 2.41 wt% H for 5 min, 3.00 wt% H for 10 min, and 4.21 wt% H for 60 min, showing that the activated pure MgH2 had a much higher hydriding rate than the activated pure Mg. The pure Mg absorbed 0.10 wt% H for 5 min, 0.38 wt% H for 30 min, and 0.51 wt% H for 60 min at the first cycle. The activated pure Mg, whose activation was also completed after five hydriding- dehydriding cycles, absorbed 1.76 wt% H for 5 min, 2.17 wt% H for 10 min and 3.40 wt% H for 60 min. The XRD pattern of the pure MgH2 after hydriding-dehydriding cycling (n=7) revealed that the sample contained Mg, a small amount of MgO, and a large amount of MgH2, showing that a large fraction of MgH2 remains even after dehydriding in vacuum at 623 K for 2 h. (Received August 27, 2013)
The Effects of C-Rate on the Discharge Capacities of LiNi1-yMyO2 (M=Ni, Ga, Al and/or Ti) Cathodes
( Myoung Youp Song ),( Chan Kee Park ),( Soon Do Yoon ),( Hye Ryoung Park ),( Daniel R. Mumm ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 ELECTRONIC MATERIALS LETTERS Vol.4 No.4
LiNi1-yMyO2 specimens with compositions of LiNiO2, LiNi0.975Ga0.025O2, LiNi0.975Al0.025O2, LiNi0.995Ti0.005O2 and LiNi0.990Al0.005Ti0.005O2 were synthesized by wet milling and solid-state reaction method. All the synthesized samples possessed the α-NaFeO2 structure of the rhombohedral system (space group; R3m) with no evidence of any impurities. Among the LiNiO2 cathodes prepared with the weight ratios of LiNiO2:acetylene black: binder = 85:10:5, 85:12:3 and 90:7:3, the cathode with the weight ratio of 85:10:5 had the best cycling performance, with a discharge capacity degradation rate of 1.06 mAh/g/cycle and a discharge capacity at n=20 of 143.5 mAh/g. Among all the samples, LiNi0.990Al0.005Ti0.005O2 had the highest first discharge capacities at 0.1 C, 0.2 C and 0.5 C rates. That sample had the smallest R-factor value, indicating that it had the lowest degree of cation mixing. Among all the samples, LiNi0.975Al0.025O2 showed the lowest rate of decrease in the first discharge capacity with C rate. The first discharge capacities at 0.1 C, 0.2 C and 0.5 C rates were 170.5 mAh/g, 155.0 mAh/g and 124.2 mAh/g, respectively.
Myoung Youp Song,Eunho Choi,곽영준 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.6
The optimum powder to ball ratio was examined, which is one of the important conditions in reactive mechanical grinding processing. Yttria (Y2O3)-stabilized zirconia (ZrO2) (YSZ), Ni, and graphene were chosen as additives to enhance the hydriding and dehydriding rates of Mg. Samples with a composition of 92.5 wt% Mg + 2.5 wt% YSZ + 2.5 wt% Ni + 2.5 wt% graphene (designated as Mg-2.5YSZ-2.5Ni-2.5graphene) were prepared by grinding in hydrogen atmosphere. Mg-2.5YSZ-2.5Ni2.5graphene had a high effective hydrogen-storage capacity of almost 7 wt% (6.85 wt%) at 623 K in 12 bar H2 at the second cycle (n = 2). Mg-2.5YSZ-2.5Ni-2.5graphene contained Mg2Ni phase after hydriding-dehydriding cycling. Mg-2.5YSZ-2.5Ni2.5graphene had a larger quantity of hydrogen absorbed for 60 min, Ha (60 min), than Mg-2.5Ni-2.5graphene and Mg2.5graphene. The addition of YSZ also increased the initial dehydriding rate and the quantity of hydrogen released for 60 min, Hd (60 min), compared with those of Mg-2.5Ni-2.5graphene. Y2O3-stabilized ZrO2, Ni, and graphene-added Mg had a higher initial hydriding rate and a larger Ha (60 min) than Fe2O3, MnO, or Ni and Fe2O3-added Mg at n = 1.
( Myoung Youp Song ),( Young Jun Kwak ),( Seong Ho Lee ),( Hye Ryoung Park ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.2
A sample with a composition of 90 wt% Mg-10 wt% TaF5 (named Mg-10TaF5) was prepared by reactive mechanical grinding, and its hydriding and dehydriding properties were examined. The activation of Mg-10TaF5 was not required. At n=1, the sample absorbed 3.63 wt% H for 5 min, 4.03 wt% H for 10 min, and 4.53 wt% H for 30 min at 593 K under 12 bar H2. At n=1, the sample desorbed 0.59 wt% H for 5 min, 1.46 wt% H for 10 min, 3.42 wt% H for 30 min, and 4.24 wt% H for 60 min at 593 K under 1.0 bar H2. Mg-10TaF5 after reactive mechanical grinding contained MgH2, Mg, and very small amounts of MgF2 and Ta2H. The XRD pattern of Mg-10TaF5 dehydrided at n=3 revealed Mg, MgH2, a small amount of MgO, and very small amounts of MgF2 and Ta2H phases. Mg-10Fe2O3 and Mg-10MnO were reported to have quite high hydriding rate and dehydriding rates, respectively. Mg-10TaF5 had a larger initial hydriding rate but a lower quantity of hydrogen absorbed for 60 min than Mg-10Fe2O3. However, Mg-10TaF5 had a higher initial dehydriding rate (after the incubation period) and a larger quantity of hydrogen desorbed for 60 min than Mg-10MnO. †(Received April 29, 2013)
Development of Mg-xFe2O3-yNi Hydrogen-Storage Alloys by Reactive Mechanical Grinding
( Myoung Youp Song ),( Sung Nam Kwon ),( Hye Ryoung Park ) 대한금속재료학회(구 대한금속학회) 2012 대한금속·재료학회지 Vol.50 No.10
Mg-x wt% Fe2O3-y wt% Ni samples were prepared by reactive mechanical grinding in a planetary ball mill, and their hydrogen-storage properties were investigated and compared. Activations of Mg-5Fe2O3-5Ni was completed after one hydriding (under 12 bar H2) - dehydriding (in vacuum) cycle at 593 K. At n = 2, Mg-5Fe2O3-5Ni absorbed 3.43 wt% H for 5 min, 3.57 wt% H for 10 min, 3.76 wt% H for 20 min, and 3.98 wt% H for 60 min. Activated Mg-10Fe2O3 had the highest hydriding rate, absorbing 2.99 wt% H for 2.5 min, 4.86 wt% H for 10 min, and 5.54 wt% H for 60 min at 593 K under 12 bar H2. Activated Mg-10Fe2O3-5Ni had the highest dehydriding rate, desorbing 1.31 wt% H for 10 min, 2.91 wt% H for 30 min, and 3.83 wt% H for 60 min at 593 K under 1.0 bar H2.