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.

Development of Mg-14Ni-6TaF5 Hydrogen Absorption-Desorption Material via Reaction-Involved Milling

SONG, Myoung Youp,KWAK, Young Jun,LEE, Seong Ho,PARK, Hye Ryoung Publishing House Technologija 2014 Medžiagotyra Vol.20 No.4

Variations of the Electrochemical Properties of LiMn₂O₄ with the Calcining Temperature

Song, Myoung-Youp,Shon, Mi-suk The Korean Ceramic Society 2002 한국세라믹학회지 Vol.39 No.6

LiMn$_2$O$_4$ compounds were synthesized by calcining a mixture of LiOH and MnO$_2$(CMD) at 47$0^{\circ}C$ for 10 h and then calcining again at $650^{\circ}C$ to 90$0^{\circ}C$ fur 48 h in air with intermediate grinding. All the synthesized samples exhibited XRD patterns for the cubic spinel phase with a space group Fd3m. The lattice parameter increased gradually as the sintering temperature rose. The electrochemical cells were charged and discharged fur 20 cycles at a current density 300$\mu$A/$\textrm{cm}^2$ between 3.5 V and 4.3 V. The voltage vs. discharge capacity curves for all the samples showed two plateaus. The LiMn$_2$O$_4$ sample calcined at 90$0^{\circ}C$ had the largest first discharge capacity. This sample exhibited the best crystallinity, had relatively large lattice parameter and had relatively large particles with rectatively homogeneous size. All the samples showed good cycling performances. Among all the samples, the LiMn$_2$O$_4$ calcined at 85$0^{\circ}C$ had relatively large first discharge capacity and very good cycling performance. The addition of excess LiOH and the mixing in ethanol considered to help the formation of the more LiMn$_2$O$_4$ phase per unit weight sample and the more stable LiMn$_2$O$_4$phase. These led to the larger discharge capacities and the better cycling performances. The cyclic voltammograms fur the second cycle of the LiMn$_2$O$_4$ samples showed the oxidation and reduction peaks around 4.05 V and 4.18 V and around 4.08 V and 3.94 V, respectively. The larger first discharge capacity of the sample calcined at the higher temperature is related to the larger lattice parameter.

PCT Curve and Cycling Performance of MgH2-Ni-NaAlH4-Ti Alloy Milled under H2

( Myoung Youp Song ),( Seong Ho Lee ),( Young Jun Kwak ),( Hye Ryoung Park ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.5

In this study, MgH2 was used as a starting material instead of Mg. A sample with a composition of 86 wt% MgH2-10 wt% Ni-2 wt% NaAlH4-2 wt% Ti (designated MgH2-10Ni-2NaAlH4-2Ti) was prepared by reactive mechanical grinding. Its Pressure-Composition-Temperature (PCT) curve measurement, hydriding-dehydriding cycling performance measurement, and microstructure observation were then performed. The desorption PCT curve at 593 K for MgH2-10Ni-2NaAlH4-2Ti at the first cycle exhibited a long plateau at around 2.6 bar, and a short plateau at about 3.6 bar, which correspond to equilibrium plateau pressures of Mg-H and Mg2Ni-H systems, respectively. The hydriding rate at 593 K under 12 bar H2 increased as the number of cycles, n, increased from 1 to 4, and it decreased from n=4 to n=15. At n=14, MgH2-10Ni-2NaAlH4-2Ti absorbed 3.02 wt% H for 2.5 min, 3.36 wt% H for 5 min, 3.51 wt% H for 10 min, and 3.58 wt% H for 30 min, which is 93.0% of the hydrogen absorbed for 30 min at n=4.

Effects of Ni, Fe₂O₃, and CNT addition by reactive mechanical grinding on the reaction rates with H₂ of Mg-based alloys

Song, Myoung Youp,Kwak, Young Jun,Lee, Byung-Soo,Park, Hye Ryoung,Kim, Byoung-Goan Elsevier 2012 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.37 No.2

<P><B>Abstract</B></P> <P>Ni, Fe<SUB>2</SUB>O<SUB>3</SUB>, and CNT were added to Mg. The content of the additives was about 20 wt % with that of Fe<SUB>2</SUB>O<SUB>3</SUB> 6 wt%. The contents of about 20 wt % additives and 6 wt% Fe<SUB>2</SUB>O<SUB>3</SUB> are known optimum ones to improve the reaction rates of Mg with H<SUB>2</SUB>. Samples with compositions of 80 wt% Mg–14 wt% Ni–6 wt% Fe<SUB>2</SUB>O<SUB>3</SUB> (named as Mg–14Ni–6Fe<SUB>2</SUB>O<SUB>3</SUB>), and 78 wt% Mg–14 wt% Ni–6 wt% Fe<SUB>2</SUB>O<SUB>3</SUB>–2 wt% CNT (named as Mg–14Ni–6Fe<SUB>2</SUB>O<SUB>3</SUB>–2CNT) were prepared by reactive mechanical grinding. The hydriding and dehydriding properties of these samples were then measured, and the effects of Ni, Fe<SUB>2</SUB>O<SUB>3</SUB>, and CNT addition on the hydriding and dehydriding rates of Mg-based alloys were investigated by comparing their hydrogen-storage properties with those of pure Mg and Mg–10 wt% Fe<SUB>2</SUB>O<SUB>3</SUB>.</P> <P><B>Highlights</B></P> <P>► Content of the additives of about 20 wt %, and 6 wt% of oxide addition. ► Preparation of Mg–14Ni–6Fe<SUB>2</SUB>O<SUB>3</SUB>, and Mg–14Ni–6Fe<SUB>2</SUB>O<SUB>3</SUB>–2CNTby RMG. ► Effects of Ni, Fe<SUB>2</SUB>O<SUB>3</SUB>, and CNT addition on hydriding and dehydriding rates. ► Addition of Ni and Fe<SUB>2</SUB>O<SUB>3</SUB> increases hydriding rate and/or dehydriding rate. ► CNT Addition made activation process unnecessary with a small decrease in capacity.</P>

Hydrogen storage properties of pure Mg

( Myoung Youp Song ),( Young Jun Kwak ),( Seong Ho Lee ),( Hye Ryoung Park ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.4

The hydrogen storage properties of pure Mg are investigated at 573 K under 12 bar H2. In addition, in order to increase the hydriding and dehydriding rates of pure Mg, it is ground under hydrogen (reactive mechanical grinding, RMG), and its hydrogen storage properties are investigated. The pure Mg absorbs hydrogen very slowly. At n = 1, the pure Mg absorbs 0.05 wt.% H for 5 min, 0.08 wt.% H for 10 min, and 0.29 wt.% H for 60 min at 573 K under 12 bar H2. The hydriding rate decreases as the number of cycles increases from n = 7. At n = 7, the pure Mg absorbs 0.96 wt.% H for 5 min, 1.29 wt.% H for 10 min, and 2.20 wt.% H for 60 min. At n = 1, the pure Mg after RMG does not absorb hydrogen. The hydriding rate of pure Mg after RMG increases as the number of cycles increases from n = 1 to n = 11. The pure Mg after RMG absorbs 1.91 wt.% H for 5 min, 2.61 wt.% H for 10 min, and 3.65 wt.% H for 60 min at n = 11. The reactive mechanical grinding of the pure Mg and the hydriding-dehydriding cycling of the pure Mg after RMG are believed to create defects on the surface and in the interior of Mg particles and to form cracks in Mg particles.

Synthesis of Cathode Materials LiNi_1-yCo_yO₂ from Various Starting Materials and their Electrochemical Properties

Song, Myoung-Youp,Rim, Ho,Bang, Eui-Yong,Kang, Seong-Gu,Chang, Soon-Ho The Korean Ceramic Society 2003 한국세라믹학회지 Vol.40 No.6

The LiN $i_{l-y}$ $Co_{y}$ $O_2$ samples were synthesized at 80$0^{\circ}C$ and 85$0^{\circ}C$, by the solid-state reaction method, from the various starting materials LiOH, L $i_2$C $O_3$, NiO, NiC $O_3$, $Co_3$ $O_4$, CoC $O_3$, and their electrochemical properties are investigated. The LiN $i_{l-y}$ $Co_{y}$ $O_2$ pre-pared from L $i_2$C $O_3$, NiO, and $Co_3$ $O_4$ exhibited the $\alpha$-NaFe $O_2$ structure of the rhombohedral system (space group; R3m). As the Co content increased, the lattice parameters a and c decreased. The reason is that the radius of Co ion is smaller than that of Ni ion. The increase in da shows that two-dimensional structure develops better as the Co content increases. The LiN $i_{0.7}$ $Co_{03}$. $O_2$[HOO(800,0.3)] synthesized at 80$0^{\circ}C$from LiOH, NiO, and $Co_3$ $O_4$ exhibited the largest first discharge capacity 162 mAh/g. The size of particles increases roughly as the valve of y increases. The samples with the larger particles have the larger first discharge capacities. The cycling performances of the samples with the first discharge capacity larger than 150 mAh/g were investigated. The LiN $i_{0.9}$ $Co_{0.1}$ $O_2$[COO(850,0.1)] synthesized at 85$0^{\circ}C$ from L $i_2$C $O_3$, NiO, and $Co_3$ $O_4$ showed an excellent cycling performance. The sample with the larger first discharge capacity will be under the more severe lattice destruction, due to the expansion and contraction of the lattice during intercalation and deintercalation, than the sample with the smaller first discharge capacity. As the first discharge capacity increases, the capacity fading rate thus increases.increases.s.s.s.

Electrochemical Properties of LiNi_yMn_2-yO₄ Prepared by the Solid-state Reaction

Song, Myoung-Youp,Kwon, Ik-Hyun,Shon, Mi-Suk The Korean Ceramic Society 2003 한국세라믹학회지 Vol.40 No.5

LiN $i_{y}$M $n_{2-y}$ $O_4$were synthesized by calcining a mixture of LiOH, Mn $O_2$(CMD), and NiO at 40$0^{\circ}C$ for 10 h and then calcining at 85$0^{\circ}C$ for 48 h in air with intermediate grinding. The voltage vs. discharge capacity curves at a current density 300 $\mu$A/c $m^2$ between 3.5 V and 4.3 V showed two plateaus, but the plateaus became ambiguous as the y value increases. The sample with y=0.02 had the largest first discharge capacity, 118.1 mAh/g. As the value y increases from 0.02 up to 0.2, on the whole, the cycling performance became better. The LiN $i_{0.10}$M $n_{1.90}$ $O_4$sample had a relatively large first discharge capacity 95.0 mAh/g and showed an excellent cycling performance. The samples with larger lattice parameter have, in general, larger discharge capacities. The reduction curves in the cyclic voltammograms for the y=0.05-0.20 samples exhibit three peak showing that the reduction may proceed in three stages in these samples. For the samples with relatively large discharge capacity, the lattice destruction induced by strain causes the capacity fading of LiN $i_{y}$M $n_{2-y}$ $O_4$ with cycling.cling.ing.

Synthesis of Cathode Materials LiNi1-yCoyO2 from various Starting Materials and their Electrochemical Properties

Myoung Youp Song,Ho Rim,Eui Yong Bang,Seong Gu Kang,Soon Ho Chang 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.6

Hydrogen Storage Properties of Hydriding-Dehydriding Cycled Magnesium-Nickel-Iron Oxide Alloy

( Myoung Youp Song ),( Sung Nam Kwon ),( Hye Ryoung Park ),( Byoung Goan Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.2

By measuring the absorbed hydrogen quantity as a function of the number of cycles, the cycling properties of the Mg-15 wt%Ni-5 wt%Fe2O3 alloy were investigated. The absorbed hydrogen quantity decreased as the number of cycles increased. The Ha value varied almost linearly with the number of cycles. The maintainability of absorbed hydrogen quantity at n=100 was 89.0% for the hydriding reaction time of 10 min. After the 150th hydriding-dehydriding cycle, Mg, Mg2Ni, Mg(OH)2, MgO, and Fe were observed. The phases were analyzed by Rietveld analysis from the XRD patterns of the Mg-15 wt%Ni-5 wt%Fe2O3 alloy after 150 hydriding-dehydriding cycles. The crystallite size and strain of Mg were then estimated with the Williamson-Hall technique.