• Applied Microscopy
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• v.36 no.spc1
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• pp.57-61
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• 2006

High-resolution microscopy was applied for surveying hydride stability in Vanadium alloys, which are candidate for hydrogen storage materials of advanced hydrogen energy systems. $V_2H$ hydride in V alloys was stable at room temperature under the vacuum condition, but it was decomposed during heating up to $100^{\circ}C$. It was confirmed from HRTEM image and FFT that $V_2H$ has a BCT structure, where hydrogen atoms locate at octahedral sites. Crystal orientation was <110> beta// <110> mat., and lattice strain is about 10%. After the decomposition of the hydride, relatively large lattice expansion was observed in the matrix, which suggests that hydrogen atoms should be trapped by lattice defects and included in the matrix. Intensive electron beam also enhanced the decomposition.

• Bulletin of the Korean Chemical Society
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• v.5 no.1
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• pp.37-41
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• 1984

The pseudolattice calculations in the CNDO/2 level of approximation are carried out for polymeric beryllium hydride, polyethylene and polymeric boron hydride. Since there is no evidence on the geometry for polymeric boron hydride, the two possible geometries are assumed. One is a polyethylene-type geometry and the other is a polymeric beryllium hydride-type geometry. In order to compare their relative stability, we calculate polyethylene and polymeric beryllium hydride and then compare with polymeric boron hydride having the assumed structures. The total energy calculation indicates that a polymeric beryllium bydride-type geometry is more stable than a polyethylene-type geometry. Our results obtained for polyethylene are in good agreement with those given by CNDO/2 crystal orbital. From the convergence problem with respect to the number of unit cells (M), the calculation with value of 4 for M can be considered to give the convergence limit results.

• Journal of Integrative Natural Science
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• v.4 no.4
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• pp.282-288
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• 2011

We describe the synthesis and characterization of silicon nanoparticles prepared by the solution reduction of silicon tetrachloride by lithium naphthalenide and subsequently with n-butyllithium at room temperature. These reactions produce silicon nanoparticles with surfaces that are covalently terminated with butyl group. Reaction with lithium aluminium hydride instead of n-butyllithium produces hydride-terminated silicon nanoparticles. The butyl or hydride terminated silicon nanoparticles can be suspended in hexane and their optical behavior have been characterized by photoluminescence spectroscopy. Stabilization of silicon nanoparticles were investigated upon illumination, indicating that as-prepared silicon nanoparticles are very stable at room temperature for several days.

• Journal of Powder Materials
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• v.17 no.5
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• pp.385-389
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• 2010

Titanium powders have been usually produced by de-hydrogenating treatment in vacuum with titanium hydride ($TiH_2$) powders prepared by milling of hydrogenated sponge titanium, $TiH_x$. The higher stoichiometry of x in $TiH_x$, whose maximum value is 2, is achieved, crushing behavior is easier. $TiH_x$ powder can be, therefore, easy to manufactured leading to obtain higher recovery factor of it. In addition, contamination of the powder can also minimized by the decrease of milling time. In this study, the hydrogenation behavior of sponge titanium was studied to find the maximum stoichiometry. The maximum stoichiometry in hydride formation of sponge titanium could be obtained at $750^{\circ}C$ for 2 hrs leading to the formation of $TiH_{{\sim}1.99}$ and the treating temperatures lower or higher than $750^{\circ}C$ caused the poor stoichiometries by the low hydrogen diffusivity and un-stability of $TiH_x$, respectively. Such experimental behavior was compared with thermodynamically calculated one. The hydrogenated $TiH_{1.99}$ sponge was fully ball-milled under -325 Mesh and the purity of pure titanium powders obtained by de-hydrogenation was about 99.6%.

• Journal of the Korean Chemical Society
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• v.60 no.4
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• pp.251-256
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• 2016

This paper describes the synthesis of alkali metal salts of urea (ureates) and their application to the direct preparation of 4-nitrosoaniline from nitrobenzene via nucleophilic aromatic substitution of hydrogen. Sodium and potassium ureates were readily prepared from the reaction of urea with sodium hydride, metal methoxides, and metal hydroxides. The effect of ureates as nucleophiles on the conversion of nitrobenzene to 4-nitrosoaniline was investigated and compared with that of a urea-metal hydroxide mixture. It was found that the ureates were superior for producing 4-nitrosoaniline owing to their higher thermal stability of the ureate. The ureate obtained from the treatment of urea with sodium hydride gave the highest yield for the preparation of 4-nitrosoaniline. The ureates generated from the reaction of urea with metal hydroxide also gave high yields of 4-nitrosoaniline. Catalytic hydrogenation of 4-nitrosoaniline afforded polymer-grade 1,4-benzenediamine in quantitative yield.

• Korean Journal of Materials Research
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• v.32 no.10
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• pp.429-434
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• 2022

There is ongoing research to develop lithium ion batteries as sustainable energy sources. Because of safety problems, solid state batteries, where electrolytes are replaced with solids, are attracting attention. Sulfide electrolytes, with a high ion conductivity of 10^-3 S/cm or more, have the highest potential performance, but the price of the main materials is high. This study investigated lithium hydride materials, which offer economic advantages and low density. To analyze the change in ion conductivity in polymer electrolyte composites, PVDF, a representative polymer substance was used at a certain mass ratio. XRD, SEM, and BET were performed for metallurgical analyses of the materials, and ion conductivity was calculated through the EIS method. In addition, thermal conductivity was measured to analyze thermal stability, which is a major parameter of lithium ion batteries. As a result, the ion conductivity of LiH was found to be 10^-6 S/cm, and the ion conductivity further decreased as the PVDF ratio increased when the composite was formed.

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.81-89
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• 1994

A study on Mm type electrode which is relatively high in electrode capacity and low in material cost was performed to develope high performance nickel-metal hydride battery. The electrode characteristics were investigated by P-C-T, charge-discharge and microencapsulation treatment experiments. The plateau pressure and hydrogen absorption capacity obtained from the P-C-T experiment were 0.4 atm and 310 mAh/g, respectively. The electrode capacity and stability of microencapsulated electrode were improved than those of conductor mixed electrode and the microencapsulation was possible without pretreatment. The electrode capacity of microencapsulated Mm type alloy was 240~250 mAh/g(0.2 C).

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.6
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• pp.505-511
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• 2009

The hydriding and electrochemical characteristics of Zr-based $AB_2$ alloy produced by gas atomization have been extensively examined. For the particle morphology of the as-cast and gas-atomized powders, it can be seen that the mechanically crushed powders are irregular, while the atomized powder particles are spherical. The increase of jet pressure of gas atomization process results in the decrease of hydrogen storage capacity and the slope of plateau pressure significantly increases. TEM and EDS studies showed the increase of jet pressure in the atomization process accelerated the phase separation within grain of the gas-atomized alloy, which brought about a poor hydrogenation property. However, the gas-atomized $AB_2$ alloy powders produced by jet pressure of 50 bar kept up the reversible $H_2$ storage capacity and discharge capacity similar to the mechanically crushed particles. In addition, the electrode of gas-atomized Zr-based $AB_2$ alloy of 50 bar showed improved cyclic stability over that of the cast and crushed particulate, which is attributed to the restriction of crack propagation by grain boundary and dislocation with ch/discharging cycling.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.3
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• pp.220-226
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• 2019

Magnesium hydride has a high hydrogen storage capacity (7.6 wt.%), and is cheap and lightweight, thus advantageous as a hydrogen storage alloy. However, Mg-based hydrides undergo hydrogenation/dehydrogenation at high temperature and pressure due to their thermodynamic stability and high oxidation reactivity. MWCNTs exhibit prominent catalytic effect on the hydrogen storage properties of $MgH_2$, weakening the interaction between Mg and H atoms and reducing the activation energy for nucleation of the metal phase by co-milling Mg with carbon nanotubes. Therefore, it is suggested that combining transition metals with carbon nanotubes as mixed dopants has a significant catalytic effect on the hydrogen storage properties of $MgH_2$. In this study, Material life cycle evaluation was performed to analyze the environmental impact characteristics of Mg-CaO-10 wt.% MWCNTs composites manufacturing process. The software of material life cycle assessment (MLCA) was Gabi 6. Through this, environmental impact assessment was performed for each process.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.6
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• pp.553-557
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• 2020

It is possible that hydrogen could replace coal and petroleum as the predominant energy source in the near future, but several challenges including cost, efficiency, and stability. Mg and Mg alloys are attractive hydrogen storage materials because of their lightweight and high absorption capacity. Their range of applications could be further extended if their hydrogenation properties could be improved. The main emphasis of this study was to investigate their hydrogenation properties for Synthesis of 10wt.% CaF2 in Mg2NiHx systems. The effect of BCR (66:1) and MA time (96 hours) on the hydrogenation properties of the composite was investigated. also, Mg2NiHx-10wt% CaF2 composites prepared by Mechanical Alloying are used in this work to illustrate the effect of catalysts on activation energy and kinetics of Magnesium hydride.