• Transactions of the Korean hydrogen and new energy society
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• v.7 no.1
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• pp.45-54
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• 1996

Electrochemical oxidation of hydrogen on PdOx and Pd electrodes were investigated in aqueous 30% KOH solution at different temperatures and hydrogen concentrations(partial pressures). Anodic reaction by hydrogen on PdOx electrode was mainly due to the oxidation of adsorbed hydrogen at -0.8V~-0.5V(vs. Hg/HgO). For Pd electrode, the anodic reaction was participated by the adsorbed hydrogen on surface, as well as by the metal hydride formed from direct reaction between Pd and hydrogen at -0.5V~0.0V(vs. Hg/HgO). With the increase of hydrogen concentration the charge transfer resistance decreased and the exchange current increased. The transfer coefficient of PdOx and Pd electrodes were found to be 0.78 and 0.72 respectively, which shows the superior reactivity of Pd electrode. The activation energies of PdOx and Pd electrodes decreased with the increase of overpotential and were found to be 23.9~20.3 kJ/mole and 7.2~3.0kJ/mole, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.92-101
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• 2005

[ $Li_3AlH_6$ ] (5.6wt% theoretical hydrogen storage capacity) powders with and without Ti-containing dopants have been successfully synthesized by mechanochemical reaction near room temperatures from mixtures of LiH and $LiAlH_4$ powders. It has been observed that single phase $Li_3AlH_6$ could be obtained within 2-3 hours of milling, but the addition of reactive $TiCl_2\;or\;TiCl_3$ to the starting mixtures. caused partial decomposition of $LiAlH_4$ into LiCl and free Al with gaseous $H_2$. By addition of these reactive dopants to the as-synthesized $Li_3AlH_6$, this problem could be solved. The addition of 2 mol% $TiCl_2\;or\;TiCl_3\;to\;Li_3AlH_6$ decreased the decomposition start temperature up to 30-50$^{\circ}C$, while that of Ti or $TiH_2$ did not change the thermal decomposition behavior of $Li_3AIH_6$.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.4
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• pp.181-185
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• 1997

The electrochemical properties of the $AB_2$-type (Zr-Ti-V-Ni-Cr-Co-Mn) metal hydride electrodes prepared by ball milling with $AB_5-type\{(LM)Ni_{3.6}Al_{0.4}Co_{0.7}Mn_{0.3}\}$(LM : Lanthanum-rich mischmetal) alloy powder as a surface activator were investigated. By ball milling with $AB_5$ type alloy powder, the activation of $AB_2$ type metal hydride electrode was accelerated resulting in an increase of discharge capacity from 35% to 85% of the maximum capacity at the first cycle. As the amount of surface activator increased the activation rate increased, whereas the discharge capacity increased with 10wt% and decreased with 20wt% addition of the surface activator. When the amount of the surface activator was kept constant as 10wt%, the discharge capacity and the activation rate increased with ball milling time up to 20 hours. However beyond 20 hours of ball milling time, they decreased drastically due to the nano-crystallization or amorphorzation of the alloy powder.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.161-167
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• 1998

It has been investigated the effects of alloying elements and binders on the corrosion behavior of metal hydride electrodes for anode of Ni/MH secondary battery. The $AB_5$-type alloys, $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ and $(LM)Ni_{3.6}Co_{0.7}Mn_{0.3}Al_{0.4}$, were used for the experiments. The electrodes were prepared by mixing and cold-pressing of alloy powders with Si sealent or PTFE powders, or cold-pressing the electroless copper coated alloy powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.256-262
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• 2012

This study investigated the hydrogen storage properties of Zr-Based $AB_{2-x}M_x$ metal hybride made by HCS (Hydriding Combustion Synthesis). The materials were prepared by HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm, HCS 80 wt% $AB_2$-20 wt% Mg and pure Zr-Based $AB_2$, These materials were activated at 298 K under 20 bar. Both HCS 80 wt% $AB_2$-20 wt% Mg and HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm were absorbed within 1 minute. In the case of the $AB_2$, it was perfectly absorbed within 6 minutes. Then, the materials were evaluated to obtain P-C-T (Pressure-Composition-Temperature) curves at 298K. As a result, the hydrogen storage capacity of HCS 80 wt% $AB_2$-20 wt% Mg, HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm and pure Zr-Based $AB_2$ were determined to be 1.2, 1.6 and 1.74 wt%, respectively. The activation energy and rate controlling step were calculated by the Johnson-Mehl Avrami equation. The activation energies of HCS 80 wt% $AB_2$-20 wt% Mg, HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm and pure Zr-Based $AB_2$ were 26.91, 20.45, and 60.41 kJ/mol, respectively. Also, the values of ${\eta}$ in the Johnson-Mehl Avrami equation for HCS 80 wt% $AB_2$-20 wt% Mg, HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm and pure Zr-Based $AB_2$ are 0.60, 0.51, and 0.44. So, the rate controlling steps which indicate hydrogen storage mechanism are an one dimensional diffusion process.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.129-136
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• 2010

Ionic liquids are expanding their applications in various fields of chemistry, due to their unique properties such as negligible volatility, immisciblity with hydrocarbons, high electrical conductivity, and tunable acidity and basicity. In this paper, the physical properties, synthesis, and commercial applications of ionic liquids are discussed. Recent research trends are also briefly reviewed, particularly on application of ionic liquids to catalysis, biomass, and $CO_{2}$ capture and utilization.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.33-36
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• 2006

The effective thermal conductivities of $Mm\;(La_{0.6-0.8})\;Ni_{4.0}Co_{0.6}Mn_{0.2}Al_{0.2}$ (TL-492) with hydrogen and helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in Low pressure range (below 0.5 MPa). And that influence decreases rapidly with increase of gas pressure. The reason is at low pressure, the mean free path of gas becomes greater than effective thickness of gas film which is important to the heat transfer mechanism in this research. And, carbon fibers have been used to try to enhance the poor thermal conductivity of TL-492. Three types of carbon fibers and three mass fractions have been examined and compared. Naturally, the highest effective thermal conductivity has been reached with carbon fiber which has highest thermal conductivity, and highest mass fraction. This method has acquired 4.33 times higher thermal conductivity than pure metal hydrides with quite low quantity of additives, only 0.99wt% of carbon fiber. This is a good result comparing to other method which can reach higher effect ive thermal conductivity but needs much higher mass fraction of additives too.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.1
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• pp.9-16
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• 2017

Hydrogen forms metal hydrides with some metals and alloys leading to solid-state storage under moderate temperature and pressure that gives them the safety advantage over the gas and liquid storage methods. However, it has disadvantages of slow hydrogen adsorption-desorption time and low thermal conductivity. To improve characteristics of metal hydrides, it is important that activation and thermal conductivity of metal hydrides are improved. In this study, we have been investigated hydrogen storage properties of Hydralloy C among Ti-Mn alloys. Also, the characteristics of activation and thermal conductivity of Hydralloy C were enhanced to improve kinetics of hydrogen adsorption-desorption. As physical activation method, PHEM (planetary high energy mill) was performed in Ar or $H_2$ atmosphere. Hydralloy C was also activated by $TiCl_3$ catalyst. To improve thermal conductivity, various types of ENG (expanded natural graphite) were used. The prepared samples were compacted at pressure of 500 bar. As a result, the activation properties of $H_2$ PHEM treated Hydralloy C was better than the other activation methods. Also, the amounts of hydrogen storage showed up to 1.6 wt%. When flake type ENG was added to Hydralloy C, thermal conductivity and hydrogen storage properties were improved.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.517-520
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• 2006

The leaching behaviors of zinc and manganese oxides of spent alkaline manganeses battery in sulfuric acid solution by using $H_{2}O_{2}$ as a reducing agent were investigated according to the concentration of $H_{2}SO_{4}$, temperature, reaction time, and the amount of $H_{2}O_{2}$. The experimental results of zinc and manganeses dissolution rates obtained without a reducing agent at 100 g/L solid/liquid ratio, 3.0 M $H_{2}SO_{4}$, $60^{\circ}C$ and 200 r.p.m. were 97.7% and 43.5%, respectively. On the other hand, zinc and manganeses dissolution rates obtained by adding 30 mL reducing agent at $60^{\circ}C$ were 99.6% and 97.1%, respectively. The addition of the reducing agent increased the leaching of manganese by two-fold compared to the absence of a reducing agent. In case of adding over 30 mL $H_{2}O_{2}$, however, the leaching rates of zinc and manganeses were independent of reducing agent amounts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5376-5383
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• 2011

The objective of this study is the development of carbon-recycle technology, that converts carbon dioxide captured from flue gas to carbon monoxide or carbon for reuse in industrial fields. It is difficult to decompose $CO_2$ because $CO_2$ is very stable molecule. And then metal oxide was used as an activation agent or catalyst for the decomposition of $CO_2$ at low temperature. Metal oxides, which converts $CO_2$ to CO or C, were prepared using Ni-ferrite by solid state method and hydrothermal synthesis in this study. TPR/TPO and TGA were used as an analysis method to analyze the decomposition characteristics of $CO_2$. As the results, the reduction area of $H_2$ was high value at 15 wt% of NiO and the decomposition area of $CO_2$ was superior capacity at 5 wt% of NiO. However, TGA data showed contrary results that reduction area of $H_2$ was 28.47wt% and oxidation area by $CO_2$ was 26.95wt% at 2.5 wt% of NiO, one of the Ni-ferrite powders synthesized using solid state method. $CO_2$ decomposition efficiency was 94.66% and it is excellent results in comparison with previous studies.