• Transactions of the Korean hydrogen and new energy society
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• 제22권2호
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• pp.168-177
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• 2011

A set of kinetics study on the reduction with $CH_4$, oxidation with steam and oxidation with air was performed for $Fe_2O_3/ZrO_2$. $Fe_2O_3/ZrO_2$ was prepared by aerial oxidation method. The reactivity experiments were performed in a thermogravimetric analyzer (TGA) with different reacting gas concentrations and temperatures. The obtained activation energy of reduction by methane, oxidation by water and oxidation by air are 219 kJ/mol, 238 and 20 respectively.

• Journal of Advanced Marine Engineering and Technology
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• 제40권2호
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• pp.112-119
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• 2016

Many studies have been conducted on the performance of a passive autocatalytic recombiner (PAR), but not many have focused on the locations where the PAR is installed. During a severe accident in a nuclear reactor containment, a large amount of hydrogen gas can be produced and released into the containment, leading to hydrogen deflagration or a detonation. A PAR is a hydrogen mitigation method that is widely implemented in current and advanced light water reactors. Therefore, for this study, a PAR was installed at different locations in order to investigate the difference in hydrogen reduction rate. The results indicate that the hydrogen reduction rate of a PAR is proportional to the distance between the hydrogen induction location and the bottom wall.

• Resources Recycling
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• 제22권3호
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• pp.43-49
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• 2013

A study on the recovery of lithium and leaching behavior of NCM powder by hydrogen reduction for NCM system Li-ion battery scraps was investigated. The reductive rate was about 93% at $800^{\circ}C$ by hydrogen treatment. The lithium carbonate with 99% purity was manufactured by using $CO_2$ gas and washing method with water for NCM powder after hydrogen reduction. As a result of comparing the powders before and after the hydrogen reduction treatment for acid leaching behavior we obtained 32% enhanced leaching rate of cobalt, 45% enhanced leaching rate of nickel and the 90% leaching effect for manganese by hydrogen reduction at 2M $H_2SO_4$ concentration condition.

• Korean Journal of Metals and Materials
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• 제49권1호
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• pp.52-57
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• 2011

Nickel ferrite ($NiFe_2O_4$) powder was prepared through the ceramic route by calcination of a stoichiometric mixture of nickel oxide (NiO) and iron oxide ($Fe_2O_3$). The pressed pellets of $NiFe_2O_4$ were isothermally reduced in pure hydrogen at 800, 900, 1000 and $1100^{\circ}C$. Based on thermogravimetric analysis, the reduction behavior and the kinetic reaction mechanisms of the synthesized ferrite were studied. The initial ferrite powder and various reduction products were characterized by XRD, SEM, reflected light microscope and VSM to reveal the effect of hydrogen reduction on the composition, microstructure, magnetic properties and reaction kinetics of the produced Fe-Ni alloy. Complete reduction of the $NiFe_2O_4$ was achieved with synthesis of homogeneous nanocrystalline Fe-Ni alloys. Arrhenius equation with the approved mathematical formulations for a gas-solid reaction was applied for calculating the activation energy ($E_a$) values and detecting the controlling reaction mechanism.

• Resources Recycling
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• 제33권1호
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• pp.15-21
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• 2024

The demand for electric vehicles powered by lithium-ion batteries is continuously increasing. Recovery of valuable metals from waste lithium-ion batteries will be necessary in the future. This research investigated the effect of reaction temperature on the lithium recovery ratio from hydrogen reduction followed by water leaching from lithium-ion battery NCM-based cathode materials. As the reaction temperature increased, the weight loss ratio observed after initiation increased rapidly owing to hydrogen reduction of NiO and CoO; at the same time, the H₂O amount generated increased. Above 602 ℃, the anode materials Ni and Co were reduced and existed in the metallic phases. As the hydrogen reduction temperature was increased, the Li recovery ratio also increased; at 704 ℃ and above, the Li recovery ratio reached a maximum of approximately 92%. Therefore, it is expected that Li can be selectively recovered by hydrogen reduction as a waste lithium-ion battery pretreatment, and the residue can be reprocessed to efficiently separate and recover valuable metals.

• Transactions of the Korean hydrogen and new energy society
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• 제22권4호
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• pp.443-450
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• 2011

The three-reactor chemical-looping process (TRCL) for the production of hydrogen from natural gas is attractive for both $CO_2$ capture and hydrogen production. In this study, redox property of $Fe_2O_3$ and $WO_3$ supported with $ZrO_2$ and $MgAl_2O_4$ were studied with temperature programmed oxidation/reduction (TPO/R) experiment. All metal oxides were prepared by ball mill method. Metal oxides supported with $ZrO_2$ showed the good redox property in TPO and TPR tests. Reduction behavior was matched well the theoretical reduction mechanism. Metal oxides supported with $MgAl_2O_4$ formed a solid solution ($MgFe_{0.6}Al_{1.4}O_4$, $MgWO_4$). $Fe_2O_3$ showed more narrow reaction range and lower reaction temperature than $WO_3$.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.288-288
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• 2012

The oxidation characteristics of tungsten line pattern during the carbon-based mask layer removal process using oxygen plasmas and the reduction characteristics of the WOx layer formed on the tungsten line surface using hydrogen plasmas have been investigated for sub-50 nm patterning processes. The surface oxidation of tungsten line during the mask layer removal process could be minimized by using a low temperature ($300^{\circ}K$) plasma processing instead of a high temperature plasma processing for the removal of the carbon-based material. Using this technique, the thickness of WOx on the tungsten line could be decreased to 25% of WOx formed by the high temperature processing. The WOx layer could be also completely removed at the low temperature of $300^{\circ}K$ using a hydrogen plasma by supplying bias power to the tungsten substrate to provide an activation energy for the reduction. When this oxidation and reduction technique was applied to actual 40 nm-CD device processing, the complete removal of WOx formed on the sidewall of tungsten line could be observed.

• Journal of Powder Materials
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• 제23권2호
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• pp.126-131
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• 2016

The recent rise in applications of thermoelectric materials has attracted interest in studies toward the fabrication of thermoelectric materials using mass production techniques. In this study, we successfully fabricate n-type $Bi_2Te_{2.7}Se_{0.3}$ material by a combination of mass production powder metallurgy techniques, gas atomization, and spark plasma sintering. In addition, to examine the effects of hydrogen reduction in the microstructure, the thermoelectric and mechanical properties are measured and analyzed. Here, almost 60% of the oxygen content of the powder are eliminated after hydrogen reduction for 4 h at $360^{\circ}C$. Micrographs of the powder show that the reduced powder had a comparatively clean surface and larger grain sizes than unreduced powder. The density of the consolidated bulk using as-atomized powder and reduced atomized powder exceeds 99%. The thermoelectric power factor of the sample prepared by reduction of powder is 20% better than that of the sample prepared using unreduced powder.

• Transactions of the Korean hydrogen and new energy society
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• 제19권4호
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• pp.348-358
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• 2008

Reduction reactivity and carbon deposition characteristics of mass produced oxygen carrier particle(OCN-650) have been investigated by using hydrogen, methane, syngas, and natural gas as fuels. For all fuels, the maximum conversion and oxygen transfer capacity increased as the temperature increase. The reduction rate and the oxygen transfer rate increased as the temperature increase for methane. However, those values showed maximum at 900$^{\circ}C$ for hydrogen, syngas, and natural gas. To explain consistently the change of maximum conversion, reduction rate, oxygen transfer capacity, oxygen transfer rate and degree of carbon deposition for different fuels, new parameters such as reactive carbon contents and require oxygen per input gas were adopted.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3668-3674
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• 2010

Mesoporous SBA-15 was synthesized using tetraethylorthosilicate (TEOS) as the silica source and Pluronic (P123) as the structure-directing agent. The defective Si-OH groups present in SBA-15 were successively grafted with 3-chloropropyltrimethoxysilane (CPTMS) followed by tris-(2-aminoethyl) amine (TAEA) and/or tetraethylenepentamine (TEPA) for effective immobilization of silver nanoparticles. Grafting of TAEA and/or TEPA amine and immobilization of silver nanoparticles inside the channels of SBA-15 was verified by XRD, TEM, IR and BET techniques. The silver nanoparticles immobilized on TAEA and /or TEPA grafted SBA-15 was subjected for electrocatalytic reduction of hydrogen peroxide ($H_2O_2$). The TEPA stabilized silver nanoparticles show higher efficiency for reduction of $H_2O_2$ than that of TAEA, due to higher number of secondary amine groups present in TEPA. The amperometric analysis indicated that both the Ag/SBA-15/TAEA and Ag/SBA-15/TEPA modified electrodes required lower over-potential and hence possess high sensitivity towards the detection of $H_2O_2$. The reduction peak currents were linearly related to hydrogen peroxide concentration in the range between $3{\times}10^{-4}\;M$ and $2.5{\times}10^{-3}\;M$ with correlation coefficient of 0.997 and detection limit was $3{\times}10^{-4}\;M$.