• Journal of the Korean Applied Science and Technology
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• v.28 no.3
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• pp.321-328
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• 2011

The autothermal reforming reaction of methane was investigated to produce hyd rogen with Ni/$CeO_2-ZrO_2$, Ni/$Al_2O_3$-MgO and Ni-Ru/$Al_2O_3$-MgO catalysts. Honeycomb metalli c monolith was applied in order to obtain high catalytic activity and stability in autothermal r eforming. The catalysts were characterized by XRD, BET and SEM. The influence of various catalysts on hydrogen production was studied for the feed ratio($O_2/CH_4$, $H_2O/CH_4$). The $O_2/CH_4$ and $H_2O/CH_4$ ratio governed the methane conversion and temperature profile of reactor. Th e reactor temperature increased as the reaction shifted from endothermic to exothermic reactio n with increasing $O_2/CH_4$ ratio. Among the catalysts used in the experiment, the Ni-Ru/$Al_2O_3$-MgO catalyst showed the highest activity. The 60% of $CH_4$ conversion was obtained, and th e reactor temperature was maintained $600^{\circ}C$ at the condition of GHSV=$10000h^{-1}$ and feed ratio S/C/O=0.5/1/0.5.

• Korean Journal of Metals and Materials
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• v.50 no.10
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• pp.769-774
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• 2012

Mg-x wt% $Fe_2O_3-y$ 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 $Mg-5Fe_2O_3-5Ni$ was completed after one hydriding (under 12 bar $H_2$) - dehydriding (in vacuum) cycle at 593 K. At n = 2, $Mg-5Fe_2O_3-5Ni$ 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 $Mg-10Fe_2O_3$ 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 $H_2$. Activated $Mg-10Fe_2O_3-5Ni$ 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 $H_2$.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.243.2-243.2
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• 2010

현재 바이오디젤(Bio diesel)은 유지와 메탄올을 염기촉매를 넣고 전이에스테르화(Trans-esterification)반응하여 생산한다. 생산된 1세대 바이오 디젤은 분자 내 산소가 다량 함유되어 여러 가지 단점을 가지기 때문에 전이에스테르화 반응을 대체한 탈산소(Deoxygenation)반응이 주목 받고 있다. 본 연구에서는 유리지방산(Free fatty acid, FFA)인 올레익 산(Oleic acid)의 탈산소반응을 수행하였다. 하이드로탈사이트(Hydrotalcites) 구조인 MgO-$Al_2O_3$(MgO=70 wt%)를 6시간 동안 $500^{\circ}C$에서 예비소성(Pre-calcination)하여 담체로 사용하였다. 제조된 MgO-$Al_2O_3$ 담체에 함침법(Incipient wetness method)으로 20 wt% Ni을 담지 시켰다. 제조된 Ni/MgO-$Al_2O_3$촉매는 소성온도를 변화시켜 반응 실험을 수행하였다. TPR 분석을 통해 산화-환원특성을 분석하였고 생성물의 원소분석을 통해 생성물의 산소함량을 측정하였다.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.884-888
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• 2004

Effects of NiO were studied in aspects of dielectric properties and microstructure of $0.96(0.91Pb(Mg_{1/3}Nb_{2/3})O_3-0.09PbTiO_3)­0.04BaTiO_3$ (PMN-PT-BT, PBT). The PBT was prepared by a conventional mixed oxide method using $(MgCO_3)_4{\cdot}Mg(OH)_2$ instead of MgO through Lewis acid-base interaction. NiO was added in the range of 0.5 to $3.0\;wt\%$ as thermally decomposable $2NiCO_3{\cdot}3Ni(OH)_2$ and it seemed to enhance densification to a large extent below $1000^{\circ}C$. But all the systems gave rise to ceramics with almost same relative sintered density of 96% by sintering at $1000^{\circ}C$ for 2 h. But it turned out that the addition of NiO was detrimental to dielectric constant but beneficial to the loss of dielectric constant.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.64-70
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• 2012

Samples of pure Mg, 76.5 wt%Mg-23.5 wt%Ni, and 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ were prepared by reactive mechanical grinding and their hydriding and dehydriding properties were then investigated. The reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation and to shorten diffusion distances of hydrogen atoms. After hydriding-dehydriding cycling, the 76.5 wt%Mg-23.5 wt%Ni and 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ samples contained $Mg_2Ni$ phase. In addition to the effects of the creation of defects and the decrease in particle size, the addition of Ni increases the hydriding and dehydriding rates by the formation of $Mg_2Ni$. Expansion and contraction of the hydride-forming materials (Mg and $Mg_2Ni$) with the hydriding and dehydriding reactions are also considered to increase the hydriding and dehydriding rates of the mixture by forming defects and cracks leading to the fragmentation of particles. The reactive mechanical grinding of Mg-Ni alloy with $Fe_2O_3$ is considered to decrease the particle size.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.52-58
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• 2020

Electrochemical characterization and thermal stability were investigated for MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ cathode. The ratio of MgF₂ was controlled by 0.5, 1, 3 wt%. Cyclic voltammetry, charge-discharge profiles, rate capability, cycle life were measured for electrochemical properties. DSC analysis was measured for thermal stability. The first discharge capacities of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ were decreased at 0.1C-rate compared to pristine LiNi_0.8Co_0.15Al_0.05O₂. But the rate capability and cycle life of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ were improved at 2C-rate. In DSC analysis result, the exothermic temperature of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ was increased and peak height was decreased.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.112-125
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• 2021

The new emerging "High entropy materials" attract the attention of the scientific society because of their simpler structure and spectacular applications in many fields. A novel nanocrystalline high entropy (Be,Mg,Ca,Sr,Zn,Ni)3O4 oxide has been successfully synthesized through mechanochemical treatment followed by sintering and air quenching. The present research work focuses on the possibility of single-phase formation in the aforementioned high entropy oxide despite the great difference in the atomic sizes of reactant alkaline earth and 3d transition metal oxides. Structural properties of (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide were explored by confirmation of its single-phase Fd-3m spinel structure by x-ray diffraction (XRD). Further, nanocrystalline nature and morphology were analyzed by scanning electron microscopy (SEM). Among thermal properties, thermogravimetric analysis (TGA) revealed that the (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide is thermally stable up to a temperature of 1200℃. Whereas phase evolution in (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide before and after sintering was analyzed through differential scanning calorimetry (DSC). Electrochemical studies of (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide consists of a comparison of thermodynamic and kinetic parameters of water and hydrazine hydrate oxidation. Values of activation energy for water oxidation (9.31 kJ mol-1) and hydrazine hydrate oxidation (13.93 kJ mol-1) reveal that (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide is catalytically more active towards water oxidation as compared to that of hydrazine hydrate oxidation. Electrochemical impedance spectroscopy is also performed to get insight into the kinetics of both types of reactions.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.106-111
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• 1999

The effect of the MG on the electrochemical charge-discharge properties of $CaNi_5$ hydrogen storage alloys was investigated under Ar and $H_2$ atmosphere. $CaNi_5$ alloy was partially decomposed to CaO and Ni phase during the MG process. The decomposition of $CaNi_5$ alloy was enhanced by the MG process which leads to crash and reformation of oxide layer on the alloy surface. As the MG process time increased, initial discharge capacity of the electrode was reduced, but the decay rate of the capacity compared to $CaNi_5$ alloys was slower. It may be described that the degradation of $MG-CaNi_5$ electrode was caused by the reduction of the reversible hydrogen reaction sites and increasing polarization resistance of hydrogen adsorption resulted from phase decomposition and disorder during the MG process, and/or by hydroxide formation during the electrochemical charge-discharge cycles.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.200-201
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• 2004

The $H_{EB}$ was investigated for exchange coupling $20\;{\AA}\;Fe/x\;{\AA}\;NiO\;(type-I samples)$, $20\;{\AA}\;Fe/x\;{\AA}$ nonmagnetic layer $(MgO, Ag, Cu)/(500-x{\AA})$ NiO (type-II smaples). In type-I samples, the $H_{EB}$ is long-range coupling when looking from the point of view of the AFM. The $H_{EB}$ consistent with a generalized Meiklejohn-Bean approach. The critical thickness, which $H_{EB}$ is observed, is $130\;{\AA}$. In type-II samples, MgO layer more decouples the thin interfacial NiO from bottom NiO than other nonmagnetic layer. Nd the decoupling of Ag smallest. This means that the Ag layer has strong coupling the thin interfacial NiO with bottom NiO.

• Journal of the Korean institute of surface engineering
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• v.50 no.3
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• pp.212-218
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• 2017

$Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrite powders were prepared by self-propagating high temperature synthesis followed by classifying with an ultrasonic wet-magnetic separation unit to get high pure nano-sized particles. The $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrites were well formed by using several powders like iron, nickel oxide, zinc oxide and magnesium oxide at 0.1 MPa of oxygen pressure. The ultrasonic wet-magnetic separation of pre-mechanical milled ferrite powders resulted in producing the powders with average size of 800 nm. The addition of a surfactant during the wet-magnetic separation process improved productivity more than twice. The coercive force, maximum magnetization and residual magnetization of the $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ nano-powders with 800 nm size were 3651 A/m, $53.92Am^2/kg$ and $4.0Am^2/kg$, respectively.