• Korean Journal of Materials Research
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• 제16권5호
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• pp.277-284
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• 2006

The alloys were prepared by a non-consumable vacuum arc melting and homogenized at $1050^{\circ}C$ for 24 hrs. Two kind of surface modifications were performed alkali treatment in 5.0M NaOH solution subsequent and heat treatment in vacuum furnace at $600^{\circ}C$, and were oxidizing treatment at the temperature range of 550 to $750^{\circ}C$ for 30 minutes. After surface modification, these samples were soaked in SBF which consists of nearly the same ion concentration as human blood plasma. Cytotoxicity tests were performed in MTT assay treated L929 fibroblast cell culture, using indirect methods. A porous and thin activated layer was formed on Titanium and Ti-8Ta-3Nb alloy by the alkali treatment. A bone-like hydroxyapatite was nucleated on the activated porous surfaces during the in vitro test. However, Ti-8Ta-3Nb alloys showed better bioactive properties than Titanium. According to XRD results, oxide layers composed of mostly $TiO_2$(rutile) phases. Cytotoxicity test also revealed that moderate oxidation treatment lowers cell toxicity and Ti-8Ta-3Nb alloy showed better results compared with Titanium.

• Transactions of the Korean hydrogen and new energy society
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• 제28권6호
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• pp.610-617
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• 2017

This paper presents a study of the effect of thickness of porous Al-Ni electrodes, on the Hydrogen Evolution Reaction (HER) in alkaline media. As varying deposition time at 300 W DC sputtering power, the thickness of the Al-Ni electrodes was controlled from 1 to $20{\mu}m$. The heat treatment was carried out in $610^{\circ}C$, followed by selective leaching of the Al-rich phase. XRD studies confirmed the presence of $Al_3Ni_2$ intermetallic compounds after the heat treatment, indicating the diffusion of Ni from the Ni-rich phase to Al-rich phase. The porous structure of the Al-Ni electrodes after the selective leaching of Al was also confirmed in SEM-EDS analysis. The double layer capacitance ($C_{dl}$) and roughness factor ($R_f$) of the electrodes were increased for the thicker Al-Ni electrodes. As opposed to the general results in above, there were no further improvements of the HER activity in the case of the electrode thickness above $10{\mu}m$. This result may indicate that the $R_f$ is not the primary factor for the HER activity in alkaline media.

• Membrane Journal
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• 제28권5호
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• pp.297-306
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• 2018

This review focused carbon-free hydrogen productions from ammonia decomposition including inorganic membranes, catalysts and the presently studied reactor configurations. It also contains general information about hydrogen productions from hydrocarbons as hydrogen carriers. A Pd-based membrane (e.g. a porous ceramic or porous metallic support with a thin selective layer of Pd alloy) shows its efficiency to produce the high purity hydrogen. Ru-based catalysts consisted of Ru, support, and promoter are the efficient catalysts for ammonia decomposition. Packed bed membrane reactor (PBMR), Fluidized bed membrane reactor (FBMR), and membrane micro-reactor have been studied mainly for the optimization and the improvement of mass transfer limitation. Various types of reactors, which contain various combinations of hydrogen-selective membranes (i.e. Pd-based membranes) and catalysts (i.e. Ru-based catalysts) including catalytic membrane reactor, have been studied for carbon-free hydrogen production to achieve high ammonia conversion and high hydrogen flux and purity.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1371-1378
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• 2004

A porous stainless steel (SUS) as a substrate of silica composite membranes for hydrogen purification was used to improve mechanical strength of the membranes for industrial application. The SUS support was successfully modified by using submicron Ni powder, $SiO_2$ sols with particle size of 500 nm and 150 nm in turns. Silica top layer was coated on the modified supports under various preparation conditions such as calcination temperature, dipping time and repeating number of dipping-drying process. The calcination temperature for proper sintering was between H ttig temperature and Tamman temperature of the coating materials. Maximum hydrogen selectivity was investigated by changing dipping time. As repeating number of dipping-drying process increased, permeances of nitrogen and hydrogen were decreased and $H_2/N_2$ selectivity was increased due to the reduction of non-selective pinholes and mesopores. For the silica membrane prepared under optimized conditions, permeance of hydrogen was about $3\;{\times}\;10^{-5}\;cm^3{\cdot}cm^{-2}{\cdot}s^{-1}{\cdot}cmHg^{-1}$ combined with $H_2/N_2$ seletivity of about 20.

• Membrane Journal
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• 제11권3호
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• pp.124-132
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• 2001

Silica membranes were prepared on a porous ${\alpha}$-alumina tube with pore size of 150nm by sol-gel and chemical vapor deposition(CVD) method for hydrogen separation at high temperatures. Silica and ${\gamma}$-lumina membranes formed by the sol-gel method possessed a large amount of mesopores of a Knudsen diffusion regime. In order to improve the $H_2$ selectivity, silica was deposited in the sol-gel derived silica/${\gamma}$-alumina layer by thermal decomposition of tetraethyl orthosilicate(TEOS) at $600^{\circ}C$. The CVD with forced cross flow through the porous wall of the support was very effective in plugging mesopores that were left unplugged in the membranes. The CVD modified silica/alumina composite membrane completely rejected nitrogen permeation and thus showed a high $H_2$ selectivity by molecular sieve effect. the permeation of hydrogen was explained by activated diffusion and the activation energy was 9.52kJ/mol.

• Journal of the Korean Electrochemical Society
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• 제16권3호
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• pp.157-161
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• 2013

Porous $LiMn_{0.6}Fe_{0.4}PO_4$ (LMFP) was synthesized by a sol-gel process. Uniform dispersion of the conductive carbon source throughout LMFP with uniform carbon coating was achieved by heating a stoichiometric mixture of raw materials at $600^{\circ}C$ for 10 h. The crystal structure of LMFP was investigated by Rietveld refinement. The surface structure and pore properties were investigated by SEM, TEM and BET. The LMFP so obtained has a high specific surface area with a uniform, porous, and web-like nano-sized carbon layer at the surface. The initial discharge capacity and energy density were 152 mAh/g and 570 Wh/kg, respectively, at 0.1 C current density, and showed stable cycle performance. The combined effect of high porosity and uniform carbon coating leads to fast lithium ion diffusion and enhanced electrochemical performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제12권7호
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• pp.3296-3301
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• 2011

The Porous pavement gains popularity because of several benefits. It is to minimize hydro-planning condition, spraying condition, and splash to increase friction resistance, and decrease noise. Also, other studies showed that it is important to have appropriate porosity to reduce noise and water flush. The purpose of this study is an evaluation on the mechanical properties of asphalt pavements for surface course. In this study the specimen was manufactured using the Gyratory compactor in order to compact the strengthened surface course that involved the two-layer pavement. This study is conducted by using Marshall stability test(KS F 2377), Impact resonance test, Schmidt hammer test(KS F 2730), and the Uniaxial compression test(KS F 2314). Using the Uniaxial compression test and Schmidt hammer test, the values of compressive strength and bearing capacity were measured, and the modulus of elasticity for each specimen was respectively measured using the Uniaxial compression test, Impact Resonance test.

• Journal of the Korean institute of surface engineering
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• 제51권5호
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• pp.277-290
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• 2018

In this study, Pd-Ni-Ag alloy hydrogen separation membranes were fabricated by Pd/Ag/Pd/Ni/Pd multi-layer sputter deposition on the modified MIM(Metal Injection Molding)-PSS(Porous Stainless Steel) support and followed heat treatment. Nickel, used as an alloying element in Pd alloy membranes, is inexpensive and stable material in a hydrogen isotope environment at high temperature up to 1123 K. Hydrogen perm-selectivity of Pd-Ni-Ag alloy membranes is affected not only by composition of membrane films but also by other factors such as surface properties of PSS support, microstructure of membrane films and inter-diffused impurities from PSS support. In order to clarify the effect of surface Ni composition on hydrogen perm-selectivity of Pd-Ni-Ag alloy membranes, the other effects were significantly minimized by the formation of dense and homogeneous Pd-Ni-Ag alloy membranes. Hydrogen permeation test showed that hydrogen permeability decreased from $7.6{\times}10^{-09}$ to $1.02{\times}10^{-09}mol/m{\cdot}s{\cdot}Pa^{0.5}$ as Ni composition increased from 0 to 16 wt% and the selectivity for $H_2/N_2$ was infinite.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 한국방사성폐기물학회 2018년도 춘계학술논문요약집
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• pp.57-57
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• 2018

The electrorefining process is generally composed of two recovery steps in pyroprocessing - the deposit of uranium onto a solid cathode and the recovery of the remaining uranium and TRU elements simultaneously by a liquid cadmium cathode. The liquid cathode processing is necessary to separate cadmium from the actinide elements since the actinide deposits are dissolved or precipitated in a liquid cathode. Distillation process was employed for the cathode processing. It is very important to avoid a splattering of cadmium during evaporation due to the high vapor pressure. In this study, a multi-layer porous round cover was proposed and examined to develop a splatter shield for the Cd distillation crucible. Cadmium vapor can be released through the holes of the shield, whereas liquid drops can be collected in the multiple hemisphere. The collected drops flow on the round surface of the cover and flow down into the crucible. The crucible cover was fabricated and tested in the Cd distiller. The cover was made with three stainless steel round plates with a diameter of 33.50 mm. The distance between the hemispheres and the diameter of the holes are 10 and 1 mm, respectively. About 40 grams of Cd and about 4 grams of Bi was distilled at a reduced pressure for two hours at $470^{\circ}C$. After the Cd distillation experiment, cadmium was not detected and more than 90 % of Bi remained in the ICP-OES analysis. Therefore the crucible cover can be a candidate for the splatter shield of the Cd distillation crucible. Further development of the crucible cover is necessary for the decision of the optimum cover geometry and the operating conditions of the Cd distiller.

• Steel and Composite Structures
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• 제46권1호
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• pp.1-13
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• 2023

Elastic bending of imperfect functionally graded sandwich plates (FGSPs) laying on the Winkler-Pasternak foundation and subjected to sinusoidal loads is analyzed. The analyses have been established using the quasi-3D sinusoidal shear deformation model. In this theory, the number of unknowns is condensed to only five unknowns using integral-undefined terms without requiring any correction shear factor. Moreover, the current constituent material properties of the middle layer is considered homogeneous and isotropic. But those of the top and bottom face sheets of the graded porous sandwich plate (FGSP) are supposed to vary regularly and continuously in the direction of thickness according to the trigonometric volume fraction's model. The corresponding equilibrium equations of FGSPs with simply supported edges are derived via the static version of the Hamilton's principle. The differential equations of the system are resolved via Navier's method for various schemes of FGSPs. The current study examine the impact of the material index, porosity, side-to-thickness ratio, aspect ratio, and the Winkler-Pasternak foundation on the displacements, axial and shear stresses of the sandwich structure.