• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.6
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• pp.276-281
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• 2021

In order to manufacture a semiconductor circuit, etching, cleaning, and deposition processes are repeated. During these processes, the inside of the processing chamber is exposed to corrosive plasma. Therefore, the coating of the inner wall of the semiconductor equipment with a plasma-resistant material has been attempted to minimize the etching of the coating and particle contaminant generation. In this study, we synthesized yttrium oxyfluoride (YOF) powder by a solid-state reaction using Y₂O₃ and YF₃ as raw materials. Mixing ratio of the Y₂O₃ and YF₃ was varied from 1.0:1.0 to 1.0:1.6. Effects of the mixing ratio on crystal structure and microstructure of the synthesized YOF powder were investigated using XRD and FE-SEM. The synthesized YOF powder was successfully applied to plasma spray coating process on Al substrate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.153-157
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• 2023

In order to manufacture a semiconductor circuit, etching, cleaning, and deposition processes are repeated. During these processes, the inside of the processing chamber is exposed to corrosive plasma. Therefore, the coating of the inner wall of the semiconductor equipment with a plasma-resistant material has been attempted to minimize the etching of the coating and particle contaminant generation. In this study, we mixed AlF₃ powder with the solid-state reacted yttrium oxyfluoride (YOF) in order to increase plasma-etching resistance of the plasma spray coated YOF layer. Effects of the mixing ratio of AlF₃ with YOF powder on crystal structure, microstructure and chemical composition were investigated using XRD and FE-SEM. The plasma-etching ratios of the plasma-spray coated layers were calculated and correlation with AlF₃ mixing ratio was analyzed.

• Journal of Power System Engineering
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• v.2 no.3
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• pp.41-48
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• 1998

This study was aimed at development of fabrication process of functionally graded materials(FGM), consisting of metal and ceramic by thermal spraying method. NiCrAIY/$Al_2O_3$ FGM were made by using plasma spraying onto the SS400 carbon steel substrate. And mechanical properties such as microhardness, thermal shock resistance and adhesive strength of the coating layer were investigated. Adhesive strength was evaluated by acoustic emission method. It was resulted that NiCrAIY/$Al_2O_3$ FGM made by thermal spraying method showed excellent thermal shock resistance and adhesive strength compared to the other lamellar structures of sprayed coatings and that AE is useful tool to evaluate the defect of thermal sprayed coating layer.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.5
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• pp.314-320
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• 2015

The present study investigates the thermal characteristics of a nanoscale superconductor material. A thin-film of $YBa_2Cu_3O_7-x$ was deposited on a $SrTiO_3$ substrate by using a pulsed-laser deposition technique and characterized using an ultrafast laser system. In order to extract a thermal conductivity value, a numerical solution for a transient one-dimensional heat conduction equation was obtained using a finite-difference method. The curve-fit shows a value 1.2 W/mK, which is relatively lower than those of bulk materials. This research provides a material property of superconductor thin-film required for the thermal design of micro or nanodevices.

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.555-560
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• 1990

High temperature superconducting films of $YBa_2Cu_3O_{7-x}$ were fabricated on the (100) single crystal faces of YSZ (yttria stabilized zirconia) and SrTi$O_3$ by aerosol spray using ultrasonic atomization. The superconducting phase was formed by a three-step process: (a) spraying of a stoichiometric solution of nitrates of yttrium, barium, and copper on heated substrates kept at 250$^{\circ}C$, (b) preheating of the sprayed films in air at 550$^{\circ}C$, and (e) sintering of the films in flowing oxygen at 950$^{\circ}C$, followed by furnace cooling. Resistances of the films were measured by the dc four-probe method and superconductivity was confirmed above the liquid nitrogen temperature.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.258-267
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• 2003

A new kind of oxygen carrier material is tested for chemical-looping combustion. NiO, CoO, $Fe_2O_3$ is chosen as metal oxide and YSZ as a binder. Hydrogen fuel is reacted with metal oxide (reduction of metal oxide) and then the reduced metal is successively oxidized by air. Dissolution method is examined to prepare the oxygen carriers. The effects of reaction temperature are measured by a TGA, mechanical strength and regenerability after 10 cycle are examined. $Fe_2O_3/YSZ$ oxygen carrier is bested in mechanical strength and we consider that NiO/YSZ after 3rd cycle are good oxygen carrier in according to reactor design.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.1
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• pp.153-159
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• 2021

A two-step process for increasing the leaching efficiency of yttrium and neodymium from coal fly ash were investigated at solid loadings of 5.0 g ash ~1,000 g ash/l of 1.0 N~10.0 N H₂SO₄, temperature ranging from 30℃ to 90℃, ultrasonic leaching time of 1~10 hours, and ultrasonic power of 25~200 W. The yttrium and neodymium from coal fly ash were effectively leached into ion phases by step change of the first conventional dissolution at room temperature and then the second heating process with the aid of ultrasonic wave, and maximum leaching efficiency of yttrium and neodymium obtained were 66 % and 63 %, respectively. The activation energies for the leaching reaction of yttrium and neodymium at second heating process dependent on leaching time and temperature were derived to be 41.540 kJmol^-1 and 507.92 kJmol^-1, respectively. The optimum conditions for the maximum leaching of yttrium and neodymium were found to be the solid loading of 250 g ash/l of H₂SO₄, solvent concentration of 2.0 N H₂SO₄, and second step process of temperatures of 30℃ for 3 hours and then 90℃ for 4 hours with ultrasonic intensity of 100 W.

• Journal of the Korean Chemical Society
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• v.17 no.1
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• pp.15-19
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• 1973

A method was developed for the separation of titanium, niobium and zirconium together in a group from the coexisting ions of various metals such as iron, cobalt, nickel, yttrium and rare earths by means of the cation exchange column using ${\alpha}$-hydroxyisobutyric acid as the eluent. In the course of the present investigation, it was found that the tailing phenomena of zirconium were attributable to the hydroxide precipitation which was made prior to the elution. For example, if zirconium was precipitated by sodium hydroxide, the tailing of zirconium became very serious in contrast to the results reported by others. This paper describes how these tailing phenomena of zirconium were prevented and how a practical procedure for the separation of these ions was, achieved using ion-exchange method. Using the present method the nuclides of $^{90m}Y$ and $^{90}Y$ were separated with radiochemical purity from the irradiated zirconium.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.5-16
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• 1991

It was grown Cubic $ZrO_2(10 mol% Y_2O_3)$ single crystals doped with 1 wt% rare earth metal oxides (RE=Ce, Pr, Nd, Eu, Er) by Skull method. It was investigated electrical properties on (111) plane of grown single crystals by Impedance Spectroscopy. It was potted relation between temperature and electrical conductivities and observed the transition at $약300-400^{\circ}$ It was obtained activation energy on the migration of oxygen vacancy between low temperature (before the transition) and high temperature (after the transition till ${\11}500^{\circ}$) and its difference can be seen the activation energy of the formation of oxygen vacancies by break up defect complexes. It was obtained the activation energy according as add yttria and rare earth metal oxides and discussed ionic conduction mechanism. Grown single crystals showed Ce: orange - red, Pr: golden - yellow, Nd: lilac, Eu: light pink, Er: pink due to dopant effect from the light absorption data in the visible range.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.6
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• pp.516-523
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• 2015

Nickel based oxygen transfer materials supported on two different YSZs were tested to evaluate their performance in methane chemical-looping reforming. The oxygen transfer materials of YSZs were selected with different amount of the doped yittrium in the $ZrO_2$ structure. The yittrium of 8 mol% stabilized the zirconia oxide to a cubic structure compare to the 3 mol% doping, which is known to be a good for oxygen transfer. Various nickel amounts (16wt.%, 32wt.%, 48wt.%) were loaded on the selected supports. The nickel amount of 32% shows the optimized catalyst structure with good physical properties and reducibility from the XRD, BET and H2-TPR analysis, especially when the support of 8YSZ was used. From the methane chemical-looping reforming, hydrogen was produced by methane decomposition catalyzed by Ni on both YSZs. Comparing two YSZ supports of 3YSZ and 8YSZ during the cycling tests, the catalyst with 8YSZ (Ni 32%) exhibits not only the higher methane conversion and hydrogen production but also a faster reaction rate reaching to the stable point.