• Journal of Environmental Science International
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• v.27 no.12
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• pp.1215-1226
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• 2018

In this study, PAN-SZ (polyacrylonitrile scoria zeolite) beads were prepared by immobilizing Na-A zeolite (SZ-A) synthesized from Jeju volcanic rocks (scoria) on the polymer PAN. FT-IR and TGA analysis results confirmed that the SZ-A was immobilized in the PAN-SZ beads. SEM images showed that the PAN-SZ beads are a spherical shape with 2 mm diameter and exhibit a porous inner structure inside the bead. The most suitable mixing ratio of PAN to SZ-A as the adsorbent for removing Sr ions was PAN/SZ-A = 0.2 g/0.3 g. The adsorption kinetic data for Cu and Sr ions were fitted well with the pseudo-second-order model. The Cu and Sr ion uptakes followed a Langmuir isotherm model and the maximum adsorption capacities at $20^{\circ}C$ were 84.03 mg/g and 75.19 mg/g, respectively. The amount of Sr ion adsorbed by SZ-A on the PAN-SZ beads was about 160 mg/g, which was similar to that adsorbed by SZ-A powder. Thus, the PAN-SZ beads prepared in this study are considered to be effective adsorbents for removing metal ions in aqueous solutions.

• Archives of Metallurgy and Materials
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• v.66 no.3
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• pp.703-707
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• 2021

In this work, we have designed a new high entropy alloy containing lightweight elements, e.g., Al, Fe, Mn, Ti, Cu, Si by high energy ball milling and spark plasma sintering. The composition of Si was kept at 0.75 at% in this study. The results showed that the produced AlCuFeMnTiSi_0.75 high entropy alloy was BCC structured. The evolution of BCC1 and BCC2 phases was observed with increasing the milling time up to 60 h. The spark plasma sintering treatment of milled compacts from 650-950℃ showed the phase separation of BCC into BCC1 and BCC2. The density and strength of these developed high entropy alloys (95-98%, and 1000 HV) improved with milling time and were maximum at 850℃ sintering temperature. The current work demonstrated desirable possibilities of Al-Si based high entropy alloys for substitution of traditional cast components at intermediate temperature applications.

• Progress in Superconductivity and Cryogenics
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• v.5 no.3
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• pp.1-5
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• 2003

The effect of CeO$_2$ coating on the surface nucleation of the top-seeded melt-growth processed YBCO superconductors was studied. It was effective that the coating of Y123 compact surfaces by CeO$_2$ powder suppressed the undesirable subsidiary YBa$_2$Cu$_3$O$_{7-y}$ (Y123) nucleation during melt processing. BaCeO$_3$ was formed in the CeO$_2$-coated layers, which might cause a CuO-excessive liquid at the partial melt stage of $Y_2$BaCuO$_{5}$(Y211) plus liquid, and thus the Y123 nucleation at the YBCO compact surfaces could be suppressed during the melt growth of Y123 grain. In addition, the CeO$_2$ refined the Y211 particles near the compact / coating interface. While the levitation forces of the top surfaces with and without CeO$_2$ coating were similar to each other, the levitation force of the interior of the CeO$_2$ coated sample was higher than that of the interior of the sample without CeO$_2$ coating, which was attributed to the suppression of subsidiary Y123 nucleation at the compact walls.s.s.

• Current Photovoltaic Research
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• v.2 no.4
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• pp.177-181
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• 2014

$Cu_2ZnSn(S_xSe_{1-x})_4$ (CZTSSe) absorber thin films were prepared on Mo coated soda lime glass substrates by sulfo-selenization of sputtered stacked Zn-Sn-Cu precursor thin films. The Zn-Sn-Cu precursor thin films were sulfo-selenized inside a graphite box containing S and Se powder using rapid thermal processing furnace at $540^{\circ}C$ in Ar atmosphere with pre-treatment at $300^{\circ}C$. The effect of different S/Se ratio on the structural, compositional, morphological and electrical properties of the CZTSSe thin films were studied using XRD (X-ray diffraction), XRF (X-ray fluorescence analysis), FE-SEM (field-emission scanning electron microscopy), respectively. The XRD, FE-SEM, XRF results indicated that the properties of sulfo-selenized CZTSSe thin films were strongly related to the S/Se composition ratio. In particular, the CZTS thin film solar cells with S/(S+Se)=0.25 shows best conversion efficiency of 4.6% ($V_{oc}$ : 348 mV, $J_{sc}$ : $26.71mA/cm^2$, FF : 50%, and active area : $0.31cm^2$). Further detailed analysis and discussion for effect of S/Se composition ratio on the properties CZTSSe thin films will be discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.869-873
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• 2002

$Cu_2ZnSnS_4$ (CZTS) thin film is one of the candidate materials for the solar cell. It has an excellent optical absorption coefficient as well as appropriate 1.4~1.5eV band gap. The purpose of this study is replacing a half of high-cost Indium(In) atoms with low-cost Zinc(Zn) atoms and the other half with low-cost Tin(Sn) atoms in the lattice of CIS. In annealing process of thin films deposited with mixture target, the thin films were appeared the peeling. The resistivity was decreased. Thin films were deposited on ITO glass substrates using a compound target which were made by $CU_2S$, ZnS, $SnS_2$ powder were sintered in the atmosphere of Al at room temperature by rf magnetron sputtering We investigated potentialities of a low-cost material for the solar cell by measuring of thin film composition, the structure and optical properties. We could get an appropriate $Cu_2ZnSnS_4$ composition A (112) preferred orientation was appeared without annealing temperature as shown in the diffraction peaks of the CIS cells and was available for photovoltaic thin film materials. The band gap increased from 1.4 to 1.7eV as the composition ratio of Zn/Sn.. The optical absorption coefficient of the thin film was above $10^4cm^{-1}$.

• Resources Recycling
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• v.15 no.5 s.73
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• pp.33-37
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• 2006

An equal-molar mixture of silver chloride (AgCl) and copper (Cu) was ground in atmosphere conditions using a planetary ball mill to investigate mechanochemical (MC) reaction for preparation of silver powders. The reaction causes the mixture of AgCl and Cu to change the composition of the mixture, such as silver (Ag) and cuprous chloride (CuCl). Through the leaching with ammonium hydroxide solution (1 mol), CuCl can be separated from MC product, so that pure Ag powders can be obtained as the final product. Moreover, polyvinylpyrrolidone (PVP) was used as the additive not only to improve dispersion of Ag pow- der during MC process, but also to control surface oxidation of Ag powders, prepared as the final product.

• Journal of Surface Science and Engineering
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• v.35 no.1
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• pp.39-46
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• 2002

$Cu_2$$ZnSnS_4$(CZTS) thin film is one of the candidate materials for the solar cell. It has an excellent optical absorption coefficient as well as appropriate 1.4~1.5eV band gap. The purpose of this study is replacing a half of high-cost Indium(In) atoms with low-cost Zinc(Zn) atoms and the other half with low-cost Tin(Sn) atoms in the lattice of CIS. Thin films were deposited on ITO glass substrates using a compact target which were made by $Cu_2$S, ZnS, SnS$_2$ powder at room temperature by rf magnetron sputtering and were annealed in the atmosphere of Ar and $S_2$(g). We investigated potentialities of a low-cost material for the solar cell by measuring of thin film composition, the structure and optical properties. We could get an appropriate $Cu_2$$ZnSnS_4$ composition. Structure was coarsened with increasing temperature and (112), (200), (220), (312) planes appeared to conform to all the reflection Kesterite structure. A (112) preferred orientation was advanced with increasing the annealing temperature as shown in the diffraction peaks of the CIS cells and was available for photovoltaic thin film materials. The band gap increased from 1.51 to 1.8eV as the annealing temperature increased. The optical absorption coefficient of the thin film was about $10^4$$cm^{-1}$.

• The Journal of Natural Sciences
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• v.14 no.2
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• pp.41-54
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• 2004

$LaMnO_3$ and A site substituted $La_{0.9}Sr_{0.1}MnO_3$(a=$5.33\AA$, c=$13.27\AA$), B site substituted $LaMn_{0.9}Cu_{0.1}O_3$(a=$5.52\AA$, c=$13.31\AA$) mixed oxides were prepared by Citrate sol-gel method. The powder X-ray diffraction patterns of these oxides were indexed with single phase hexagonal perovskite structures. According to the TRR result, oxygen stoichiometry of these oxides were oxidative nonstoichiometry as like $LaMnO_{3.16}$, $La_{0.9}Sr_{0.1}MnO_{3.10}$ and $LaMn_{0.9}Cu_{0.1}O_{3.14}$ Reduction reactions of un-substituted $LaMnO_3$ was two steps, but specific site(A site of B site) partially substituted $LaMnO_3$ oxides were procees to three reactions.

• Journal of Magnetics
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• v.7 no.2
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• pp.29-39
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• 2002

The initial NiCuZn synthetic ferrite were acquired from thermally decomposing the metal nitrates $Fe(NO_3)_39H_2O, Zn(NO_3)_26H_2O, Ni(NO_3)_26H_2O, and Cu(NO_3)_23H_2O$ at $150^circ{C}$ for 24 hours, and then we calcined the synthetic powder at $500^circ{C}$, pulverized each of those for 3, 6, 9, 12, and 15 hours in a steel ball mill, sintered each at $700^circ{C}$ to $1,000^circ{C}$ for 1 hour, and thus studied their microstructures and electromagnetic properties. We could make the initial specimens chemically bonded in liquidity at a low-temperature $150^circ{C}$, by using the low melting points less than $200^circ{C}$ of the metal nitrates instead of the mechanical ball-mill pulverization, then narrow a distance between the particles into a molecular one, and thus lower the reaction point of sintering by at least $200^circ{C}$ to $300^circ{C}$. Their initial permeability was 50 to 400 and their maximum magnetic induction density and coercive force, 2,400 G and 0.3 Oe to 0.5 Oe respectively, which was similar to those of NiZnCu ferrite synthesized in the conventional process. In the graph of initial permeability by frequencies, a $180^circ{C}$ rotation of the magnetic domains which appears in a broad band of micro-wave before and after the resonance frequency, could be perceived.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.461-465
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• 2021

A diffusion heat treatment process for YBa₂Cu₃O_7-y bulk superconductor in a Gd₂O₃ powder was attempted. As a result of measuring the critical temperature of the superconducting bulk, there was no change in the superconducting transition temperature as the Gd particles diffused into the YBa₂Cu₃O_7-y lattice, resulting in dense microstructure. As a result of measuring the critical current, the critical current density (J_c) of the superconducting bulk having treated by the Gd thermal diffusion treatment at 0 T increased to 3×10⁴ A/cm² at 0 T, which was higher than that of the superconducting bulk without thermal diffusion treatment. The surface magnetic force of the superconducting bulk with Gd thermal diffusion treatment was observed at the center of the superconducting bulk with the maximum trapped magnetic force (Hmax) of 1.51 kG. This result means that the Gd thermal diffusion treatment contributes to improving the critical current density Jc of YBa₂Cu₃O_7-y, and it is believed that Gd particles migrating into the superconducting bulk through thermal diffusion either fill the surface pores of YBa₂Cu₃O_7-y superconductors or act as a flux pinning center.