• Clean Technology
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• v.20 no.4
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• pp.375-382
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• 2014

This work investigated the plasma-catalytic decomposition of isopropyl alcohol (IPA) and the behavior of the byproduct compounds over monolith-supported metal oxide catalysts. Iron oxide ($Fe_2O_3$) or copper oxide (CuO) was loaded on a monolithic porous ${\alpha}-Al_2O_3$ support, which was placed inside the coaxial electrodes of plasma reactor. The IPA decomposition efficiency itself hardly depended on the presence and type of metal oxides because the rate of plasma-induced decomposition was so fast, but the behavior of byproduct formation was largely affected by them. The concentrations of the unwanted byproducts, including acetone, formaldehyde, acetaldehyde, methane, carbon monoxide, etc., were in order of $Fe_2O_3/{\alpha}-Al_2O_3$ < $CuO/{\alpha}-Al_2O_3$ < ${\alpha}-Al_2O_3$ from low to high. Under the condition (flow rate: $1L\;min^{-1}$; IPA concentration: 5,000 ppm; $O_2$ content: 10%; discharge power: 47 W), the selectivity towards $CO_2$ was about 40, 80 and 95% for ${\alpha}-Al_2O_3$, $CuO/{\alpha}-Al_2O_3$ and $Fe_2O_3/{\alpha}-Al_2O_3$, respectively, indicating that $Fe_2O_3/{\alpha}-Al_2O_3$ is the most effective for plasma-catalytic oxidation of IPA. Unlike plasma-alone processes in which tar-like products formed from volatile organic compounds are deposited, the present plasma-catalyst hybrid system did not exhibit such a phenomenon, thus retaining the original catalytic activity.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.828-836
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• 1994

In order to investigate the high temperature deformation characteristics in YBaiCu307-, oxide superconductor, the compression test was performed at temperatures from $890^{\circ}C$ to $930^{\circ}C$ at initial strain rate between $1.0 x 10^{-5}s^{-1}\; and \; 1.0^{-4}s^{-1}$. As the temperature increased and the initial strain rate decreased, the flow stress decreased. The strain rate sensitivity exponent measured as 0.41-0.46, supporting occurence of a superplastic deformation. The activation energy for superplastic deformation was calculated as 500-580KJ/mol, which decreased with increasing Ag content. Microstructure of the superplastically-deformed specimens showed that a grain growth occurred during deformation, and it appeared to be considerable when Ag content increased, but most grains still remained equiaxed after deformation. In this study, the deformation mechanism of YBCO superconductor was the grain boundary sliding with the diffusional accommodation and the contribution of the gram boundary sliding to the total strain was estimated to be 65%.

• Korean Journal of Materials Research
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• v.11 no.3
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• pp.215-220
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• 2001

Amorphous Ti-Si-N films of approximately 200 and 650 thickness were reactively sputtered on Si wafers using a dc magnetron sputtering system at various $N_2$/Ar flow ratios. Their barrier properties between Cu (750 ) and Si were investigated by using sheet resistance measurements, XRD, SEM, RBS, and AES depth profiling focused on the effect of the nitrogen content in Ti-Si-N thin film on the Ti-Si-N barrier properties. As the nitrogen content increases, first the failure temperature tends to increase up to 46 % and then decrease. Barrier failure seems to occur by the diffusion of Cu into the Si substrate to form Cu$_3$Si, since no other X- ray diffraction intensity peak (for example, that for titanium silicide) than Cu and Cu$_3$Si Peaks appears up to 80$0^{\circ}C$. The optimal composition of Ti-Si-N in this study is $Ti_{29}$Si$_{25}$N$_{46}$. The failure temperatures of the $Ti_{29}$Si$_{25}$N$_{465}$ barrier layers 200 and 650 thick are 650 and $700^{\circ}C$, respectively.ely.

• Korean Journal of Environmental Agriculture
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• v.20 no.4
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• pp.238-243
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• 2001

Mass reduction and physicochemical properties of the produced compost were investigated during composting domestic food wastes without additive. A small composter used in this study had the height of 15 cm from the center of bottom half circle (diameter 24 cm) up to under the lid, the side length of 50 cm and the horizontal lid angle of $50^{\circ}$ and was operated at the heating unit temperature of $85^{\circ}$. It was mixed by the rotating arm for two minutes in every half hour while supplied with air flow at 3 L/min for 10 minutes in every half hour. This condition was found in a preliminary experiment as optimal for keeping the water content of composting material in the optimal range without adding any bulking materials. The domestic food wastes were added into the composter at the rate of 1 kg/day without additives during composting. The results were as follows; during the composting process, water content maintained in the range of $51.0{\sim}53.5%$. Hemicellulose and lignin contents did not show any tendency, but cellulose content decreased. During the composting process, $NH_3-N$ and $NO_2-N$ were not detected due to nitrification. The contents of inorganic compounds did not increase during the composting process. They were in the range of $1.32{\sim}1.71%\;P_2O_5$, $1.29{\sim}1.48%\;CaO$, $0.41{\sim}0.49%\;MgO$, and $0.38{\sim}0.74%\;K_2O$. For 20 days, weight reduction rate was 67.5% in wet basis, and decomposition rate was 48% in dry basis. Concentration of heavy metals (Cu, Cr, Cd, Pb, Zn, Hg, As) was less than the limiting value of the compost. Maturity of the produced compost was 3 grade through reaching maximum temperature of $46{\sim}48^{\circ}C$.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.423-427
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• 2010

Carbon nano sphere(CNS) and nano bowl of carbon(NBC) containing 1.0 wt% copper were prepared by impregnation method and their catalytic activity was compared in the phenol hydroxylation with hydrogen peroxide in the presence of water and acetonitrile as a solvent, respectively. Cu content of catalysts was determined by EDS, and BET, pore volume, pore size and pore size distribution were compared. For both catalysts, phenol conversion, $H_2O_2$ efficiency and yield of catechol and hydroquinone were higher in the presence of water as a solvent than those in the presence of actonitrile. And catalytic activity such as phenol conversion and $H_2O_2$ efficiency of 1.0 Cu/CNS is about two times higher than that of 1.0 Cu/NBC in water solvent.

• Progress in Superconductivity and Cryogenics
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• v.22 no.1
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• pp.1-6
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• 2020

This is a parameter study for the direct fabrication of a large grain YBCO bulk superconductors using Y₂O₃, BaCO₃ and CuO powders without any grinding step. The cracks, which have been formed due to volume contraction during calcination step, have been prevented by controlling the heating rate at 930~950 ℃. It has been observed that multi-grain growth has occurred due to the dissolution of Sm123 seed due to the retention of carbon in Ba-Cu-O melt. In order to accelerate the carbon release in prior calcination heat treatment, the reduction of pellet thickness and the drilling of artificial holes have been applied. Single-grain YBCO bulk superconductor has been successfully fabricated by stacking multiple thin slab. However, the crack formation has been rather prominent for the compact with artificial holes. The use of buffer pellet, which is supposed to act as diffusion barrier, has prevented the dissolution of Sm123 seed crystal and has led to the growth of single grain of high content of carbon containing specimen.

• Journal of the Korean earth science society
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• v.22 no.3
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• pp.208-222
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• 2001

Geochemical investigations on suspended amorphous iron oxide material from the Kwangyang gold mine and its surrounding area, Cheonnam, Korea have been carried out. The sediments samples were collected from 11 location along Kwangyang mine area and were air dried and sieved to -80 mesh. These samples consist mainly of iron, silicon and alumina. The Fe$_2$O$_3$ contents ranges from 17.9 wt.% to 72.3 wt.%. The content of Fe$_2$O$_3$ increase with decreasing Si, Al, Mg, Na, K, Mn, and Ti, whereas the contents of Te, Au, Ga, Bi, Cd, Hg, Sb, and Se increase in the amorphous stream sediments. Amorphous stream sediments have been severely enriched for As (up to 54.9 ppm), Bi (up to 3.77 ppm), Cd (up to 3.65 ppm), Hg (up to 64 ppm), Sb (up to 10.1 ppm), Cu (up to 37.1 ppm), Mo (up to 8.86 ppm), Pb (up to 9.45 ppm) and Zn (up to 29.7 ppm). At the upstream site, the Au content (up to 4.4 ppm) in the amorphous stream sediments are relatively high but those contents decrease with distance of mine location. The content of Ag (up to 0.24 ppm) were low in upstream site but those contents increase significantly in the downstream sites. The X-ray diffraction patterns of the samples have virtually no sharp and discrete peaks, indicating that some samples are amorphous or poorly-ordered. The quartz, goethite, kaolinite and illite were associated in amorphous stream sediments. The infrared spectra for amorphous stream sediments show major absorption bands due to OH stretching, adsorbed molecular water, sulfate and Fe-O stretching, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.1
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• pp.41-47
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• 2014

Agricultural soils surrounding mine areas in South Korea are often contaminated with multiple metals such as Cd, Pb and Zn. It poses potential risks to plants, soil organisms, groundwater, and eventually human health. The aim of this study was to examine the changes in phytoavailability of Cd, Cu, Pb and Zn after application with calcined eggshell (CES; 0, 1, 3, and 5% W/W) in an agricultural soil contaminated by mine tailings. The contents of Cd, Cu, Pb and Zn in soils were 8.79, 65.4, 1602, and $692mgkg^{-1}$ (aqua regia dissolution), respectively. The experiments were conducted with lettuce (Lactuca sativa L. var. longifolia) grown under greenhouse conditions during a 30-d period. $NH_4NO_3$ solution was used to examine the mobile fraction of these metals in soil. The application of CES dramatically increased soil pH and inorganic carbon content in soil due to CaO and $CaCO_3$ of CES. The increased soil pH decreased the mobile fraction of Cd, Pb, Zn: from 3.49 to < $0.01mgkg^{-1}$ for Cd, from 79.4 to $1.75mgkg^{-1}$ for Pb, and from 29.6 to $1.13mgkg^{-1}$ for Zn with increasing treatment of CES from 0 to 5%. In contrast, the mobile fraction of Cu was increased from 0.05 to $3.08mgkg^{-1}$, probably due to the formation of soluble $CuCO_3{^0}$ and Cu-organic complex. This changes in the mobile fraction resulted in a diminished uptake of Cd, Pb and Zn by lettuce and an increased uptake of Cu: from 4.19 to < $0.001mgkg^{-1}$ dry weight (DW) for Cd, from 0.78 to < $0.001mgkg^{-1}$ DW for Pb, and from 133 to $50.0mgkg^{-1}$ DW for Zn and conversely, from 3.79 up to $8.21kg^{-1}$ DW for Cu. The increased contents of Cu in lettuce shoots did not exceed the toxic level of $>25mgkg^{-1}$ DW. The mobile contents of these metals in soils showed a strong relationship with their contents in plant roots and shoots. These results showed that CES effectively reduced the phytoavailability of Cd, Pb, and Zn to lettuce but elevated that of Cu in consequence of the changed binding forms of Cd, Cu, Pb, and Zn in soils. Based on these conclusions, CES can be used as an effective immobilization agent for Cd, Pb and Zn in contaminated soils. However, the CES should be applied in restricted doses due to too high increased pH in soils.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.879-884
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• 2001

In this paper, the structural and dielectric properties of (Sr$_{l-x}$Ca$_{x}$)TiO$_3$ (0$\leq$x$\leq$0.2) -based grain boundary layer ceramics were investigated by XRD, SEM and HP4194A. The ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were 1420~152$0^{\circ}C$ and 4 hours, respectively. The average grain size and the lattice constant were decreased with increasing content of Ca. The average grain size was increased with increase of sintering temperature. The relative density of all specimens was 96~98%. The 2nd Phase formed by the thermal diffusion of CuO from the surface leads to very excellent dielectric properties, that is, $\varepsilon$$_{r}$>50000, tan $\delta$<0.05, $\Delta$C<$\pm$10%. The appropriate Ca content was under 15 ㏖%.s under 15 ㏖%.%.

• Polymer(Korea)
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• v.36 no.1
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• pp.98-103
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• 2012

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was synthesized using $Cu(NO_2)_2{\cdot}3H_2O$ or CuCl catalyst with various amounts of ligand and base in several different solvent systems. CuCl/1-methylimidazole/ammonium hydroxide was found to be an effective catalyst system which showed the highest polymer yield and molecular weight. The effects of catalyst/monomer ratio, different amine ligands, and the content of mono-functional reagent 2,4,6-trimethylphenol (TMP) additive on the polymer yield and molecular weight were investigated. Among the co-solvent systems used in this polymerization, chloroform/methanol 9/1(v/v) gave the highest polymer yield and molecular weight ($\overline{M_n}$ 55 K, $\overline{M_w}$ 92 K, PDI 1.7). The catalytic activity between CuCl and CuI was compared by oxygen-uptake experiments and the formation of sideproduct, 5,5'-tetramethyl-4,4'-diphenoquinone (DPQ), was analyzed by ultraviolet spectroscopy.