• Korean Journal of Materials Research
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• v.17 no.3
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• pp.147-151
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• 2007

Cu-free multi-component sol, of which final oxide composition becomes $Bi_{1.9}Pb{0.35}SrCaO,\;Bi_{1.8}Pb_{0.2}SrCaO\;and\;Bi_{1.5}SrCaO$, respectively, was prepared through sol-gel route and coated on a bare Cu substrate. Starting materials were metal-alkoxides as follows.; [$Bi(OC_{2}H_{5})_{3}\;Pb(O^{1}C_{3}H_{7})_{2},\;Sr(O^{i}C_{3}H_{7})_{2},\;Ca(OC_{2}H_{5})_{2}$] as a reagent grade. Transparent light yellowish sol was obtained in the case of $Bi_{1.9}Pb_{0.35}SrCaO\;and\;Bi_{1.8}Pb_{0.2}SrCaO$ composition and $Bi_{1.5}SrCaO$ composition's sol was light greenish. Each sol was repeatedly dip-coated on Cu substrate four times and pre-heated at $400^{\circ}C$ and finally heat-treated in the range of $740{\sim}900^{\circ}C$. In the results, crystalline phases confirmed by XRD were (2201) orthorhombic and monoclinic phases. However, only $Bi_{1.9}Pb_{0.35}SrCaO_{x}$ composition showed pseudo-superconductive behavior after heat-treatment at $900^{\circ}C$ for 12 seconds and then onset temperature was 77 K, even though it did not exhibit zero resistance below Tc.

• Journal of the Korean Ceramic Society
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• v.49 no.2
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• pp.151-154
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• 2012

Flower-like and plate-like CuO nanopowder has been successfully synthesized using a facile microwave-assisted synthetic route. The morphology and size of the final products strongly depended on microwave power. The phase, structures and morphologies of the as-prepared products were investigated in detail by BET surface area analysis, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). In addition, the chemical oxygen demand of polluted lake water was employed for characterization of these new photocatalysts. The results showed correlations between the morphology of CuO micro-crystals and their catalytic properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.550-553
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• 2010

The enhancement of quantum efficiency using a surface modified Ag anode in top-emitting organic light emitting diodes (TEOLEDs) is reported. The operation voltage at the current density of $1\;mA/cm^2$ of TEOLEDs decreased from 9.3 V to 4.3 V as the surface of anode coated with $CuO_x$ layer. The work function of these structures were quantitatively determined using synchrotron radiation photoemission spectroscopy. Secondary electron emission spectra revealed that the work function of the Ag/$CuO_x$ structure is higher by 0.6 eV than that of Ag. Thus, the $CuO_x$ structure acts as a role in reducing the hole injection barrier by about 0.6 eV, resulting in a decrease of the turn-on voltage of top-emitting light emitting diodes.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.394-403
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• 2016

$H_2$ production by chemical looping is an efficient method to convert hydrocarbon fuel into hydrogen with the simultaneous capture of concentrated $CO_2$. This process involves the use of an iron based oxygen carrier that transfers pure oxygen from oxidizing gases to fuels by alternating reduction and oxidation (redox) reactions. The enhanced reactivities of copper oxide doped iron-based oxygen carrier were reported, however, the fundamental understandings on the interaction between $Fe_2O_3$ and CuO are still lacking. In this study, we studied the effect of dopant of CuO to $Fe_2O_3/ZrO_2$ particle on the morphological changes and the associated reactivity using various methods such as SEM/EDX, XRD, BET, TPR, XPS, and TGA. It was found that copper oxide acted as a chemical promoter that change chemical environment in the iron based oxygen carrier as well as a structural promoter which inhibit the agglomeration. The enhanced reduction reactivity was mainly ascribed to the increase in concentration of $Fe^{2+}$ on the surface, resulting in formation of charge imbalance and oxygen vacancies. The CuO doped $Fe_2O_3/ZrO_2$ particle also showed the improved reactivity in the steam oxidation compared to $Fe_2O_3/ZrO_2$ particle probably due to acting as a structural promoter inhibiting the agglomeration of iron species.

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.104-110
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• 2019

The low-temperature sintering behavior of AlN was investigated through a conventional method. $CaF_2$, CuO and Cu were selected as additives based on their low melting points. When sintered at $1600^{\circ}C$ for 8 h in $N_2$ atmosphere, a sample density > 98% was obtained. The X-ray data indicated that eutectic reactions below $1200^{\circ}C$ were found. Therefore, the current systems have lower liquid formation temperatures than other systems. The liquid phase showed high dihedral angles at triple grain junctions, indicating that the liquid had poor wettability on the grain surfaces. Eventually, the liquid was likely to vaporize due to the unfavorable wetting condition. As a result, a microstructure with clean grain boundaries was obtained, resulting in higher contiguity between grains. From EDS analysis, oxygen impurity seems to be well removed in AlN lattice. Therefore, it is believed that the current systems are beneficial for reducing sintering temperature and improving oxygen removal.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.622-629
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• 2015

Cu circuits were successfully fabricated on flexible PET(polyethylene terephthalate) substrates using wettability difference and electroless plating without an etching process. The wettability of Cu plating solution on PET was controlled by oxygen plasma treatment and $SiO_x$-DLC(silicon oxide containing diamond like carbon) coating by HMDSO(hexamethyldisiloxane) plasma. With an increase of the height of the nanostructures on the PET surface with the oxygen plasma treatment time, the wettability difference between the hydrophilicity and hydrophobicity increased, which allowed the etchless formation of a Cu pattern with high peel strength by selective Cu plating. When the height of the nanostructure was more than 1400 nm (60 min oxygen plasma treatment), the reduction of the critical impalement pressure with the decreasing density of the nanostructure caused the precipitation of copper in the hydrophobic region.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.394-399
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• 2015

In this study, the Cu catalyst decorated with activated carbon fibers were prepared for improving $SO_2$ adsorption properties. Flame retardant and heat treatments of Lyocell fibers were carried out to obtain carbon fibers with high yield. The prepared carbon fibers were activated by KOH solution for the high specific surface area and controlled pore size to improve $SO_2$ adsorption properties. Copper nitrate was also used to introduce the Cu catalyst on the activated carbon fibers (ACFs), which can induce various reactions in the process; i) copper nitrate promotes the decomposition reaction of oxygen group on the carbon fiber and ii) oxygen radical is generated by the decomposition of copper oxide and nitrates to promote the activation reaction of carbon fibers. As a result, the micro and meso pores were formed and Cu catalysts evenly distributed on ACFs. By Cu-impregnation process, both the specific surface area and micropore volume of carbon fibers increased over 10% compared to those of ACFs only. Also, this resulted in an increase in $SO_2$ adsorption capacity over 149% than that of using the raw ACF. The improvement in $SO_2$ adsorption properties may be originated from the synergy effect of two properties; (i) the physical adsorption from micro, meso and specific surface area due to the transition metal catalyst effect appeared during Cu-impregnation process and ii) the chemical adsorption of $SO_2$ gas promoted by the Cu catalyst on ACFs.

• Journal of the Korean Chemical Society
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• v.32 no.1
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• pp.22-29
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• 1988

The reaction of methanol-water mixture to $CO_2$ and $H_2$ on alkaline earth metal-copper-zinc oxide has been studied in the temperature range of 150 ${\sim}\;300^{\circ}C$. Generally the addition of the alkaline earth metal to Cu/ZnO resulted in an enhancement of selectivity for $CO_2$ formation and a reduction of catalytic activity. Measurable activities were found from 150$^{\circ}C$, 200$^{\circ}C$, and 250$^{\circ}C$ on Mg/Cu/ZnO, Ca/Cu/ZnO, and Ba/Cu/ZnO respectively. However, the highest selectivity for $CO_2$ formation was observed in Ba/Cu/ZnO catalyst at 250$^{\circ}C$. The effect of alkaline earth metal or ZnO on the reactivity was investigated using temperature programmed desorption of $CO_2$ or temperature programmed reduction with $H_2$ over catalysts respectively. It was found that $CO_2$ interacts more strongly in the sequence of MgO < CaO < BaO and ZnO decereases the reduction temperature of CuO. From the results, it was suggested that ZnO activates $H_2$ in the redox process of Cu component and alkaline earth metals adsorbs $CO_2$ in the catalytic process.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.651-656
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• 2005

Toluene, which is emitted from textile process, is considered as an important hazardous air pollutant. In this study, the catalytic activity of transition metal oxides(Cu, Mn, V, Cr, Co, Ni, Ce, Sn, Fe, Sr, Cs, Mo, La, W, Zn)/${\gamma}-Al_2O_3$ catalysts was investigated to carry out the complete oxidation of toluene. The metal catalysts were characterized by XRD-ray diffraction), FE-SEM(Field Emission Scanning Electron Micrograph), BET(Brunauer Emmett Teller) method and TPR(Temperature Programmed Reduction). Among the catalysts, Cu/${\gamma}-Al_2O_3$ was highly promising catalyst for the oxidation of toluene. From the BET results, it seems that the catalytic activity is not correlated to the specific surface area. XRD results indicated that most of catalysts exist as amorphous phase. From the FE-SEM results, it was observed that copper on ${\gamma}-Al_2O_3$ surface was well dispersed among catalysts. The catalytic activity for the toluene oxidation could be explained with that metal oxide catalyst was dispersed well over supports and was attributed to reduction activity in surface of catalysts.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.44-51
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• 2016

The powder core, conventionally fabricated from iron particles coated with insulator, showed large eddy current loss under high frequency, because of small specific resistance. To overcome the eddy current loss, the increase in the specific resistance of powder cores was needed. In this study, copper oxide coating onto electrically conductive iron particles was performed using a planetary ball mill to increase the specific resistance. Coating factors were optimized by the Response surface methodology. The independent variables were the CuO mass fraction, mill revolution number, coating time, ball size, ball mass and sample mass. The response variable was the specific resistance. The optimization of six factors by the fractional factorial design indicated that CuO mass fraction, mill revolution number, and coating time were the key factors. The levels of these three factors were selected by the three-factors full factorial design and steepest ascent method. The steepest ascent method was used to approach the optimum range for maximum specific resistance. The Box-Behnken design was finally used to analyze the response surfaces of the screened factors for further optimization. The results of the Box-Behnken design showed that the CuO mass fraction and mill revolution number were the main factors affecting the efficiency of coating process. As the CuO mass fraction increased, the specific resistance increased. In contrast, the specific resistance increased with decreasing mill revolution number. The process optimization results revealed a high agreement between the experimental and the predicted data ($Adj-R^2=0.944$). The optimized CuO mass fraction, mill revolution number, and coating time were 0.4, 200 rpm, and 15 min, respectively. The measured value of the specific resistance of the coated pellet under the optimized conditions of the maximum specific resistance was $530k{\Omega}{\cdot}cm$.