• Carbon letters
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• v.25
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• pp.33-42
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• 2018

Activated carbon (AC) was modified by ammonium persulphate or nitric acid, respectively. AC and the modified materials were used as catalyst supports. The oxygen groups were introduced in the supports during the modifications. All the supports were characterized by $N_2$-physisorption, Raman, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis. Methanol synthesis catalysts were prepared through wet impregnation of copper nitrate and zinc nitrate on the supports followed by thermal decomposition. These catalysts were measured by the means of $N_2$-physisorption, X-ray diffraction, XPS, temperature programmed reduction and TEM tests. The catalytic performances of the prepared catalysts were compared with a commercial catalyst (CZA) in this work. The results showed that the methanol production rate of AC-CZ ($23mmol-CH_3OH/(g-Cu{\cdot}h)$) was higher, on Cu loading basis, than that of CZA ($9mmol-CH_3OH/(g-Cu{\cdot}h)$). We also found that the modification methods produced strong metal-support interactions leading to poor catalytic performance. AC without any modification can prompt the catalytic performance of the resulted catalyst.

• Proceedings of the KIEE Conference
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• 2009.04a
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• pp.30-32
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• 2009

In this study, $CuInS_2$ powders have been synthesized using polyol process of a mixture of copper nitrate, indium nitrate, and thiourea with various stoichiometric molar ratios in ethylene glycol at 196$^{\circ}C$. As boiling time goes by, the color of metal ion mixed solutions were changed transparent green to dark green and finally fumed to black by reduction of $OH^-$ radicals. The prepared powders were fully characterized by SEM, XRD and UV-Vis. The particle shape of black colored powders showed sphere with about 30 nm in particle size compared to those with dark green colored powders showed irregular shape with about 1 ${\mu}m$ in particle size. The XRD results showed highly crystallized $CuInS_2$. The UV-Vis spectra showed broad shoulder at 430 and 780 nm corresponding to 2.78 and 1.58 eV for the dark green colored one and black colored one, respectively.

• Corrosion Science and Technology
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• v.8 no.4
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• pp.153-156
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• 2009

The water cooling system for VFD (Variable Frequency Drive) of a fossil fuel power plant was reported to be shut down due to a water leak at the metal connection of the heat-sink to the hoses. In order to identify the cause of the failure, the system was visually inspected, and corrosion products were analyzed with SEM equipped with EDX. The failure was observed repeatedly at the nipples of certain location, suggesting galvanic corrosion. In a U-shaped heat sink with two nipples, for inlet and outlet, only one nipple was corrosively damaged at the tip, while the other was not. Most of the corrosion products were observed at the sound nipple and in the filter, identified as $Cu(OH)_2$. Some other corrosion products, composed of mostly $Cu_2O$, were found at the corrosively attacked nipple. A fair amount of Cl was also detected on the surface of the damaged nipple. It was concluded that galvanic corrosion was occurred due to a current leakage over the whole system, and the damage was accelerated by the accumulated chlorine ions in the cooling water.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.222-222
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• 2012

Metal oxide gas sensors based on semiconductor type have attracted a great deal of attention due to their low cost, flexible production and simple usability. However, most works have been focused on n-type oxides, while the characteristics of p-type oxide gas sensors have been barely studied. An investigation on p-type oxides is very important in that the use of them makes possible the novel sensors such as p-n diode and tandem devices. Monoclinic cupric oxide (CuO) is p-type semiconductor with narrow band gap (~1.2 eV). This is composed of abundant, nontoxic elements on earth, and thus low-cost, environment-friendly devices can be realized. However, gas sensing properties of neat CuO were rarely explored and the mechanism still remains unclear. In this work, the neat CuO layers with highly ordered mesoporous structures were prepared by a template-free, one-pot solution-based method using novel ink solutions, formulated with copper formate tetrahydrate, hexylamine and ethyl cellulose. The shear viscosity of the formulated solutions was 5.79 Pa s at a shear rate of 1 s-1. The solutions were coated on SiO2/Si substrates by spin-coating (ink) and calcined for 1 h at the temperature of $200{\sim}600^{\circ}C$ in air. The surface and cross-sectional morphologies of the formed CuO layers were observed by a focused ion beam scanning electron microscopy (FIB-SEM) and porosity was determined by image analysis using simple computer-programming. XRD analysis showed phase evolutions of the layers, depending on the calcination temperature, and thermal decompositions of the neat precursor and the formulated ink were investigated by TGA and DSC. As a result, the formation of the porous structures was attributed to the vaporization of ethyl cellulose contained in the solutions. Mesoporous CuO, formed with the ink solution, consisted of grains and pores with nano-meter size. All of them were strongly dependent on calcination temperature. Sensing properties toward H2 and C2H5OH gases were examined as a function of operating temperature. High and fast responses toward H2 and C2H5OH gases were discussed in terms of crystallinity, nonstoichiometry and morphological factors such as porosity, grain size and surface-to-volume ratio. To our knowledge, the responses toward H2 and C2H5OH gases of these CuO gas sensors are comparable to previously reported values.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.63-69
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• 2007

We investigated interconnection processes using Cu vias for MEMS sensor packages. Ag paste layer was formed on a glass substrate and used as a seed layer for electrodeposition of Cu vias after bonding a Si substrate with through-via holes. With applying electrodeposition current densities of $20mA/cm^2\;and\;30mA/cm^2$ at direct current mode to the Ag paste seed-layer, Cu vias of $200{\mu}m$ diameter and $350{\mu}m$ depth were formed successfully without electrodeposition defects. Interconnection processes for MEMS sensor packages could be accomplished with Ti/Cu/Ti line formation, Au pad electrodeposition, Sn solder electrodeposition and reflow process on the Si substrate where Cu vias were formed by Cu electrodeposition into through-via holes.

• Journal of Powder Materials
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• v.25 no.4
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• pp.322-326
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• 2018

The hydrogen reduction behavior of $MoO_3-CuO$ powder mixture for the synthesis of homogeneous Mo-20 wt% Cu composite powder is investigated. The reduction behavior of ball-milled powder mixture is analyzed by XRD and temperature programmed reduction method at various heating rates in Ar-10% $H_2$ atmosphere. The XRD analysis of the heat-treated powder at $300^{\circ}C$ shows Cu, $MoO_3$, and $Cu_2MoO_5$ phases. In contrast, the powder mixture heated at $400^{\circ}C$ is composed of Cu and $MoO_2$ phases. The hydrogen reduction kinetic is evaluated by the amount of peak shift with heating rates. The activation energies for the reduction, estimated by the slope of the Kissinger plot, are measured as 112.2 kJ/mol and 65.2 kJ/mol, depending on the reduction steps from CuO to Cu and from $MoO_3$ to $MoO_2$, respectively. The measured activation energy for the reduction of $MoO_3$ is explained by the effect of pre-reduced Cu particles. The powder mixture, hydrogen-reduced at $700^{\circ}C$, shows the dispersion of nano-sized Cu agglomerates on the surface of Mo powders.

• Journal of Powder Materials
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• v.16 no.4
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• pp.280-284
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• 2009

The pressureless sintering behavior of $Al_2O_3$/Cu powder mixtures, prepared from $Al_2O_3$/CuO and $Al_2O_3$/Cu-nitrate, has been investigated. Microstructural observation revealed that $Al_2O_3$ powders with nano-sized Cu particles could be synthesized by hydrogen reduction method. The specimens, pressureless-sintered at $1400^{\circ}C$ for 4 min using infrared heating furnace with the heating rate of $200^{\circ}C$/min, showed the relative density of above 90%. Maximum hardness of 16.1 GPa was obtained in $Al_2O_3$/MgO/Cu nanocomposites. The nanocomposites exhibited the enhanced fracture toughness of 4.3-5.7 $MPa{\cdot}m^{1/2}$, compared with monolithic $Al_2O_3$. The mechanical properties were discussed in terms of microstructural characteristics.

• Journal of Powder Materials
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• v.22 no.5
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• pp.362-366
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• 2015

The effect of sublimable vehicle composition in the camphor-naphthalene system on the pore structure of porous Cu-Ni alloy is investigated. The CuO-NiO mixed slurries with hypoeutectic, eutectic and hypereutectic compositions are frozen into a mold at $-25^{\circ}C$. Pores are generated by sublimation of the vehicles at room temperature. After hydrogen reduction at $300^{\circ}C$ and sintering at $850^{\circ}C$ for 1 h, the green body of CuO-NiO is completely converted to porous Cu-Ni alloy with various pore structures. The sintered samples show large pores which are aligned parallel to the sublimable vehicle growth direction. The pore size and porosity decrease with increase in powder content due to the degree of powder rearrangement in slurry. In the hypoeutectic composition slurry, small pores with dendritic morphology are observed in the sintered Cu-Ni, whereas the specimen of hypereutectic composition shows pore structure of plate shape. The change of pore structure is explained by growth behavior of primary camphor and naphthalene crystals during solidification of camphor-naphthalene alloys.

• Journal of Powder Materials
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• v.20 no.4
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• pp.245-252
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• 2013

This study attempted to manufacture a Cu-Ga coating layer via the cold spray process and to investigate the applicability of the layer as a sputtering target material. In addition, changes made to the microstructure and properties of the layer due to annealing heat treatment were evaluated, compared, and analyzed. The results showed that coating layers with a thickness of 520 mm could be manufactured via the cold spray process under optimal conditions. With the Cu-Ga coating layer, the ${\alpha}$-Cu and $Cu_3Ga$ were found to exist inside the layer regardless of annealing heat treatment. The microstructure that was minute and inhomogeneous prior to thermal treatment changed to homogeneous and dense with a more clear division of phases. A sputtering test was actually conducted using the sputtering target Cu-Ga coating layer (~2 mm thickness) that was additionally manufactured via the cold-spray coating process. Consequently, this test result confirmed that the cold sprayed Cu-Ga coating layer may be applied as a sputtering target material.

• Korean Journal of Materials Research
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• v.16 no.2
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• pp.80-84
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• 2006

The removal efficiency of Cu and Fe contaminants on the silicon wafer surface was examined to investigate the effect of cleaning solutions on the behavior of metallic impurities. Silicon wafers were intentionally contaminated with Cu and Fe solutions by spin coating and cleaned in different types of cleaning solutions based on $NH_4OH/H_2O_2/H_2O\;(SC1),\;H_2O_2/HCl/H_2O$ (SC2), and/or HCl/$H_2O$ (m-SC2) mixtures. The concentration of metallic contaminants on the silicon wafer surface before and after cleaning was analyzed by vapor phase decomposition/inductively coupled plasma-mass spectrometry (VPD/ICP-MS). Cu ions were effectively removed both in alkali (SC1) and in acid (SC2) based solutions. When $H_2O_2$ was not added to SC2 solution like m-SC2, the removal efficiency of Cu impurities was decreased drastically. The efficiency of Cu ions in SC1 was not changed by increasing cleaning temperature. Fe ions were soluble only in acid solution like SC2 or m-SC2 solution. The removal efficiencies of Fe ions in acid solutions were enhanced by increasing cleaning temperature. It is found that the behavior of metallic contaminants as Cu and Fe from silicon surfaces in cleaning solutions could be explained in terms of Pourbaix diagram.