• Korean Journal of Materials Research
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• v.8 no.7
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• pp.621-627
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• 1998

The formation of Co-silicide between Co/Zr bilayer on the amorphous and crystalline Si substrates has been investigated. The films of Zr(50$\AA$) and Co(l50$\AA$) were deposited with e-beam evaporation system and were heattreated with the rapid thermal annealing system at the temperatures between 50$0^{\circ}C$ and 80$0^{\circ}C$ with 10$0^{\circ}C$ increments for 30 seconds. The phase identification of Co-silicide was carried out by XRD and the chemical analysis was examined by AES and RBS. The interface morphologies of Co/Zr bilayer films were investigated by cross sectional TEM and HRTEM. $CoSi_2$ was formed epitaxially on the crystalline Si substrate above $700^{\circ}C$ while polycrystalline $CoSi_2$ was grown on the amorphous Si substrate. The formation temperature of Co-silicide on the amorphous Si substrate was about 100 C lower than that on the crystalline Si. The COzSi phase was not identified on the both Si substrates. The formation temperature of first phase of Co-silicide on ColZr bilayer was higher than that on Co mono layer. CoSizlayer formed on the amorphous Si substrate exhibits better uniformity compared to the CoSiz formed on the crystalline substrate. The sheet resistance of CoSiz layer on crystalline Si was lower than that on the amorphous Si at high temperatures.tures.

• Korean Chemical Engineering Research
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• v.43 no.4
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• pp.503-510
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• 2005

In this research, composite alumina was prepared to add the various promoters by sol-gel method and examined its thermal stability. After sintering at $1,200^{\circ}C$, the thermal stability resulted in following order, $Si{\fallingdotseq}La$ > Ti > $Ba{\fallingdotseq}Ce$ > Y > $Zr{\fallingdotseq}Mg$, in accordance with adding the promoters. Especially in case of silica-added alumina, a phase transformation temperature to ${\alpha}$-alumina increased about $150^{\circ}C$ and after sintering at $1,200^{\circ}C$, it showed to maintain in ${\gamma}$-form and ${\delta}$-form alumina phase. Also it showed an increase of surface area from $3m^2/g$ to $71m^2/g$ compared with pure ${\alpha}$-alumina. In the case of silicaadded alumina, the characterization change of this alumina particle resulted in a delay of phase transformation because Si-O-Al bond was increased when sintered at high temperature. In case of lanthanum-added alumina, there was a sintering delay phenomenon in inter-particles as $LaAlO_3$ structure existed. The existence of lanthanum structure was confirmed by XRD and XPS analysis. It appeared on the alumina surface as $La_2O_3$ structure when it was sintered under $1,000^{\circ}C$, as the perovskite structure of $LaAlO_3$ at above $1,000^{\circ}C$ and as the magneto-plumbite structure of $LaAl_{11}O_{18}$ at above $1,300^{\circ}C$.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.12
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• pp.654-664
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• 2000

Thin films of ZnO are deposited by using an RF magnetron sputtering with varying the substrate temperature(RT~39$0^{\circ}C$) and RF power(50~250W). Cu-doped ZnO(denoted by ZnO:Cu) films have also been prepared by co-spputtering of a ZnO target on which some Cu-chips are attached. Different substrate materials, such as Si, $SiO_{2}/Si$, sapphire, DLC/Si, and poly-diamond/Si, are employed to compare the c-axial growth features of deposited ZnO films. Texture coefficient(TC) values for the (002)-preferential growth are estimated from the XRD spectra of deposited films. Optimal ranges of RF powers and substrate temperatures for obtaining high TC values are determined. Effects of Cu-doping conditions, such as relative Cu-chip sputtering areas, $O_{2}/(Ar+O_{2})$ mixing ratios, and reactor pressures, on TC values, electrical resistivities, and relative Cu-compositions of deposited ZnO:Cu films have been systematically investigated. XPS study shows that the relative densities of metallic $Cu(Cu^{0})$ atoms and $CuO(Cu^{2+})$-phases within deposited films may play an important role of determining their electrical resistivities. It should be noted from the experimental results that highly resistive(> $10^{10}{\Omega}cm$ ZnO films with high TC values(> 80%) can be achieved by Cu-doping. SAW devices with ZnO(or Zn):Cu)/IDT/$SiO_{2}$/Si configuration are also fabricated to estimate the effective electric-mechanical coupling coefficient($k_{eff}^{2}$) and the insertion loss. It is observed that the devices using the Cu-doped ZnO films have a higher $k_{eff}^{2}$ and a lower insertion loss, compared with those using the undoped films.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.376-381
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• 2018

The purpose of this study is to investigate and optimize an effectiveness process for the recovery of Pd from the spent Pd/C catalyst by the process of hydrogenation of maleic anhydride over Pd/C. Pd solution recovered from Pd/C catalyst was used to prepare Pd/C catalysts. Their characteristics were compared to those of Pd/C catalyst prepared by using a reagent grade precursor solution. Pd in the spent catalyst was leached by the modified process with dry and wet methods to obtain the high recovery ratio of Pd. The burn-out of carbon in the spent Pd/C catalyst was carried out in the rage of $600-900^{\circ}C$. Pd content of carbonized catalyst was confirmed by XRF and ICP. Pd was extracted from carbonized spent catalysts with acid solutions of 1,2 and 4 M HCl at a leaching temperature of $90^{\circ}C$ for 2 h. The high recovery ratio of Pd was shown as 92.4% that leached in 4 M HCl. Also Pd/C catalysts were prepared by using the leached solution and the reagent grade of $H_2PdCl_4$ as a precursor solution and the characteristics were analyzed by XRD, CO-chemisorption and FE-TEM. As a result, the dispersion of the catalyst prepared by using the leached solution was 34.6%, which was found to be equal to or more than that of the Pd/C catalyst prepared by the reagent grade precursor solution.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.163-176
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• 2009

The pyrophyllite deposits located in Jinhae area have been studied through field observations and laboratory works including the X-ray diffraction (XRD), X-ray fluorescence (XRF), Electron probe microanalyzer (EPMA) and Inductively Coupled Plasma (ICP). The pyrophyllite deposits consist of mainly illite, dickite, pyrophyllite, diaspore, chlorite, pyrite and copiapite. According to the mineral assemblages, geological occurrences and alteration modes, the altered rocks can be classified into four types: Type A; quartz with silicifictaion, Type B; quartz + illite with illitization, Type C; quartz + dickite + illite with kaolin alteration, Type D; pyrophyllite + illite + dickite + diaspore with pyrophyllite alteraion. Rocks in Type A, which is generated by silicifictaion, have high $SiO_2$ contents more than 90 wt% and distinctive equigranular textures with microcrtstalline quartz. The pyrophyllites from the study area belong to 2M polytype. The host rocks of the pyrophyllite ore in this mine are rhyolitic rock, andecitic tuff and volcanic breccia. The alteration products seem to be controlled by the different lithology of the host rocks. The hydrothermal solution formed the deposits would be inferred to the acidic and have relatively high ionic activity of hydrogen and silica judging from alteration mineral assemblage. Pyrophyllite alteraion zone is generated by highest temperature condition of all alteration zone.

• Journal of Sensor Science and Technology
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• v.11 no.1
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• pp.18-27
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• 2002

$LaFeO_3$-based thick films with 2wt.%, 5wt.% and 10wt.% $Al_2O_3$ additives were fabricated by screen printing method on $Al_2O_3$ substrates. Structural, electrical and ammonia gas sensing characteristics of the thick films with different heat treatment temperatures were examined. From XRD results, the compound of $LaFeO_3$ and $Al_2O_3$ was not found until the heat treatment at $1200^{\circ}C$. SEM microphotograph showed similar grain growth despite the amount of $Al_2O_3$ additives with the heat treatment. Thick films with high activation energy and low resistance in the electrical properties showed high sensitivity for gases. Thick films with 2wt % $Al_2O_3$ additives heat-treated at $1200^{\circ}C$ showed the sensitivities of 210% for 100 ppm $NH_3$ gas at the working temperature of $350^{\circ}C$. The thick films showed food selectivity to $NH_3$ gas.

• Journal of the Korean Ceramic Society
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• v.44 no.11
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• pp.639-644
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• 2007

Spinel pigments, developing black color in high temperature glazes at oxidation or reduction atmosphere, without CoO because of its high price were synthesized by solid solution method. Ten mixed compositions consisted of NiO, MnO, $Fe_2O_3 and $Mn_2O_3$ were fired at $1250^{\circ}C$ for 1h. The resulting pigments were characterized by using XRD, FT-IR, SEM and UV-vis spectrometer. Structure of the pigments are spinel and particles' shape are spherical or cubic. Glazed tiles containing 5 wt% pigments were fired at $1260^{\circ}C$ and $1240^{\circ}C$ in reduction atmosphere. Color in glazes were analyzed by UV-vis spectrometer. Colors of NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0125 mole% and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole% in lime glaze showed black in oxidation, in reduction NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0125 mole% and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.55{\cdot}Mn_2O_3$ 0.0125 mole% showed black. In case of lime-barium glaze, NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole%, NiO 0.975 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% and NiO 0.925 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% showed black color in oxidation and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole%, NiO 0.925 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% and NiO 0.725 MnO $0.275{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% showed black one in reduction.

• Journal of the Mineralogical Society of Korea
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• v.28 no.4
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• pp.325-332
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• 2015

Apophyllite (KF)($K_{0.84}Ca_{3.99}Si_{7.70}O_{20}F_{0.72}{\cdot}8H_2O$), one of the sheet silicates, was compressed up to 7.7 GPa at ambient temperature and 15 high pressure data were obtained. Lattice parameters of the starting specimen were as follows: $a_0=8.954(2)\;{\AA}$, $c_0=15.795(2)\;{\AA}$, $V_0=1266.4(4)\;{\AA}^3$. Symmetrical diamond anvil cell was employed with synchrotron radiation in the mode of angular dispersive X-ray diffraction. Bulk modulus was determined to be 59(4) GPa when ${K_0}^{\prime}$ is 4. No clear first order phase transition symptom was observed in the series of XRD pattern. However, second-order phase transition cannot be ruled out from the correlation between normalized pressure and strain.

• Journal of Hydrogen and New Energy
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• v.17 no.2
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• pp.166-173
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• 2006

Catalytic reforming of $CO_2$ by $CH_4$ over Ni-YSZ based catalysts was investigated to produce syngas as raw material of high valued chemicals and develop high performance catalyst electrode for an internal reforming of $CO_2$ in SOFC system. Ni-YSZ based catalysts were prepared using physical mixing and maleic acid methods to improve catalytic activity and inhibition of carbon deposition. The catalysts before and after the reaction were characterized by $N_2$ physisorption, TPR(temperature programed reduction), XRD and impedance analyzer. The conversions for $CO_2$ and $CH_4$ over Ni-MgO catalyst showed 90% but much amount of carbon deposition was detected on catalyst surface. On the other hand, the conversions for $CO_2$ and $CH_4$ over NiO-YSZ-$CeO_2$ catalyst showed 100% and 85% respectively, and carbon deposition on catalyst surface was inhibited under the tested condition. It was concluded that NiO-YSZ-$CeO_2$ catalyst is a promising candidate for the catalytic reforming of $CO_2$ and the internal reforming in SOFC system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.25-32
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• 2007

We investigated the silicide reaction stability between 10 nm-Col-xNix alloy films and silicon substrates with the existence of 4 nm-thick natural oxide layers. We thermally evaporated 10 nm-Col-xNix alloy films by varying $x=0.1{\sim}0.9$ on naturally oxidized single crystal and 70 nm-thick polycrystalline silicon substrates. The films structures were annealed by rapid thermal annealing (RTA) from $600^{\circ}C$ to $1100^{\circ}C$ for 40 seconds with the purpose of silicidation. After the removal of residual metallic residue with sulfuric acid, the sheet resistance, microstructure, composition, and surface roughness were investigated using a four-point probe, a field emission scanning electron microscope, a field ion bean4 an X-ray diffractometer, and an Auger electron depth profiling spectroscope, respectively, to confirm the silicide reaction. The residual stress of silicon substrate was also analyzed using a micro-Raman spectrometer We report that the silicide reaction does not occur if natural oxides are present. Metallic oxide residues may be present on a polysilicon substrate at high silicidation temperatures. Huge residual stress is possible on a single crystal silicon substrate at high temperature, and these may result in micro-pinholes. Our results imply that the natural oxide layer removal process is of importance to ensure the successful completion of the silicide process with CoNi alloy films.