• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.231-236
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• 1999

Several series of morphologically controlled $MoO_3$/$SiO_2$ catalysts were prepared, characterized, and tested for hydrodesulfurization (HDS) of dibenzothiophene (DBT) activity. Molybdenum surface loaded with 4.0 atoms $Mo/nm^2$ was prepared as sintered hexagonal and sintered orthorhombic, as well as a novel "well dispersed hexagonal" phase. Characterization by XRD, Raman, and $O_2$ chemisorption results reveals that the dispersion of $MoO_3$ over silica depends on the final $MoO_3$ phase in the order of; sintered hexagonal < sintered orthorhombic < dispersed hexagonal phase. Temperature programmed reduction (TPR) results show that both bulk and dispersed microcrystalline of $MoO_3$ reduce to $MoO_2$ at $650^{\circ}C$ and to Mo metal at $1000^{\circ}C$. HDS of DBT was performed in a differential reactor at 30 atm over the temperature range $350{\sim}500^{\circ}C$. Activity of $MoO_3$/$SiO_2$ toward HDS of DBT is proportional to dispersion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.593-596
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• 2003

A proposed way to prepare $YBa_2Cu_3O_y$ wires or tapes is that Ag is used as substrate and melting point of $YBa_2Cu_3O_y$ is decreased to lower than the melting point of silver ($961\;^{\circ}C$). Therefore after the deposition of $YBa_2Cu_3O_y$ film on Ag substrate, the heat treatment can be carried out below the Ag melting point. Silver (Ag) and Lead oxide(PbO) were selected to be additives for $YBa_2Cu_3O_y$. Different Ag and PbO contents were added in $YBa_2Cu_3O_y$, the melting points of which were measured by DTA. In order to guarantee that the superconductivity of $YBa_2Cu_3O_y$ was not reduced after Ag and PbO added into $YBa_2Cu_3O_y$, their superconductivities were measured. It is proved that as additives, both Ag and PbO can reduce the melting point of $YBa_2Cu_3O_y$. For Ag doped $YBa_2Cu_3O_y$, $T_c$ is about 93K and ${\Delta}Tc$ is $2{\sim}3K$. For PbO doped $YBa_2Cu_3O_y$, $T_c$ is $88K{\sim}92K$ and ${\Delta}T_c$ is $11{\sim}12K$. When 10 wt% of Ag and 10 wt% PbO were added in $YBa_2Cu_3O_y$, the melting point of the mixture of $YBa_2Cu_3O_y$ (80 wt%), Ag (10 wt%) and PbO (l0 wt%) is $943^{\circ}C$. The transition temperatures ($T_c$) of the sample is 91.8 K.

• Journal of the Korean Ceramic Society
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• v.32 no.12
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• pp.1331-1336
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• 1995

The glass-ceramics for ferro-electric were made from compositions of 70PbO.16TiO2.8SiO2.4B2O3.2AlPO4 (wt%) and 67.5PbO.20TiO2.8.5SiO2.2B2O3.2AlPO4 (wt%). The crystallization kinetics for PbTiO3 crystalline phase formation from glass was studied using non-isothermal DSC techniques. The values of activation energy, ΔE using variables of heating rate and temperature were calculated at various reaction fractions obtained from peak area over DSC. The results indicated that activation energy was lowest at 60% reaction fractions and the activation energy of glass containing 20.0 wt% TiO2 is higher than that of glass containing 16.0 wt% TiO2. The crystallization mechanism was three dimensional growth (n=4).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.532-542
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• 1996

The electrical and optical properties of the annealed $LiNbO_{3}$ single crystal with congruently melting composition and MgO or ZnO doped $LiNbO_{3}$ single crystal grown by the FZ method. The electrical and optical properties such as electrical conductivity, dielectric constant (Curie temperature), electro-mechanical coupling factor, optical transmittance and refractive indices of the grown crystals were measured and the nonlinear refractive indices of the grown crystals were calculated theoretically. The doping effects of MgO and ZnO were investigated by comparing the electrical and optical properties of the undoped $LiNbO_{3}$ single crystal and those of the $LiNbO_{3}$ single crystals doped with MgO or ZnO.

• Journal of the Korean Ceramic Society
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• v.22 no.6
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• pp.37-41
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• 1985

Several $Al_2O_3$-based polycrystalline which had different dopant ratio in the range of 0.5mol% were prepared by doping pure $Cr_2O_3$, $ZrO_2$, $HfO_3$ Single crystalline which had same composition with above polycrystalline were made by means of floating zone method. This study examined the role of each dopant for enhancing the mefchanical properties of $Al_2O_3$-based Ceramics. Optical micrographs $({\times}200)$ of $Al_2O_3-Cr_2O_3$ single crystal showing not only radial crack (rc) on the specimen surface but median crack (mc) and lateral crack (lc) under surface at the edge of indentation mark. Fracture toughness of $Al_2O_3$-based Ceramics was increased with $ZrO_2$ content. Alloying effect of $Cr_2O_3$ contributed to the hardness of $Al_2O_3$ based ceramics.

• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.83-89
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• 1995

YBa2Cu3O7-$\delta$, Y2BaCuO5, and binary compounds in the Ba-Cu-O system with the nominal composition of Ba2CuO3, BaCuO2, Ba3Cu4O7, Ba3Cu5O8 were synthesized to investigate the heat evolutions and crystalline phases in the hydration reaction of orthorhombic YBa2Cu3O7-$\delta$ phase. The observed crystalline phases were YBa2Cu3O7-$\delta$, Y2BaCuO5, and BaCuO2, or Ba2Cu3O5＋x, and some amount of noncrystalline phase in the Ba-Cu system comounds. In contact with distilled water, YBa2Cu3O7-$\delta$ and Y2BaCuO5 did not have considerable heat liberation, but in the binary compounds of the Ba-Cu-O system, the amount of total heat liberation was increased with respect to the Cu content. It might be that the reaction of high temperature superconductor YBa2Cu3O7-$\delta$ with water and/or moisture originated from the unusual oxidation state of Cu ion and the presence of amorphous Ba-Cu oxide compound. The degradation of high Tc superconductor by moisture and water could be controlled by restricting the heterogeneous distribution of Tc comlposition and the formation of second phase, such as stable Y2BaCuO5, and the resulting unstable Ba-Cu oxide compound.

• Natural Product Sciences
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• v.18 no.1
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• pp.32-38
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• 2012

The herbs of Orostachys japonicus (Crassulaceae) have been used to treat gastric cancer, gastric ulcer or hemorrhage. Flavonoid glycosides, mainly kaempferol (Kp)- and quercetin (Qc) glycosides, have been isolated from O. japonicus; however, no quantitative information on those flavonol glycosides and no peroxynitritescavenging activity of the Orostachys extracts have been reported. In this study, Kp- and Qc glycosides were qualitatively and quantitatively analyzed by high-performance liquid chromatography (HPLC) in eight Orostachys and a Meterostachys species including O. japonicas, O. margaritifolius, O. chongsunensis, O. minuta, O. ramosus, O. malacophylla, O. latiellipticus, O. iwarenge, O. iwarenge for. magnus, and Meterostachys sikokiana distributed or cultivated in Korea. Distinctively, O. margaritifolius contained two flavonol 3,7-di-O-glycosides of Kp 3,7-di-O-glucoside and Kp 3-rhamnosyl-7-glucoside, but O. japonicus had two flavonol 3-O-rutinosides, Kp 3-rutinoside and Qc 3-rutinoside. The three species of O. margaritifolius (24.36 mg/g MeOH extract), O. japonicus (21.28 mg/g), and O. minuta (19.50 mg/g) showed relatively higher flavonoid contents. The flavonol glycosides were analyzed using eight standard compounds (Kp, Qc, Qc 3-O-rhamnoside, Qc 3-O-glucoside, Kp 3- O-rutinoside, Qc 3-O-rutinoside, Kp 3-O-rhamnosyl-7-O-glucoside, Kp 3,7-di-O-glucoside). The present HPLC method was validated to verify the linearity, precision, and accuracy. In addition, the peroxynitrite-scavenging activity was also discussed.

• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.82-87
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• 1998

In the oxidation process of the $NH_3/O_2$ oxidation method, adding $NH_3$ gas to $O_2$ gas, the detected outlet gases in the reaction quartz chamber are N2, $O_2$ and $H_2O$ and in addition, a very small quantity of $CO_2$, NO and $NO_2$ are detected. Two kinds of species ($O_2$ and H2O) contribute to oxidation, so the growth rate is determined by oxidation temperature and by also partial pressure of the NH3 and $O_2$ gases. The slop of growth rate is identified to be medial and in parallel between that of the dry and wet oxidation. Auger electron spectroscopy (AES) indicates that $NH_3/O_2$ oxide film has a certain stoichiomerty of $SiO_2$, this oxidation method restrains the generation of defects in the $SiO_2/Si$ interface, minimizing fixed charges. The breakdown voltage of $NH_3/O_2$ oxide film (470$\AA$) is 57.5 volts, and the profile of the C-V curve including flat band voltage (0.29 volts) agree with the ideal curve.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1109-1113
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• 1999

sothemal reduction at $50^{\circ}C$ using $Pt/MoO_3$ or $Pt/MoO_3/SiO_2$ made by dry impregnation or physical mixture of $Pt^{\circ}$ and $MoO_3$ demonstrated that the $H_2$ uptake vis $H_2$ spillover from Pt into $MoO_3$ was enhanced as calcination temperature was increased. Surface area of exposed Pt crystallites measured by CO chemisorption was decreased with higher calcination temperature. In addition, TEM showed that $MoO_x$ overlayers were formed on Pt crystallites after calcination at $400^{\circ}C$. Consequentially, it was found that this increased active contact sites between Pt and $MoO_3$ due to surface morphological change was one of the dominant factors for this increased $H_2$uptake via $H_2$ spillover from Pt crystallites into $MoO_3$.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.1
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• pp.41-52
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• 2021

NiO and Co3O4-doped porous La(CoNi)O3 perovskite oxides were prepared from excess Ni addition by a hydrothermal method using porous silica template, and characterized as bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for Zn-air rechargeable batteries in alkaline solution. Excess Ni induced to form NiO and Co3O4 in La(CoNi)O3 particles. The NiO and Co3O4-doped porous La(CoNi)O3 showed high specific surface area, up to nine times of conventionally synthesized perovskite oxide, and abundant pore volume with similar structure. Extra added Ni was partially substituted for Co as B site of ABO3 perovskite structure and formed to NiO and Co3O4 which was highly dispersed in particles. Excess Ni in La(CoNi)O3 catalysts increased OER performance (259 mA/㎠ at 2.4 V) in alkaline solution, although the activities (211 mA/㎠ at 0.5 V) for ORR were not changed with the content of excess Ni. La(CoNi)O3 with excess Ni showed very stable cyclability and low capacity fading rate (0.38 & 0.07 ㎶/hour for ORR & OER) until 300 hours (~70 cycles) but more excess content of Ni in La(CoNi)O3 gave negative effect to cyclability.