• Nuclear Engineering and Technology
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• v.35 no.1
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• pp.14-24
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• 2003

This work investigates the effects of Cr$_2$O$_3$ and oxygen potential on grain growth and densification of UO$_2$ pellets. Powder mixtures of UO$_2$ and 0.03-0.4wt% Cr$_2$O$_3$ were pressed and sintered in 3 different gas atmospheres: the $H_2O$-to-H$_2$ ratios were 5$\times$10$^{-4}$ , 1$\times$10$^{-2}$ and 3$\times$10$^{-2}$ In the first gas atmosphere the Cr$_2$O$_3$ contents below 0.2 wt% have an insignificant effect on grain size, but the Cr$_2$O$_3$ contents more than 0.3 wt% promote grain growth in the inner zone of a pellet but not in the outer zone. In both the second and third atmospheres, the grain size increases with the Cr$_2$O$_3$ content. With the same level of Cr$_2$O$_3$ content the grain size is larger in the second atmosphere than in the third. Sintering behavior and developed microstructure are discussed in terms of the reduction of C$r^2$O$^3$ to Cr, the dissolution of C$r^2$O$^3$ in UO$_2$, and liquid phase sintering.

• Membrane Journal
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• v.16 no.2
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• pp.123-132
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• 2006

The PTMSP-silica-PEI composite membranes were synthesized from tetraethoxysilane (TEOS) and poly (1-trimethylsilyl-1-propyne) (PTMSP) by sol-gel process. The PTMSP-silica nanocomposite membranes were characterized by $^1H-NMR$, FT-IR, TGA, XPS, SEM, GPC and gas permeation measurements were accomplished with $H_2,\;O_2,\;N_2,\;CO_2,\;CH_4$. The gases permeability increased with increasing TEOS content. Both the permeability and selectivity of $H_2,\;CH_4$ increased to 15 wt% TEOS. While the permeability of $O_2,\;CO_2$ increased without decrease of selectivity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.2
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• pp.99-104
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• 2017

Refractories used in low-rank coal gasification reactors are usually exposed in a highly corrosive $H_2S$ gas at less than $1000^{\circ}C$, and their mechanical properties such as erosion resistance and fracture strength decline with the exposure time. However, the cause of the degradation of the mechanical properties has little reported yet. In this paper, two kinds of castable refractories with different refractoriness had been exposed in a $H_2O/N_2/H_2S$ mixed gas with high $H_2S$ content for 100 hours at $900^{\circ}C$, and the changes of microstructure, crystalline phases and erosion resistance were compared before and after the corrosion test. The weight of the refractories decreases due to the elution of silica in the specimens after the corrosion test. The capillary porosities of the samples are reduced, but the erosion resistance of the samples is fatally weakened after the corrosion test. There also are changes in constituent phases; dmitryivanovite ($CaAl_2O_4$) and amorphous silica ($SiO_2$) disappear, and gypsum ($CaSO_4{\cdot}2H_2OS$) and kaolinite ($Al_2Si_2O_5(OH)_4$) newly appear after the corrosion test. It is obvious that the phase change from dmitryivanovite that works as a binding agent in the castable refractory to gypsum is the main reason of the degradation of the erosion resistance, because the mechanical properties of gypsum are much poorer than those of dmitryivanovite.

• Journal of the Korean Ceramic Society
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• v.31 no.10
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• pp.1147-1158
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• 1994

From Zr(O-nC3H7)4-H2O-C2H5OH-HNO3 starting solutions, MgO-doped stabilized zirconia fibers with varying content of MgO (10~18 mol%) from different MgO sources were fabricated by sol-gel method. The MgO sources used are magnesium nitrate hexahydrate, magnesium acetate tetrahydrate, and magnesium ethylate. The phase transformation studies of a drawn MgO-ZrO2 fiber were carried out using X-ray diffraction, IR spectroscopy, and Raman spectroscopy. The microstructure, tensile strength, and microporosity of fibers were investigated using SEM, tensile strength test, and microporosimeter. Although various MgO sources such as magnesium nitrate, acetate, and ethylate were used, the crystallization behavior of MgO-ZrO2 fibers at different temperatures could be summarized as follows: CubiclongrightarrowMetastable TetragonallongrightarrowMonocliniclongrightarrowCoexistence of Monoclinic and CubiclongrightarrowCubic(trace of monoclinic). At 150$0^{\circ}C$, the phase transformation of MgO-ZrO2 fibers shows the following change depending on the amount of MgO[Mg(NO3)2.6H2O]: At 10 mol%, both monoclinic and cubic phase coexist, at 12 mol%, monoclinic phase decreases rapidly, and then at 14 mol%, only cubic phase remains. When the MgO-ZrO2 fibers containing 12 mol% magnesium nitrate were heated at 80$0^{\circ}C$ for 1hr, average tensile strength of fibers is 4.0 GPa at diameters of 20 to 30 ${\mu}{\textrm}{m}$. As the heat-treatment temperatures increase to 100$0^{\circ}C$ for 1 hr, tensile strength of MgO-ZrO2 fibers decreases rapidly to 0.7 GPa.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2056-2062
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• 2013

The dihydroxy naphthalene/$TiO_2$ complexes with different substitution patterns were prepared by surface modification. X-ray diffraction, UV-Vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared composite materials. The results indicated that the surface modification did not influence the crystallization of $TiO_2$. The visible-light absorbances of prepared dihydroxy naphthalene/$TiO_2$ complexes could be assigned to the ligand-to-metal charge transfer. The obtained catalyst exhibited outstanding photocatalytic activity and stability under visible light. A linear relationship existed between the percentages of hydroxynaphthalenes coordinated on $TiO_2$ surface and $H_2$ production ability. The substitution pattern of dihydroxy naphthalene and $CH_3OH$ content could also influence the photocatalytic performance remarkably. The photocatalytic $H_2$ production ability was further improved after loading with ultra low concentration of Pt, 0.02 wt %. The possible mechanism was proposed.

• Journal of Environmental Science International
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• v.25 no.3
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• pp.417-424
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• 2016

The objective of this study was to evaluate the microwave drying characteristics of mixtures of chemical wastewater sludge (70~90%) and anthracite coal (10~30%) with respect to physical and economic factors such as mass, volume reduction, moisture content, drying rate and heating value when the wastes were dried at different weight mixing ratio and for different microwave irradiation time. The drying process were carried out in a microwave oven, the combined drying process with a 2,450 MHz frequency and 1 kW of power. Maximum dry rates per unit area on the microwave drying of mixtures with chemical wastewater sludge and anthracite coal were $35.5kg\;H_2O/m^2{\cdot}hr$ for Cs90-Ac10; $40.1kg\;H_2O/m^2{\cdot}hr$ for Cs80-Ac20 and $35.0kg\;H_2O/m^2{\cdot}hr$ for Cs70-Ac30. The result clearly indicated that moisture can be effectively and inexpensively removed from the wastes through use of the microwave drying process.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.1
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• pp.97-101
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• 2001

This study was done to investigate the protective effects of Diospyrus kaki Folium on carbon tetrachloride intoxicated rats. Male Sprague-Dawley rats (200~230g) was used. Experimental groups were divided into normal group and $CCl_{4}$-treated group and then $CCl_{4}$-treated groups were divided into 7 groups: only $CCl_{4}$-treated group, methanol extract pretreated group, butanol fraction pretreated group and $H_{2}O$ fraction pretreated group, $CCl_{4}$ treated groups were injected with $CCl_{4}$ 0.6 mg/kg (ip). The activities of ananine aminotransferasein hexane, chloroform and $H_{2}O$ fraction pretreated groups were significantly decreased (p<0.05) compared to the only $CCl_{4}$-treated group and also activity of aspartate aminotransferase and hepatic malondialdehyde content in $H_{2}O$ fraction pretreated group were significantly decreased (p<0.05) compared to the only $CCl_{4}$-treated group. The activity of alkaline phosphatase in chloroform and $H_{2}O$ fraction pretreated groups were decreased compared to the only $CCl_{4}$-treated group but the difference was not statistically significant. The activity of ${\gamma}$-glutamyltranspeptidase in hexane, chloroform and ethylacetate fraction pretreated groups were significantly decreased (p<0.05) compared to the only $CCl_{4}$-treated group. The contents of cholesterol and triglyceride were not influenced in any fraction pretreated groups, but HDL-cholesterol content in hexane and chloroform fraction pretreated groups were significantly increased (p<0.05) compared to the only $CCl_{4}$-treated group. Therefore, these results demonstrate a possible hepatoprotective role of $H_{2}O$ fraction of Diospyrus kaki Folium methanol extract in carbon tetrachloride intoxicated rats.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.249-250
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• 2022

In this study, two types of chitosan-catechol polymers (a-CP and b-CP) were synthesized and mixed with polyvinyl alcohol (PVA) and sodium tetraborate decahydrate (Na₂B4O₇·10H₂O) to form hydrogels. The characteristics of these polymers were tuned by varying the pH during their syntheses, and their structures were characterized using nuclear magnetic resonance spectroscopy and ultraviolet-visible spectroscopy. Rheological and self-healing properties of hydrogels were evaluated. As a result, the viscoelastic modulus was improved due to the increased functional group content, and the self-healing property was excellent regardless of the functional group content.

• The Journal of Korean Medicine
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• v.18 no.1
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• pp.375-384
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• 1997

This study was undertaken to determine Juglandis Semen extraction (JS) has a protective effect against the cell injury caused by oxidants, t-butylhydroperoxide (t-BHP) and $H_{2}O_2$ in rabbit lung slices. Cell injury was estimated by measuring tissue water content and peroxidation of membrane lipids was assessed by measuring malondialdehyde (MDA), an end-product of lipid peroxidation. t-BHP significantly increased water content in lung tissues over concentrations of 2-10 mM, and such effects were prevented by 5% JS. JS exerted the beneficial effect in a dose-dependent manner. $H_{2}O_2$ (100 mM) also increased water content in tissues, which was almost completely prevented by 5% JS. t-BHP induced lipid peroxidation in a dose-dependent fashion in lung tissues over concentrations of 0.5-10 mM. JS significantly reduced t-BHP induced lipid peroxidation and oxidant-independent endogenous lipid peroxidation, and such effects were dose-dependent at concentration of 0.5-10%. JS prevented $H_{2}O_2$ (100 mM)-dependent lipid peroxidation. These results suggest that JS prevents ceil injury induced by oxidants in the lung, and such effects may be attributed to inhibition of lipid peroxidation. The precise mechanisms remains to be explored.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.497-504
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• 2000

In this study, mullite-zirconia comosite was fabricated by adding ZrOCl2.8H2O using of boehmite gel coating to Hadong kaolin (pink A grade) in order to enhance strength of the mullite specimens. The influence of ZrOCl2.8H2O content and fireing temperature on the crystall phase, microstructure, bulk density, strength of the specimens was investigated. Mullite-zirconia composite was produced in the process of coating zirconia to mullite powder synthesized thereafter and mixing simultaneously of starting materials with boehmite-zirconia gel. Maximum strength with in this study was 251 sintered at 1$600^{\circ}C$ for 2h. Bulk density and strength of the composite with zirconia coated mullite was higher than simultaneous on mixture of starting materials.