• Journal of the Korean Ceramic Society
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• v.33 no.6
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• pp.693-699
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• 1996

YIG precursor powder was obtained by homogeneous precipitation in chloride salt solution by thermal decom-position of urea. It was found that ferric ions precipitated prior to yttrium ions. The precipitate was minute and spherical in shape. The precipitate formed consisted of the mixture of amorphous and ferric oxyhydroxide. Crystallization of YIG was proceeded by solid state reaction of intermediate YFeO3 and Fe2O3 in the temperature range of 85$0^{\circ}C$ to 140$0^{\circ}C$. Single phase of YIG was obtained by heat-treatment of the powder at 140$0^{\circ}C$ for 6 hrs in air. The powder calcined was molded into pellets and sintered in air. The maximum density of 4,92 g/cm3(95.1% of theoretical density) was obtainable for the pellet sintered at 145$0^{\circ}C$ using the powder calcined at 90$0^{\circ}C$.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.2
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• pp.77-85
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• 2012

This study was carried out to remove (/recover) the uranium from the Uranium-bearing Lime Precipitate (ULP). An oxidative dissolution of ULP with carbonate-acidified precipitation and a dissolution of ULP with nitric acid-hydrogen peroxide precipitation were discussed, respectively. In point of view the dissolution of uranium in ULP, nitric acid dissolution which could dissolved more than 98% of uranium was more effective than carbonate dissolution. However, in this case, uranium was dissolved together with a large amount of impurities such as Al, Ca, Fe, Mg, Si, etc. and some impurities were also co-precipitated with uranium during a hydrogen peroxide precipitation. On the other hand, in the case of carbonate dissolution-acidified precipitation, U was dissolved less than 90%. Therefore, it was less effective than nitric acid dissolution for the volume reduction of radioactive solid waste. However, it was very effective to recover the pure uranium, because impurities were hardly dissolved and hardly co-precipitated with uranium.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.110-112
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• 2009

• Journal of the Korean Society for Heat Treatment
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• v.9 no.4
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• pp.252-260
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• 1996

A study was conducted to examine the precipitation phenomena of Al-2.1Li-2.9Cu alloy by differential scanning calorimetry and transmission electron microscopy. DSC curves were measured over the temperature range of $25{\sim}550^{\circ}C$ at a heating rate of $2{\sim}20^{\circ}C$/min.. Three heat evolution peaks and three heat absorption peaks were observed in the DSC curve for the as-quenched specimen. From DSC results and TEM analysis, it was proved that the precipitation sequence in the as-quenched specimen is supersaturated solid solution ${\rightarrow}$ GP zone ${\rightarrow}{\delta}^{\prime}{\rightarrow}T_1{\rightarrow}T_2$ and ${\theta}^{\prime}$ was detected in the peak aged specimen at $160^{\circ}C$. The major phase formed at peak hardeness in the aging at $160^{\circ}C$ was ${\delta}^{\prime}$ phase. The activation energies for the formation of ${\delta}^{\prime}$ and $T_1$ phases were 22.3kcal/mole and 24.3kcal/mole, respectively. These lower activation energies than those for diffusion of Cu and Li in Al are ascribed to the quenched-in excess vacancies.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.904-911
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• 2001

High-density lead zirconate titanate(Pb(Zr$\_$0.53/Ti$\_$0.47/)O$_3$, PZT) ceramics were fabricated by a new milling-precipitation(MP) process improved from the conventional solid state process. This process was progressed by a milling impregnation through mixing ZrO$_2$ and TiO$_2$ powders with lead nitrate(Pb(NO$_3$)$_2$) water solution in zirconia ball media, and then milling precipitation was induced from precipitation of PbC$_2$O$_4$ by adding ammonium of oxalate monohydrate((NH$_4$)$_2$C$_2$O$_4$$.$H$_2$O) as a precipitant. As a result of this process, single-phase perovskite structure was formed at the calcination temperature of 750$\^{C}$ for Pb(Zr$\_$0.53/Ti$\_$0.47/)O$_3$ powders. In addition, the highest density at the sintering temperature of 1100$\^{C}$ was obtained, because of the highly sinterable PZT Powders ground through the re-milling process. Piezoelectric and dielectric properties of sintered sample were improved by MP process.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.5
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• pp.283-292
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• 2004

The effects of the annealing parameters on microstructures were examined in a cold-rolled high strength steel containing 0.1% C, 0.5% Si, 1.5% Mn, and 0.04% Nb. It was impossible to avoid martensite in the microstructure even though the continuous annealing parameters were controlled. This indicates that the alloying elements such as silicon and manganese contributing to manganese equivalent($Mn_{eq}$) should be reduced to produce the ferrite-pearlite microstructure for the solid solution and precipitation hardened steel. It was found that a decrease in the rapid cooling temperature to $520^{\circ}C$ was effective to change the microstructure from ferrite-martensite to ferrite-pearlite-martensite. Typical dual-phase properties exhibiting a low yield ratio and a continuous yielding behavior were obtained when the rapid cooling temperature was in the range of $680^{\circ}C$ to $600^{\circ}C$. The critical volume fraction of martensite for the typical properties of dual-phase steel was about 11 percent.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.681-688
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• 2014

Hydride reorientation behaviors of PWR cladding tubes under typical interim dry storage conditions were investigated with the use of as-received 250 and 485ppm hydrogen-charged Zr-Nb alloy cladding tubes. In order to evaluate the effect of typical cool-down processes on the radial hydride precipitation, two terminal heat-up temperatures of 300 and $400^{\circ}C$, as well as two terminal cool-down temperatures of 200 and $300^{\circ}C$, were considered. In addition, two cooling rates of 2.5 and $8.0^{\circ}C/min$ during the cool-down processes were taken into account along with zero stress or a tensile hoop stress of 150MPa. It was found that the 250ppm hydrogen-charged specimen experiencing the higher terminal heat-up temperature and the lower terminal cool-down temperature generated the highest number of radial hydrides during the cool-down process under 150MPa hoop tensile stress, which may be explained by terminal solid hydrogen solubilities for precipitation, and dissolution and remaining circumferential hydrides at the terminal heat-up temperatures. In addition, the slower cool-down rate generates the larger number of radial hydrides due to a cooling rate-dependent, longer residence time at a relatively high temperature that can accelerate the radial hydride nucleation and growth.

• Journal of Microbiology and Biotechnology
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• v.26 no.2
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• pp.364-372
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• 2016

Sand tubules, made up of sand grains cemented by microbe-induced calcium carbonate precipitation, have been found in China's Ningxia Province. Sand tubules grow like a tree's roots about 40-60 cm below the surface. The properties of sand tubules and their bacterial community were examined. X-Ray diffraction analysis revealed that the sand tubules were associated with crystalline calcite. Scanning electron microscopy showed that the crystalline solid had a lamellar structure and lacked the presence of cells, suggesting that no bacteria acted as nucleation sites, nor that the crystalline solid was formed by the aggregation of bacteria. Denaturing gradient gel electrophoresis analysis showed 11 of the 12 detectable bands were uncultured bacteria by BLAST analysis in the GenBank database, and the rest were closely related to Paenibacillus sp. (100% identity). By cultivation techniques, the only strain isolated from the sand tubule was suggested to be related to Paenibacillus sp.; no archaea were found. Furthermore, Paenibacillus sp. was demonstrated to induce calcium carbonate precipitation in vitro.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.234-238
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• 1995

MgFe2O4 formation, grain growth in Fe2O3, Fe solid-solution limit in MgO for MgO-Fe2O3 mixture were studied by means of investigating the distribution of phases and compositions in reaction area between MgO and Fe2O3. The reaction area at equlibrium was composed with MgO-FexO matrix and MgFe2O4 precipitation, MgFe2O4 was formed by precipitating from MgO-FexO matrix dependent on oxygen partial pressure. Fe contents was exponentially decreased with diffusion distance in MgO single crystal, and thus Fe solid-solution limitation in MgO was about 4mol%. The grain growth rate in Fe2O3 base was increased with Mg contents diffused from MgO single crystal.

• Mass Spectrometry Letters
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• v.5 no.1
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• pp.30-33
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• 2014

A solid phase extraction (SPE) method was optimized for the quantitative analysis of perfluorooctanoic acid (PFOA) in serum using hydrophilic-lipophilic balance SPE and LC-MS/MS. Fetal bovine serums spiked with $^{13}C_8$-PFOA before or after SPE were used as test samples for evaluation of the SPE efficiency. Simultaneous evaluation of matrix effects and absolute SPE recovery for $^{13}C_8$-PFOA in serum using different sample pre-treatments and SPE conditions allowed optimization of SPE process efficiency with minimal matrix effect and decent SPE recovery. Introduction of protein precipitation as a sample pre-treatment procedure for serum samples before SPE generally decreased matrix effect in LC-MS/MS analysis and provided more stable recovery of PFOA.