• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.3
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• pp.235-243
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• 2014

Surface oxidation behavior of ZIRLO (ZIRconium Low Oxidation) hulls was investigated using an X-ray photoelectron spectroscopy (XPS) technique. The effects of oxidation time (10-336 h at $500^{\circ}C$) and temperature ($400-700^{\circ}C$ for 10 h) were studied. Deconvolution results of the hulls oxidized at $500^{\circ}C$ revealed that a $ZrO_2$ phase appeared after 24 h (11.86%), and an increase in the $ZrO_2$ ratio was observed when the hulls were oxidized for 336 h (17.93%). On the other hand, the ZrO phase which employed 5.68% in the 10 h oxidized sample disappeared when the oxidation time increased to 24 h. The XPS results also showed that an increase in the oxidation temperature resulted in an increase in the ratio of ZrO, which increased from 0 to 5.68, 8.31, and 9.16% when the oxidation temperature increased from 400 to 500, 600, and $700^{\circ}C$, respectively. $ZrO_2$ phase was observed only in the sample that was oxidized at $700^{\circ}C$. The mechanism of ZrO formation was not conclusive, but it was suggested that a formation of hydroxide might have been accelerated at elevated temperatures leading to a formation of a $Zr(OH)_4$ phase. The relationship between the surface oxidation status of the hulls oxidized at $500^{\circ}C$ and their chlorination reaction feasibility was discussed, and it was suggested that the thickness of the oxide layer is an important parameter that determines the chlorination reaction feasibility.

• Journal of the Korean Ceramic Society
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• v.24 no.3
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• pp.243-250
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• 1987

The effects aging on some properties and thermal-shock behavior of zirconia partially stabilized with 9 mol% MgO (9MZ) were studied. 9MZ specimens were aged over $1200^{\circ}$-$1400^{\circ}C$ for 12hours subsequently, after sintering at $1650^{\circ}C$ for 4 hours. Fracture strength(both before and after thermal-shock test), linear thermal expansion, monoclinic fraction and phase transition by XRD, density, galvanic potential and microstructure were measured. Quantitative chemical analysis around the grain-boundary of the specimen aged at $1350^{\circ}C$ was also conducted by EDX. The aging of 9MZ specimen causes a thermal decomposition of cubic-$ZrO^{2}$ into the formation metastable tetragonal-$ZrO^{2}$ and MgO. The former increases the residual strength after thermal-shock test and the latter improves the thermal-shock resistance due to thermal conduction through the continuous magnesia phase and the formation of monoclinic phase content in matrix were increased with decreasing the aging temperature from $1400^{\circ}C$ to $1200^{\circ}C$. Galvanic potential of the aged specimen exhibited a proper emf characteristic.

• Economic and Environmental Geology
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• v.40 no.6
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• pp.727-738
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• 2007

The present study investigation the geochemical characteristics of the stream sediments in the Unbong area was conducted to enable a understanding the natural background and a prediction the prospects of geochemical disaster as a result of that bed rocks(mylonitic granites, Kim et al., 1992). We systematically collected seventy three stream sediments samples by wet sieving along the primary channels. Major, trace and rare earth element(REE) concentrations, combined with mineralogical characteristics, were determined by XRD, XRF, ICP-AES and NAA analysis methods. Major element concentrations for the stream sediments in the Unbong area were $SiO_2\;36.94{\sim}65.39wt.%,\;Al_2O_3\;10.15{\sim}21.77wt.%,\;Fe_2O_3\;3.17{\sim}10.90wt.%,\;CaO\;0.55{\sim}5.27wt.%,\;MgO\;0.52{\sim}4.94wt.%,\;K_2O\;1.38{\sim}4.54wt.%,\;Na_2O\;0.49{\sim}3.36wt.%,\;TiO_2\;0.39{\sim}1.27wt.%,\;MnO\;0.04{\sim}0.22wt.%,\;P_2O_5\;0.08{\sim}0.54wt.%$. Trace and REE concentrations for the stream sediments were $Cu\;4.8{\sim}134ppm,\;Pb\;24.2{\sim}82.5ppm,\;Sr\;95.9{\sim}739ppm,\;V\;19.9{\sim}124ppm,\;Zr\;52.9{\sim}145ppm,\;Li\;25.2{\sim}3.3ppm,\;Co\;3.87{\sim}50.0ppm,\;Cr\;17.4{\sim}234ppm,\;Hf\;3.93{\sim}25.2ppm,\;Sc\;4.60{\sim}20.6ppm,\;Th\;3.82{\sim}36.9ppm,\;Ce\;45.7{\sim}243ppm,\;Eu\;0.89{\sim}2.69ppm,\;Yb\;1.42{\sim}5.18ppm$. According to the comparison of average major element concentrations, CaO, $Na_2O\;and\;K_2O$ contents are higher in stream sediments than in bed rocks(mylonitic granites, Kim et al., 1992) $Al_2O_3\;and\;SiO_2$ contents show good correlation both stream sediments and bed rocks(mylonitic granites, Kim et al., 1992). Yb and Eu in the stream sediments show a positive correlation with $SiO_2$. In contrast, the stream sediments display a negative correlation.