• Title/Summary/Keyword: metal oxides.

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A Chemical Reaction Calculation and a Semi-Empirical Model for the Dynamic Simulation of an Electrolytic Reduction of Spent Oxide Fuels (산화물 사용후핵연료 전해환원 화학 반응 계산 및 동적 모사를 위한 반실험 모델)

  • Park, Byung-Heung;Hur, Jin-Mok;Lee, Han-Soo
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.8 no.1
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    • pp.19-32
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    • 2010

  • Electrolytic reduction technology is essential for the purpose of adopting pyroprocessing into spent oxide fuel as an alternative option in a back-end fuel cycle. Spent fuel consists of various metal oxides, and each metal oxide releases an oxygen element depending on its chemical characteristic during the electrolytic reduction process. In the present work, an electrolytic reduction behavior was estimated for voloxidized spent fuel based on the assumption that each metal-oxygen system is independent and behaves as an ideal solid solution. The electrolytic reduction was considered as a combination of a Li recovery and chemical reactions between the metal oxides such as uranium oxide and the produced Li metal. The calculated result revealed that most of the metal oxides were reduced by the process. It was evaluated that a reduced fraction of lanthanide oxides increased with a decreasing $Li_2O$ concentration. However, most of the lanthanides were expected to be stable in their oxide forms. In addition, a semi-empirical model for describing $U_3O_8$ electrolytic reduction behavior was proposed by considering Li diffusion and a chemical reaction between $U_3O_8$ and Li. Experimental data was used to determine model parameters and, then, the model was applied to calculate the reduction yield with time and to estimate the required time for a 99.9% reduction.

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Steam Pressure Effects on the Oxidation of Low-Sn Zircaloy-4 at High Temperatures (고압 수증기에 따른 Low-Sn Zircaloy-4의 고온 산화 거동)

  • Yang, Sung-Woo;Park, Kwang-Heon
    • Journal of the Korean institute of surface engineering
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    • v.40 no.4
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    • pp.180-184
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    • 2007

  • A new zirconium alloy, low-Sn Zircaloy-4 was investigated to see the effects of high pressure steam on the oxidation at high temperatures. High pressure steam turned out to enhance the oxidation at high temperatures below $1000^{\circ}C$. The oxide layer groved to deviate from the uniform layer under high steam pressures, and usually cracks were found at the thicker parts in the oxide layer. High pressure steam seems to destabilize the tetragonal oxides near the metal layer, and the monoclinic oxides transformed from the destabilized tetragonal oxides are structurally not sound, resulting in enhanced oxidation under high pressure steam.

  • https://doi.org/10.5695/JKISE.2007.40.4.180 인용 PDF KSCI

Influence of various metal oxides on mechanical and physical properties of heat-cured polymethyl methacrylate denture base resins

  • Asar, Neset Volkan;Albayrak, Hamdi;Korkmaz, Turan;Turkyilmaz, Ilser
    • The Journal of Advanced Prosthodontics
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    • v.5 no.3
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    • pp.241-247
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    • 2013

  • PURPOSE. To evaluate the effect of various metal oxides on impact strength (IS), fracture toughness (FT), water sorption (WSP) and solubility (WSL) of heat-cured acrylic resin. MATERIALS AND METHODS. Fifty acrylic resin specimens were fabricated for each test and divided into five groups. Group 1 was the control group and Group 2, 3, 4 and 5 (test groups) included a mixture of 1% $TiO_2$ and 1% $ZrO_2$, 2% $Al_2O_3$, 2% $TiO_2$, and 2% $ZrO_2$ by volume, respectively. Rectangular unnotched specimens ($50mm{\times}6.0mm{\times}4.0mm$) were fabricated and drop-tower impact testing machine was used to determine IS. For FT, compact test specimens were fabricated and tests were done with a universal testing machine with a cross-head speed of 5 mm/min. For WSP and WSL, disc-shaped specimens were fabricated and tests were performed in accordance to ISO 1567. ANOVA and Kruskal-Wallis tests were used for statistical analyses. RESULTS. IS and FT values were significantly higher and WSP and WSL values were significantly lower in test groups than in control group (P<.05). Group 5 had significantly higher IS and FT values and significantly lower WSP values than other groups (P<.05) and provided 40% and 30% increase in IS and FT, respectively, compared to control group. Significantly lower WSL values were detected for Group 2 and 5 (P<.05). CONCLUSION. Modification of heat-cured acrylic resin with metal oxides, especially with $ZrO_2$, may be useful in preventing denture fractures and undesirable physical changes resulting from oral fluids clinically.

  • https://doi.org/10.4047/jap.2013.5.3.241 인용 PDF KSCI