In this study, Nd-bearing zirconolite-rich ceramics were prepared by solid-state reaction process using CaF2,ZrO2, Ti,TiO2, Fe2 O3 and Nd2O3 as the raw materials. Neodymium was used as trivalent actinide surrogate and...In this study, Nd-bearing zirconolite-rich ceramics were prepared by solid-state reaction process using CaF2,ZrO2, Ti,TiO2, Fe2 O3 and Nd2O3 as the raw materials. Neodymium was used as trivalent actinide surrogate and designed to substitute the Ca and Zr sites of zirconolite with general stoichiometry of Ca1-xZr1-xNd2 xTi2O7（0≤x≤0.3）. Density of Fe-Nd-O sample reaches a maximum value of 4.13 g/cm^2 after being sintered at 1325 ℃ for 42 h. Three major phases, namely zirconolite, perovskite and pseudobrookite, are observed in all these samples. The EDX result shows that Nd2O3 can be successfully incorporated into the lattice structure of the prepared zirconolite-rich minerals and replace the Ca sites of zirconolite and perovskite with Fe3＋ as the charge-compensating ion. Furthermore, the thermal conductivities are all in the range of 1.51-1.67 W/（m·K）. The normalized elemental leaching rates of Ca and Nd in the Fe-Nd-0.2 sample keep in low values of 6.20 × 10^-2 and 4.86 × 10^-4 g/（m^2·d） after 42 d.展开更多
In this research, Zr-doped Gd_2Ti_2O_7 pyrochlores, with the composition of Gd_2(Ti_(1-x)Zr_x)_2O_7, were firstly synthesized by self-propagating high-temperature synthesis plus quick pressing(SHS/QP) using CuO as the...In this research, Zr-doped Gd_2Ti_2O_7 pyrochlores, with the composition of Gd_2(Ti_(1-x)Zr_x)_2O_7, were firstly synthesized by self-propagating high-temperature synthesis plus quick pressing(SHS/QP) using CuO as the oxidant and Ti as the reductant. To improve the radiation resistance of titanate–pyrochlore, up to 35 at% Zr was incorporated to substitute the Ti site of Gd_2Ti_2O_7 pyrochlore(Gd_2(Ti_(0.75)Zr_(0.35))_2O_7). XRD and SEM microstructural characterizations showed the formation of a composite ceramic with the major pyrochlore phase and the minor Cu phase. The generated temperature of samples decreased from 1702to 1011 ℃ with increasing Zr content. The effects of sintering temperature and pressure time on phase composition and microstructure were systematically studied. Besides, the influence of thermal transmission on the whole combustion process was also explored. The pyrochlore-based waste form possessed high bulk density of 6.25 g/cm^3 and Vickers hardness of 10.81 GPa. The MCC-1 leaching test showed the normalized elemental leaching rates(42d) of Cu, Gd, and Zr are 1.27×10^(-2), 1.33×10^(-3), and 8.44×10^(-7)g·m^(-2)·d^(-1), respectively.展开更多
基金Project supported by the National Natural Science Foundation of China(51672228)the Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials(11zxfk26)Science Development Foundation of China Academy of Engineering Physics
文摘In this study, Nd-bearing zirconolite-rich ceramics were prepared by solid-state reaction process using CaF2,ZrO2, Ti,TiO2, Fe2 O3 and Nd2O3 as the raw materials. Neodymium was used as trivalent actinide surrogate and designed to substitute the Ca and Zr sites of zirconolite with general stoichiometry of Ca1-xZr1-xNd2 xTi2O7（0≤x≤0.3）. Density of Fe-Nd-O sample reaches a maximum value of 4.13 g/cm^2 after being sintered at 1325 ℃ for 42 h. Three major phases, namely zirconolite, perovskite and pseudobrookite, are observed in all these samples. The EDX result shows that Nd2O3 can be successfully incorporated into the lattice structure of the prepared zirconolite-rich minerals and replace the Ca sites of zirconolite and perovskite with Fe3＋ as the charge-compensating ion. Furthermore, the thermal conductivities are all in the range of 1.51-1.67 W/（m·K）. The normalized elemental leaching rates of Ca and Nd in the Fe-Nd-0.2 sample keep in low values of 6.20 × 10^-2 and 4.86 × 10^-4 g/（m^2·d） after 42 d.
基金supported by the National Natural Science Foundation of China(Nos.51672228 and 51202203)the Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials(No.11zxfk26)+1 种基金the Young Outstanding Scientist Fund of Southwest University of Science and Technology(No.13zx9108)the Postgraduate Innovation Fund Project by Southwest University of Science and Technology(No.16ycx010)
文摘In this research, Zr-doped Gd_2Ti_2O_7 pyrochlores, with the composition of Gd_2(Ti_(1-x)Zr_x)_2O_7, were firstly synthesized by self-propagating high-temperature synthesis plus quick pressing(SHS/QP) using CuO as the oxidant and Ti as the reductant. To improve the radiation resistance of titanate–pyrochlore, up to 35 at% Zr was incorporated to substitute the Ti site of Gd_2Ti_2O_7 pyrochlore(Gd_2(Ti_(0.75)Zr_(0.35))_2O_7). XRD and SEM microstructural characterizations showed the formation of a composite ceramic with the major pyrochlore phase and the minor Cu phase. The generated temperature of samples decreased from 1702to 1011 ℃ with increasing Zr content. The effects of sintering temperature and pressure time on phase composition and microstructure were systematically studied. Besides, the influence of thermal transmission on the whole combustion process was also explored. The pyrochlore-based waste form possessed high bulk density of 6.25 g/cm^3 and Vickers hardness of 10.81 GPa. The MCC-1 leaching test showed the normalized elemental leaching rates(42d) of Cu, Gd, and Zr are 1.27×10^(-2), 1.33×10^(-3), and 8.44×10^(-7)g·m^(-2)·d^(-1), respectively.
