Sihao Wang,Yongde Yan,Linglin Jiao,Xu Wang,Yining Zhang,Fuqiu Ma,Yun Xue,Jingping Wang
The conventional solid-phase sintering method for the preparation of Ln 2 Ti 2 O 7 ceramics using oxides as reactants generally requires higher temperature, larger pressure, and greater energy consumption. In this paper, we synthesize a Eu 2 Ti 2 O 7 ceramic powder in relatively low-temperature molten salt (KCl–NaCl) using Eu 2 O 3 powder and TiO 2 powder as reactants at 1000 °C. The results of XRD , SEM, and element mapping indicate that the product have high phase purity, good crystal morphology and uniform chemical composition. Moreover, Eu 2 Ti 2 O 7 -based glass-ceramics are obtained by sintering with different contents of borosilicate glass . The SEM images of glass-ceramic show that almost no obvious defects or voids are found on the surface of the samples. The values of water absorption for all glass-ceramic waste forms are less than 0.5 %. With the increase of ceramic embedding rate, the hardness of the glass-ceramics first increases and then decreases, while the density gradually increases. When the embedding rate increased to 30 wt%, the hardness of glass-ceramic reaches a maximum of 19.53 GPa. The glass-ceramic waste form embedded with 30 wt% Eu 2 Ti 2 O 7 exhibits very stable chemical durability with a low leaching rate of 1.42 × 10 −8 g m −2 d −1 at 90 °C even after 28 days.
Sihao Wang,Xiaoling Zhang,Yanghai Zheng,Yun Xue,Jingping Wang,Yongde Yan
Zinc Titanate (ZIT) glass-ceramic matrix is a promising candidate for immobilizing radioactive Eu element based on the reactions between Eu and raw material of Zn 2 TiO 4 /CaHPO 4 . However, the generated Eu 2 Ti 2 O 7 ceramic with unstable fluorite defect structure hampers the mechanical properties and chemical durability of ZIT-Eu (ZIT glass-ceramic waste form immobilized with Eu 2 O 3 ). This study addresses the issue by developing the Ce-doping ZIT-Eu waste forms using a solid-phase sintering method at high temperature, realizing the conversion from unstable defective fluorite to stable pyrochlore. As evidenced by the experimental measurements, the density, hardness, water absorption and chemical stability are significantly improved after Ce doping, with the 6 wt% Ce exhibiting the best aqueous durability, retaining a leach value of only 0.11 × 10 −9 g·m −2 ·d −1 at 90 ℃ after 28 days. Furthermore, the density functional theory calculation reveals the potential mechanism that Ce doping decreases the adsorption capability for H 2 O and increases the lattice energy for Eu ion diffusion. In conclusion, this simple doping strategy promotes the application of ZIT glass-ceramic matrix in the field of radioactive waste treatment.
危险品化学品经营许可证（带存储）