Chufei Cheng,Fengnian Zhang,Fuhao Cheng,Jiadong Hou,Bei Ren,Yang Miao,Libiao Xin,Xiaomin Wang
The sintering process of high entropy fluorite oxide ceramics prepared by the conventional solid-phase reaction method suffers from high single-phase synthesis temperature, low densities, and abnormal grain growth . To improve the sintering characteristics of high entropy fluorite oxide ceramics, the oxide mixture was dealt with dielectric barrier discharge plasma-assisted ball milling. The samples were analyzed using XRD , SEM, TEM, TG/DTG, visual high-temperature deformation analyzer, and nanoindentation meter. The results show that the plasma field activates the raw material powder and promotes powder finer. The rapid heating effect of the plasma during the ball milling process causes micro-area sintering and micro-area melting on the powder surface, which increases the active sites of the solid phase reaction of the material, accelerates the mass transfer process, and improves the sintering activity. Compared with conventional ball milling, plasma-assisted ball milling reduces the single-phase synthesis temperature of high entropy ceramics from 1500 °C to 1300 °C. The sintered ceramic pellets have intact grain growth, no noticeable abnormal grain growth, and improved density and mechanical properties .
High-entropy oxides have gained more attention in recent years due to their excellent performance. In this work, five new Ce-free high entropy fluorite oxides ((Zr 0.2 Ti 0.2 Y 0.2 Nd 0.2 Sc 0.2 )O 2-δ , (Zr 0.2 Ti 0.2 Y 0.2 La 0.2 Sc 0.2 )O 2-δ , (Zr 0.2 Ti 0.2 La 0.2 Nd 0.2 Sc 0.2 )O 2-δ , (Zr 0.2 Ti 0.2 Y 0.2 Nd 0.2 La 0.2 )O 2-δ and (Zr 0.2 Ti 0.2 Dy 0.2 Nd 0.2 La 0.2 )O 2-δ ) were successfully synthesized by solution combustion synthesis with glycine as fuel. Their formation, oxygen vacancy, and long-term thermal stability were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques. XRD results show that single fluorite phase was observed in (Zr 0.2 Ti 0.2 Y 0.2 La 0.2 Sc 0.2 )O 2-δ , (Zr 0.2 Ti 0.2 Y 0.2 Nd 0.2 La 0.2 )O 2-δ and (Zr 0.2 Ti 0.2 Dy 0.2 Nd 0.2 La 0.2 )O 2-δ samples when sintering at 300, 600 and 900 °C, respectively, but (Zr 0.2 Ti 0.2 Y 0.2 Nd 0.2 Sc 0.2 )O 2-δ sample with single-phase fluorite structure can only obtain by sintering at 900 °C and 1200 °C. For (Zr 0.2 Ti 0.2 La 0.2 Nd 0.2 Sc 0.2 )O 2-δ sample, single fluorite phase can be obtained at 300 °C using calculated fuel and at 900 °C with using excess fuel. In addition, all the samples may have lower crystallinity due to excess glycine. XPS results indicate that factors of sintering temperature, fuel ratio and cationic radii strongly affect the generation of oxygen vacancy, especially for the sintering temperature. Morphology of the high entropy fluorite oxides presents in sponge-like microstructure. Superior long-term stability at high temperature was found in samples (Zr 0.2 Ti 0.2 Y 0.2 Nd 0.2 Sc 0.2 )O 2-δ and (Zr 0.2 Ti 0.2 Y 0.2 Nd 0.2 La 0.2 )O 2-δ . The findings in this work may have great potential applications in oxygen-deficient catalyst and high temperature catalyst.
危险品化学品经营许可证（带存储）