Characterization of nanocrystalline (Th1?xCex)Oy powders synthesized by co-precipitation process

摘要

Nanocrystalline thoria–ceria (Th1-xCex)Oy powders in a ratio of x = 0.05–0.5 mol% were prepared by a co-precipitation process, which employs thorium and cerium nitrate as thorium and cerium source material, deionized water as solvent and ammonia gas as precipitant. Cerium was used as a simulator for plutonium and the other actinides with a +4 valency. After co-precipitation the aqueous (Th1-xCex)(OH)y · nH2O cakes had been dried at 110 °C, these powders were separately milled in acetone, carbon tetrachloride, n-dodecane, isopropanol and water before and/or after calcination at different temperatures (300–600 °C). DTA-TG, XRD, TEM and BET analyses were performed to characterize the produced powders. Characterization results revealed that the materials were not crystallized, even the temperature reached up to 600 °C. The crystallization of (Th1-xCex)Oy began at about 600 °C. The crystal growth took place between the temperatures 600 °C and 1200 °C. The powders have a range average crystallite sizes from 5 to 115 nm, with a specific surface area from 6 to 111 m2/g depending on the calcination temperature and Ce mol%. In this way the crystallized nano (Th1-xCex)O2 powder with a higher specific surface area is able to be produced to obtain the pellets in very high density.