Synthesis, Characterization and sintering of nanocrystalline (U1-yCey)O2±x

Abstract

Nanocrystalline solid solutions of (U1-yCey)O2±x [y = 0.15, 0.22, 0.28, 0.35] have been synthesized by citrate gel-combustion route with a fuel to oxidant ratio of 1. The “as prepared” powders were calcined at 873 K in air for 6 h and were consolidated into pellets at 220 MPa. These green pellets were reduced at 1073 K under flowing hydrogen for 8 h and were sintered at 1873 K under flowing Ar+8% H2 for 6 h. All these powders were characterized for their X-ray crystallite size (XCS), specific surface area (SSA), particle size distribution (PSD), porosity, bulk density (BD) and residual carbon (RC). The morphology and microstructures of these powders were studied by using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM), respectively. The Hall–Williamson analysis of the X-ray diffraction (XRD) data revealed that the “as-prepared” powders consist of nano grains with a size of about 10 to 20 nm and the results have been substantiated by bright field HRTEM image analysis of these samples. These sintered pellets were characterized for their phase composition, density and microstructure. Presence of a single phase fluorite solid solution was confirmed by XRD. A sintered density of 95.88±0.62% of theoretical density (TD) could be achieved. A systematic study on the gel-combustion synthesis of nanocrystalline (U1-yCey)O2±x [y = 0.15, 0.22, 0.28, 0.35] powders is being reported for the first time.