Self-propagating synthesis, mechanical property and aqueous durability of Gd2Ti2O7 pyrochlore

Abstract

Synroc is recognized as the second generation waste form for the immobilization of high-level radioactive waste (HLW). In this paper, Gd2Ti2O7/Cu composite was rapidly synthesized by self-propagating high-temperature synthesis plus quick pressing (SHS/QP) using CuO as the oxidant and Ti as the reductant. Different TiO2/Ti ratios were explored to investigate the reactivity of the designed SHS reactions. The result shows that all designed reactions could be ignited and Gd2Ti2O7 pyrochlore was successfully prepared with Cu as the secondary phase. The sample performs an analogous self-encapsulated morphology with Gd2Ti2O7 core and Cu clapping. The synthesized pyrochlore-based waste form possesses high bulk density of 5.53g/cm3 and Vickers hardness of 1047.84 HV0.1. The aqueous durability is also evaluated. There are some fluctuations in the normalized leaching rate of Gd, but it is still acceptable and its average leaching rate is 1.97×10−4gm−2d−1.