Preparation of ThO2 as a structural analogue for nuclear fuel via surfactant-templated sol-gel route

Abstract

Sol-gel synthesis of surfactant-templated nanostructured ceramic materials is usually carried out via controlled hydrolysis and condensation of a starting material in the presence of micelles of a polymer, followed by its removal by extraction or calcination. In this work, surfactant template sol-gel route for the synthesis of thorium dioxide gels using thorium nitrate and octyl phenol ethoxylate polymer as a structure directing agent was described, and the sinterability of the produced ThO2 powder (ThO2-S) was investigated in comparison with commercial one (ThO2-C). Prepared ThO2-S composed of micro and meso pores and exhibited high surface area as 31.23 m2/g and particle size as 15.1 nm. The produced powder ThO2-S was pressed and sintered to form the high density ThO2 pellet. The final grain size of the pellets reached below micrometer size. The calculated green and sintered densities of the fabricated pellets, and their microstructural characteristics studies, utilizing SEM images, show that this synthesizing route yielded a good sinterability of the synthesized ThO2 nanopowder at low temperature. Prepared ThO2-S sample and commercial ThO2 were sintered under the atmospheres “Ar" and “Ar-8%H2, and comparison of data from samples sintered under the both of two different atmospheres at 1500 °C, show that the atmosphere had no effect on density value. Furthermore, the green density of ThO2-S pellets is less than ThO2-C but the pellets which were fabricated from the ThO2-S have reached better sintered density than the pellets fabricated by ThO2-C.