Synthesis of ordered mesoporous uranium dioxide by a nanocasting route

Abstract

Abstract Ordered mesoporous UO2 with 3-D structure (for UO2-KIT-6) and nanowire bundles (for UO2-SBA-15) was synthesized for the first time by a nanocasting route using different ordered mesoporous silica (KIT-6 and SBA-15, respectively) as templates and uranyl nitrate hexahydrate as the metal precursor. The uranyl nitrate was impregnated into the mesopore of the silica template and was converted to U3O8 after the first step. The synthesis of ordered UO2 mesostructure was achieved by reducing the mesoporous U3O8 with silica composites under 5% H2/Ar atmosphere at 700°C, followed by a template removal process. The as-prepared UO2-KIT-6 had a particle size of several millimeters, and was constructed with uncoupled subframework mesostructure and crystalline walls, while UO2-SBA-15 possessed a rope-like morphology and consisted of nanowire arrays. The surface area and pore volume of ordered UO2 mesostructure are 47.2 m2 g−1 and 0.23 cm3 g−1 for the UO2-KIT-6, and 54.4 m2 g−1 and 0.28 cm3 g−1 for the UO2-SBA-15, respectively.