Hollow UO2 Tetrapods via Single-Step Sacrificial Templating Unveiled by In Situ Electron Microscopy

The ongoing global nuclear renaissance and expansion of nuclear power capacity demand advanced materials that enhance fuel performance, improve waste management, and enhance radiation resilience. Research on nuclear nanomaterials could help address such challenges. While uranium dioxide remains the archetypal nuclear fuel, its nanostructured morphologies remain largely unexplored beyond simple particles. Here, the family of nuclear nanomaterials was enlarged by new members, hollow tetrapodal and microtubular uranium dioxides. These nanostructures were formed through sacrificial templating using tetrapodal zinc oxide and a uranyl complex at elevated temperatures in a reducing atmosphere. While the uranyl complex initially decomposed, forming a shell of nanocrystalline UO2 on the template surface, the ZnO tetrapods evaporated at elevated temperature, leaving hollow cavities. Synthesized materials were structurally and chemically analyzed by various techniques. Importantly, the mechanism and reaction conditions of material formation were investigated by advanced in situ imaging. Obtained tetrapodal UO2 delivers low-density voluminous material that could find applications in heat shielding, an expedient sorbent of nuclear waste, or as a structure guiding additive to nuclear fuel forming sinks for fission gases.