Nano goes nuclear

Uranium dioxide nanocrystals can be made with good size control using a thermal decomposition method

Credit: © 2006 ACS

In its enriched form, uranium dioxide is the major component of nuclear fuel. When depleted of its radioactive isotopes, it is used in a wide range of applications including radiation shielding, radiography and catalysis. Now, Charles Cao and co-workers¹ from the University of Florida in the USA have made nanoparticles of UO₂ by thermally decomposing uranyl acetylacetonate — a compound comprising uranium ions and organic ligands.

This uranium precursor was mixed with two organic compounds — each containing long-chain hydrocarbons — and heated slowly to 150 °C before being cooled back down to room temperature. An amino compound was then added to the mixture before it was heated to 295 °C in an argon atmosphere. Nanocrystals were precipitated from the reaction using a combination of solvents. X-ray-diffraction studies confirmed that the crystals were pure uranium dioxide, and transmission electron microscope images showed them to be spherical and have a very narrow size distribution.

It was found that the size of the nanoparticles could be controlled by changing the ratio of the organic additives in the reaction. This study not only details an efficient method of producing high-quality UO₂ nanocrystals, but also offers further insight into the mechanisms that govern the formation of such materials.