Synthesis of Metal Oxide Microparticles for Use as Carriers of Intentional Forensic
Signatures

The trafficking of illicit and counterfeit materials is a far-reaching problem with significant economic impacts. The development and commercialization of taggant technologies, which can be introduced intentionally into commodity products to trace fraud or diversion through the rapid determination of commodity provenance, has received considerable interest within the context of forensics as a key deterrence strategy. Among the candidate taggant technologies, engineered microparticles (EμPs) offer a promising route for the introduction of intentional forensic signatures due to their highly uniform and tailorable physical and compositional properties. Taggant EμPs are a promising strategy for identifying the provenance of high consequence commodities such as nuclear material, including reactor fuel. Spray drying-based methods offer a facile and scalable route for the synthesis of EμPs with uniform composition, morphology, and particle size distribution. This work investigates the suitability of aerosol-based methods for the manufacture of taggant EμPs using the Savannah River National Laboratory (SRNL)-developed THermally Evaporated Spray for Engineered Uniform particulateS (THESEUS) system. In this system, uniform droplets of a feedstock solution containing a metal ion of the desired final composition are aerosolized, carried through a tube furnace (up to 1000 °C) for drying and oxide conversion, and collected using an electrostatic precipitator. Metal oxides of early candidate taggants for nuclear fuel (Mo and W) were used as an initial demonstration for the synthesis of taggant EμPs. The uniformity of the generated particles of MoO3 and WO3 were assessed using both in situ aerodynamic particle sizing measurements, as well as ex-situ automated particle analysis using scanning electron microscopy (SEM). The generated particles displayed highly uniform particle size distributions, with geometric standard deviations (σG) below 1.25. The material phase of the generated particles was confirmed using a combination of X-ray diffraction and Raman spectroscopy. This work demonstrates a facile route for the manufacture of particles with tailored physical and chemical properties for potential use as taggants in the nuclear fuel cycle.