Expedited spark plasma sintering of high‐density uranium mononitride pellet utilizing U<sub>2</sub>N<sub>3</sub> powder

Abstract

The feasibility of a non-stoichiometric synthesis strategy for uranium mononitride (UN) pellet fabrication is experimentally verified with spark plasma sintering of U2N3 powder in this study. The method removes the denitride process (reduction of U2N3 to UN powder) from the conventional UN pellet fabrication, and it still successfully provided near-perfect UN stoichiometry and high density (94 %TD). During the spark plasma sintering of U2N3 powder, vacuum pressure increase and powder height, decrease were concurrently measured above ∼1173 K, which indicates the nitrogen gas emission and higher density UN powder formation from the in-situ decomposition of lower-density U2N3 powder. The X-ray diffraction (XRD) analysis on the sintered pellets obtained directly from U2N3 powder showed an excellent match with the existing XRD reference data of UN. The measured density of U2N3-sintered UN pellets was higher (85 %TD) than that of UN-sintered UN pellets (79 %TD) at relatively low sintering temperature (1773 K). With a higher sintering temperature of 2073 K, high pellet densities (94 %TD) were obtained from both U2N3 and UN powders.