Reaction sequence and kinetics of uranium nitride decomposition.
The reaction mechanism and kinetics of the thermal decomposition of uranium dinitride/uranium sesquinitride to uranium mononitride under inert atmosphere at elevated temperature were studied. An increase in the lattice parameter of the UN(2)/alpha-U(2)N(3) phase was observed as the reaction temperature increased, corresponding to a continuous removal of nitrogen. Electron density calculations for these two compounds using XRD powder patterns of the samples utilizing charge-flipping technique were performed for the first time to visualize the decrease in nitrogen level as a function of temperature. Complete decomposition of UN(2) into alpha-U(2)N(3) at 675 degrees C and the UN formation after a partial decomposition of alpha-U(2)N(3) at 975 degrees C were also identified in this study. The activation energy for the decomposition of the UN(2)/alpha-U(2)N(3) phase into UN, 423.8 +/- 0.3 kJ/mol (101.3 kcal/mol), was determined under an inert argon atmosphere and is reported here experimentally for the first time.
Silva
G W Chinthaka
GW
Harry Reid Center for Environmental Studies, University of Nevada, Las Vegas, Box 454009, 4505 Maryland Parkway, Las Vegas, Nevada 89154, USA.
Yeamans
Charles B
CB
Sattelberger
Alfred P
AP
Hartmann
Thomas
T
Cerefice
Gary S
GS
Czerwinski
Kenneth R
KR