Vacancy Formation Enthalpy in Polycrystalline Depleted Uranium

16th International Conference on Positron Annihilation

Lund, K.R.^1 ; Lynn, K.G.^1 ; Weber, M.H.^1 ; Okuniewski, M.A.^2

Washington State University, Center for Materials Research, Pullman, WA, United States^1

Idaho National Laboratory, Idaho Falls, ID, United States^2

关键词: Beam energies;    Depleted uranium;    Doppler broadening data;    Heat cycle;    Heat profiles;    Oxygen diffusion;    Polycrystalline;    Vacancy formation;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/443/1/012021/pdf
DOI  :  10.1088/1742-6596/443/1/012021

来源: IOP

【 摘 要 】

Positron Annihilation Spectroscopy was performed as a function of temperature and beam energy on polycrystalline depleted uranium (DU) foil. Samples were run with varying heat profiles all starting at room temperature. While collecting Doppler-Broadening data, the temperature of the sample was cycled several times. The first heat cycle shows an increasing S-parameter near temperatures of 400K to 500K much lower than the first phase transition of 941K indicating increasing vacancies possibly due to oxygen diffusion from the bulk to the surface. Vacancy formation enthalpies were calculated fitting a model to the data to be 1.6± 0.16 eV. Results are compared to previous work [3,4].