Direct comparisons between statistically sound simulations of ion-tracks and published experimental measurements of range densities of iodine implants in uranium dioxide have been made with implant energies in the range of 100-800 keV. Our simulations are conducted with REED-MD (Rare Event Enhanced Domain-following Molecular Dynamics) in order to account for the materials structure in both single crystalline and polycrystalline experimental samples. We find near-perfect agreement between REED-MD results and experiments for polycrystalline target materials.
A Topotactic Phase Transition in the Uranium Oxide System
University of Bristol（布里斯托大学）；ICSM, Univ Montpellier, CEA, CNRS, ENSCM（蒙彼利埃大学 ICSM 研究所）；Department of Materials, University of Oxford（牛津大学材料系）；Department of Materials Design and Manufacturing, School of Engineering, University of Liverpool（利物浦大学工程学院材料设计与制造系）
At the atomic scale, uranium-plutonium mixed oxides (U,Pu)O_2 are characterized by cationic chemical disorder, which entails that U and Pu cations are randomly distributed on the cation sublattice. In the present work, we study the impact of disorder on point-defect formation energies in (U,Pu)O_2 using interatomic-potential and Density Functional Theory (DFT+U) calculations. We focus on bound Schottky defects (BSD) that are among the most stable defects in these oxides. As a first step, we estimate the distance R_D around the BSD up to which the local chemical environment significantly affect…
A R&D program is developed at the ALTO facility to provide new beams of exotic neutron-rich nuclei, as intense as possible. In the framework of European projects, it has been shown that the use of refractory targets with nanometric structure allows us to obtain beams of nuclei unreachable until now. The first parameter to be controlled in the processing to obtain targets with a homogeneous nanostructure is the grinding of uranium dioxide, down to 100 nm grain size. In this study, dry and wet grinding routes are studied and the powders are analyzed in terms of phase stabilization, specific surf…
A multiphase-field model for simulating the hydrogen-induced multi-spot corrosion on the surface of polycrystalline metals: Application to uranium metal
This paper reports experiments investigating the reaction of H$_{2}$ with uranium metal-oxide bilayers. The bilayers consist of $\leq$ 100 nm of epitaxial $α$-U (grown on a Nb buffer deposited on sapphire) with a UO$_{2}$ overlayer of thicknesses of between 20 and 80 nm. The oxides were made either by depositing via reactive magnetron sputtering, or allowing the uranium metal to oxidise in air at room temperature. The bilayers were exposed to hydrogen, with sample temperatures between 80 and 200 C, and monitored via in-situ x-ray diffraction and complimentary experiments conducted using Scanni…
Mastery of order-disorder processes in highly non-equilibrium nanostructured oxides has significant implications for the development of emerging energy technologies. However, we are presently limited in our ability to quantify and harness these processes at high spatial, chemical, and temporal resolution, particularly in extreme environments. Here we describe the percolation of disorder at the model oxide interface LaMnO$_3$ / SrTiO$_3$, which we visualize during in situ ion irradiation in the transmission electron microscope. We observe the formation of a network of disorder during the initia…
Anisotropic Core-Shell Swift Heavy Ion Tracks in beta-Ga2O3
School of Nuclear Science and Technology, Xi’an Jiaotong University（西安交通大学核科学与技术学院）；Materials Science and Environmental Engineering Unit, Tampere University（坦佩雷大学材料科学与环境工程单元）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；Department of Nuclear Physics, China Institute of Atomic Energy（中国原子能科学研究院核物理系）；Department of Physics and Helsinki Institute of Physics, University of Helsinki（赫尔辛基大学物理系与赫尔辛基物理研究所）；The Hong Kong Microelectronics Research and（香港微电子研究）
The rare-earth-metal-oxide based electronic materials were produced via a conventional mixed-oxide route. Thermal analysis, XRD and SEM were used to follow phase evolution and demonstrate the phase purity. Analytical TEM were used to analyze crystal structural defects and to track the presence of secondary phases, especially at grain boundaries. A crystal structure determination was also performed. Phonon modes were analyzed with FTIR and Raman spectroscopies and correlated with the origin of dielectric permittivity (εr) and radiation losses (tan δ) characteristics. In some compound and mixed …
Transition metal oxides are state-of-the-art materials for catalysing the oxygen evolution reaction (OER), whose slow kinetics currently limit the efficiency of water electrolysis. However, microscale physicochemical heterogeneity between particles, dynamic reactions both in the bulk and at the surface, and an interplay between particle reactivity and electrolyte makes probing the OER challenging. Here, we overcome these limitations by applying state-of-the-art compressive Raman imaging to uncover competing bias-dependent mechanisms for the OER in a solid electrocatalyst, α-Li2IrO3. By spatial…
