Sarah Finkeldei

In a recent manuscript, Lawrence Bright et al (2023 J. Phys.: Condens. Matter 35 175501) reported the resonant inelastic x-ray scattering spectra of U₃O₈, as well as UN. Their goal was to identify electronic multiplets associated with a 5f ¹ configuration with ground state 2 F 5 / 2 . Complete active space self-consistent field with spin–orbit coupling (CASSCF-SOC) predicted that 2 F 5 / 2 transitions should be observable at 190 and 328 meV. However, these energies were not accessible in their experiment. They suggested that the recent inelastic neutron scattering results of Miskowiec et al (2021 Phys. Rev. B 103 205101) could have been sensitive to these transitions. Here we show that transitions of this possible origin appear in that dataset near 198, 262, 362, and potentially 448 meV.

Ruhrstahl Heraeus (RH) degassers are globally used to manufacture vacuum‐treated steel for automotive and railroad applications. The state‐of‐the‐art environment‐friendly chromium‐free alternatives for direct‐bonded magnesia‐chrome refractories used in RH degassers are expensive, and the scientific literature lacks direct correlation between materials chemistry, processing, and functional properties. We have designed a novel spinel‐periclase‐15 wt% ZrO₂ composition containing 14 wt% in situ spinel which exhibited 7.2 MPa hot modulus of rupture (1500℃), exceeding all reported Cr‐free refractories for RH degasser applications. Investigation with scanning electron microscopy coupled with energy dispersive spectroscopy (SEM‐EDS) attributed this improvement to a reduction in interparticle Ca and Si content which forms low‐melting phases, as supported by FactSage thermodynamic simulations. The spinel‐periclase composition SP exhibited superior thermal shock resistance because thermal shock‐induced cracks were stopped by fracture porosity around MgO particles, formed due to thermal expansion mismatch. SEM‐EDS analysis of the SP composition corroded by RH slag at 1650°C revealed that Fe is the most corrosive element followed by Ca and Si. Contradicting the consensus, it was observed that corrosion resistance of fused MgO was better than that of ZrO₂. The cubic ZrO₂ phase reduced FeO_x penetration locally by incorporating CaO from the RH slag into a solid solution and forming a CaZrO₃ phase creating a “slag barrier”. Lastly, pore size was found to greatly exacerbate slag penetration following the Washburn percolation model.

Experimental & theoretical insights into the structural response of complex oxides to dopant elements – the example of plutonium within pyrochlore.

High H₂O₂ exposure leads to an irreversible change in redox reactivity of UO₂ surfaces.