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Protection against surface corrosion is essential for ensuring the reliability and long-term durability of uranium materials. Atomically thin two-dimensional (2D) nanomaterials, known for their unique chemical inertness, are particularly promising as anticorrosion coatings. The representative 2D nanomaterials from different classes (insulator, semimetal, semiconductor, and conductor), including BN, graphene, MoSe2, MoS2, and oxygen-passivated Ti2C layers (Ti2CO2 and Ti2CO), were selected to investigate their interactions with the UO2(111) surface using quantum mechanical calculations. Our results show that graphene and h-BN exhibit physical adsorption with the lowest binding energies, less than 1.0 J/m2. In contrast, MoS2 and MoSe2 demonstrate chemical adsorption in the range of 1.0 to 1.5 J/m2. The highest binding energy of 1.7 and 3.1 J/m2 was predicted for Ti2C-based MXenes (Ti2CO2 and Ti2CO, respectively). These results establish the MXene class as the most promising coating for UO2 among the 2D materials considered. It is worth noting that surface defects, whether induced by oxidation or reduction, can influence the strength of the coating, with the primary determinant being the nature of the 2D nanomaterial. [ABSTRACT FROM AUTHOR]

Uranium trichloride (UCl 3 ) has received growing interest for its use in uranium-fueled molten salt reactors and in the pyrochemical processing of used fuel. In this paper, we report for the first time the experimentally determined Raman spectra of UCl 3 , at both ambient condition and in situ high temperatures up to 871 K. The frequencies of five of the Raman-active vibrational modes ( v i ) of UCl 3 exhibit a negative temperature derivative ((∂ν i /∂ T ) P ) with increasing temperature. This red-shift behavior is likely due to the elongation of U-Cl bonds. The average isobaric mode Grüneisen parameter (γ iP = 0.91 ± 0.02) of UCl 3 was determined through use of the coefficient of thermal expansion published in Vogel et al. (2021) and the (∂ν i /∂ T ) P values determined in this study. These results are in general agreement with those calculated here by density functional theory (DFT+ U ). Finally, a comparison of the ambient band positions of UCl 3 to those of isostructural lanthanide (La-Eu) and actinide chlorides (Am-Cf) has been made.

Fundamental understanding of the electronic, chemical, and structural properties of uranium oxides requires the synthesis of high-crystalline-quality epitaxial films of different polymorphs of one material or different phases with various oxygen valence states. We report the growth of single-phase epitaxial UO 2 , α-U 3 O 8 , and α-UO 3 thin films using pulsed laser deposition. Both oxygen partial pressure and substrate temperature play critical roles in determining the crystal structure of the uranium oxide films. X-ray diffraction and Raman spectroscopy demonstrate that the films are single phase with excellent crystallinity and epitaxially grown on a variety of substrates. Chemical valance states and optical properties of epitaxial uranium oxide films are studied by X-ray photoelectron spectroscopy and UV-vis spectroscopy, which further confirm the high-quality stoichiometric phase-pure uranium oxide thin films. Epitaxial UO 2 films show a direct band gap of 2.61 eV, while epitaxial α-U 3 O 8 and α-UO 3 films exhibit indirect band gaps of 1.89 and 2.26 eV, respectively. The ability to grow high-quality epitaxy actinide oxide thin films and to access their different phases and polymorphous will have significant benefits to the future applications in nuclear science and technology.

Group V elemental monolayers including phosphorene are emerging as promising 2D materials with semiconducting electronic properties. Here, we present the results of first-principles calculations on stability, mechanical and electronic properties of 2D antimony (Sb), antimonene. Our calculations show that free-standing α and β allotropes of antimonene are stable and semiconducting. The α-Sb has a puckered structure with two atomic sublayers and β-Sb has a buckled hexagonal lattice. The calculated Raman spectra and STM images have distinct features thus facilitating characterization of both allotropes. The β-Sb has nearly isotropic mechanical properties, whereas α-Sb shows strongly anisotropic characteristics. An indirect-direct band gap transition is expected with moderate tensile strains applied to the monolayers, which opens up the possibility of their applications in optoelectronics.