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Al2O3‐Y2O3‐SiC composite coatings were prepared on depleted uranium by cathode plasma electrolytic deposition in Al(NO3)3, Y(NO3)3, SiC nanoparticles and anhydrous ethyl alcohol mixture. The resulting coating consisted of an inner barrier layer and an outer porous layer. The SiC nanoparticles were incorporated into the composite coating and decreased the coating porosity by filling the pores. The potentiodynamic polarization test and neutral salt spray test revealed that the corrosion resistance of depleted uranium was enhanced by the composite coating. Moreover, with increasing the content of SiC nanoparticles in the coating, the coating corrosion resistance was improved gradually. [ABSTRACT FROM AUTHOR]

Epoxy polymer with damage indicating ability was very usable for ships and bridges to detect the cracks at an early stage and to prevent corrosion. 2′, 7′-dichlorofluorescein (DCF), as a damage indicator, was used to report the mechanical damage of epoxy-amine polymer by a strong color change from a light yellow to bright red due to the molecular structure transition from the acid molecular form to the base ion form. The effect of water on damage indicator and damaged epoxy-amine polymer film was evaluated by an immersion test and the properties were characterized by ultraviolet-visible spectrophotometry (UV-Vis), scanning electronic microscopy (SEM), energy dispersive X-ray spectrometer (EDS), zeta potential and thermal gravimetric analysis (TGA). The results showed that DCF was an easy, stable and permanent indicator for epoxy-amine polymer and the water only had a slight influence on the indication stability of damaged epoxy polymer. [ABSTRACT FROM AUTHOR]

Hydrogen absorption–desorption properties of the UZr0.29 alloy and uranium metal were investigated in detail at hydrogen pressures as high as to 0.4 MPa and over the temperature range of 300–723 K. Both UZr0.29 alloy and uranium metal showed similar hydrogen isotopic effect and hysteresis effect. UZr0.29 alloy absorbed hydrogen (deuterium) up to 2.3H (2.18D) atoms per F.U. (formula unit) by only one-step reaction and hence each desorption isotherm had a single plateau over nearly the whole hydrogen composition range. The UZr0.29 alloy showed a little lower dissociation pressure than that of pure uranium; however, it exhibited high durability against powdering upon hydrogenation and may have good heat conductivity. The UZr0.29 hydride has the potentiality to substitute pure uranium hydride as a material for tritium treatment and storage. [Copyright &y& Elsevier]

Elucidating molecular-level interactions between dihydrogen (H 2 ) and uranium oxides reveals fundamental insights into the intrinsic H 2 activation mechanisms underlying processes such as heterogeneous catalysis over uranium oxides and corrosion of uranium induced by H 2 . Herein, the reactions of H 2 with uranium monoxide (UO) molecules have been investigated via a combination of matrix-isolation infrared spectroscopy and quantum chemical calculations. A side-on bonded H 2 complex, OU(η 2 -H 2 ), is identified at 3733.7 and 800.3 cm -1 . This species is regarded as a crucial intermediate along H 2 activation pathways. Bonding analysis reveals cooperative U(π 5 f /6d ) → H 2 (σ*) π // backdonation and U ← H 2 (σ) σ donation in OU(η 2 -H 2 ) that facilitate the activation of the H 2 moiety. Upon λ > 550 nm photoirradiation, OU(η 2 -H 2 ) isomerizes into H 2 UO, indicating the homolytic H 2 cleavage on UO. Mechanistic details of H 2 adsorption and dissociation on UO molecules have been further elucidated.

Investigations on the reactions of uranium oxide molecules with CO offer new inspiration for the design of promising high-efficiency catalysts for CO activation using actinide materials. Herein, we contribute a combined matrix-isolation infrared spectroscopic and theoretical study of CO oxidation to CO 2 on uranium dioxide (UO 2 ) molecules in solid argon. The reaction intermediate O 2 U(η 1 -CO) is generated spontaneously at the bands of 1893.0, 870.6, and 801.3 cm -1 during codeposition and annealing. Upon the following irradiation, CO 2 is substantially produced by the consumption of O 2 U(η 1 -CO), indicating the catalytic conversion of CO to CO 2 through the intermediate O 2 U(η 1 -CO). In C 18 O isotopic substitution experiments, the yields of 16 OC 18 O convincingly confirm that one of the oxygen atoms in CO 2 derives from UO 2 . The reaction pathways are discussed based on the theoretical and experimental results.

Fundamental investigation of metal-CO interactions is of great importance for the development of high-performance catalysts to CO activation. Herein, a series of side-on bonded mononuclear lanthanide (Ln) oxocarbonyl complexes OLn(η 2 -CO) (Ln = La, Ce, Pr, and Nd) have been prepared and identified in solid argon matrices. The complexes exhibit uncommonly low C-O stretching bands near 1630 cm -1 , indicating remarkable C-O bond activation in these Ln analogues. The η 2 -CO ligand in OLn(η 2 -CO) can be claimed as an anion on the basis of the experimental observations and quantum chemistry investigations, although the CO anion is commonly considered to be unstable with electron auto-detachment. The CO activation in OLn(η 2 -CO) is attributed to the photoinduced intramolecular charge transfer from LnO to CO rather than the generally accepted metal → CO π back-donation, which conforms to the traditional Dewar-Chatt-Duncanson motif. Energy decomposition analysis combined with natural orbitals for chemical valence calculations demonstrates that the bonding between LnO and η 2 -CO arises from the combination of dominant ionic forces (>76%) and normal Lewis "acid-base" interactions. The fundamental findings provide guidelines for the catalyst design of CO activation.

Investigations of the interactions of uranium trioxide (UO 3 ) with other species are expected to provide a new perspective on its reaction and bonding behaviors. Herein, we present a combined matrix-isolation infrared spectroscopy and theoretical study of the geometries, vibrational frequencies, electronic structures, and bonding patterns for a series of dinitrogen (N 2 ) complexes with UO 3 moieties UO 3 (η 1 -NN) 1-4 . The complexes are prepared by reactions of laser-ablated uranium atoms with O 2 /N 2 mixtures or laser-ablated UO 3 molecules with N 2 in solid argon. UO 3 (η 1 -NN) 1-4 are classified as "nonclassical" metal-N 2 complexes with increased Δν(N 2 ) values according to the experimental observations and the computed blue-shifts of N-N stretching frequencies and N-N bond length contractions. Electronic structure analysis suggests that UO 3 (η 1 -NN) 1-4 are σ-only complexes with a total lack of π-back-donation. The energy decomposition analysis combined with natural orbitals for chemical valence calculations reveal that the bonding between the UO 3 moiety and N 2 ligands in UO 3 (η 1 -NN) 1-4 arises from the roughly equal electrostatic attractions and orbital mixings. The inspection of orbital interactions from pairwise contributions indicates that the strongest orbital stabilization comes from the σ-donations of the 4σ*- and 5σ-based ligand molecular orbitals (MOs) into the hybrid 7s/6d x 2 - y 2 MO of the U center. The electron polarization induced by electrostatic effects in the N inner ← N outer direction provides complementary contributions to the orbital stabilization in UO 3 (η 1 -NN) 1-4 . In addition, the reactions of UO 3 with N 2 ligands and the origination of the nonclassical behavior in UO 3 (η 1 -NN) 1-4 are discussed.

Investigations on the structures and bonding properties of metal carbonyl compounds provide fundamental understandings on the origin of small-molecule activations. Herein, the geometry and bonding trends of a series of isovalent metal oxocarbonyl complexes O 2 M(η 1 -CO) (M = Cr, Mo, W, Nd, and U) were studied by combined matrix-isolation infrared spectroscopy and advanced quantum chemical calculations. The title complexes present red shift of C-O stretching bands in the range from 122 to 244 cm -1 , indicating the difference of CO activation ability for the series of isovalent metal dioxides. Density functional theory calculations predict T-shaped structures with a C 2v symmetry for all the title molecules. O 2 Nd(η 1 -CO) bears little resemblance to the other complexes in bonding characters because of the weak interactions between the NdO 2 and CO moiety. For the other complexes, natural localized molecular orbital analysis reveals a gradual increase of covalent character in M-CO bonds along the metal series Cr → Mo → W→ U. Energy decomposition analysis with natural orbitals for chemical valence calculations demonstrates that the M-CO bonding patterns conform to the conventional Dewar-Chatt-Duncanson motif. The contributions from orbital interactions in total attractions increase from Cr (41.7%) to U (52.7%). The breakdown of the orbital term into pairwise interactions shows that contributions of the M ← CO σ donation decrease from Cr (59.2%) to U (28.4%), while the M → CO π* backdonation increases significantly from Cr (23.8%) to U (67.3%). The more effective overlap and the better energy matching of U 5f and U 6d valence orbitals with CO π* orbitals result in much stronger U → CO π backdonation than the other metal elements.

Correction for 'Insights into the enhanced Ce[triple bond, length as m-dash]N triple bond in the HCe[triple bond, length as m-dash]N molecule' by Zhen Pu et al., Phys. Chem. Chem. Phys., 2017, 19, 8216-8222.

Herein, an experimental study of the vibrational spectra of HCeN was carried out in solid argon, followed by theoretical investigations of molecular structures and the nature of Ce[triple bond, length as m-dash]N bond. The absorption band at 937.7 cm -1 with the 1.0311 14 N/ 15 N isotopic shift ratio is characteristic of Ce[triple bond, length as m-dash]N stretching band for HCeN, showing a 94 cm -1 higher shift relative to that of the diatomic CeN molecule. This large frequency shift indicates a much stronger Ce[triple bond, length as m-dash]N bond in HCeN, which is confirmed by DFT calculations. Qualitative orbital interaction and orbital composition analyses suggest that the addition of the H ligand to the Ce center will activate the 4f valence shell and strengthen the covalent bond between Ce and N, which may contribute to enhance the Ce[triple bond, length as m-dash]N triple bond in the HCeN molecule.