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We report a flux crystal growth of Ba2[(UO2)2Ti2O8] and subsequent structural and spectroscopic studies using multiple techniques. The layered crystal structure, built up with sheets of edge‐sharing dimeric uranyl pentagonal bipyramids and dimeric TiO5 square pyramids with interlayer Ba(II) ions, was revealed by synchrotron single crystal x‐ray diffraction and confirmed with electron diffraction using a transmission electron microscope. The presence of only hexavalent uranium was confirmed by both diffuse reflectance and x‐ray absorption near‐edge structure spectroscopies, consistent with the bond valence sum calculations. Its vibrational modes were revealed by Raman spectroscopy. In addition, its implications as a potential hexavalent uranium waste form for the immobilization of uranium‐rich radioactive wastes were discussed. [ABSTRACT FROM AUTHOR]

Abstract: Brannerite‐based glass‐ceramics with relatively high actinide waste loadings are potential waste forms for the immobilization of actinide‐rich radioactive wastes containing process chemicals. In this work, the crystallization of pentavalent uranium brannerite phases in glass with the incorporation of yttrium/cerium/europium has been investigated. The formation of brannerite phases in glass has been confirmed with X‐ray diffraction and Raman spectroscopy. The evolution of microstructures and the development of micro pores in brannerite phases have been revealed by scanning electron microscopy with the nominal formula, Y0.51U0.49Ti2O6, Ce0.65U0.35Ti2O6, and Eu0.53U0.47Ti2O6, being determined with energy‐dispersive spectroscopy. The presence of dominant U5+ species has been proven with both diffuse reflectance spectroscopy and X‐ray absorption near‐edge spectroscopy. In addition, the systematic Raman band shifts with the mean cation radius in the studied brannerite series have been observed and discussed. [ABSTRACT FROM AUTHOR]

Two thorium(Th) complexes with lactate or formate have been synthesized and characterized. Th(C 3 H 5 O 3 ) 4 (H 2 O) 2 ( 1 ) [C 3 H 5 O 3 H = lactic acid] has a mononuclear structure with ten-fold coordinated Th polyhedron in deformed bicapped square antiprism by four chelating lactate ligands via both carboxylate O and the alcohol O atoms in addition to two coordinated water molecules. The lactate ligands are enantiomer with equal proportion of R - and S -isomers. [Th 6 (O) 4 (OH) 4 (HCO 2 ) 12 (H 2 O) 6 ]·5H 2 O ( 2 ) [HCO 2 H = formic acid] is a hexanuclear Th nanocluster constructed by four oxo-, four hydroxyl, twelve μ 2 -bridging formate ligands and six water molecules. The calculated bond valence sums are in good agreement with the presence of equal numbers of oxo- and hydroxyl groups in the cluster. Thermal studies confirmed that both complexes lost water molecules first followed by the decomposition of the organic ligands to form ThO 2 as the final product. The presence of bridging OH-groups in both complexes has been proven by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Two new double thorium oxalates with sodium ions have been prepared and characterized by using scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), Raman spectroscopy and single-crystal X-ray diffraction. The crystal structure of Na4[Th(C2O4)4] ·5.5H2O ( 1) contains infinite chains, [Th(μ2-C2O4)2(C2O4)3] n4 n-, with three terminating bidentate and two bridging tetradentate oxalate ligands. The crystal structure of Na10[Th2(C2O4)9] ·15H2O ( 2) comprises unique dimers, [Th2(μ2-C2O4)(C2O4)8]10-, with Th atoms being coordinated by five oxalato ligands, four terminating bidentate and one bridging tetradentate. The structure is the first dimer of tetravalent actinide oxalato complexes. The spectroscopic results are in good agreement with the crystal structures. [ABSTRACT FROM AUTHOR]

Abstract: Raman spectra of a well-characterized natural brannerite and some synthetic brannerite samples have been collected and analysed. For the first time, all 12 theoretical Raman vibrational modes of CeTi2O6 with brannerite structure have been positively identified by using quantum chemical calculations based on density functional theory (DFT) and assigned to the spectra. For synthetic samples with Y or Ca substitution on the U site and Fe substitution on the Ti site, Y–O, Fe–O and U–O vibrational modes are tentatively assigned. The U–O bond lengths for the uranyl (UO2)2+ groups, have been calculated by using the measured wavenumbers of ν 1 (UO2)2+ symmetric stretching vibrations and compared with the published U–O bond lengths of a natural brannerite. [Copyright &y& Elsevier]

The first tetravalent actinide [thorium(IV) and uranium(IV)] complexes with cucurbit [8] uril have been synthesized via self-assembly in HCl solutions. Supramolecular structures constructed with both direct coordination and second-shell interactions have been revealed and compared to those for lanthanide counterparts. Vibrational modes and the roles of transition metal chloride species as structure inducers have also been investigated and discussed. • The first tetravalent actinide complexes with cucurbit [8] uril have been synthesized. • Supramolecular structures are constructed with both direct coordination and second-shell interactions. • Vibrational modes have been revealed by Raman Spectroscopy. • The roles of transition metal chloride species as structure inducers have been discussed. In this work, we investigated thorium(IV) and uranium(IV) complexes of cucurbit [8] uril {Q[8]} in HCl solutions with the addition of various transition metal chlorides as structure inducers. Consequently, three complexes with similar supramolecular structures built up with both direct coordination and second-shell interactions have been synthesized and structurally characterized. In the presence of CdCl 2 /RuCl 3 , {[ThCl(H 2 O) 6 ] 2 (Q[8])}·(Q[8])·2(CdCl 4)·2Cl·6H 2 O (Q[8] -Th-Cd) or {[Th(H 2 O) 7 ] 2 (Q[8])}·(Q[8])·2(RuCl 5) 2 O·3(HCl)·22H 2 O (Q[8] -Th-Ru) were synthesized while {[U(H 2 O) 7 ] 2 (Q[8])}·(Q[8])·5(ZnCl 4)·8H 2 O (Q[8] -U-Zn) was prepared with U(IV) ions generated in situ by direct reduction of uranyl nitrate with zinc metal. All these complexes have Q[8] directly coordinated to Th(IV)/U(IV) ions, one on each side of the two Q[8] portals in bidentate mode. Subsequent second-shell interactions between (Th 2 -Q[8])/(U 2 -Q[8]) complexes and Q[8] molecules form one-dimensional polymers which are further connected through C H···Cl [Cd/Ru/Zn chloride species] interactions forming extended supramolecular networks. [ABSTRACT FROM AUTHOR]

Three new coordination polymers of uranium(VI) with pyromellitic acid (H 4 btca) have been synthesized and structurally characterized. (ED)[(UO 2 )(btca)]·(DMSO)·3H 2 O ( 1 ) (ED=ethylenediammonium; DMSO=dimethylsulfoxide) has a lamellar structure with intercalation of ED and DMSO. (NH 4 ) 2 [(UO 2 ) 6 O 2 (OH) 6 (btca)]·~6H 2 O ( 2 ) has a 3D framework built from 7-fold coordinated uranyl trinuclear units and btca ligands with 1D diamond-shaped channels (~8.5 Å×~8.6 Å). [(UO 2 ) 2 (H 2 O)(btca)]·4H 2 O ( 3 ) has a 3D network constructed by two types of 7-fold coordinated uranium polyhedron. The unique μ 5 -coordination mode of btca in 3 enables the formation of 1D olive-shaped large channels (~4.5 Å×~19 Å). Vibrational modes, thermal stabilities and fluorescence properties have been investigated. [ABSTRACT FROM AUTHOR]

Abstract: Raman spectra of synthetic non-substituted and U/Np/Pu- substituted thorutite (ThTi2O6) samples were collected. Factor group analysis was used to analyse the possible vibration modes. Theoretical simulations based on density functional theory (DFT) were performed on both CeTi2O6 and ThTi2O6. All possible vibrational modes for thorutite have been identified and assigned to the measured spectra. The presence and the effect of higher valence of U in thorutite has been discussed and the U–O bond lengths have been calculated by using the measured wavenumbers of ν 1 (UO2)2+ symmetric stretching vibrations. The presence of U6+ in uranyl form can be inferred from the wavenumbers of U–O vibrations. Corresponding Np–O and Pu–O vibrations were not observed in the Raman spectra. Thus the presence of Np6+ and Pu6+ in the studied samples was not established. [Copyright &y& Elsevier]

Abstract: Pyrochlore structured Nd2Sn x Zr2−x O7 (x=0–2) ceramics were prepared by a new chemical synthesis route in an aqueous media. Raman spectra and X-ray diffraction patterns confirmed the formation of the pyrochlore structure after sintering at 1400°C. SEM results showed pelletized materials became dense with increasing Zr/Sn mole ratio and sintering temperature. These candidate materials have characteristic structures for the development of nuclear waste forms or inert matrix nuclear fuels. [Copyright &y& Elsevier]

An aqueous solution route was employed to prepare cerium titanate oxide brannerite. Thermal analysis, X-ray diffraction, Raman spectroscopy, transmission and scanning electron spectroscopy, were used to investigate the brannerite structure formation and bulk properties. Mixed metal oxides (TiO 2 , CeO 2 and brannerite CeTi 2 O 6 ) were formed upon calcination at 800 °C for 12 h. The amount of brannerite phase decreased to form the constituent oxides with increasing calcination temperature and only pure TiO 2 and CeO 2 were present after 1200 °C calcination. The brannerite CeTi 2 O 6 phase reformed at 1300 °C, and its relative amount was increased with dwell time. After 48 h calcination at 1300 °C, brannerite with only minor metal oxide impurities (<1%) was observed. The sample melted at 1400 °C which led to the collapse of brannerite back to its constituent oxides. Further, the phase formation was influenced by pelletization of the powders, which may be explained by a molar volume increase during brannerite formation. Attempts to confirm this hypothesis using Pu brannerite were inconclusive. [ABSTRACT FROM AUTHOR]

3C-β SiC was implanted with He and H ions using plasma immersion ion implantation (PIII). Regions of damage were created at various depths by applying a sample stage bias of 5 kV, 10 kV, 20 kV or 30 kV. Raman spectroscopy results indicate that He irradiation leads to more damage compared to H irradiation, as observed via increased disordered C and Si signals, as well as broadening of the SiC peaks. X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS) results indicate significant change to the SiC structure and that surface oxidation has occurred following irradiation, with the degree of change varying dependent on impinging He fluence. The distributions of implanted species were measured using elastic recoil detection analysis. Despite the varying degree and depth of damage created in the SiC by the He ion irradiations, the retained H distribution was observed to not be affected by preceding He implantation. [ABSTRACT FROM AUTHOR]

CVD diamond is irradiated by 5 MeV carbon ions, with each sample held at a different temperature (300–873 K) during irradiations. The defect structures resulting from the irradiations are evident as vacancy, interstitial and amorphous carbon signals in Raman spectra. The observed variation of the full width at half maximum (FWHM) and peak position of the diamond peak suggests that disorder in the diamond lattice is reduced for high temperature irradiations. The dumbbell interstitial signal is reduced for irradiations at 873 K, which suggests this defect is unstable at these temperatures and that interstitials have migrated to crystal surfaces. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy results indicate that damage to the diamond structure at the surface has occurred for room temperature irradiations, however, this structure is at least partially recovered for irradiations performed at 473 K and above. The results suggest that, in a high temperature irradiation environment such as a nuclear fusion device, in situ annealing of radiation-created defects can maintain the diamond structure and prolong the lifetime of diamond components. [ABSTRACT FROM AUTHOR]

The title compound is synthesized in aqueous medium from a mixture of titanium(IV) bis(ammonium lactato)dihydroxide and Ce(NO3)3 (sintering between 800 and 1400 °C). [ABSTRACT FROM AUTHOR]

Two uranyl peroxide nanoclusters with etidronate ligand (L), a U 20 L 10 and a U 26 L 6 , have been synthesized via self-assembly in aqueous solutions and structurally investigated. Two uranyl peroxide nanoclusters with etidronate ligand [L = (PO 3) 2 C(OH)CH 3 ]4−] have been prepared via self-assembly in aqueous solutions and structurally characterized. K 40 [(UO 2) 20 (O 2) 20 L 10 ]· n H 2 O (1) has a barrel-shaped structure constructed by linking two pentagonal and one decagonal uranyl peroxide rings with ten etidronate ligands. K 38 [(UO 2) 26 (O 2) 33 L 6 ]· n H 2 O (2) has a round top and flat bottom structure constructed by linking a double connected pentagonal uranyl peroxide unit (U 8) and a dome-shaped uranyl peroxide unit (U 18) with six etidronate ligands. The presence of uranyl ion, peroxide and etidronate ligands has been confirmed by Raman spectroscopy and the role of K+ counter ions on the formation of such clusters has been examined. [ABSTRACT FROM AUTHOR]