Acceder

Bibliografías temáticas / Actinides – Structure / Artículos de revistas

Siga este enlace para ver otros tipos de publicaciones sobre el tema: Actinides – Structure.

Artículos de revistas sobre el tema "Actinides – Structure"

Autor: Grafiati

Publicado: 1 de junio de 2024

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros

Elija tipo de fuente:

Consulte los 50 mejores artículos de revistas para su investigación sobre el tema "Actinides – Structure".

Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.

También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.

Explore artículos de revistas sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.

1

Saha, Saumitra y Udo Becker. "A first principles study of energetics and electronic structural responses of uranium-based coordination polymers to Np incorporation". Radiochimica Acta 106, n.º 1 (26 de enero de 2018): 1–13. http://dx.doi.org/10.1515/ract-2016-2732.

Texto completo

Resumen

AbstractRecently developed coordination polymers (CPs) and metal organic frameworks (MOFs) may find applications in areas such as catalysis, hydrogen storage, and heavy metal immobilization. Research on the potential application of actinide-based CPs (An-CP/MOFs) is not as advanced as transition metal-based MOFs. In order to modify their structures necessary for optimizing thermodynamic and electronic properties, here, we described how a specific topology of a particular actinide-based CP or MOF responds to the incorporation of other actinides considering their diverse coordination chemistry associated with the multiple valence states and charge-balancing mechanisms. In this study, we apply a recently developed DFT-based method to determine the relative stability of transuranium incorporated CPs in comparison to their uranium counterpart considering both solid and aqueous state sources and sinks to understand the mechanism and energetics of charge-balanced Np5+incorporation into three uranium-based CPs. The calculated Np5++H+incorporation energies for these CPs range from 0.33 to 0.52 eV, depending on the organic linker, when using the solid oxide Np source Np2O5and U sink UO3. Incorporation energies of these CPs using aqueous sources and sinks increase to 2.85–3.14 eV. The thermodynamic and structural analysis in this study aides in determining, why certain MOF topologies and ligands are selective for some actinides and not for others. This means that once this method is extended across a variety of CPs with their respective linker molecules and different actinides, it can be used to identify certain CPs with certain organic ligands being specific for certain actinides. This information can be used to construct CPs for actinide separation. This is the first determination of the electronic structure (band structure, density of states) of these uranium- and transuranium-based CPs which may eventually lead to design CPs with certain optical or catalytic properties. While the reduction of the DFT-determined-bandgap goes from 3.1 eV to 2.4 eV when going from CP1 to CP3, showing the influence of the linker, Np6+incorporation reduces the bandgap for CP1 and CP3, while increasing it for CP2. The coupled substitution of U6+→Np5++H+reduces the bandgap significantly, but only for CP3.

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Nadykto, B. A. "Electronic structure of actinides". Journal of Nuclear Science and Technology 39, sup3 (noviembre de 2002): 221–24. http://dx.doi.org/10.1080/00223131.2002.10875449.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Laatiaoui, Mustapha y Sebastian Raeder. "New Developments in the Production and Research of Actinide Elements". Atoms 10, n.º 2 (8 de junio de 2022): 61. http://dx.doi.org/10.3390/atoms10020061.

Texto completo

Resumen

This article briefly reviews topics related to actinide research discussed at the virtual workshop Atomic Structure of Actinides & Related Topics organized by the University of Mainz, the Helmholtz Institute Mainz, and the GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany, and held on the 26–28 May 2021. It includes references to recent theoretical and experimental work on atomic structure and related topics, such as element production, access to nuclear properties, trace analysis, and medical applications.

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Kwon, Youngjin, Hee-Kyung Kim y Keunhong Jeong. "Assessment of Various Density Functional Theory Methods for Finding Accurate Structures of Actinide Complexes". Molecules 27, n.º 5 (23 de febrero de 2022): 1500. http://dx.doi.org/10.3390/molecules27051500.

Texto completo

Resumen

Density functional theory (DFT) is a widely used computational method for predicting the physical and chemical properties of metals and organometals. As the number of electrons and orbitals in an atom increases, DFT calculations for actinide complexes become more demanding due to increased complexity. Moreover, reasonable levels of theory for calculating the structures of actinide complexes are not extensively studied. In this study, 38 calculations, based on various combinations, were performed on molecules containing two representative actinides to determine the optimal combination for predicting the geometries of actinide complexes. Among the 38 calculations, four optimal combinations were identified and compared with experimental data. The optimal combinations were applied to a more complicated and practical actinide compound, the uranyl complex (UO2(2,2′-(1E,1′E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene)(CH3OH)), for further confirmation. The corresponding optimal calculation combination provides a reasonable level of theory for accurately optimizing the structure of actinide complexes using DFT.

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Silva, Ricardo F., Jorge M. Sampaio, Pedro Amaro, Andreas Flörs, Gabriel Martínez-Pinedo y José P. Marques. "Structure Calculations in Nd III and U III Relevant for Kilonovae Modelling". Atoms 10, n.º 1 (7 de febrero de 2022): 18. http://dx.doi.org/10.3390/atoms10010018.

Texto completo

Resumen

The detection of gravitational waves and electromagnetic signals from the neutron star merger GW170817 has provided evidence that these astrophysical events are sites where the r-process nucleosynthesis operates. The electromagnetic signal, commonly known as kilonova, is powered by the radioactive decay of freshly synthesized nuclei. However, its luminosity, colour and spectra depend on the atomic opacities of the produced elements. In particular, opacities of lanthanides and actinides elements, due to their large density of bound–bound transitions, are fundamental. The current work focuses on atomic structure calculations for lanthanide and actinide ions, which are important in kilonovae modelling of ejecta spectra. Calculations for Nd III and U III, two representative rare-earth ions, were achieved. Our aim is to provide valuable insights for future opacity calculations for all heavy elements. We noticed that the opacity of U III is about an order of magnitude greater than the opacity of Nd III due to a higher density of levels in the case of the actinide.

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Kovács, Attila. "Theoretical Study of Complexes of Tetravalent Actinides with DOTA". Symmetry 14, n.º 11 (18 de noviembre de 2022): 2451. http://dx.doi.org/10.3390/sym14112451.

Texto completo

Resumen

1,4,7,10-Tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (H4DOTA) is a prominent chelating ligand with potential applications in various fields, from radiotherapy to the separation of fission products. The present study explores the stability, structure, and bonding properties of its complexes with tetravalent actinides (An = Th, U, Np, Pu) using density functional theory and relativistic multireference calculations. Neutral complexes prefer to form symmetric (C4) structures with DOTA. The first coordination sphere of the actinide ions is readily saturated by a weakly bonded H2O ligand. The latter ligand reduces the molecular symmetry while exerting only marginal effects on the properties of the parent complex. An-ligand bonding is mainly electrostatic, but there are also significant charge-transfer contributions from DOTA to the An 6d/5f orbitals. The charge-transfer interactions and the covalent character of bonding increase gradually in the order of Th < U < Np < Pu, as indicated by analysis of the electron density distribution using the Quantum Theory of Atoms in Molecules.

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Bai, Li Jun, Ping Qian, Yao Wen Hu y Jiu Li Liu. "Atomistic Study on the Structure and Thermodynamic Properties of Afe₂al₁₀ (A = Th, U)". Advanced Materials Research 261-263 (mayo de 2011): 735–39. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.735.

Texto completo

Resumen

An atomistic study is presented on the phase stability, interatomic distances and lattice parameters of the new actinide intermetallic compounds AFe2Al10(A = Th, U). Calculations are based on a series of interatomic pair potentials related to the actinides and transition metals, which are obtained by lattice inversion method. The cohesive energy of AFe2Al10with two possible structures of YbFe2Al10-type and ThMn12-type are calculated and compared with each other. Calculated lattice parameters of AFe2Al10are found to agree with reports in the literatures. In particular, the phonon densities of states, vibrational entropy and Debye temperature related to dynamic phenomena are evaluated for the first time.

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

Livshits, Tatiana, Sergey Yudintsev, Sergey V. Stefanovsky y Rodney Charles Ewing. "New Actinide Waste Forms with Pyrochlore and Garnet Structures". Advances in Science and Technology 73 (octubre de 2010): 142–47. http://dx.doi.org/10.4028/www.scientific.net/ast.73.142.

Texto completo

Resumen

Cubic oxides with pyrochlore and garnet structures are promising matrices for long-lived actinides immobilization. Their isomorphic capacity with respect to An and REE was determined. To predict the long-term behavior of these matrices under their underground disposal radiation stability of synthetic pyrochlores and garnets was studied. Most of titanate phases have the critical (amorphization) doses close to 0.2 displacements per atom at 298 K. This value is significantly higher for Sn- and Zr-rich pyrochlores. Corrosion behavior of the pyrochlore- and garnet-composed matrices was investigated. The lowest actinides leach rates were observed in water and alkaline solutions most typical for underground waste repositories. Amorphization of the phases has a low influence on their corrosion behavior in solutions. Possibility for joint incorporation of actinides and Tc into zirconate- and titanate-based matrices with the pyrochlore structure is discussed.

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Block, Michael. "Direct mass measurements and ionization potential measurements of the actinides". Radiochimica Acta 107, n.º 9-11 (25 de septiembre de 2019): 821–31. http://dx.doi.org/10.1515/ract-2019-3143.

Texto completo

Resumen

Abstract The precise determination of atomic and nuclear properties such as masses, differential charge radii, nuclear spins, electromagnetic moments and the ionization potential of the actinides has been extended to the late actinides in recent years. In particular, laser spectroscopy and mass spectrometry have reached the region of heavy actinides that can only be produced only at accelerator facilities. The new results provide deeper insight into the impact of relativistic effects on the atomic structure and the evolution of nuclear shell effects around the deformed neutron shell closure at N = 152. All these experimental activities have also opened the door to extend such measurements to the transactinide elements in the near future. This contribution summarizes recent achievements in Penning trap mass spectrometry and laser spectroscopy of the late actinides and addresses future perspectives.

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

PETIT-MAIRE, D., J. PETIAU, G. CALAS y N. JACQUET-FRANCILLON. "LOCAL STRUCTURE AROUND ACTINIDES IN BOROSILICATE GLASSES". Le Journal de Physique Colloques 47, n.º C8 (diciembre de 1986): C8–849—C8–852. http://dx.doi.org/10.1051/jphyscol:19868163.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Carter, Korey P., Jennifer N. Wacker, Kurt F. Smith, Gauthier J. P. Deblonde, Liane M. Moreau, Julian A. Rees, Corwin H. Booth y Rebecca J. Abergel. "In situ beam reduction of Pu(IV) and Bk(IV) as a route to trivalent transuranic coordination complexes with hydroxypyridinone chelators". Journal of Synchrotron Radiation 29, n.º 2 (25 de febrero de 2022): 315–22. http://dx.doi.org/10.1107/s1600577522000200.

Texto completo

Resumen

The solution-state interactions of plutonium and berkelium with the octadentate chelator 3,4,3-LI(1,2-HOPO) (343-HOPO) were investigated and characterized by X-ray absorption spectroscopy, which revealed in situ reductive decomposition of the tetravalent species of both actinide metals to yield Pu(III) and Bk(III) coordination complexes. X-ray absorption near-edge structure (XANES) measurements were the first indication of in situ synchrotron redox chemistry as the Pu threshold and white-line position energies for Pu-343-HOPO were in good agreement with known diagnostic Pu(III) species, whereas Bk-343-HOPO results were found to mirror the XANES behavior of Bk(III)-DTPA. Extended X-ray absorption fine structure results revealed An—OHOPO bond distances of 2.498 (5) and 2.415 (2) Å for Pu and Bk, respectively, which match well with bond distances obtained for trivalent actinides and 343-HOPO via density functional theory calculations. Pu(III)- and Bk(III)-343-HOPO data also provide initial insight into actinide periodicity as they can be compared with previous results with Am(III)-, Cm(III)-, Cf(III)-, and Es(III)-343-HOPO, which indicate there is likely an increase in 5f covalency and heterogeneity across the actinide series.

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Buck, B., A. C. Merchant y S. M. Perez. "Exotic cluster model of band structure in actinides". Journal of Physics G: Nuclear and Particle Physics 25, n.º 4 (1 de enero de 1999): 901–3. http://dx.doi.org/10.1088/0954-3899/25/4/065.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Barbanel', Yu A., G. P. Chudnovskaya, Yu I. Gavrish, R. B. Dushin, V. V. Kolin y V. P. Kotlin. "Spectral-luminescent properties of actinides in elpasolite structure". Journal of Radioanalytical and Nuclear Chemistry Articles 143, n.º 1 (noviembre de 1990): 113–23. http://dx.doi.org/10.1007/bf02117553.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

Adam, Nicole, Michael Trumm, Val C. Smith, Ross T. A. MacGillivray y Petra J. Panak. "Incorporation of transuranium elements: coordination of Cm(iii) to human serum transferrin". Dalton Transactions 47, n.º 41 (2018): 14612–20. http://dx.doi.org/10.1039/c8dt02915f.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Lawson, A. C., J. A. Goldstone, B. Cort, R. J. Martinez, F. A. Vigil, T. G. Zocco, J. W. Richardson y M. H. Mueller. "Structure of ζ-phase plutonium–uranium". Acta Crystallographica Section B Structural Science 52, n.º 1 (1 de febrero de 1996): 32–37. http://dx.doi.org/10.1107/s0108768195006811.

Texto completo

Resumen

The structure of the ζ-phase in the Pu—U system has been determined by neutron powder diffraction. The phase crystallizes in space group R{\bar 3}m with 58 atoms in the primitive unit cell and 10 atoms in the asymmetric unit. The structure is characterized by many short bonds and fits the general pattern of the light actinides. Thermal expansion and elastic data were obtained from the diffraction experiments.

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Dumas, Thomas, Dominique Guillaumont, Philippe Moisy, David K. Shuh, Tolek Tyliszczak, Pier Lorenzo Solari y Christophe Den Auwer. "The electronic structure of f-element Prussian blue analogs determined by soft X-ray absorption spectroscopy". Chemical Communications 54, n.º 86 (2018): 12206–9. http://dx.doi.org/10.1039/c8cc05176c.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Soulet, S., J. Chaumont, C. Sabathier y J.-C. Krupa. "Irradiation-disorder Creation in SrTiO3". Journal of Materials Research 17, n.º 1 (enero de 2002): 9–13. http://dx.doi.org/10.1557/jmr.2002.0003.

Texto completo

Resumen

The chemical durability of crystalline matrices loaded with actinides can be stronglyreduced when α-decays generate enough disorder to induce a crystalline to amorphoustransition. The alpha decay of actinides in SrTiO3 (α-recoils and α-particles) was simulated using Pb and He irradiation. This study shows that the He-ion annealingprocess that operates in some apatitic structure is negligible in SrTiO3 where thedisorder evolution at room temperature has a strong sigmoid dependence on dose. Thedirect-impact/defect-stimulated model, the cascade quenching/epitaxial recrystallizationmodel, and a direct-impact/cascade-overlap model were used to reproduce the SrTiO3-disorder evolution under Pb-ion irradiation.

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

Belkhiri, Lotfi, Boris Le Guennic y Abdou Boucekkine. "DFT Investigations of the Magnetic Properties of Actinide Complexes". Magnetochemistry 5, n.º 1 (17 de febrero de 2019): 15. http://dx.doi.org/10.3390/magnetochemistry5010015.

Texto completo

Resumen

Over the past 25 years, magnetic actinide complexes have been the object of considerable attention, not only at the experimental level, but also at the theoretical one. Such systems are of great interest, owing to the well-known larger spin–orbit coupling for actinide ions, and could exhibit slow relaxation of the magnetization, arising from a large anisotropy barrier, and magnetic hysteresis of purely molecular origin below a given blocking temperature. Furthermore, more diffuse 5f orbitals than lanthanide 4f ones (more covalency) could lead to stronger magnetic super-exchange. On the other hand, the extraordinary experimental challenges of actinide complexes chemistry, because of their rarity and toxicity, afford computational chemistry a particularly valuable role. However, for such a purpose, the use of a multiconfigurational post-Hartree-Fock approach is required, but such an approach is computationally demanding for polymetallic systems—notably for actinide ones—and usually simplified models are considered instead of the actual systems. Thus, Density Functional Theory (DFT) appears as an alternative tool to compute magnetic exchange coupling and to explore the electronic structure and magnetic properties of actinide-containing molecules, especially when the considered systems are very large. In this paper, relevant achievements regarding DFT investigations of the magnetic properties of actinide complexes are surveyed, with particular emphasis on some representative examples that illustrate the subject, including actinides in Single Molecular Magnets (SMMs) and systems featuring metal-metal super-exchange coupling interactions. Examples are drawn from studies that are either entirely computational or are combined experimental/computational investigations in which the latter play a significant role.

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Shneidman, T. M., G. G. Adamian, N. V. Antonenko, R. V. Jolos y Shan-Gui Zhou. "Manifestation of cluster effects in the structure of actinides". EPJ Web of Conferences 107 (2016): 03009. http://dx.doi.org/10.1051/epjconf/201610703009.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Zhang, Mei, M. Vallieres, R. Gilmore, Da Hsuan Feng, Richard W. Hoff y Hong-Zhou Sun. "Structure of the actinides by the interacting boson model". Physical Review C 32, n.º 3 (1 de septiembre de 1985): 1076–79. http://dx.doi.org/10.1103/physrevc.32.1076.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Kalvius, G. M. "5f-Electron structure in light actinides from Mössbauer studies". Hyperfine Interactions 26, n.º 1-4 (noviembre de 1985): 793–816. http://dx.doi.org/10.1007/bf02354639.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Kovács, Attila, Christos Apostolidis y Olaf Walter. "Competing Metal–Ligand Interactions in Tris(cyclopentadienyl)-cyclohexylisonitrile Complexes of Trivalent Actinides and Lanthanides". Molecules 27, n.º 12 (14 de junio de 2022): 3811. http://dx.doi.org/10.3390/molecules27123811.

Texto completo

Resumen

The structure and bonding properties of 16 complexes formed by trivalent f elements (M=U, Np, Pu and lanthanides except for Pm and Pr) with cyclopentadienyl (Cp) and cyclohexylisonitrile (C≡NCy) ligands, (Cp)3M(C≡NCy), were studied by a joint experimental (XRD, NMR) and theoretical (DFT) analysis. For the large La(III) ion, the bis-adduct (Cp)3La(C≡NCy)2 could also be synthesized and characterized. The metal–ligand interactions, focusing on the comparison of the actinides and lanthanides as well as on the competition of the two different ligands for M, were elucidated using the Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) models. The results point to interactions of comparable strengths with the anionic Cp and neutral C≡NCy ligands in the complexes. The structural and bonding properties of the actinide complexes reflect small but characteristic differences with respect to the lanthanide analogues. They include larger ligand-to-metal charge transfers as well as metal–ligand electron-sharing interactions. The most significant experimental marker of these covalent interactions is the C≡N stretching frequency.

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

Sood, P. C. y R. K. Sheline. "First identification of a four-quasiparticle structure in the actinides". Journal of Physics G: Nuclear and Particle Physics 18, n.º 5 (1 de mayo de 1992): L93—L98. http://dx.doi.org/10.1088/0954-3899/18/5/002.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

SZABO, Z., T. TORAISHI, V. VALLET y I. GRENTHE. "Solution coordination chemistry of actinides: Thermodynamics, structure and reaction mechanisms". Coordination Chemistry Reviews 250, n.º 7-8 (abril de 2006): 784–815. http://dx.doi.org/10.1016/j.ccr.2005.10.005.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Edelstein, N. M. "Comparison of the electronic structure of the lanthanides and actinides". Journal of Alloys and Compounds 223, n.º 2 (junio de 1995): 197–203. http://dx.doi.org/10.1016/0925-8388(94)09003-3.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Creff, Gaëlle, Cyril Zurita, Aurélie Jeanson, Georges Carle, Claude Vidaud y Christophe Den Auwer. "What do we know about actinides-proteins interactions?" Radiochimica Acta 107, n.º 9-11 (25 de septiembre de 2019): 993–1009. http://dx.doi.org/10.1515/ract-2019-3120.

Texto completo

Resumen

Abstract Since the early 40s when the first research related to the development of the atomic bomb began for the Manhattan Project, actinides (An) and their association with the use of nuclear energy for civil applications, such as in the generation of electricity, have been a constant source of interest and fear. In 1962, the first Society of Toxicology (SOT), led by H. Hodge, was established at the University of Rochester (USA). It was commissioned as part of the Manhattan Project to assess the impact of nuclear weapons production on workers’ health. As a result of this initiative, the retention and excretion rates of radioactive heavy metals, their physiological impact in the event of acute exposure and their main biological targets were assessed. In this context, the scientific community began to focus on the role of proteins in the transportation and in vivo accumulation of An. The first studies focused on the identification of these proteins. Thereafter, the continuous development of physico-chemical characterization techniques has made it possible to go further and specify the modes of interaction with proteins from both a thermodynamic and structural point of view, as well as from the point of view of their biological activity. This article reviews the work performed in this area since the Manhattan Project. It is divided into three parts: first, the identification of the most affine proteins; second, the study of the affinity and structure of protein-An complexes; and third, the impact of actinide ligation on protein conformation and function.

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Manjunatha, H. C. y K. N. Sridhar. "Pocket formula for nuclear deformations of actinides". Modern Physics Letters A 33, n.º 17 (7 de junio de 2018): 1850096. http://dx.doi.org/10.1142/s0217732318500967.

Texto completo

Resumen

We have formulated a pocket formula for quadrupole [Formula: see text], octupole [Formula: see text], hexadecapole [Formula: see text] and hexacontatetrapole [Formula: see text] deformation of the nuclear ground state of all isotopes of actinide nuclei (89 [Formula: see text] Z [Formula: see text] 103). This formula is first of its kind and produces a nuclear deformation of all isotopes actinide nuclei 89 [Formula: see text] Z [Formula: see text] 103 with simple inputs of Z and A. Hence, this formula is useful in the fields of nuclear physics to study the structure and interaction of nuclei.

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Fábián, Margit y Csaba Araczki. "Development of Glass Matrix for Radioactive Waste Conditioning". Materials Science Forum 885 (febrero de 2017): 48–54. http://dx.doi.org/10.4028/www.scientific.net/msf.885.48.

Texto completo

Resumen

Understanding of the incorporation of actinides in borosilicate matrix used for nuclear waste storage is of a great importance for radioactive waste immobilization. This study carried out on matrix glasses doped respectively with 30wt% UO3 and CeO2, Nd2O3 used for chemical modelling of the actinides. Neutron and X-ray diffraction measurements and Reverse Monte Carlo (RMC) simulations were performed. For several glasses, it was found that the basic network structure consists of tetrahedral SiO4 units and of mixed trigonal BO3 and tetrahedral BO4. The BO3 and BO4 units are linked to SiO4, forming mixed [4]Si-O-[3]B and [4]Si-O-[4]B bond-linkages. From significant second neighbour atomic pair correlations have been revealed that U, Ce, Nd accommodates in both silicate and borate site.

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Wills, J. M. y Olle Eriksson. "Crystal-structure stabilities and electronic structure for the light actinides Th, Pa, and U". Physical Review B 45, n.º 24 (15 de junio de 1992): 13879–90. http://dx.doi.org/10.1103/physrevb.45.13879.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Kratz, Jens-Volker. "Development of nuclear chemistry at Mainz and Darmstadt". Radiochimica Acta 107, n.º 1 (19 de diciembre de 2018): 1–25. http://dx.doi.org/10.1515/ract-2018-2948.

Texto completo

Resumen

Abstract This review describes some key accomplishments of Günter Herrmann such as the establishment of the TRIGA Mark II research reactor at Mainz University, the identification of a large number of very neutron-rich fission products by fast, automated chemical separations, the study of their nuclear structure by spectroscopy with modern detection techniques, and the measurement of fission yields. After getting the nuclear chemistry group, the target laboratory, and the mass separator group established at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, a number of large international collaborations were organized exploring the mechanism of deeply inelastic multi-nucleon transfer reactions in collisions of Xe and U ions with U targets, Ca and U ions with Cm targets, and the search for superheavy elements with chemical separations after these bombardments. After the Chernobyl accident, together with members of the Institute of Physics, a powerful laser technique, the resonance ionization mass spectometry (RIMS) was established for the ultra-trace detection of actinides and long-lived fission products in environmental samples. RIMS was also applied to determine with high precision the first ionization potentials of actinides all the way up to einsteinium. In the late 1980ies, high interest arose in results obtained in fusion-evaporation reactions between light projectiles and heavy actinide targets investigating the chemical properties of transactinide elements (Z≥104). Remarkable was the observation, that their chemical properties deviated from those of their lighter homologs in the Periodic Table because their valence electrons are increasingly influenced by relativistic effects. These chemical results could be reproduced with relativistic quantum-chemical calculations. The present review is selecting and describing examples for fast chemical separations that were successful at the TRIGA Mainz and heavy-ion reaction studies at GSI Darmstadt.

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Yu, Xiaojuan, Jeffrey D. Einkauf, Vyacheslav S. Bryantsev, Michael C. Cheshire, Benjamin J. Reinhart, Jochen Autschbach y Jonathan D. Burns. "Spectroscopic characterization of neptunium(vi), plutonium(vi), americium(vi) and neptunium(v) encapsulated in uranyl nitrate hexahydrate". Physical Chemistry Chemical Physics 23, n.º 23 (2021): 13228–41. http://dx.doi.org/10.1039/d1cp01047f.

Texto completo

Resumen

The solid-state electronic structure of oxidized actinides was probed by co-crystallization of Np(vi), Pu(vi), Am(vi), and Np(v) with UO₂(NO₃)₂·6H₂O. XAS measurements and the solid-state absorption spectra were coupled with theoretical calculations.

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Zhang, F. X., M. Lang, Zhenxian Liu y R. C. Ewing. "Phase stability of some actinides with brannerite structure at high pressures". Journal of Solid State Chemistry 184, n.º 11 (noviembre de 2011): 2834–39. http://dx.doi.org/10.1016/j.jssc.2011.08.022.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Nadykto, B. A. "Instability of the electronic structure of actinides under the high pressure". Journal of Alloys and Compounds 444-445 (octubre de 2007): 145–48. http://dx.doi.org/10.1016/j.jallcom.2006.10.087.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Bullock, J. I. "Structure and Bonding, Vol. 59/60, Actinides-Chemistry and Physical Properties." Polyhedron 5, n.º 3 (enero de 1986): 927. http://dx.doi.org/10.1016/s0277-5387(00)84464-2.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

Das, Tanmoy, Jian-Xin Zhu y Matthias J. Graf. "Self-consistent spin fluctuation spectrum and correlated electronic structure of actinides". Journal of Materials Research 28, n.º 5 (8 de febrero de 2013): 659–72. http://dx.doi.org/10.1557/jmr.2012.423.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

Ioannidis, Ioannis, Ioannis Pashalidis y Michael Arkas. "Actinide Ion (Americium-241 and Uranium-232) Interaction with Hybrid Silica–Hyperbranched Poly(ethylene imine) Nanoparticles and Xerogels". Gels 9, n.º 9 (27 de agosto de 2023): 690. http://dx.doi.org/10.3390/gels9090690.

Texto completo

Resumen

The binding of actinide ions (Am(III) and U(VI)) in aqueous solutions by hybrid silica–hyperbranched poly(ethylene imine) nanoparticles (NPs) and xerogels (XGs) has been studied by means of batch experiments at different pH values (4, 7, and 9) under ambient atmospheric conditions. Both materials present relatively high removal efficiency at pH 4 and pH 7 (>70%) for Am(III) and U(VI). The lower removal efficiency for the nanoparticles is basically associated with the compact structure of the nanoparticles and the lower permeability and access to active amine groups compared to xerogels, and the negative charge of the radionuclide species is formed under alkaline conditions (e.g., UO2(CO3)34− and Am(CO3)2−). Generally, the adsorption process is relatively slow due to the very low radionuclide concentrations used in the study and is basically governed by the actinide diffusion from the aqueous phase to the solid surface. On the other hand, adsorption is favored with increasing temperature, assuming that the reaction is endothermic and entropy-driven, which is associated with increasing randomness at the solid–liquid interphase upon actinide adsorption. To the best of our knowledge, this is the first study on hybrid silica–hyperbranched poly(ethylene imine) nanoparticle and xerogel materials used as adsorbents for americium and uranium at ultra-trace levels. Compared to other adsorbent materials used for binding americium and uranium ions, both materials show far higher binding efficiency. Xerogels could remove both actinides even from seawater by almost 90%, whereas nanoparticles could remove uranium by 80% and americium by 70%. The above, along with their simple derivatization to increase the selectivity towards a specific radionuclide and their easy processing to be included in separation technologies, could make these materials attractive candidates for the treatment of radionuclide/actinide-contaminated water.

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Kerveno, Maëlle, Marc Dupuis, Catalin Borcea, Marian Boromiza, Roberto Capote, Philippe Dessagne, Greg Henning et al. "What can we learn from (n,xnγ) cross sections about reaction mechanism and nuclear structure?" EPJ Web of Conferences 239 (2020): 01023. http://dx.doi.org/10.1051/epjconf/202023901023.

Texto completo

Resumen

Inelastic (n,n') cross section is a key quantity to accurately simulate reactor cores, and its precision was shown to need significant improvements. To bypass the experimental difficulties to detect neutrons from (n,xn) reaction and to discriminate inelastically scattered neutrons from those following the fission process in case of fissile targets, an indirect but yet powerful method is used: the prompt γ-ray spectroscopy. Along this line, our collaboration has developed the GRAPhEME setup, optimized for actinides, at the GELINA facility to measure partial (n,xn γ) cross sections, from which the total (n,xn) cross section can be inferred. (n,xn γ) experiments with actinides are still particularly challenging, as their structure presents a high level density at low energy, and the competing neutron-induced fission reaction contaminates the γ-energy distribution. New precise measurements of the partial (n,xn γ) cross sections provide a stringent test to theoretical model and offer a way to improve them. This is a path to a better determination of the total inelastic scattering cross sections. In this contribution we discuss modeling aspects of the 238U and 182W (n,n' γ) reactions, also measured with GRAPhEME, using the three codes TALYS, EMPIRE and CoH. We will highlight the needed/expected improvements on reaction modeling and nuclear structure input.

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Gouder, T., F. Wastin, J. Rebizant y G. H. Lander. "Understanding Actinides through the Role of 5f Electrons". MRS Bulletin 26, n.º 9 (septiembre de 2001): 684–88. http://dx.doi.org/10.1557/mrs2001.178.

Texto completo

Resumen

Studies of the actinide elements and compounds were (and are) motivated by the need to characterize their structural and thermodynamic properties for the development of nuclear fuels and the treatment of waste, whether it be for long-term storage or ideas involving transmutation in high-powered accelerators. For the most part, tables giving these data exist, although the data for transuranium compounds are rather sparse. A much more difficult task is to understand the data and develop theories that have predictive power in this part of the periodic table. In doing this, however, we are confronted with the extremely complicated electronic structure of the 5f shell and the great paucity of high-quality data on materials containing transuranium isotopes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Andreev, G. B., N. A. Budantseva y A. M. Fedoseev. "Structure and properties of complex chromates of hexavalent actinides with urea molecules". Radiochemistry 57, n.º 5 (septiembre de 2015): 468–74. http://dx.doi.org/10.1134/s1066362215050033.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Wang, Xiaohuan, Yuancheng Teng, Yi Huang, Lang Wu y Pan Zeng. "Synthesis and structure of Ce1−xEuxPO4 solid solutions for minor actinides immobilization". Journal of Nuclear Materials 451, n.º 1-3 (agosto de 2014): 147–52. http://dx.doi.org/10.1016/j.jnucmat.2014.03.049.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Kurazhkovskaya, V. S., D. M. Bykov y A. I. Orlova. "Infrared Spectroscopy and Structure of Trigonal Zirconium Orthophosphates with Lanthanides and Actinides". Journal of Structural Chemistry 45, n.º 6 (noviembre de 2004): 966–73. http://dx.doi.org/10.1007/s10947-005-0087-5.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Matrosov, E. I., E. I. Goryunov, T. V. Baulina, I. B. Goryunova, P. V. Petrovskii y E. E. Nifant’ev. "First complexes of N-diphenylphosphorylureas with actinides and lanthanides: Synthesis and structure". Doklady Chemistry 432, n.º 1 (mayo de 2010): 136–39. http://dx.doi.org/10.1134/s0012500810050058.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Marsh, M. L. y T. E. Albrecht-Schmitt. "Directed evolution of the periodic table: probing the electronic structure of late actinides". Dalton Transactions 46, n.º 29 (2017): 9316–33. http://dx.doi.org/10.1039/c7dt00664k.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

Bisson, J., C. Berthon, L. Berthon, N. Boubals, D. Dubreuil y M. C. Charbonnel. "Effect of the Structure of Amido-polynitrogen Molecules on the Complexation of Actinides". Procedia Chemistry 7 (2012): 13–19. http://dx.doi.org/10.1016/j.proche.2012.10.004.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

Shick, Alexander B., Jindrich Kolorenc, Alexander I. Lichtenstein y Ladislav Havela. "Electronic structure and spectral properties of heavy actinides Pu, Am, Cm and Bk". IOP Conference Series: Materials Science and Engineering 9 (1 de marzo de 2010): 012049. http://dx.doi.org/10.1088/1757-899x/9/1/012049.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Nevolin, Iurii M., Vladimir G. Petrov, Mikhail S. Grigoriev, Alexei A. Averin, Andrey A. Shiryaev, Anna D. Krot, Konstantin I. Maslakov, Yury A. Teterin y Alexander M. Fedoseev. "Crystal Structure of Mixed Np(V)-Ammonium Carbonate". Symmetry 14, n.º 12 (13 de diciembre de 2022): 2634. http://dx.doi.org/10.3390/sym14122634.

Texto completo

Resumen

This work presents details of the synthesis, properties and structure of a novel neptunium carbonate (NH4)[NpO2CO3], a member of the M[AnO2CO3] (M = K, (NH4), Rb, Cs) class of compounds. Carbonates play an important role in the migration of actinides in the environment, and thus are relevant for handling and disposal of radioactive wastes, including spent nuclear fuel and vitrified raffinates. Knowledge of the crystallographic structure of these compounds is important for models of the environmental migration behavior based on thermodynamic descriptions of such chemical processes. (NH4)[NpO2CO3] crystals were obtained during long-term hydrothermal treatment of Np(VI) in aqueous ammonia at 250 °C. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) show that a single-phase sample containing only Np(V) was obtained. Structural features of (NH4)[NpO2CO3] were elucidated from single crystal X-ray diffraction and confirmed by vibrational spectroscopy. The results obtained are of interest both for fundamental radiochemistry and for applied problems of the nuclear fuel cycle.

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

Korobeinikov, Valery V., Valery V. Kolesov y Aleksandr V. Mikhalev. "Comparison of the minor actinide transmutation efficiency in models of a fast neutron uranium-thorium fueled reactor". Nuclear Energy and Technology 8, n.º 1 (18 de marzo de 2022): 49–53. http://dx.doi.org/10.3897/nucet.8.82757.

Texto completo

Resumen

In terms of nuclear raw materials, the issue of involving thorium in the fuel cycle is hardly very relevant. However, in view of the large-scale nuclear power development, the use of thorium seems to be quite natural and reasonable. The substitution of traditional uranium-plutonium fuel for uranium-thorium fuel in fast neutron reactors will significantly reduce the production of minor actinides, which will make it attractive for the transmutation of long-lived radioactive isotopes of americium, curium and neptunium that have already been and are still being accumulated. Due to the absence of uranium-233 in nature, the use of thorium in the nuclear power industry requires a closed fuel cycle. At the initial stage of developing the uranium-thorium cycle, it is proposed to use uranium-235 instead of uranium-233 as nuclear fuel. Studies have been carried out on the transmutation of minor actinides in a fast neutron reactor in which the uranium-thorium cycle is implemented. Several options for the structure of the core of such a reactor have been considered. It has been shown that heterogeneous placement of americium leads to higher rates of its transmutation than homogeneous placement does.

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

Gorden, Anne E. V., G. Szigethy, D. K. Shuh, B. E. F. Tiedemann, J. Xu y K. N. Raymond. "Structural Characterization of a Plutonium Sequestering Agent Complex by Synchrotron X-Ray Diffraction". MRS Proceedings 986 (2006). http://dx.doi.org/10.1557/proc-986-0986-oo08-01.

Texto completo

Resumen

AbstractNew ligands and materials are required that can coordinate, sense, and purify actinides for selective extraction and reduction of toxic, radioactive wastes from the mining and purification of actinides. The similarities in the chemical, biological transport, and distribution properties of Fe(III) and Pu(IV) inspired a biomimetic approach to the development of sequestering agents for actinides. A detailed evaluation of the structure and bonding of actinide coordinating ligands like these is important for the design of new selective ligand systems. Knowing the difficulty with working with the crystals resulting from these ligand systems and safe handling considerations for working with Pu, procedures were developed that utilize the Advanced Light Source of Lawrence Berkeley National Laboratory to determine the solid-state structures of Pu complexes by X-ray diffraction.

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Ioudintseva, Tatiana S. y Soo-Chun Chae. "Formation Rate and Compositions of the Actinide Hosts with Garnet Structure". MRS Proceedings 824 (2004). http://dx.doi.org/10.1557/proc-824-cc8.12.

Texto completo

Resumen

AbstractGarnet phases have been considered as a durable crystalline waste form for hosting actinide. The garnet-structure phases with stoichiometries of Ca2,5Ce0,5Zr2Fe3O12, Ca2CeZrFeFe3O12, and Ca1,5GdCe0,5ZrFeFe3O12 were synthesized through cold pressing and sintering in air and oxygen to determine the optimum parameters for the formation of actinide waste forms. Cerium (Ce) was used as an imitator of plutonium due to its similarity in oxidation state and ionic radii. Gadolinium (Gd) plays a major role as an absorber of neutrons that prevents nuclear chain reaction. It also serves as imitators of the trivalent actinides. Ce-garnet or (Ce,Gd)-garnet is chemically analogous to the garnets with plutonium and/or trivalent actinides. The results of XRD and SEM-EDS examination of the products of experiments reveal that equilibrium state was reached at the temperatures of 1300 °C and 1200 °C for 1 and 5 hours heating, respectively.

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Grandjean, Stephane, Chapelet-Arab Bénédicte, Lemonnier Stéphane, Robisson Anne-Charlotte y Vigier Nicolas. "Innovative Synthesis Methods of Mixed Actinides Compounds with Control of the Composition Homogeneity at a Molecular or Nanometric Scale". MRS Proceedings 893 (2005). http://dx.doi.org/10.1557/proc-0893-jj08-03.

Texto completo

Resumen

AbstractActinides contained in the used nuclear fuel need to be managed in the future fuel cycles for the sustainability of this source of energy. The major ones such as uranium or plutonium are very valuable for energy production within a new fuel. The minor ones such as neptunium, americium or curium are responsible for the long-term radiotoxicity of the ultimate waste if not separated and transmuted within new fuels or dedicated targets. Whatever the choice of management in the present or future, innovative synthesis methods are studied in many research institutions to elaborate new actinides based materials.Innovative concepts for future fuels or transmutation targets focus on mixed actinides or mixed actinide-inert element materials. For their synthesis, wet methods fulfill very useful requirements such as flexibility, compatibility with a hydrometallurgical fuel processing, less dissemination of radioactive dusts during processing, and above all a better accessibility to very homogeneous compounds and interesting nanostructures. When dealing with plutonium or minor actinides, this last characteristic is of great importance in order to avoid the so-called “hot spots” and to limit macroscopic defects in the fuel material.In this communication, experimental results are given to illustrate interesting achievements to control the composition or the structure of mixed actinides compounds at a molecular or at a nanometric scale using co-precipitating techniques or sol-gel methods.The first illustration describes the flexibility of the oxalate ligand to modulate the nanostructure of actinides-based solid precursors and obtain mixed actinides oxide following a thermal treatment of the oxalate precursor. New mixed oxalate structures which present original features such as accepting in the same crystallographic site either a tetravalent actinide or a trivalent one are noticeably detailed. Monocharged cations equilibrate the charge in the 3D structure depending on the molar ratio of trivalent to tetravalent actinides. These oxalate compounds are particularly suitable precursors of oxide solid solutions for various actinides systems.The second illustration deals with the control of inorganic condensation reactions of tri- and tetravalent cations in solution by using suitable ligands with a view to obtaining homogeneous oxy-hydroxyde mixtures. The results obtained using Zr(IV), Y(III) and Am(III) or Nd(III) are quite original: a very stable colloidal sol is obtained at pH 5-6 and a nanostructured mixed oxy-hydroxide phase is formed by adapting the sol-gel transition conditions. The initial interactions between the oxy-hydroxide Zr nanoparticles, the ligand and the trivalent cations at a nanometric scale in the sol give access, after gel formation and thermal treatment, to a crystallized phase (Am-bearing cubic Y-stabilized Zirconia) at comparatively low temperatures.In both cases, the simultaneous co-precipitation or co-gelation of the involved actinides remains a challenge because of the specific properties of each actinide, properties which moreover differ according to various possible oxidation states.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Ofrecemos descuentos en todos los planes premium para autores cuyas obras están incluidas en selecciones literarias temáticas. ¡Contáctenos para obtener un código promocional único!