Symposium Organizers
Brandon Chung Lawrence Livermore National Laboratory
Thomas Albrecht-Schmitt Auburn University
Thomas Gouder Institute for Transuranium Elements
David Shuh Lawrence Berkeley National Laboratory
Joe Thompson Los Alamos National Laboratory
Symposium Support
Lawrence Berkeley National Laboratory
Lawrence Livermore National Laboratory
Los Alamos National Laboratory
The Actinide Steering Committee (LLNL)
NN1: Phase Transformation and Metallurgy
Session Chairs
Tuesday PM, March 25, 2008
Room 2014 (Moscone West)
9:30 AM - **NN1.1
Low-Temperature Martensitic and Pressure-Induced δ to α’ Phase Transformations in a Pu-Ga Alloy.
Adam Schwartz 1 , Mark Wall 2 , Daniel Farber 2 , Kevin Moore 2 , Kerri Blobaum 2
1 Physical Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Chemistry, Materials, Energy, and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractWell-homogenized Pu-2 at.% Ga alloys can be retained in the metastable face centered cubic δ phase at room temperature. Ultimately, this metastable δ phase will decompose via a eutectoid transformation to the thermodynamically stable monoclinic α phase and the intermetallic compound Pu3Ga over a period of approximately 10,000 years. In addition, these low solute-containing δ-phase Pu alloys are also metastable with respect to low temperature excursions or increases in pressure. δ-phase alloys are known to undergo an incomplete isothermal martensitic phase transformation that results in a microstructure consisting of ~20 μm long lath-shaped particles of the α’ phase dispersed within the δ matrix. The ~20% volume contraction between the δ and α’ phases requires significant elastic and plastic accommodation. Transmission electron microscopy (TEM) has shown that the dislocation density in the vicinity of the tips of the α’ particles is about an order of magnitude larger than in the δ-phase matrix. The δ-phase will also transform to the monoclinic α’ phase at slightly elevated pressure. In this study, δ-phase Pu-Ga specimens, 2.3 mm diameter by 100 microns thick were compressed to approximately 1 GPa in a large volume moissanite anvil cell to induce the transformation to α’. The recovered samples were characterized at ambient pressure with optical microscopy, x-ray diffraction, and transmission electron microscopy. Optical microscopy revealed a very fine microstructure that appears to be single phase. This preliminary conclusion was supported by x-ray diffraction, which showed the monoclinic reflections from the α’ phase and weak reflections from the δ-phase. TEM and electron diffraction revealed small regions of δ phase with a very high dislocation density interspersed between the 10 – 100 nm α’ grains and no evidence of an amorphous phase.This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
10:00 AM - **NN1.2
Unusual Electronic Phase Transitions of f-Electron Metals at High Pressures.
Choong-Shik Yoo 1
1 Department of Chemistry, Washington State University, Pullman, Washington, United States
Show Abstract10:45 AM - NN1.4
High Pressure Phase Transformations in Heavy Rare Earth Metals and Connections to Actinide Crystal Structures.
Yogesh Vohra 1 , Kevin Hope 2 , Andrew Stemshorn 1
1 Physics, University of Alabama at Birmingham (UAB), Birmingham, Alabama, United States, 2 Biology, Chemistry, and Mathematics, University of Montevallo, Montevallo, Alabama, United States
Show AbstractHeavy rare earth metals Terbium (Tb) and Holmium (Ho) have been studied at synchrotron sources using both angular and energy dispersive x-ray diffraction to a maximum pressure of 155 GPa and 135 GPa respectively. The complete regular trivalent rare earth structural sequence, hcp to α-Sm to dhcp to fcc to distorted-fcc (hR24), is observed at low pressures except for the undistorted fcc. The low pressure phase transformations below 50 GPa are due to the well established s-band to d-band electronic transfer under high pressures. Additional phase transformations are observed at extreme compressions above 50 GPa resulting in low symmetry crystal structures. These low symmetry crystal structures are attributed to 4-f shell delocalization and a comparison is made to the light actinide crystal structures at ambient conditions as well as crystal structures observed in heavy actinides under high pressures. We will also present pressure-volume (P-V) equation of state of the two heavy rare earth metals to extreme pressures at ambient temperature.This material is based upon work supported by the Department of Energy (DOE) – National Nuclear Security Administration (NNSA) under Grant No. DE-FG52-06NA26168.
11:30 AM - **NN1.5
Influence of Radiation Damage in Pu(Am) Alloys.
Scott McCall 1 , Michael Fluss 1 , Brandon Chung 1 , Richard Haire 2
1 , LLNL, Livermore, California, United States, 2 , ORNL, Oak Ridge, Tennessee, United States
Show AbstractPlutonium and its alloys are known to be extremely sensitive to perturbations, particularly disorder. One method to add disorder is through the radioactive decay of Pu which produces a 5 MeV α-particle and corresponding 86 Kev U recoil that create a large number of vacancies and interstitials, of which a substantial fraction remain frozen in place at low temperatures. Disorder from self-damage increases with time and is observable through magnetic susceptibility measurements, where Curie Weiss behavior evolves and thus demonstrates the creation of local magnetic moments. These emergent moments may be removed by thermal annealing, proving they arise from the disorder created by vacancies and interstitials. Another method of adding disorder is to alloy plutonium with americium, Pu1-xAmx, which forms a stable fcc phase (δ-Pu, β-Am) from 0.06 < x < 0.80 where the lattice parameter increases with x. The electronic structure of americium is 5f6, thus it has a J=0 ground state and its magnetic susceptibility is primarily due to a Van Vleck contribution. This is a single ion effect that should be largely independent of the local environment and thus insensitive to the effects of radiation damage. Radiation damage studies on Pu1-xAmx alloys thus allow investigation of how inherent chemical disorder influences the behavior of the plutonium electrons and their sensitivity to additional disorder. Results of radiation damage measurements on a series of Pu1-xAmx (0.18 < x < 0.29) alloys will be presented and discussed. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
12:00 PM - NN1.6
Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. % Ga.
Jason Jeffries 1 , Kerri Blobaum 1 , Mark Wall 1 , Adam Schwartz 1
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractThe gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable delta phase to the gallium-containing, monoclinic alpha-prime phase near -120 °C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation (TTT) diagram, where two nose temperatures anchoring an upper- and lower-C describe minima in the time for the initiation of transformation. The underlying mechanisms responsible for the double-C behavior are currently unresolved, although recent experiments suggest that a conditioning treatment—wherein, following an anneal, the sample is held at a sub-anneal temperature for a period of time—significantly influences the upper-C of the TTT diagram. As such, elucidating the effects of the conditioning treatment upon the delta/alpha-prime transformation can provide valuable insights into the fundamental mechanisms governing the double-C kinetics of the transition. Following a high-temperature anneal, a differential scanning calorimeter (DSC) is used to establish an optimal conditioning curve that depicts the amount of alpha-prime formed during the transformation as a function of conditioning temperature for a specified time. With the optimal conditioning curve as a baseline, the DSC will be used to explore the circumstances under which the effects of the conditioning treatment can be destroyed, which would result in little or no transformation in the region of the upper-C. The results will be discussed as they pertain to radiation damage, nucleation, embryo formation, or phase-field stability.This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
12:15 PM - NN1.7
Enabling the Upper-C Curve in Pu-Ga Alloy TTT Diagrams.
Kerri Blobaum 1 , Jason Jeffries 1 , Mark Wall 1 , Adam Schwartz 2
1 Chemistry, Materials, Earth, and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Physical Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show Abstract12:30 PM - NN1.8
Solute Diffusion and Self-Irradiation Damage in δ-phase Pu-Ga Alloys.
Franz Freibert 1 , Tarik Saleh 1 , Albert Migliori 1 , Jeremy Mitchell 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract12:45 PM - NN1.9
Resonant Ultrasound Spectroscopy Studies of Alpha and Delta Phase Plutonium Alloys.
Tarik Saleh 1 , Albert Migliori 2 , Franz Freibert 1
1 Materals Science and Technology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractResonant ultrasound spectroscopy (RUS) is a powerful non destructive technique for measuring the elastic moduli of regular specimens. In combination with immersion density, dilatometry, and differential scanning calorimetry, RUS is used in the Nuclear Materials Science Group at Los Alamos National Laboratory to assess the properties and phases of small plutonium samples. This talk will present the elastic moduli of alpha and delta phase plutonium alloys measured as a part of the R&D efforts at LANL. A brief overview of the experimental technique of RUS as it applies to plutonium will be presented. Sample quality, age, density and alloy content will be compared to the mechanical properties of plutonium alloys measured using this technique. Correlation between RUS derived moduli and varying sample state evidenced by density and solute segregation will also be discussed.
Symposium Organizers
Brandon Chung Lawrence Livermore National Laboratory
Thomas Albrecht-Schmitt Auburn University
Thomas Gouder Institute for Transuranium Elements
David Shuh Lawrence Berkeley National Laboratory
Joe Thompson Los Alamos National Laboratory
NN7: Poster Session: Actinides
Session Chairs
Thursday PM, March 27, 2008
Salon Level (Marriott)
9:00 PM - NN7.1
Soft X-ray Studies of Pu Electronic Structure: Past Lessons and Future Directions.
James Tobin 1 , Sung Woo Yu 1
1 , LLNS-LLC, Livermore, California, United States
Show AbstractPhotoelectron Spectroscopy [1] and X-ray Absorption Spectroscopy [2-4] have contributed greatly to our improved understanding of Pu electronic structure. From these and related measurements, the following has been determined.1.The Pu 5f spin-orbit splitting is large.2.The number of Pu5f electrons is 5.3.The Pu 5f spin-orbit splitting effect dominates 5f itineracy.Significant questions remain concerning the nature of Pu electronic structure. Perhaps the missing piece of the puzzle is the direct experimental determination of the unoccupied electronic structure using high energy inverse photoelectron spectroscopy or Bremstrahlung Isochromat Spectroscopy (BIS). [5] Past BIS studies of Th and U indicate the feasibility and utility of Pu studies. [6]To this end, a new BIS capability has been developed in our laboratory. [7] Electron stimulated emission of photons has been carried out using the XES-350 monochromator and detector system. Our preliminary results and future plans will be presented.Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. Work that was performed by LLNL and UMR personnel was supported in part by the Office of Basic Energy Science at the U.S Department of Energy.1.J.G. Tobin et al, Phys. Rev. B 68, 155109 (2003).2.K.T. Moore et al , Phys. Rev. Lett. 90, 196404 (2003).3.G. van der Laan et al, Phys. Rev. Lett. 93, 097401 (2004).4.J.G. Tobin et al, Phys. Rev. B 72, 085109 (2005).5.J.G. Tobin, M.T. Butterfield, N.E. Teslich Jr., R.A. Bliss, M.A. Wall, A.K. McMahan, B.W. Chung and A.J. Schwartz, “Using Nano-focussed Bremstrahlung Isochromat Spectroscopy (nBIS) to Determine the Unoccupied Electronic Structure of Pu,” in “Recent Advances in Actinide Science,” Royal Society of Chemistry, ed. R. Alvarez, N.D. Bryan and I. May, page 773 (2006).6.Y. Baer and J.K. Lang, Phys. Rev B 21, 2060 (1980).7.J.G. Tobin, S.W. Yu, T. Komesu, B.W. Chung, S.A. Morton and G.D. Waddill. MRS Symp. Proc. 986, 63 (2007), Document # 0986-OO01-08.
9:00 PM - NN7.10
FT-IR Spectroscopy Study of Corrosion Mechanisms of Actinides Alloys.
Veronique Magnien 1 , Marx Cadignan 1 , Olivier Faivret 1 , Gaelle Rosa 1
1 , CEA VALDUC, Is sur Tille France
Show AbstractThe study of corrosion reactions is important for numerous industrial or fundamental fields as obviously metallurgy or nuclear industry. Indeed significant degradation of actinides could result from the corrosion of those materials during their storage. Due to this degradation, a rupture of storage containers and a nuclear material release could occur. Thus a significant amount of work has been done to understand corrosion kinetics and mechanisms as illustrated for the oxidation of Pu in air or in moisted atmospheres [1, 2]. Nevertheless those results require to be completed by further investigations in various experimental conditions and especially various atmospheres. Moreover corrosion reactions are relatively complex because they involve as well some adsorption at metal surface and reaction in gaseous atmosphere. So our experimental approach is to couple atmosphere and surface analyses during the corrosion of actinides alloys to get information on kinetics and mechanisms as rate-limiting steps, intermediate reactions and species.Fourier Transform Infrared Spectroscopy, which allows the characterization of gas, liquid or solid phases, has shown its ability in atmosphere [1, 3] and adsorption processes [4-6] analysis. Thus in this work, we propose to perform coupled investigations of corrosion reactions by FT-IR spectroscopy. So the first step of our experimental approach is focused on gas analysis and calibration of FT-IR method to obtain quantitative determination of atmosphere. Preliminary investigations have shown a significant reproducible increase of the most significant peak areas with gas concentration and clearly highlighted that a precise calibration of IR method will be achievable for gas concentration estimation [7]. A more straightforward analysis of gas spectra and absorbency versus concentration evolution in agreement with vibration theory has been performed in order to define a suitable integration process of IR data. According to these bases, calibration area-concentration curves have been drawn for several pure gases (CH4, CO2, H2, CO,….) and binary mixes and should be extended to ternary mixtures. From these calibration curves, gaseous phases proportions could then be estimated in situ during actinides corrosion. [1] Haschke et al., 1998. J. Alloys Comp., 271-273, 211-215 .[2] Haschke et al., 1996. J. Alloys Comp., 243, 23-35.[3] Xian-Yong L. et al., 2005. Proc. SPIE vol 5640, 219-226, Ed by Haimei Gong, Yi Cai and J.P Chatard, Bellingham, WA.[4] Solymosi F. and Zakar T.S., 2005. J. Mol. Catalysis A: Chemical, 235, 260-266. [5] Li et al., 1989. J. Chem. Soc. Faraday. Trans., 1, 85 (4), 929.[6] Colmenares C., 1974. J. Phys. Chem., 78, 21, 2117-2122.[7] Magnien et al., 2007. Surf. Interface Analysis, submitted.
9:00 PM - NN7.11
Multi Scale Study of Self-irradiation Effects in Plutonium Alloys.
Lilian Berlu 1 , Gerald Jomard 2 , Gaelle Rosa 1
1 , CEA-centre de Valduc, Is sur Tille France, 2 , CEA-Bruyères le Châtel, Bruyères le Châtel France
Show Abstract9:00 PM - NN7.12
A Modelling Study of Gas Radiolytic Decomposition by Actinides Materials.
Lilian Berlu 1 , Gaelle Rosa 1
1 , CEA-centre de Valduc, Is sur Tille France
Show Abstract9:00 PM - NN7.13
Uranium Complexes Supported by Redox Active Ligands: Electronic Structure, Bonding and Reactivity.
Eric Schelter 1 , Brian Scott 1 , Joe Thompson 1 , David Morris 1 , Jaqueline Kiplinger 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract9:00 PM - NN7.14
Analytical Model of Defect Configurational Entropy of PuO2-x and CeO2-x.
Petrica Cristea 1 , Marius Stan 2
1 Faculty of Physics, University of Bucharest, Bucharest - Magurele Romania, 2 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract9:00 PM - NN7.15
Stability of Uranophane, Soddyite, Sodium Weeksite and Sodium Boltwoodite in the Presence of Hydrogen Peroxide.
Karrie-Ann Kubatko 1 , Alex Burum 1
1 Geological Sciences, University of Miami, Coral Gables, Florida, United States
Show Abstract9:00 PM - NN7.16
Actinide Sample Preparation for Materials Science, Chemistry and Physics.
Mark Wall 1 , Jessee Welch 1 , Adam Schwartz 1 , Michael Fluss 1
1 CMLES, LLNL, Livermore, California, United States
Show Abstract9:00 PM - NN7.17
Thermodynamics of Actinide Alloys: Results and Challenges.
Patrice Turchi 1
1 CMELS Directorate (L-352), LLNL, Livermore, California, United States
Show Abstract9:00 PM - NN7.18
Systematic Evaluation of the Ammonium-actinide-fluoride System.
G. W. Chinthaka Silva 1 , Garry Cerefice 1 , Ken Czerwinski 1
1 Harry Reid center for Environmental Studies, University of Nevada, Las Vegas, Las Vegas, Nevada, United States
Show Abstract9:00 PM - NN7.19
Search for Charge Density Waves in α-Np and α-Pu.
Martin Butterfield 1 , Mark Wall 1 , Kevin Moore 1
1 Chemistry and Matrials Science, Lawrence Livermore Nationa Labs, Livermore, California, United States
Show Abstract9:00 PM - NN7.2
The Utilization of Spin Polarized Photoelectron Spectroscopy as a Probe of Electron Correlation with an Ultimate Goal of Pu.
James Tobin 1 , Sung Woo Yu 1 , Brandon Chung 1 , Simon Morton 2 1 3 , Takashi Komesu 3 , G. Waddill 3
1 , LLNS-LLC, Livermore, California, United States, 2 , LBNL, Berkeley, California, United States, 3 , University of Missouri, Rolla, Missouri, United States
Show AbstractWe are developing the technique of spin-polarized photoelectron spectroscopy as a probe of electron correlation with the ultimate goal of resolving the Pu electronic structure controversy. Over the last several years, we have demonstrated the utility of spin polarized photoelectron spectroscopy for determining the fine details of the electronic structure in complex systems such as the proposed half-metallic ferro-magnet Fe3O4 [2], the 2p core levels of ultra-thin films such as Fe [3], the valence states of Fe/GaAs [4], and the non-magnetic systems Ce [5-7] and Pt [8]. Various recent publications have addressed the ongoing question of the nature of the Pu electronic structure. [9,10] One possibility is the existence of a Kondo-like shielding of the 5f electrons. [1] We propose that spin resolved PES is the most promising approach to resolving this question. [7,11] Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. Work that was performed by LLNL and UMR personnel was supported in part by the Office of Basic Energy Science at the U.S Department of Energy.*Present Address, Spring8 Synchrotron Radiation Facility, Japan1.J.H. Shim, K. Haule and G. Kotliar, Nature 446, 513 (2007).2.J.G. Tobin, S.A. Morton, S.W. Yu, G.D. Waddill, I.K. Schuller, and S.A. Chambers, J. Phys. Condens. Matter 19, 315218 (2007).3.T. Komesu, G.D. Waddill, S.-W. Yu, M. Butterfield, and J.G. Tobin, “Spin-Orbit Effects in Spin-Resolved L2,3 Core Level Photoemission of 3d Ferromagnetic Thin Films,” under preparation.4.J.G. Tobin, S.A. Morton, S.W. Yu, T. Komesu, G.D. Waddill and P. Boyd, Nuclear Instrum. Methods A, in press 2007; J. D. W. Thompson, J. R. Neal, T. H. Shen, S. A. Morton, J. G. Tobin, G. D. Waddill, J.A.D. Matthew, D. Greig, and M. Hopkinson, submitted to PRB, 2007.5.S.W. Yu et al, Phys. Rev. B 73, 075116 (2006).6.J.G. Tobin, S.A. Morton, B.W. Chung, S.W. Yu and G.D. Waddill, Physica B 378-380, 925 (2006).7.J.G. Tobin, S.W. Yu, T. Komesu, B.W. Chung, S.A. Morton, and G.D. Waddill, Europhysics Lett., 77, 17004 (2007).8.S.-W. Yu and J.G. Tobin, Surface Science Letters, 2007, in press.9.J.G. Tobin et al, Phys. Rev. B 68, 155109 (2003).10.J.G. Tobin et al, Phys. Rev. B 72, 085109 (2005).11.J.G. Tobin, J. Alloys Cmpds 444-445, 154 (2007).
9:00 PM - NN7.20
Direct Energy Conversion Nano-hybrid Fuel.
Liviu Popa-Simil 1 , Claudiu Muntele 2
1 , LAVM LLC, Los Alamos, New Mexico, United States, 2 , CIM_AAMURI, Huntsville, Alabama, United States
Show Abstract9:00 PM - NN7.21
Recoil Based Fuel Breeding Fuel Structure.
Liviu Popa-Simil 1 , Claudiu Muntele 2
1 , LAVM LLC, Los Alamos, New Mexico, United States, 2 , CIM_AAMURI, Huntsville, Alabama, United States
Show Abstract9:00 PM - NN7.22
Influence of Lattice Expansion on the 5f electrons in Pu(Am).
Michael Fluss 1 , Scott McCall 1 , Brandon Chung 1 , Richard Haire 2
1 , LLNL, Livermore, California, United States, 2 , ORNL, Oak Ridge, Tennessee, United States
Show Abstract9:00 PM - NN7.23
Optical Properties Of Single Crystalline UO2 Determined By Ellipsometric Spectroscopy.
Wigbert Siekhaus 1
1 , LLNL, Livermore, California, United States
Show Abstract9:00 PM - NN7.3
Adsorption of Uraniumm(VI) on Silica Particles Modified with Functional Groups.
Naofumi Kozai 1 , Yoshinori Suzuki 1 , Takuya Nankawa 1 , Fuminori Sakamoto 1 , Toshihiko Ohnuki 1 , Arokiasamy Francis 2
1 Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki Japan, 2 Environmental Sciences Department, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractOne of the biomolecules at the cell surface of bacteria to bind uranium is protein. To clarify adsorption mechanism of uranium on protein, this study investigated the adsorption of uranium (VI) on silica particles modified with functional groups since functional groups have been considered as the adsorption site of protein. Unmodified silica particles (Si-OH) and the silica particles on which the following functional group, -COOH, -NH2, or -OPO3H2, was fixed were used. These silica particles were about 15µm in diameter. Carboxyl and phosphate groups were fixed on silica particles by amide binding with the amino groups preliminarily fixed on the silica particles. Each silica sample was dispersed in a 4x10-6 M uranium (VI) solution in a centrifuge tube to have a solid to liquid ratio of 4g/L. After standing for 4 h at 25 oC, the liquid phase was collected by centrifugation at 6000 rpm for 10 min. The uranium concentration in the supernatant was determined with a liquid scintillation analyzer. The densities of the functional groups on silica particles were estimated by acid-base titration. The results of the titration and the uranium adsorption were fitted with the computer program, FITEQL.As for the carboxyl group-modified particles, the density of the proton-dissociable carboxyl groups was low and most of the effective surface charge was due to the amino groups. The dissociation constants of the amino groups were slightly different from those of the amino group-modified particles. Most of the phosphate groups on the phosphate group-modified particles were proton dissociable and most of the amino groups on this sample were not. Uranyl ions, which are the predominant uranium (VI) species below pH 4, were not adsorbed on unmodified particles and most of the uranium was adsorbed above pH 6. This trend in adsorption vs. pH is very similar to that in the fraction of the uranium (VI) hydrolysis species estimated by a thermodynamic calculation using the thermodynamic modeling program, Geochemist’s Workbench. Uranyl ions were well adsorbed on the other particles. Each of the adsorption edges occurred in a different pH range: pH < 2.5 for the phosphate group-modified particles, 2.5 < pH < 3.5 for the amino group-modified particles, and 2 < pH < 3.5 for the carboxyl group-modified particles. Above these pH ranges, the adsorption is almost 100 %. The adsorption of uranyl ions on the carboxyl group-modified particles probably occurred on the amino groups preliminarily fixed on these particles because most of the effective surface charge of these particles was due to the amino groups. These results suggest that amino group is a powerful adsorption (complexation) site on protein for uranyl ions. The decrease of the adsorption from pH 3.5 to lower pH could be due to the increase of hydronium ions in solution, i.e., the increase of the protonated amino groups.
9:00 PM - NN7.4
Suppression of Hidden Order and Emergence of Ferromagnetism in URu2-xRexSi2.
Nicholas Butch 1 2 , Jason Jeffries 1 2 , Benjamin Yukich 1 2 , Todd Sayles 1 2 , Johnpierre Paglione 1 2 , Pei-Chun Ho 1 2 , M. Maple 1 2
1 Department of Physics, UC San Diego, La Jolla, California, United States, 2 Institute for Pure and Applied Physical Sciences, UC San Diego, La Jolla, California, United States
Show AbstractSubstitution of Re for Ru in URu2Si2 reduces the transition temperature of the hidden order state and quickly destroys superconductivity. At intermediate Re concentrations, weak ferromagnetism emerges, and non Fermi liquid (NFL) behavior is observed in the low-temperature specific heat and electrical resistivity. Recent inelastic neutron scattering measurements on polycrystalline samples have demonstrated energy/temperature scaling in the dynamic susceptibility at Re concentrations in the vicinity of the onset of ferromagnetism, a phenomenon observed in several other compounds in the vicinity of chemically tuned magnetic instabilities. Magnetization, electrical resistivity, and specific heat measurements on URu2-xRexSi2 single crystals have confirmed that NFL behavior is not an artifact of polycrystalline disorder or defects, and has made possible the study of magnetic and transport anisotropy along with more precise characterization of this unusual material.
9:00 PM - NN7.5
Physical Property Changes in Aging Plutonium Alloys.
Brandon Chung 1 , Stephen Thompson 1
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractPlutonium-based alloys, because of its self-irradiation by alpha decay, ages by means of lattice damage, Frenkel-type defects and clusters, and helium in-growth. These integrated aging effects will result in microstructural and physical property changes. Because these effects would normally require decades to measure, studies are underway to asses the effects of extended aging on the physical properties of plutonium alloys by incorporating roughly 7.5 wt% of highly specific activity isotope 238Pu into the weapons-grade plutonium to accelerate the aging process. This paper presents self-irradiation effects to enriched and reference alloys observed from the immersion density, dilatometry, and mechanical test measurements. After nearly 80 equivalent years of aging, both the immersion density and dilatometry show that the enriched alloys at 35°C have decreased in density by 0.17 to 0.18 % and now exhibit a near linear density decrease, without void swelling. Both tensile and compression measurements show that the aging process increases the strength of plutonium alloys. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
9:00 PM - NN7.6
Pentavalent Uranium Chemistry: Synthesis, Structure, and Reactivity.
Christopher Graves 1 , Ping Yang 1 , Anthony Vaughn 2 , Brian Scott 1 , Joe Thompson 1 , P. Jeffrey Hay 1 , David Morris 1 , Jaqueline Kiplinger 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 , University of Missouri, Columbia, Missouri, United States
Show AbstractTo date, the most successful supporting ligand in non-aqueous organouranium chemistry has been the pentamethylcyclopentadienyl moiety (C5Me5)-, which not only possesses desirable steric requirements but also has the ability to sustain a continuum of uranium oxidation states ranging from U(III) to U(VI). While examples of U(IV) and U(VI) organometallic complexes are now prevalent in the literature, corresponding U(V) systems are relatively scarce as a result of the redox instability of U(V), and systematic synthetic routes to gain entry to this rare oxidation state are essentially unknown. Herein we report a simple approach to access a host of organouranium(V) imido species by way of oxidation from tetravalent precursors using copper(I) salts. This chemistry is also extended to a variety of derivatives, including amido, aryloxo, and ketimido analogues with the intent to probe the extent of covalent interaction on the single 5f valence electron with subtle variation of the ligand field. Synthesis and characterization of U(V)/U(V)-bimetallic systems will also be presented.
9:00 PM - NN7.7
Steric Control of Actinide Reactivity: Synthesis and Chemistry of a Uranium Metallocene that Bridges the Gap Between Sterically Crowded and Sterically Normal Complexes.
Justin Walensky 1 , William Evans 1 , Filipp Furche 1 , Arnold Rheingold 2 , Antonio DiPasquale 2
1 Chemistry, University of California, Irvine, Irvine, California, United States, 2 Chemistry, University of California, San Diego, San Diego, California, United States
Show AbstractThe synthesis of sterically crowded f-element complexes such as (C5Me5)3U has led to unexpected structural results and reactivity patterns. Sterically crowded complexes of this type have shown a new way to modify actinide reactivity. For example, ligand-based reductive reactivity can be activated by the steric crowding that brings redox chemistry to complexes of redox inactive metals. A correlation has been noted between metallocene complexes that display enhanced ligand-based reactivity and the methyl displacements from the cyclopentadienyl ring plane in (C5Me5)1- ligands. Some 17 sterically crowded complexes with methyl displacements from 0.48-0.54 Å have been shown to have special reactivity, while the rest of the known metallocenes with displacements ranging from 0.12-0.42 Å show none of this reactivity. Despite the large number of structures known, a gap existed in the displacement range from 0.42-0.48 Å: no compounds with displacements in this gap were known. We now report the synthesis of a compound, (C5Me5)2(C5Me4H)UMe, with displacements in this range. The synthesis, structure, unusual spectroscopy, and reactivity of (C5Me5)2(C5Me4H)UX, where X = Me, Cl will be described and the implications of these results in controlling actinide reactivity via steric crowding will be analyzed.
9:00 PM - NN7.8
In Situ Formation and Identification of Uranium Minerals in Waste Form Concrete.
Shas Mattigod 1 , Dawn Wellman 1 , Bruce Arey 1 , Marcus Wood 2
1 , Pacific Northwest National Laboratory, Richland, Washington, United States, 2 , Fluor Hanford Inc., Richland, Washington, United States
Show Abstract