bluuebunny/crossref_metadata_2025_split huggingface dataset:
Redox State and Transition Metal Concentration Effects on Microstructure of Simulated Simplified Glasses for Waste Immobilization
Authors: Kim C.-W. , Muller I. S. , Buechele A. C. , Pegg I. L. , Macedo P. B. 
Published: April 2011

AbstractChromium, iron, and nickel are present in many waste-streams from DOE sites. This study considers a simplified lime-aluminosilicate glass system, similar to one proposed for high temperature (1250–1450°C) vitrification of soil and wastes from DOE sites, in which concentrations of Cr, Fe. and Ni are being varied and different redox states induced for selected melting conditions. The solubilities of Cr 2O3 and NiO in the simplified system are determined at 1350°C, 1400°C, and 1450°C. The enthalpies of solution calculated from the solubility data for Cr2O3 and NiO are 12.2 and 15.2 kcal/mol, respectively. The iron redox ratio, Fe2+/Fetotal in selected glasses is determined by Mössbauer Spectroscopy and related to changes in microstructure. The crystallization of eskolaite (Cr2O3) seems to be favored at intermediate states of reduction (Fe2+/Fetotal ≈0.8) in Cr-containing glass at near the solubility limit. Pseudoternary diagrams are plotted for melts in air at 1450°C in which Fe2O3 + SiO2 + X (X = NiO or Cr2O33) is held constant. Time-Temperature-Transformation (TTT) curves are plotted using data from heat treatment studies. Liquidus temperatures of base, 1.5 wt% Cr2O3 glass and 8 wt% NiO, 7 wt% Fe2O3 glass are found to be 1150°C, 1175°C, and 1175°C, respectively.
Plutonium Incineration in LWR's by a Once-Through Cycle with a Rock-Like Fuel
Authors: Degueldre C. , Kasemeyer U. , Botta F. , Ledergerber G. 
Published: April 2011

AbstractPlutonium incineration in a uranium-free fuel by a once-through burning cycle in LWR’s followed by geological disposal of the rock-like material as a high level waste is discussed here. For burning plutonium of various origins, zirconium oxide is a promising candidate as inert matrix because it is stabilised by rare earth oxides (Er, Ho, Eu … Y) in a single phase solid solution with a stable cubic structure. In this material, selected rare earth isotopes can also act as burnable poisons. The spent fuel may be licensed as waste material on the basis of the inventory, the stability of the material and the behaviour of natural analogue material (e.g. baddeleyite). A fuel composed of 90-80% ZrO2, 7–14% PuO2 and 3–6% Er2O3 (At%), with potential addition of Y2O3 (as additional stabiliser), is suggested for experimental study. Such a fuel employed in LWR's could generate power effectively while transmuting about 95% of the 239Pu
Corrosion Resistance of Ceramic Refractories to Simulated Waste Glasses at High Temperatures
Authors: Xing Shi-Ben , Lin Yijing , Mohr Robert K. , Pegg Ian L. 
Published: April 2011

AbstractIn many vitrification processes, refractory materials are used to contain the waste glass melt. The corrosive nature of the high-temperature melt consumes the waste feed materials but also limits refractory life. As vitrification is applied to more diverse waste streams, and particularly in higher-temperature applications, increasingly severe demands are placed on the refractory materials. A variety of potential refractory materials including Fused-cast AZS, Monofrax K3, Monofrax E, and the Corhart refractories ER1195, ER2161, C1215, C1215Z, Rechrome, and TI 186, were subjected to corrosion testing at 1450°C using the ASTM C-621 procedure. A series of simulated waste glasses was used which included F, Cl, S, Cu, Zn, Pb; these minor components were found to cause significant, and in some cases drastic, increases in corrosion rates. The corrosion tests were conducted over a range of time intervals extending to 144 hrs in order to investigate the kinetics of the corrosion processes. The change of the concentrations of constituents in the glass was monitored by compositional analysis of glass samples and correlated to the observed extent of corrosion; typically, components of the material under test increase with time while key minor components, such as Cu and Pb, decrease. The rate of corrosion of high-zirconia refractories was slowed considerably by adding zirconia to the waste glass composition; this has the added benefit of improving the aqueous leach resistance of the waste form that is produced.
Effects of Redox Condition on Waste Glass Corrosion in the Presence of Magnetite
Authors: Ylnagaki  , Ogata A. , Furuya H. , Idemitsu K. , Banba T. , Maeda T. 
Published: April 2011

AbstractStatic corrosion tests of a powdered simulated waste glass were performed in the presence of magnetite under oxic and anoxic conditions, respectively. The corrosion tests under oxic conditions were performed in air, and those under anoxic conditions were performed in a glove box purged with mixed gas(Ar+5%H2). The experimental results showed that the presence of magnetite can enhance glass corrosion under both oxic and anoxic conditions, and the enhancement under anoxic conditions was small compared to that under oxic conditions. A large portion of the Si and insoluble elements were sorbed onto the magnetite surface, and the sorption under anoxic conditions was small compared to that under oxic conditions.It was suggested that the enhancement of glass corrosion by magnetite results from the sorption or precipitation of silica on the magnetite surface, which can be greatly affected by redox condition. Under anoxic conditions, it was suggested that precipitation of amorphous silica on the magnetite surface may be the dominant process for enhancement of glass corrosion in addition to sorption.
The Indefinite Containment of Nuclear Fuel Wastes
Authors: Shoesmith D. W. , King F. , Ikeda B. M. 
Published: April 2011

AbstractThe safe disposal of used fuel or vitrified reprocessed waste could be guaranteed if the containers remained intact indefinitely (> 106 a). Justification of indefinite containment may be possible if two criteria are met; (i) a sound mechanistic understanding of the corrosion and mechanical behaviour of the container material is available, and (ii) the disposal environment and its evolution with time can be confidently predicted. In disposal vaults in which the environmental conditions evolve from a short aggressive period to a long-term benign period, long container lifetimes are achievable. This approach is illustrated by discussing the possibility of indefinite containment of used fuel in a Canadian disposal vault using Ti alloys or Cu.
Spectroscopy of Plutonium-Organic Complexes
Authors: Richmann M. K. , Reed D. T. 
Published: April 2011

AbstractInformation on the spectroscopy of plutonium-organic complexes is needed to help establish the speciation of these complexes under environmentally relevant conditions. Laser photoacoustic spectroscopy (LPAS) and absorption spectrometry were used to characterize the Pu(IV)-citrate and Pu(IV)-nitrilotriacetic acid (NTA) complexes at concentrations of 1−3 – 10−7 M in aqueous solution. Good agreement was observed between the band shape of the LPAS and absorption spectra for the Pu(IV)-NTA complex. Agreement for the Pu(IV)-citrate complex was not quite as good. In both cases, a linear dependence of the LPAS signal on laser power and total concentration of the complexes was noted. This work is part of an ongoing research effort to study key subsurface interactions of plutonium-organic complexes.
Effect of Swelling Pressure on Local Volume Change in Unsaturated Sand-Bentonite Buffer Material
Authors: I Shooshpasha , A.M.O Mohamed , Yong R. N. 
Published: April 2011

AbstractThis study was designed to investigate the effect of swelling pressure on local volume changes in unsaturated sand-bentonite based buffer material. A laboratory mixture of sodium bentonite and graded silica sand in equal proportion by dry weight was used in both ambient and elevated temperatures experiments. At high water content locations within the tested specimens, the density was reduced by 3.57% from its initial values due to swelling. The swelling pressure as a function of distance was calculated by 4 different models. The calculated results have indicated that the density distribution within the specimen is affected by swelling potential distribution. The calculated swelling pressure values vary as a function of water content, reaching 1 MPa at the source of water intake, i.e., at high water content zone, and 2 MPa at the heater side, i.e., at low water content zone.
Diffusion of Uranium in Compacted Bentonites in the Reducing Condition with Corrosion Products of Iron
Authors: Idemitsu Kazuya , Tachi Y. , Furuya H. , Inagaki Y. , Arima T. 
Published: April 2011

AbstractIn high-level waste repository, a carbon steel overpack will be corroded after closure. This will create a reducing environment in the vicinity of the repository. Reducing conditions are expected to retard the migration of redox-sensitive radionuclides such as uranium.The apparent diffusion coefficients of uranium were measured in compacted bentonites (Kunigel VI® and Kunipia F®, JAPAN) in contact with carbon steel and its corrosion products under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusion coefficients measured were 10-12 to 10-14 m2/s under oxidizing conditions and 10-13 to 10-14 m2/s under reducing conditions. There were significant effects of redox conditions, dry density (0.8 to 2.0 g/cm3) and montmorillonite contents (60% for Kunigel VI or 100% for Kunipia F) on the apparent diffusion coefficients. The sorption of uranium on corrosion products of iron was smaller than that on montmorillonite. Montmorillonite density could be a good index to explain density dependence of the diffusion coefficients under the reducing conditions. Uranium would diffuse in free pore water with diffusion coefficients greater than 10-13 m2/s in low density bentonites under both redox conditions because the diffusion coefficients depended on sorption coefficients. Since diffusion coefficients were independent of sorption coefficients in high density bentonites where free pore water is scarce, surface diffusion might occur with coefficients were of about 10-13 m2/s.
Theoretical Relationships Between Reactivity and Permeability for Monomineralic Porous Media
Authors: Smith Robert W. , Schafer Annette L. , Tompson Andrew F. B. 
Published: April 2011

AbstractThe release of contaminants to the subsurface has lead to potential or actual contamination of groundwater resources. The remediation of these plumes requires improved capability for the prediction of contaminant fate and transport. Key to improving predictive capabilities is an increased understanding of natural chemical (or reactive) heterogeneity in subsurface media and how chemical and physical heterogeneity are related. Although the effects of physical heterogeneity on transport has received significant attention, similar investigations of chemical heterogeneity, and the correlation of chemical and physical heterogeneity are in their infancy.Theoretical considerations for unconsolidated porous media composed of sand-sized grains of a single reactive phase suggest that chemical reactivity and permeability are inversely related. This correlation is consistent with measured permeability, porosity, and surface area data for unconsolidated sands. The correlation arises because both reactivity and permeability are functions of the surface area of the porous media. This relationship suggests that for a heterogeneous porous media, significant contaminant transport will occur in zones of minimal reactivity.
Improved Radionuclide Transport Models for a Nuclear Waste Repository
Authors: Codell Richard B. 
Published: April 2011

AbstractNRC is developing improved models for transport of chain decay radionuclides in porous and fractured/porous media using finite-difference for spatial discretization, and numerical inversion of Laplace transforms for time. This hybrid technique allows great flexibility for spatial variability, flow rate changes and boundary conditions that are difficult with analytical solutions, and are much faster than solutions fully in the time domain. This paper presents the status of NRC's development of a method for transport through fractured porous media at the proposed Yucca Mountain repository, building on the work of a number of authors.
Predicted Behavior of Technetium in a Geological Disposal Vault For Used Nuclear Fuel - Ramifications of a Recent Determination of the Enthalpy of Formation of TcO2(cr)
Authors: Lemire R. J. , Jobe D. J. 
Published: April 2011

AbstractRecently, we reported a value of ΔH°(TcO2(cr)) = -(458 ± 6) kJ·mol-1based on heat of solution measurements. The implications of this value on the database used in the Canadian Nuclear Fuel Waste Management Program for the evaluation of the technetium released by congruent dissolution of used UO2fuel have now been assessed.It is probable that the Tc(IV) oxides are more stable than previously predicted and, hence, they are less likely to be oxidized to TcO4(aq) under moderately reducing conditions. We have revised earlier calculations done to predict the solution concentrations of technetium species in a vault as a function of the oxidation conditions in model groundwaters.
Bulk Self-Assembled Films for Photonics
Authors: Tripathy S. K. , Kim D. Y. , Kim W. H. , Kumar J. 
Published: April 2011

ABSTRACTRecently we have reported, significant second harmonic generation from spin coated and bulk films of a soluble polydiacetylene (PDA), namely poly{8-[[[butoxy carbonyl] methyl]urethanyl]-1-(5-pyrimidyl)-octa-l,3,-diyne}} (BPOD) without recourse to poling. Poly(BPOD) is an asymmetrically substituted PDA in which a polarizable heteroaromatic pyrimidyl group is attached as one of the side groups. In addition to reviewing the earlier results, we report a series of new soluble PDAs of the same class with further functionalization, elaborating on the already defined design principle.A second class of polymers with azo dye based NLO chromophores incorporated into the structure has been processed optically to fabricate holographic elements. Trans-cis-trans isomerization driven reorientation and macromolecular motion leads to the formation of surface relief gratings upon exposure to an interference pattern. Fabrication of optical elements based on these polymers will be elaborated.
The Synthesis And Optoelectronic Properties Of Oxadiazole-Based Polymers
Authors: Li X.-C. , Kraft A. , Cervini R. , Spencer G. C. W. , Cacialli F. , Friend R. H. , Gruener J. , Holmes A. B. , Mello J. C. De , Moratti S. C. 
Published: April 2011

ABSTRACTNew oxadiazole-based polymeric materials have been synthesized either as side chain copolymers with polymethacrylate or as main chain copolymers carrying solubilizing elements such as hexafluoropropylidene or meta-linked aromatic spacer units. Many of these materials exhibit blue luminescence in the solid state. The materials have been evaluated by photoluminescence and cyclic voltammetry studies, and as the electron transporting layer in a two-layer electroluminescent device with poly(p-phenylenevinylene) (PPV) as the emissive layer. The major conclusion is that these materials function by providing large heterojunction offsets at the Highest Occupied Molecular Orbital (HOMO) which block the passage of holes through the device.
Synthesis And Characterization Of 1,3-Bis(Dicyanomethylene)Indane (Bdmi) Derived Second Order Nlo Materials
Authors: Sunt Sam-Shajing , Harpert Aaron W. , Zhangt Cheng , Daltont Larry R. , Garner Sean M. , Chen Antao , Yacoubian Araz , Steier William H. 
Published: April 2011

ABSTRACTDifunctionalized aminophenylenethienylidene-1,3-bisdicyanomethyleneindane (BDMI) derived second order push-pull chromophores and polymers have been synthesized and characterized. Preliminary studies of doped polymeric composite thin films reveal large SHG signals as well as good chemical and thermal stabilities under poling conditions.
Photo-Induced Surface Alignment Of Nematic Liquid Crystals On Polyamide-Imide Layers
Authors: Rich David C. , Sichel Enid K. , Cebet Peggy 
Published: April 2011

ABSTRACTA technique for producing surface-induced liquid crystal nematic alignment is presented. The alignment film is a simple, inexpensive polyamide-imide, which is treated with linearly polarized short wavelength ultraviolet radiation (λ = 254 nm). The alignment performance of UV-aligned layers is shown by optical transmission of the liquid crystal cells to be comparable to that of brushed layers. Strong alignment is produced within minutes of UV exposure and is maintained with long exposures.
Demonstration Set-Up for Fast Switchable Diffraction of Laser Light Using the Computer Controlled Diffraction Grating Based on Ferroelectric Liquid Crystal
Authors: Beresnev L. A. , Hossfeld J. , Dultz W. , Onokhov A. P. , Haase W. 
Published: April 2011

ABSTRACTSwitchable diffraction grating with 80 “idependently drived transparent stripe electrodes with spatial resolution 40 l/mm based on ferroelectric liquid crystal is presented. The switching of the diffraction angle till frequency 1kHz is demonstrated using the computer choise of assemblies of electrodes.
Growth of Organic Periodic Structures by Molecular Layer Deposition
Authors: Dietrich T. , Schlesser R. , Sitar Z. , Günter P. 
Published: April 2011

ABSTRACTThin films of organic nonlinear optical materials have become of increasing interest for potential electro-optic and nonlinear optical applications. Organic molecular layer deposition (OMLD) consists of an alternating evaporation of suitable difunctional monomers under UHV conditions and allows self-terminating monolayer growth and in-situ polymerization of periodic structures. Film stability is increased due to chemical bonding between the alternating layers. Moreover, in contrast to epitaxial growth techniques, the choice of interesting inorganic substrates is not limited by lattice-matching conditions. We have investigated the xperimental requirements for OMLD in detail, with pyromellitic acid dianhydride (PAD), terephthalic acid dichloride (TOC), and 4,4′-diamino-diphenylether (DDE) as prototype precursors. After optimization of material fluxes and growth temperatures, covalently bonded monolayers were formed via a self-terminating surface reaction while excessive material was desorbed.
Contact Dependence of α-Sexithienyl Thin Film Transistor Characteristics
Authors: Lin Y. Y. , Gundlach D. J. , Jackson T. N. 
Published: April 2011

ABSTRACTWe have fabricated thin film transistors (TFTs) using ca-sexithienyl (α-6T) as the active material and have investigated the dependence of transistor characteristics on the choice of source/drain contact metal. Using α-6T synthesized from terthiophene and purified by vacuum gradient sublimation, we have fabricated TFTs with material deposited by evaporation onto substrates held at both room and elevated temperature. We have studied devices fabricated by depositing the active material onto previously patterned source/drain contacts and also by depositing the source/drain contacts after the active layer deposition, in both cases with the gate contact and dielectric underneath the active material. For both device types we find a clear dependence on the choice of source/drain contact metal with correlation to the metal work function. For our devices the best performance is obtained using metals with largest work function (Pd, Pt, or Au), intermediate performance is obtained using a metal with somewhat smaller work function (Cr), and significantly degraded performance is obtained using a metal with relatively small work function (Al). Despite the apparent correlation to the metal work function, we cannot yet rule out oxidation or other chemical effects with the more reactive metals. We have also examined doping of the α-6T layer as a possible route to improved contacts and find that FeCI3 can be used to shift the threshold voltage of α-6T TFTs by more than 50 V.
Low Temiperature Band Transport in Alpha-Hexathienylene Thinfilm-Transistors
Authors: Torsi L. , Dodabalapur A. , Rothberg L. J. , Fung A. W. P. , Katz H. E. 
Published: April 2011

ABSTRACTWe provide experimental evidence of a transition from thermally activated hopping of small polarons to band transport of delocalized polarons in polycrystalline oligothiophene fieldeffect transistors. We demonstrate that these transport mechanisms are intrinsic, i.e. governed by material-specific parameters such as the electronic overlap integral and the polaron binding energy. At high temperatures the field-effect mobility decreases with decreasing temperature and the transport mechanism is thermally activated hopping. Below a critical temperature Tτ, the field-effect mobility abruptly increases by more than two orders of magnitude and the transport becomes band-like. This behavior is consistent with the theory T. Holstein developed in 1959 for small polaron transport.
Bioactive Polypyrrole Thin Films with Conductimetric Response to Analyte
Authors: Guiseppi-Elie A. , Tour J. M. , Allarat D. L. , Sheppard N. F. 
Published: April 2011

ABSTRACTThin films of electroconductive poly[pyrrole-co-3−(1−pyrrolyl)propionic acid] were prepared by electropolymerization onto 3-aminopropyltrimethoxysilane modified and 3−(1−pyrrolyl)propionic acid derivatized interdigitated microsensor electrode (IME) arrays. The ω−(1−pyrrolyl) moiety on the surface of the device provides for specific adhesion of the polymer film to the device and the (N-pyrrolyl)propionic acid moiety on the polymer backbone provides for covalent attachment of bioactive molecules, such as biotin and urease, to the polymer surface. The immobilized, bioactive urease produces an ON/OFF conductimetric response traceable to analyte concentration.
Poly(3′,4′-Dibutyl-α-Terthiophene-Phenylene-Vinylene), and Poly(3′,4′-Dibutyla-α-Terthiophene-Phenylene-Imine): Synthesis and Properties of Two New Isoelectronic Soluble Conjugated Polymers.
Authors: Wang Chenggang , Xie Xusheng , LeGoff Eugene , Kanatzidis Mercouri G. 
Published: April 2011

ABSTRACTA new soluble and dopable copolymer consisting of 3‘,4‘-dibutyl-2,2‘:5‘,2”-terthiophene and phenylene vinylene units has been designed and prepared via a Wittig reaction. This copolymer is soluble in common organic solvents such as THF and CHC13, and can be doped with various oxidants increasing its electrical conductivity by several orders of magnitude. Its films are electrochromic and turn reversibly and rapidly from red to green-blue upon doping and undoping electrochemically. If the phenylene vinylene units are replaced with phenylene imine units, another interesting new polymer forms which is not readily dopable with the same oxidants but is dopable with acids. The new material exhibits strong chemochromism with dramatic shifts in its optical absorption spectra. In the undoped state both copolymers show strong photoluminescence.
Strategies for Conducting Polymer Solutions: Solvato-Controlled Oxidative Doping Using Metal Cations
Authors: Lebedev M. , Holdcroft S. 
Published: April 2011

ABSTRACTSolutions of Ag(I) and poly(3-alkylthiophenes), which usually precipitate immediately upon contact, are stabilized with Ag(l)-coordinating ligands. Casting of polymer-Ag(I)-ligand solutions followed by evaporation of the ligand yields an electronically conducting polymer film. It is postulated that Ag(I) either undergoes nucleophillic addition to poly(3-alkylthiophenes), in a manner similar to which polythiophenes are protonated by acids, or forms a charge transfer complex with the polymer. The “doped” polymer exhibits enhanced stability over films oxidized using conventional oxidants. Ag(I)-doping of poly(3-alkylthiophenes) represents a new strategy for doping conjugated systems.