bluuebunny/crossref_metadata_2025 huggingface dataset:
Substantially Transparent Pt, Pd, Rh, And Re Films: Preparation and Properties
Authors: Aspnes D. E. , Heller A.
Published: March 2011

Films of Pt, Pd, Rh, and Re with metal volume fractions of 0.3 to 0.5 have been prepared by mass-transport-limited photoelectrodeposition onto (001) p-InP photocathodes from ∼5 × 10−5 M solutions of the metal ions in 1 M HClO4. These films exhibit their normal catalytic activities (e.g., in hydrogen evolution) and have normal crystal structures, yet are substantially more transparent than equivalent dense films of the same metal loading per unit area. Effective-medium analysis of the spectroellipsometrically measured dielectric functions of these films shows that the anomalous transparency is due to microstructure: depolarization factors and metal packing fractions obtained by best-fit model calculations indicate dendritic (Rh), particulate (Pt, Pd), or platelet (Re) forms that are poorly interconnected in directions parallel to the surface, and whose dimensions are all small compared to the wavelength of light. Transmission electron micrographs confirm these results and reveal that these films consist of primary building blocks of ca. 5 nm crystallites that are organized into relatively loosely packed secondary structures. Potential applications of these films include the formation of efficient metallic-catalyst-coated photoelectrodes on poor-quality semiconductors.
The Composition and Stability of Nicu Surface Alloys Grown by Ni(CO), Decomposition on Cu
Authors: Alkemade Paul F.A. , Fortuin H. , Balkenende R. , Habraken F. H. P. M. , Weg W. F. Van Der
Published: March 2011

The composition of NiCu surface alloys, prepared by decomposition of nickel carbonyl on a Cu(100) surface, has been studied before as well as after annealing using MeV Rutherford Backscattering Spectroscopy.

NiCu films with a thickness of 2 nm and of 10 nm, respectively, having a sharp interface with the copper substrate, were grown. The nickel fraction is found to be 65% and 93% respectively. The outermost monolayer is slightly enriched in copper. During annealing interdiffusion between the film and the interface occurs and the enrichment of the surface increases. In case of the 10 nm film the observed diffusion rate is much higher than is expected on the basis of diffusion coefficients published in the literature. This is ascribed to the presence of defects and/or grain boundaries in the grown surface alloy.
Kinetics and Mechanism of the Copper-Catalyzed Etching of Silicon by F2
Authors: Selamoglu N. , Mucha J. A. , Flamm D. L. , Ibbotson D. E.
Published: March 2011

The copper catalyzed fluorination of silicon is first-order in [F2] and in [Cu]s until the coverage reaches ∼4 monolayers. Above ∼4 monolayers the reaction rate is zero order in copper, suggesting a limited number of catalytically active Cu/Si sites. Surface diffusion of copper leads to decrease in the etch rate as a function of time as well as feature size-dependent etch depths. The copper compounds CuF2, CuO, and copper silicides, Cu5 Si and Cu3 Si all catalyzed the F2-Si reaction which suggests that they are all converted to the same active species. The results can be explained by mechanisms involving copper fluorides or copper silicides as active intermediates.
Atomic Force Michoscxpy-Feasibility for Materials Research.
Authors: Bryant P. J. , Yang R. , Miller R.
Published: March 2011

The applicability of atomic force microscopy (AFM) to both conductive and dielectric materials is the subject of this study. A representative conductor, Cu, and two dielectrics, mica and selenite, were examined. Microstructure and single lamellar steps were resolved. Surface areas on Cu and mica generated reproducible images when scanned repeatedly. There was no evidence of damage to the probe or the sample as a result of the AFM investigations. Selenite did show evidence of change after repeated scans with an AFM lever of 12 N/m spring constant exerting a 10−6N force.
High Temperature limit for the Growth of Carbon Filaments on Catalytic iron Particles
Authors: Tibbetts Gary G. , Rodda Eric J.
Published: March 2011

Carbon filaments of macroscopic length may be produced by heating transition metal catalyst particles in a hydrocarbon-hydrogen mixture. Because the nanometer-sized catalyst particles contain relatively many surface atoms, they melt at a temperature considerably below that of bulk material; this depression of the melting point is difficult both to calcu-late and measure. This work addresses the fundamental question of whether the catalyst particles are in the liquid or solid state during filament growth.

We present measurements of the average number of filaments grown per unit area of substrate as a function of temperature which show that the the activity of the catalyst particles drops precipitously above 1030°C and nearly disappears above 1120°C. This compares with the melting point of the Fe-C eutectic of 1154°C. TEM observations show that the average dia-meter of an active catalyst particle is 15±7 nm. Calculations based on the model of Ross and Andres [1] for the melting temperature of small clusters of atoms predict a drop in activity above 1050°C similar to our observa-tions.
Entropy and Melting in Small Particles
Authors: Ajayan P. M. , Marks L. D.
Published: March 2011

We describe theoretical results for part of the Gibbs free energy surface as a function of shape and temperature for small particles. We predict the existence of true ‘quasi-melting’ at temperatures much below the conventional melting points and also phase transitions between different stable forms as the temperature is varied. A phase diagram for small particles is constructed for the first time, showing the stability ranges for different particle shapes as a function of size and temperature.
Perspective on the use of gas Adsorption for Particle-Shape Control in Supported Metal Catalysis
Authors: Shi A -C. , Fung K. K. , Welch J. F. , Wortis M. , Masel R. I.
Published: March 2011

This paper explores the possibility of using gas adsorption for particle-shape control in supported metal catalysis. Calculations are done to identify the kinds of shape changes which are possible due to treatment in an appropriate adgas. Experiments are done to try to verify the concepts. The results show that gas adsorption can be used for particle shape control in supported metal catalysis.
NMR and Quantum Effects in Metal Particles
Authors: Halperin W. P. , Yu Insuk
Published: March 2011

abstract

The considerable interest in metallic clusters spans a wide range. In this paper we discuss quantum effects and we suggest that there may be important interrelationships between such behavior and heterogeneous catalysis. Of course, the physical and chemical behavior of the metal particle are the key to understanding principles of catalytic activity. The quantum effects are found at progressively lower temperatures where the metallic properties change. In both cases a fundamental question is posed, “Do these particles exhibit metallic behavior?;” One of the common features of research in these two areas is the important role played by nuclear magnetic resonance(NMR) techniques since the signatures of a metal and an insulator are so dramatically different. The issue of metallic or nonmetallic behavior is therefore best addressed with this experimental approach and we will review the current situation by comparing a number of results on quantum size effects deduced from NMR experiments
Technical Challenges Facing Regulators–Assessment of Long-Term Materials Performance
Authors: Stephens Kenneth W.
Published: March 2011

For a number of years, nuclear regulators have grappled with difficult questions such as: “How safe is safe enough?” Such issues take on new dimensions in the long time-frame of high-level waste disposal.

Many of the challenges facing regulators involve assessment of long-term materials performance. Because real-time experiments cannot be conducted, it is necessary to rely extensively on modeling. This raises issues regarding the extent to which long-term extrapolations of short-term data are justified, the question of how closely models must represent reality to be trusted, and practical matters such as methods for validating unique computer codes.

Issues such as these illustrate how regulators must make decisions in a climate of uncertainty. Methods used by non-technical disciplines to make decisions under uncertainty have been examined and offer solutions for regulators and licensees alike.
The Radlonuclide Migration Experiment at the Grimsel Rock Laboratory, Switzerland
Authors: McKinley Ian G. , Alexander W. Russell , Bajo Claudine , Frick Urs , Hadermann Jörg , Herzog Franz A. , Höhn Eduard
Published: March 2011

This paper describes the programme for an in-situ radionuclide migration experiment in fractured crystalline rock and presents the first results of site characterisation work. This study is particularly notable for its extensive hydrologic/geochemical support programme and the use of radiotracers identified as important in safety assessment studies.
Immobilization of Technetium and Nitrate in Cement-Based Materials
Authors: Tallent O. K. , McDaniel E. W. , Cul G. D. Del , Dodson K. E. , Trotter D. R.
Published: March 2011

The leachabilities of technetium and nitrate wastes immobilized in cement-based materials (i.e., grouts) have been investigated using ANS 16.1 test procedures. Factors found to affect the leachabilities include (1) grout mix ratio, (2) grout fluid density, (3) dry solid blend composition (including ground blast furnace slag), and (4) waste concentration.
Natural Radionuclides in Hanford Site Ground Waters
Authors: Smith M. R. , Laul J. C. , Johnson V. G.
Published: March 2011

Uranium, Th, Ra, Rn, Pb and Po radionuclide concentrations in ground waters from the Hanford Site indicate that U, Th, and Ra are highly jorbed. Relative to Rn, these radionuclides are low by factors of 10−3 to 10−6. Uranium sorption is likely due to its reduction from the +6 state, where it is introduced via surface waters, to the +4 state found in the confined aquifers. The distribution of radionuclides is very similar in all of the confined aquifers and significantly different from the distribution observed in the unconfined and surface waters. Barium correlates well with Ra over three orders of magnitude indicating that stable element analogs may be useful for inferring the behavior of radioactive waste radionuclides in this candidate geologic repository.
Radionuclide Transport through Perforations in Nuclear Waste Containers
Authors: Aidun Cyrus K. , Bloom Sanford G. , Raines Gilbert E.
Published: March 2011

Previous analytical models for the steady-state radionuclide release rate through perforations in nuclear waste containers into the surrounding medium, are based on a zero wall thickness assumption. In this paper we investigate the effect of the wall thickness on the mass transfer rate through isolated circular holes. We solve the steady-state diffusion equation for the concentration field and derive a model based on the analytical solution. By direct comparison, we show that the zero wall thickness model overpredicts the mass transfer rate by about 1300 percent for a circular hole with 1 cm radius and a wall thickness of 10 cm. As expected, the zero-thickness model becomes even less accurate as the hole radius decreases; it predicts a greater release rate from a large number of small holes than the mass transfer rate from an uncontained waste form cylinder. In contrast, the results predicted by our model remain bounded for isolated holes and never exceed the mass transfer from an uncontained waste form.
Gas-Phase Transport of Carbon-14 Released from Nuclear Waste into the Unsaturated Zone
Authors: Ross Benjamin
Published: March 2011

Gas-phase carbon-14 dioxide released from spent fuel buried in unsaturated rocks will move upward by molecular diffusion and advection. The flux resulting from molecular diffusion will be determined by the concentration gradient of gaseous carbon-14 dioxide. Advection will be caused by density-driven flow of the pore gas. Such flow occurs under present conditions as a result of annual and diurnal temperature changes and differences in chemical composition between pore gas and air, and it will be enhanced when the spent fuel heats the rock. The advective flux will be determined by the gas-phase concentration of carbon-14 and by the velocity of convective flow of the pore gas. Gas-phase concentrations of carbon-14 dioxide will be strongly influenced by isotopic exchange with bicarbonate dissolved in water that is retained in the unsaturated zone by capillary forces. Isotopic equilibrium between these two phases will be attained very rapidly on repository time scales. If the liquid phase is saturated with calcium carbonate, precipitation of calcite may provide a sink for removal of carbon-14 from the mobile phases.
Three-Dimensional Code for Groundwater Flow and advection Diffusion With a Decay Chain of Radioactive Materials Using Finite Element Method
Authors: Kawamura Ryuji , Ishihara Takehiko
Published: March 2011

A code(PER8MIGR) for the finite element method (F.E.M.) using 8-node point isoparametric elements has been developed for solving three-dimensional groundwater flow and advection diffusion equations with a decay chain of radioactive materials. Galerkin's method is applied to discretize the equations, and asymmetric band matrix method is used to solve the equation. Some simple problems for groundwater flow and migration of nuclides were solved by the code to compare the results for groundwater flow with the one- and three-dimensional analytical solutions. The results for migration of nuclides were also compared with the results obtained by some existing available codes. Our results and those by the other codes were in good agreement. The present work makes it possible to solve the groundwater flow and diffusion problems more accurately for radioactive waste disposal in complex geometry.
Geochemical Simulation of Reaction Between Spent Fuel Waste Form and J-13 Water at 25°C and 90°C
Authors: Bruton Carol J. , Shaw Henry F.
Published: March 2011

Geochemical simulations of the degradation of spent fuel waste form in the presence of groundwater at the candidate Yucca Mountain, Nevada repository have been carried out to attempt to predict elemental concentrations in solution and to identify potential radionuclide-bearing precipitates. Spent fuel was assumed to dissolve congruently into a static mass of J-13 groundwater at 25°C and 90°C. No inhibitions to the precipitation and dissolution of secondary phases were assumed to exist. The elements Ac, Zr, Nb, Pd, Sm, Mo, Sb and Cm were not considered in the simulations because of a lack of thermodynamic data.

Simulation results indicate that haiweeite, soddyite, Na2U2O7(c) and schoepite are potential U-bearing precipitates. Na2U2O7(c) is only predicted to occur at 90°C. U concentrations in solution and the identity of the U-bearing precipitate depend on the activity of SiO2(aq) in solution. U concentrations are limited to < 1 mg/kg when sufficient SiO2(aq) exists in solution to precipitate uranyl silicates. Depletion of SiO2(aq) in solution by the precipitation of silicates results in predicted increases of U concentrations to 87 and 619 mg/kg at 25°C and 90°C, respectively. Subsequent reaction and precipitation of schoepite cause U concentrations to decrease.

Radionuclides other than U commonly precipitate as oxides in the simulations. The precipitation of solid phases appears to be extremely effective in limiting the concentrations of some radionuclides, such as Pu and Th, in solution. Concentrations of other elements are held constant (Sn) or are alternately held constant and then increase (Am, Ni, Np) as various solid phases precipitate and pH decreases from 8.5 to 6.5 at 25°C and 8.7 to 8 at 90°C. No solid phases containing Cs or Tc are predicted to form. Increasing the temperature from 25°C to 90°C does not impact greatly the identity of precipitated phases or solution composition, except in the case of U.

A technique involving isotope dilution measurements may allow determination of the rates of spent fuel dissolution in future experiments.
Experimental Glass-Ceramic Products to Immobilize ICPP HLW
Authors: Baker Roseanne S. , Staples Bruce A. , Knecht Dieter A. , Berreth Julius R.
Published: March 2011

Candidate products are being evaluated to immobilize the routinely calcined waste at the Idaho Chemical Processing Plant (ICPP). A potential product with minimal volume for immobilizing ICPP high-level waste (HLW) for final disposal is a high-waste-loading and high-density glass-ceramic. Glass-ceramics are formed by Hot Isostatic Pressing (HIPing) the HLW with selected additives, such as SiO2, B2O3, Li2O, Na2O, and Y2O3. Glass-ceramic products have been formed with calcine loa ings up to 80 wt% and densities up to 3.4 g/cm3. Crystalline phases observed in the glass-ceramic products include calcium fluoride, monoclinic and cubic zirconia, calcium- and yttrium-stabilized zirconia, and zircon. An interstitial amorphous phase also exists consisting of the oxides of silicon, aluminum, boron, and alkalis. The glass-ceramic waste forms give leach rates comparable to simulated HLW glass products.
Structural Thermodynamic Model for the Durability and Viscosity of Nuclear Waste Glasses
Authors: Feng Xiangdong , Barkatt Aaron
Published: March 2011

A model based upon structural thermodynamic considerations has been proposed for both chemical durability and viscosity of nuclear waste glasses. This model assumes the bond strength between atoms in the glass to be the predominant factor in controlling the composition dependence of physical properties such as viscosity and chemical properties like durability. These characteristic bond strengths in the glass are obtained from known heats of formation of the constituent oxides with a few simple structural rules deduced by distinguishing the structural roles of the various oxides, i.e., separating those components that are clearly “network-formers” (e.g. SiO2, Al2O3, ZrO2) from those that are clearly “network-breakers” (e.g. alkali oxides). This model has been successfully applied to the correlation of glass composition with modified MCC-3 leach test results on nuclear waste glasses measured at various laboratories on one hand and with the viscosities of numerous glasses over a temperature range of 850°C to 1600°C with remarkable accuracy on the other hand.
Temperature Dependence of R7T7 Nuclear Waste Glass Alteration Mechanisms
Authors: Vernaz E. Y. , Dussossoy J L. , Fillet S.
Published: March 2011

The French LWR reference glass R7T7 was leached at temperatures between 100°C and 300°C at a pressure of 10 MPa.

An activation energy of 25 kJ/mole was found between 100°C and 250°C which is different from the 60 kJ/mole previously found between 25°C and 70°C. It is suggested that a potential glass hydration mechanism becomes predominant when dissolution is significantly slowed by high concentrations of silica in solution. At 300°C, a complete change in the corrosion mechanisms is found as the glass undergoes a rapid hydrothermal alteration
Leaching of Am-241 from a Radioactive Waste Glass Corroded in the Presence of Stainless Steel Corrosion Products and/or Bentonite
Authors: Tsukamoto Masaki , Björner Inga-Kari , Christensen Hilbert , Hermansson Hans-Peter , Werme Lars
Published: March 2011

The release of Am-241 during corrosion of the radioactive waste glass, JSS-A, has been studied in the presence of corrosion products and/or uncom-pacted bentonite. The corrosion behaviour of Am-241 has been analyzed using gamma spectrometry. Adsorption of Am-241 on bentonite is observed in all cases. The contents of Am-241 in centrifuged leachates are in most cases less than 1/100 of total values. The normalized elemental mass loss of Am increases initially with corrosion time, and the values in the presence of bentonite and corrosion products are larger than those in the presence of bentonite alone. This tendency is in agreement with results previously found for other elements. The release of Am is low, only about 10–20 % of the corresponding total mass loss.
Modeling The Dissolution Behavior of Defense Waste Glass in A Salt Repository Environment
Authors: McGrail B. P.
Published: March 2011

A mechanistic model describing a dynamic mass balance between the production and consumption of dissolved silica was found to describe the dissolution behavior of SRL-165 defense waste glass in a high-magnesium brine (PBB3) at a temperature of 90°C. The synergistic effect of the waste package container on the glass dissolution rate was found to depend on a precipitation reaction for a ferrous silicate mineral.

The model predicted that the ferrous silicate precipitate should be variable in composition where the iron/silica stoichiometry depended on the metal/glass surface area ratio used in the experiment. This prediction was confirmed experimentally by the variable iron/silica ratios observed in filtered leachates. However, the interaction between dissolved silica and iron corrosion products needs to be much better understood before the model can be used with confidence in predicting radionuclide release rates for a salt repository.
Geochemical Simulation of Dissolution of West Valley and Dnpf Glasses in J-13 Water at 90°C
Authors: Bruton Carol J.
Published: March 2011

Dissolution of West Valley and Defense Waste Product Facility (DWPF) glasses in J-13 water at 90°C at the candidate Yucca Mountain, Nevada repository was simulated using the EQ316 computer code package. The objectives of the study were to attempt to predict the concentrations of radionuclides and other glass components in solution resulting from glass dissolution, and to identify potential precipitates that sequester glass components.

Modified projected inventories of 10,000 year-old Nest Valley and DNPF SRL-165 frit glasses were used as starting glass compositions. J-13 water was considered to be representative of groundwater at Yucca Mountain. A total of 10 grams of each glass was assumed to dissolve congruently into a kilogram of J-13 water in a closed system. No inhibitions to precipitation, except for crystalline SiO2 polymorphs, were assumed to exist. Radiolysis and materials interactions were not considered.

Simulation results predict that radionuclides and other glass components precipitate predominantly in the form of oxides and hydroxides, together with carbonates, silicates and phosphates. Precipitates appear to be effective in limiting the concentrations of radionuclides and other elements in solution. The general compositional trends in precipitates and solution chemistry are the same in the West Valley and DMPF simulations, except for variations arising from differences in glass chemistry.

Concentrations of elements released from glass increase until the solution reaches saturation with respect to solids that contain these elements. Elemental concentrations are then predicted to remain constant, increase or decrease depending on: 1) whether the reaction between the dominant aqueous species of the element in solution and its precipitate is pH and/or Eh-dependent; 2) whether the species distribution of the element in solution changes significantly in response to changes in pH, Eh, or other factors; and 3) the competition with other phases for elements required to form the precipitate. pH increases from 7.3 to 9.8 and from 7.2 to 10 in the West Valley and DWPF simulations, respectively. Eh decreases abruptly from about 0.5 to 0.3 volts after dissolution of 3.4 and 5.8 grams of glass in the Nest Valley and DMPF simulations, respectively, because of depletion of dissolved oxygen in solution. Complexing of aqueous species has a significant impact on radionuclide concentrations in solution; predicted concentrations of U in solution, for example, are controlled by the presence or absence of P in solution because H2PO4 is an extremely effective complexing agent for U.
Slag-Based Saltstone Formulations
Authors: Langton C. A.
Published: March 2011

Approximately 400 × 106 liters of low-level alkaline salt solution will be treated at the Savannah River Plant (SRP) Defense Waste Processing Facility (DWPF) prior to disposal in concrete vaults at SRP. Treatment involves removal of Ca+and Sr+2 followed by solidification and stabilization of potential contaminants in saltstone, a hydrated ceramic waste form.

Chromium, technetium, and nitrate releases from saltstone can be significantly reduced by substituting hydraulic blast furnace slag for portland cement in the formulation designs. Slag-based mixes are also compatible with Class F fly ash used in saltstone as a functional extender to control heat of hydration and reduce permeability. (Class F fly ash is locally available at SRP.)

A monolithic waste form is produced by the hydration of the slag and fly ash. Soluble ion release (NO3−) is controlled by the saltstone microstructure (bulk porosity and pore size and connectivity). Chromium and technetium are 103−104 times less leachable from slag mixes than from cement-based waste forms. Results suggest that chemical stabilization rather than physical entrapment, as in the case of nitrate is responsible for this improved leaching. Reduction of Cr+6 and Tc+7 to Cr+3 and Tc+4 by ferrous iron or Mn+2 in the slag and subsequent precipitation of the relatively insoluble phses Cr(OH)3 and TcO2 are proposed as the stabilizing reactions.
The Performance Of Actinide-Containing Srl 165 Type Glass In Unsaturated Conditions
Authors: Bates John K. , Gerding Thomas J.
Published: March 2011

As part of the effort by the Nevada Nuclear Waste Storage Investigations (NNWSI) Project to evaluate the volcanic tuff beds of Yucca Mountain, Nevada, as a repository for the permanent storage of high-level nuclear waste, the interaction of actinide-doped Savannah River Laboratory (SRL) 165 type glass with the unsaturated repository environment has been studied. The NNWSI Unsaturated Test method has been used, and the results from batch and continuous tests completed through 18 months demonstrate that several interactions are important for controlling both the reaction of the glass and the release of radionuclides. These interactions include (1) the reaction between the glass and moist air with interludes of liquid water contact, which results in the release of alkali metals from the glass; and (2) the reaction between standing water, glass, and presensitized 304 L type stainless steel which results in breakdown of the glass matrix and the release of radionuclides from the glass-metal assemblage. A comparison of the results of the Unsaturated Test with those of parametric experiments illustrates the importance of presensitized steel in enhancing the glass reaction, and demonstrates the applicability of the Unsaturated Test to those conditions anticipated to exist in the NNWSI repository horizon.
Mineral Phase Identificaticn Along two Profiles from the LRW French Reference Glass: Use of an X-Ray Position Sensitive Detector
Authors: Caurel J. , Beaufort D. , Vernaz E. Y.
Published: March 2011

This study was undertaken to clarify the alteration process of French LWR synthetic glass leached by distilled water at 250 and 300°C for 28 days. The present experiments emphasize “in situ” identification of the alteration products in small areas (20 × 10−4 mm2 ) along the alteration profile by a specific X-ray diffraction technique.

Experimental assembly: The sample is irradiated by an incident X-ray beam (Co k α, 40 mA, 40 Kv) focused to a 150 μ m diameter. The sample oscillates around a θ central selected position and the diffracted X-rays are detected simultaneously in a 14.5 (2 θ ) solid angle, then recorded by the linear position sensitive detector and stored in a multichannel analyzer.
Systematic Composition Studies on the Durability of Waste Glass WV205
Authors: Feng Xiangdong , Barkatt Aaron , Jiang Tian
Published: March 2011

A systematic study of the chemical durability of glass compositions developed for the immobilization of high-level radioactive wastes at West Valley is described. Most of the compositions studied here represent variations around the nonradioactive WV205 composition. The results from this study indicate that the effectiveness of the various oxides tested in increasing the durability of WV205, when considered in terms of 2% additions by weight to the central composition, decreases in the following order: A12O3>ZrO2>SiO2>Cr2O3>Fe2O3>TiO2>CuO>ZnO>NiO. The addition of 2–6% Cr2O3 or NiO to WV205 was observed to cause extensive crystallization. The addition of 2% or 6% ZnO or 2% TiO2, CuO or NiO to the glass actually enhances corrosion rates. A12O3 and ZrO2 are the best additives in terms of increasing the durability. The additions of ThO2 and U3O8 slightly increase the durability. The effects of various oxides on the durability of WV-205-based glasses with ThO2 and U3O8 were found to be very similar to the effects of these oxides on the durability of the corresponding glasses which did not contain ThO2 and U3O8. This study also showed that Fe2O3 has little effect on the durability. However, FeO greatly enhances the corrosion rates of WV205-based glasses. Much less pronounced effects of the redox state of iron were found in the case of more durable base glass compositions.
Annealing and Leaching Studies With Natural and Artificial Obsidian Glass
Authors: MÄrk T. D. , Walder G.
Published: March 2011

Annealing kinetics of fission tracks (produced by induced fission of U235 in natural and artificial (doped) obsidian glass has been studied by etching microscopy as a function of annealing time and temperature. The observed annealing characteristics can be best decribed by a two term exponential function with an Arrhenius type temperature dependence of the annealing coefficients. The activation energies deduced are (0.94 ± 0.16)eV and (1.04 ± 0.15)eV for artificial obsidian and (0.83 ± O.13)eV and (0.60 ± 0.16)eV for natural (fossil) obsidian, respectively. In addition, leaching experiments of obsidian samples exposed to different radiation, doses and rates have been made at two different leachate temperatures. At a temperature of 60°C the leaching rate of irradiated samples is much larger than that of unirradiated samples, whereas at a temperature of 90°C observed leaching rates are similar.
A Comparison of the Performance of Nuclear Waste Glasses by Modeling
Authors: Grambow B. , Strachan D. M.
Published: March 2011

The reprocessing of spent fuel from nuclear reactors and processing of fuels for defense purposes have generated large volumes of high-level liquid waste that need to be immobilized prior to final storage. For immobilization, the wastes must be converted to a less soluble solid, and, although other waste forms exist, glass currently appears to be the choice for the transuranic-containing portion of the reprocessed waste. Once produced, this glass will be sent in canisters to a geologic repository located some 200 to 500 m below the surface of the earth.
Corrosion of Candidate Container Materials in Air-Steam Mixtures
Authors: Lutton James M. , Dewees D. A. , Robinson C. G. , Brehm W. F. , Anantatmula R. P.
Published: March 2011

The environment during the operating period of a high-level nuclear waste repository in basalt is expected to be air saturated with steam. Liquid groundwater is not expected to be in contact with the container surface during that time.

The report presents corrosion findings from tests conducted for one to twenty-five months in an air-steam environment. Tests were carried out with bare metal specimens exposed to an air atmosphere containing 12% moisture in chambers maintained at temperatures between 150°C and 300°C. Cast carbon steel exhibited total penetrations less than 0.002 mm for exposures up to 25 months. A ferritic alloy steel, Fe9CrlMo, showed corrosion results very similar to cast carbon steel. Unalloyed copper materials showed essentially linear corrosion rates, with total penetrations between 0.002 mm at 150°C and 0.14 mm at 300°C in 25 months. Cupronickel 90−10 exhibited total penetrations between 0.001 mm at 150°C and 0.05 mm at 300°C in 25 months. There was a tendency for the corrosion rate to increase with time for cupronickel at 250°C and 300°C possibly because of a mid-test change in the corrosion mechanism. Limited testing of specimens surrounded with bentonite/basalt packing material indicated that the presence of packing has no strong effect on the corrosion of iron-base materials; however, copper-base and cupronickel materials corroded at higher rates in the presence of packing, with a possible shift towards the lower bare specimen corrosion rates with increasing time.
Monitoring of Fluctuations in the Physical and Chemical Properties of a High-Calcium Fly Ash
Authors: Schlorholtz Scott , Bergeson Ken , Demirel Turgut
Published: March 2011

The physical and chemical properties of fly ash produced at Ottumwa Generating Station have been monitored since April, 1985. The fly ash is produced from burning a low sulfur, sub-bituminous coal obtained from the Powder River Basin near Gillette, Wyoming. One-hundred and sixty samples of fly ash were obtained during the two year period. All of the samples were subjected to physical testing as specified by ASTM C 311. About one-hundred of the samples were also subjected to a series of tests designed to monitor the self-cementing properties of the fly ash. Many of the fly ash samples were subjected to x-ray diffraction and fluorescence analysis to define the mineralogical and chemical composition of the bulk fly ash as a function of sampling date. Hydration products in selected hardened fly ash pastes, were studied by x-ray diffraction and scanning electron microscopy. The studies indicated that power plant operating conditions influenced the compressive strength of the fly ash paste specimens. Mineralogical and morphological studies of the fly ash pastes indicated that stratlingite formation occurred in the highstrength specimens, while ettringite was the major hydration product evident in the low-strength specimens.
Scientific Basis for Determining the Sulfate Resistance of Blended Cements
Authors: Mehta P. K.
Published: March 2011

The physical and chemical processes underlying the sulfate attack on concrete are briefly reviewed with special reference to blended portland cements containing natural pozzolans, fly ash, or granulated iron blast-furnace slag. Published literature contains empirical guidelines for evaluating the suitability of blending materials for sulfate resistance; however a critical examination shows that some of the guidelines are not satisfactory. Ideas for establishing a scientific basis for determining the sulfate resistance of blended cements are presented in the paper.
Characterization of Solid Wastes from Advanced SO2 Control Technologies for Electric Utilities
Authors: Eklund A. G. , Golden D. M.
Published: March 2011

Alternate approaches to conventional control of sulfur dioxide emissions from electric utilities burning coal have resulted in “advanced SO2 control technologies”, among which are furnace sorbent injection, fluid bed combustion, and the use of spray dryers. This summary is a review of laboratory-measured properties of wastes produced from these advanced SO2 control technologies. Chemical composition, leaching properties, physical characteristics, and engineering properties of these wastes were determined using standard methods. These properties were measured to aid in design strategies for subsequent disposal and/or utilization of the wastes under RP 2708, which was funded by the Electric Power Research Institute under the direction of Mr. D.M. Golden. Complete, final reports documenting the sampling and analytical protocol, waste characterization per process, and waste utilization will be published over the next two years by the Electric Power Research Institute.
Micromorphology and Mineralogy of Fly Ash and Lime Stabilized Bentonite
Authors: Ferrell Ray E. , Arman Ara , Baykal Gokhan
Published: March 2011

Compacted fly ash, lime, bentonite and water mixtures were cured at 23° and 50°C, for 1, 28, 90 and 180 days. Cementitious products and microstructure were observed by scanning electron microscopy, energy dispersive x-ray spectrometry and x-ray diffractometry. Unconfined compressive strength changes are correlated to the formation of new mineral phases. For bentonite-limefly ash mixtures, strength increased from 1050 kPa (I day) to 2,300 kPa (90 days) and then slightly increased to 2,400 kPa after 180 days at ∼ 230C. Ettringite is the most abundant mineral associated with the increased compressive strength.

New minerals identified in the 23°C mixtures include calcium silicate hydrate - Type 1, afwillite and ettringite. Acicular crystals of these and other minerals were formed by the hydration of lime and fly ash in the montmorillonitic clay. The cementitious phases create a rigid framework joining spheres and clay aggregates. Continued reaction dissolves some of the spheres and slightly reduces the rigidity of the cured samples.
Fundamental Approach for Predicting Pore-Water Composition in Fossil Fuel Combustion Wastes
Authors: Rai Dhanpat , Mattigod S. V. , Eary L. E. , Ainsworth C. C.
Published: March 2011

An application of a fundamental thermochemical approach that relates the aqueous concentrations of elements to specific chemical reactions in waste/water systems is described. The approach involves the concept of waste as consisting of mixtures of discrete solids (pure solid phases and solid solution phases) that control aqueous concentrations of individual solutes through their solubilization or adsorption/desorption characteristics. Thermochemical data can then be used in conjunction with knowledge of the specific solid phases present in the wastes to calculate the aqueous concentrations of elements. This approach does not explicitly consider specific rates of kinetically controlled reactions but does incorporate empirical knowledge of the relative rates of several reaction types. Overall, the thermochemical approach is applicable to all waste types and environments, and is appropriate because (1) most waste solids that either are present or are expected to form during weathering have relatively rapid precipitation/dissolution kinetics, and (2) experimental results, enrichment of many constituents on particle surfaces, and the large specific surface areas of wastes suggest that many of the constituents present in the wastes are accessible to solution attack and are mobilized fairly rapidly. Supporting evidence for the successful application of this approach to predicting pore-water concentrations of several major and trace elements in utility wastes is discussed.
Preparation of Zeolites for TEM Using Microtomy
Authors: Csencsits Roseann , Gronsky Ronald
Published: March 2011

The application of microtomy to Transmission Electron Microscopy (TEM) specimen preparation of zeolite catalysts is explained. Using a new acrylic resin (LR White®) thin sections (≤60 nm) may be cut with relative ease. Although the details described are specific to catalysts, microtomy and the use of the acrylic resin are applicable to any hard ceramic powder sample.
In Situ High-Temperature Cross-Sectional TEM Specimen Preparation
Authors: Fiore Eric M. , Herring Rodney A.
Published: March 2011

We describe a technique for preparing transmission electron microscope (TEM) cross-sectional specimens for observation during in situ annealing to high temperatures. The process utilizes a ceramic adhesive that is stable to a temperature of 1650°C. The technique, which was successfully used to observe the recrystallization of amorphized silicon, is being applied to high-energy ion-implanted silicon in an attempt to better understand the amorphous-to-crystalline phase transformation and defect formation mechanisms resulting from thermal processing.
Preparation of Crazed Specimens of Rubber-Toughened Glassy Polymers for Transmission Electron Microscopy
Authors: Gebizlioglu O. S. , Argon A. S. , Cohen R. E.
Published: March 2011

Upon staining with OsO4, crazes in rubber-toughened themplastics show inverted contrast in microscopy of ultra-thin sections and the details of the craze microstructure are masked. This report presents a method of specimen preparation for obtaining correct contrast of light crazes in a darker background.
Preparation of Semiconductor Cross Sections by Cleaving
Authors: Hetherington Crispin J. D.
Published: March 2011

The practical details are presented for preparing cross-sectional samples of semiconductor epitaxial layers by cleaving. Examples of results are shown and a number of possible applications for the samples are discussed. A variation of the method can be used to prepare a TEM sample of a high Tcsuperconductor.
The Art of the Possible: An Overview of Catalyst Specimen Preparation Techniques for TEM Studies
Authors: Rice Stephen B. , Treacy Michael M. J.
Published: March 2011

Obtaining useful microstructural information about catalysts requires appropriate procedures for preparing specimens for the transmission electron microscope. Unfortunately, most descriptions of catalyst specimen preparation are scattered throughout numerous journal articles or are unavailable. Traditional techniques for preparing heterogeneous catalyst powders include primarily dilute dispersion and ultramicrotomy. The advantages and disadvantages of these will be discussed in terms of information obtainable and possible artifacts. In addition, techniques for preparing layered materials, as well as some novel approaches and model systems, will be presented. With these, as with more traditional approaches, the best method for a specific material will be arrived at only through experimentation. Our aim is to describe a variety of possibilities for getting an already synthesized catalyst into the microscope suitably neat, thin, and artifactfree.
Microstructural Changes Produced by Ion-Beam Thinning in Al-Li-Cu Alloys
Authors: Singh A. K. , Imam M. A. , Michel D. J. , Sadananda K.
Published: March 2011

Thin specimens for transmission electron microscopy examination may be prepared by several techniques, such as electropolishing and ion-beam thinning. Ion-beam thinning, which employs the use of an argon ion-beam at high voltage (e.g. 6kV) to bombard the specimen, is a commonly used technique for preparing and/or cleaning thin foil specimens. The experimental results show that even short-time thinning of Al-Li-Cu alloys with argon ion-beams introduce dramatic microstructural changes. Interesting observations concerning the effect of the ion-beam on quasi-crystals in Al-Li-Cu alloys during the thinning process are presented. The results and causes of the ion-beam thinning in Al-Li-Cu alloys are discussed.
Developments in the Tem Examination Of Pu and Pu Alloys
Authors: Zocco T. G. , Rohr D. L.
Published: March 2011

Microstructural characterization of plutonium utilizing Transmission Electron Microscopy (TEN) has previously been difficult because of the extreme toxicity and high oxidation rate of plutonium metal. Recent developments in plutonium sample preparation have shown that foils of both alpha and delta phases of plutonium may be prepared for TEN without the use of inert atmospheric systems or complex preparation devices. Samples may be produced, using standard electropolishing techniques, that yield important microstructural data on plutonium and plutonium alloys.
Techniques for the Study of the Initial Stages of Electrocrystallization Using TEM
Authors: Hanson K. J. , Gibson J. M. , McDonald M. L.
Published: March 2011

A cell to permit in-situ imaging of the electrodeposition of silver on gold <100> from a polymer electrolyte by TEM is described. The extremely thin electrochemical cells were composed of a layer of polyethylene oxide containing a silver salt between evaporated silver and gold electrodes. Observations from preliminary in-situ TEM experiments include the nucleation and growth, and coalescence of silver islands oriented epitaxially to the gold electrode.
A Microscopic Marker Technique For Documenting Interface Motion in Corrosion Scales Using TEM
Authors: Fan Shou-Kong , Hobbs Linn W.
Published: March 2011

We report here on a microscopic marker technique designed for use with cross-section TEM examination of corrosion scales. The technique involves microphotolithographic methods for sputter deposition of inert markers and has been used to document substrate/scale interface motion during high-temperature oxidation of Ni and Ni-base alloys.
The Preparation of TEM Specimens from Hazardous or Difficult Materials
Authors: Sklad Philip S.
Published: March 2011

The first, and often the most critical, step in any electron microscopy investigation is the preparation of an electron transparent specimen which is representative of the bulk material and in which the features of interest can be clearly observed and interpreted. However, for many materials of technological importance, specimen preparation procedures are far from routine. The application of standard, established techniques may be limited by material inhomogeneities, by physical constraints such as size or geometry, or by material constraints such as toxicity, radioactivity, or reactivity. Examples illustrating techniques for overcoming some of these difficulties will be reviewed.
Preparation Techniques For Structural Characterization of Powdered and Composite Materials
Authors: Ekmejian Evelyn M. , Bulko John B.
Published: March 2011

Standard preparation techniques such as ultramicrotomy and ion-milling are essential for obtaining accurate and detailed information about the structural and/or chemical properties of various categories of materials. The choice of a formulated matrix media has improved the preparation of thin sections of various powders ranging in degree of hardness from zinc oxide to tungsten carbide. This medium has shown superior performance when utilized in ion-milling powders and composites of high hardness such as boron carbide. This support vehicle has facilitated analysis of various geometric structures including hollow ceramic spheres. The homogeneity of chemically derived dielectric powders has been investigated by studying crystallite lattice parameter data derived from analysis of thin sections.
An Automated Jet Polishing Technique for Preparation of Transmission Electron Microscope Specimens for In-Situ Straining
Authors: Clark W. A. T. , Hardiman B. , Wagoner R. H.
Published: March 2011

The increasing availability of intermediate and high voltage transmission electron microscopes, together with recent improvements in video recording equipment, have led to renewed interest in in situ dynamic experiments. To alleviate the problems encountered in preparing TEM specimens with the awkward geometries required for straining stages, a jet polishing technique has been developed which allows the use of a conventional twin-jet electropolishing unit, with all its attendant advantages. A pair of Teflon sheet inserts, with rectangular openings cut to a specific shape and size, are used in the conventional specimen holder. Specimens with elliptical holes close to the center of the gauge section, and with large electron transparent areas at both ends of the long axis, are produced routinely and rapidly. Samples of many annealed metals, such as brass, molybdenum, and aluminum, prepared by this method are stronger, and can be handled more easily, than those prepared by conventional methods.