bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption and Reaction Mechanisms of Thiophene over Sulfided Ruthenium Catalysts
Authors: Cocco Ray A. , Tatarchuk Bruce J. 
Published: March 2011

AbstractAdjustable (hydrogenolysis/hydrogenation) ratios (i.e., selectivity) of thiophene over sulfided ruthenium catalysts have been observed to depend on the method of presulfidization. Sulfidization in 10% H2S/H2 at 300–800K yielded a selectivity greater than 100, whereas a ratio of ca. 1 was noted after presulfidization in 100% H2S. The transition from one selectivity regime to another is reversible and can be changed via subsequent annealing or resulfidization procedures. X-Ray photoelectron spectroscopy shows similar results where sulfidization in 100% H2S yields: (i) a higher sulfur uptake with a corresponding 0.5 eV shift of the S 2P1/2–3/2 peaks to higher binding energy; (ii) multilayer sulfur incorporation at lower temperatures; and (iii) similar reversible behavior following subsequent annealing or resulfidization. Secondary ion mass spectroscopy and temperature programmed desorption studies also reveal that sulfur coverages affect thiophene adsorption, orientation and cracking on ruthenium surfaces.
Surface Chemical Characterization of Internal Interfaces Generated Within Thin-Film Fe-Ti Hydrides
Authors: Sanders Jeffrey H. , Tatarchuk Bruce J. 
Published: March 2011

AbstractFeTi is considered an excellent candidate for the reversible storage of hydrogen and has been studied extensively in an attempt to understand the bulk activation needed for this material before use. Segregation of TiO2 to the surface has been noted to occur during activation explaining a slight loss of efficiency per hydride cycle, however, characterization by a host of bulk and surface sensitive techniques has not revealed the cause of this decomposition process.10 nm FeTi samples were prepared in a UHV evaporator both with and without palladium coatings. Post treatment characterization was performed with backscatter conversion electron Mossbauer spectroscopy (CEMS), XPS and SIMS. CEMS is a powerful tool for providing stoichiometric, electronic, magnetic, chemical, and particle size information of iron at depths down to 100 nm. XPS and SIMS are useful to gain quantitative and chemical state information from the topmost 2 nm and the topmost monolayer, respectively. Activation treatments consisted of annealing at 573K and 623K followed by reduction at 573K. Results indicate that ppm levels of H2O in H2 are sufficient to decompose the FeTi alloy and produce TiO2 and Fe metal domains at the surface. Also, at 573K in vacuum, a solid-state reaction was found to occur between Fe oxides and FeTi to produce Fe metal and TiO2. The Pd-FeTi interface was probed with CEMS and the results demonstrate hydrogen dissociation and migration in the absence of alloy decomposition. Our approach uses nondestructive-depth profiling of non-Pd coated FeTi samples along with interfacial information from Pd-FeTi specimens to obtain unique insight into the decomposition process.
The Characterization of Hydrocarbon Intermediates in H-ZSM-5
Authors: Kofke T. J. Gricus , Gorte R. J. , Farneth W. E. 
Published: March 2011

AbstractWe have examined the adsorption of simple alcohols and 2-propanamine on H-ZSM-5 zeolites with Si/Al2 ratios between 38 and 520. Thermogravimetric analysis (TGA) demonstrated that most of the molecules display a clearly defined adsorption state corresponding to a coverage of one molecule per Al site. Temperature programmed desorption (TPD) and transmission infrared spectroscopy results for each of the molecules in this 1:1 adsorption state are consistent with adsorption being due to the transfer of a proton from the zeolite to the adsorbed molecule. These results provide additional evidence that carefully prepared H-ZSM-5 is a Bronsted acid, with one acid site per framework Al atom, in which all of the acid sites are identical in strength.
Brine Transport in the Bedded Salt of the Waste Isolation Pilot Plant (wipp): Field Measurements and a Darcy Flow Model
Authors: Mctigue David F. , Nowak E. James 
Published: March 2011

AbstractBrine flow has been measured to unheated boreholes for periods of a few days and to heated holes for two years in the WIPP facility. It is proposed that Darcy flow may dominate the observed influx of brine. Exact solutions to a linearized model for one-dimensional, radial flow are evaluated for conditions approximating the field experiments. Flow rates of the correct order of magnitude are calculated for permeabilities in the range 10−21–1020 m2 (1–10 nanodarcy) for both the unheated and heated cases.
Modelling approach to the prediction of Equilibrium Phase Distribution in Slag-Cement Blends and their Solubility Properties.
Authors: Glasser Frederik P. , Macphee Donald E. , Lachowski Eric E. 
Published: March 2011

AbstractBlended cements containing mixtures of granulated blast-furnace slag (BFS) and Portland cement give low permeability matrices with initially favourable leach characteristics. Their retention arises from a combination of physical and chemical effects which include high pH and sorption. It is not practical though, in either laboratory or site-based experimentation, to determine changes in matrix chemistry over long timescales and the development of realistic models for long-term property predictions therefore becomes increasingly important. This paper pursues the development of such a model enabling changes in chemical and mineralogical balances during ageing to be predicted.Phase development is assessed in the system CaO-Al2O3-SiO2-MgO-H2O. In the relevant composition range, the phases occurring include crystalline hydrates: portlandite, (Ca(OH)2); gehlenite hydrate, (2CaO.Al2O3.SiO2.8H2O); a hydrotalcite-structured phase (nominally 6MgO.Al2O3.(OH)x.yH2O). an AFm type phase, (nominally 4CaO.Al2O3 SO3.12H2O); and a poorly crysiallised c~lcium silicate hydrogel, C-S-H. All five phases are observed to occur together in slag-cements which are still hydrating. Given, as input, the chemical analyses of both the slag and the cement, and the initial blending proportions, the model predicts the equilibrium distribution between the five components and additionally, the Ca/Si ratio of the C-S-H. The aqueous chemistry in the system is predicted from the calculated phase distribution and appropriate solubility products.
Effect of Ionizing Radiation on Moist Air Systems
Authors: Reed Donald T. , Van Konynenburg Richard A. 
Published: March 2011

AbstractThe radiation chemistry of nitrogen/oxygen/water systems is reviewed. General radiolytic effects in dry nitrogen/oxygen systems are relatively well characterized. Irradiation results in the formation of steady state concentrations of ozone, nitrous oxide and nitrogen dioxide. In closed systems, the concentration observed depends on the total dose, temperature and initial gas composition. Only three studies have been published that focus on the radiation chemistry of nitrogen/oxygen/water homogeneous gas systems. Mixed phase work that is relevant to the gaseous system is also summarized. The presence of water vapor results in the formation of nitric acid and significantly changes the chemistry observed in dry air systems. Mechanistic evidence from the studies reviewed are summarized and discussed in relation to characterizing the gas phase during the containment period of a repository in tuff.
Evolution of the Groundwater Chemistry Around a Nuclear Waste Repository.
Authors: Haworth A. , Sharland S. M. , Tasker P. W. , Tweed C. J. 
Published: March 2011

AbstractPerturbations to the natural chemistry of the geology surrounding a nuclear waste repository may affect the overall nuclide release rates through properties such as their solubilities and sorption characteristics. In this paper, we develop some of the necessary techniques to construct a detailed research model of the evolution of the groundwater under the influence of the backfill material. These techniques involve various extensions to the coupled ionic migration and chemical equilibria code, CHEQMATE and are used in the first stages of such a model. Although the design and location of a deep low- and intermediate-level nuclear waste repository have not yet been finalised in the U.K., we have considered a concrete backfill material embedded in a clay geology. Preliminary results suggest that over timescales of about a thousand years the natural buffering action of the clay against changes in pH has a significant effect on the scale of perturbation by the ingress of highly alkaline porewater. It seems likely therefore that this type of modelling will have considerable relevance to the safety assessment models.
Xps and Xrd Studies of Uranium Rich Minerals from Cigar Lake, Saskatchewan
Authors: Sunder S. , Taylor P. , Cramer J. J. 
Published: March 2011

AbstractSamples of uranium ore from the 1,300 million year old Cigar Lake deposits in northern Saskatchewan have been investigated using X ray Photoelectron Spectroscopy (XPS) and X ray Diffraction (XRD). The XPS spectra showed the peaks for U, Pb, 0, C, Si, Ca and Mg. Analysis of highresolution XPS spectra showed that the oxidation state of uranium in these minerals is equal to, or lower than, that of U3O7. The XRD data confirm the presence of an oxidized phase, most likely α U3O7., in addition to UO2. The low U(VI)/U(IV) ratio in these minerals is consistent with the low uranium concentration found in groundwater in contact with these uranium minerals. The relevance of these results to the disposal concept of used nuclear fuel in the Canadian Nuclear Fuel Waste Management Program is discussed.
An Annealing Study of Alpha-Decay Damage in Natural UO2 and ThO2
Authors: Stout P. J. , Lumpkin G. R. , Ewing R. C. , Eyal Y. 
Published: March 2011

AbstractIsochronal annealing (100°–1200°C) of alpha-decay damage was performed on UO2 and ThO2 and isothermal annealing (400°C and 750°C) of UO2 was done to determine the change in unit cell parameter (UO2: ao = 5.501Å to 5.458Å ± 0.001; ThO2: ao = 5.548Å to 5.523Å ± 0.001), strain, and crystallite size (data inconclusive). Two recovery stages (UO2: Stage I at ≈225°C, Stage II at ≈675°C; ThO2: Stage I at ≈250°C, Stage II at ≈550°C) were observed for each. Strain decreased with temperature for both, but never completely recovered in either (UO2 final value: ≈2.37 × 10−3; ThO2 final value: ≈2.06 × 10−3).
Performance Assessment of Glass As A Long-Term Barrier To The Release of Radionuclides Into The Environment
Authors: Grambow B. , Lutze W. , Ewing R. C. 
Published: March 2011

AbstractPerformance assessment of high-level nuclear waste forms in a repository must cover periods of time on the order of hundreds of thousands of years. There has rarely been a need to extrapolate the properties of a material over such long periods of time (except in the geologic sciences, e.g., the evaluation of long-term weathering effects based on results from laboratory experiments) and there has never been a more important need to make accurate and -verifiable “predictions” of the long-term materials performance. The results of such extrapolations could affect decisions concerning the selection of a repository and the number and types of barriers that are required to insure isolation over long periods of time. In typical safety analyses [1,2] waste form corrosion is described by a single constant rate, and no effort is made to evluate whther the modal of the “source term” can be substantiated or verified by comparison similar or analogous processes [3].
Leaching Tc-99 from SRP Glass in Simulated Tuff and Salt Groundwaters
Authors: Bibler N. E. , Jurgensen A. R. 
Published: March 2011

AbstractResults of leach tests with Tc-99 doped SRP borosilicate waste glass are presented. The glass was prepared by melting a mixture of SRP 165 powdered frit doped with a carrier free solution of Tc-99 at 1150°C. Dissolution of portions of the resulting glass indicated that the Tc-99 was distributed homogeneously throughout the glass. Static leach tests up to 90 days were performed at 90°C in J-13 tuff groundwater or WIPP brine A at a SA/V of 100m−1. Normalized mass losses were calculated for Tc-99 as well as all the major elements in the glass. Results indicated that under ambient oxidizing conditions Tc-99 leached no faster than the glass-forming elements of the glass. In J-13 water, Tc-99 leached congruently with B. In WIPP brine A, it leached congruently with Si. Leach rates for Li were higher in both groundwaters, probably due to a contribution from an ion exchange mechanism. Leach tests were performed under reducing conditions in J-13 water by adding Zn/Hg amalgam to the leachate. In these tests the pH increased significantly, probably because of the reaction of the amalgam with the water. In a 21-day test, the pH Increased to 13 and leach rates for the glass were very high. Even though there was significant dissolutiop of the glass, the normalized mass loss based on Tc-99 was only 0.02g/m2. This result and the fact that reducing conditions at normal pH values do not significantly affect the dissolution of the glass, indicate that the low concentrations for Tc-99 obtained under reducing conditions are due to its solubility and not due to an increased durability of the glass.
Influence of Groundwater Composition on Glass Leaching and Actinide Speciation
Authors: Bidoglio G. , Offermann P. , De Plano A. , Lazzari G. P. 
Published: March 2011

AbstractFlow-leaching studies were conducted using borosilicate glass beads containing 241-Am, 237-Np and 238-Pu. The leachates were a bicarbonate groundwater and a brine. Tests were carried out unger oxidizing and reducing conditions. In bicarbonate groundwater (2.6 × 10−3M NaHCO3, pH 8.4) under oxic conditions, steady-state leach-rates were found to increase in the order Pu∼Am<Np, with Np species leached congruently with sodium. Direct identification of Np carbonate complexes in the leachate was carried out by. electromigration. A reversed order of leachability was obtained in a reducing environment. In this case, Pu was found to be associated with particulate matter. In a salt brine leachate (5.4 M NaCl, pH∼6) a periodic cycle of increasing-decreasing concentrations was observed under reducing conditions. This was found to be dependent upon the redox state of actinides. Radionuclide adsorption into an unstable gel layer was postulated.
The Long-Term Corrosion and Modelling of Two Simulated Belgian Reference High-Level Waste Glasses
Authors: Van Iseghem P. , Grambow B. 
Published: March 2011

AbstractThe corrosion behaviour in distilled water of two simulated candidate high level waste borosilicate glasses (SAN602519L3C2 and SM58LW11) his been investigated at 90°C for different SA/V condition's 10, 100, 7800 m−1). The experimental data were modelled using the PHREEQE and GLASSOL computer codes. The model is quite successful for describing the corrosion behaviour, using experimentally derived values for the forward rate, silica saturation and the final rate. GWss SAN60 is more stable than glass SM58 at SA/V values of 10 and 100 m−1, but in the long term the relative performance is inverse. Indeed, the high Al content of SAN60 induces the creation of analcime crystals after SiO2 has reached its saturation concentration in solution, which cause an enhancement of the final rate of dissolution of the glass; for SM58 on the contrary the SiO2 solution is a stable condition.
Borosilicate HLW Glass Leaching in Silica Saturated Solution
Authors: Lanza F. , Manara A. , Mammarella L. , Blasi P. , Ceccone G. 
Published: March 2011

AbstractThe aim of these measurements is to study how a silica saturated solution influences leaching from a HLW glass matrix. Cylindrical samples of I117 borosilicate glasses were suspended in polycarbonate vials containing a SiO2 saturated solution and leached at temperature of 50 or 80°C for different times (from 1/2 to 28 days). Mass loss, X-ray photoelectron spectroscopy (XPS) and nuclear reaction techniques were applied for post leaching tests on the glass samples.Analysis of boron and sodium released from the glass were performed in the leachate. Sodium and boron release followed a square root time dependence at all the observed leaching times.XPS measurements revealed a surface increase of silicon content with respect to unleached samples, with aluminium showing the same behaviour as silicon. The presence of the layer enriched in silicon and aluminium does not stop the release of sodium and boron, whereas the mass loss does slow down because of the formation of aluminio-silicate compounds.
Corrosion Studies of A216 Grade WCA Steel in Hydrothermal Magnesium-Containing Brines
Authors: Haberman J. H. , Frydrych D. J. 
Published: March 2011

AbstractThe U.S. Department of Energy's Salt Repository Project (SRP) is investigating the general corrosion resistance of cast mild steel as a candidate material for waste package containers. Evaluation of this material is being performed at the Pacific Northwest Laboratory in environments simulating expected repository conditions.General corrosion studies of mild steel (ASTM A216 grade WCA) in the as-cast and normalized conditions were conducted in hydrothermal halitesaturated (saturated at ambient temperature) brine environments simulating a “dissolution” and an “inclusion” brine. Corrosion tests were also performed in brines similar to the inclusion brine but containing magnesium concentrations ranging from 1000 to 30,000 ppm to investigate the effect of magnesium on the corrosion behavior.Corrosion rates of the cast mild steel were found to increase with increasing temperature and with increasing magnesium concentration. Some possible mechanisms that explain the observed behavior are presented.
Characterization of Fly Ash Reactivity by Isothermal Conduction Calorimetry
Authors: Cook David J. , Cao H. Trinh , Baweja Daksh 
Published: March 2011

SUMMARYThe reactivity of fly ash is generally difficult to determine because neither a single physical nor chemical property nor any combination of these can be used characterize a particular sample completely. A direct reflection of this is the range of pozzolanicity tests proposed by standards worldwide and the applicability and relevance of such tests is currently being debated.In many countries, codes of practice and standards relating to fly ashes are currently under review. Some work has been carried out in countries including Australia, United Kingdom, and the United States on commercial fly ashes with a view to possible classification and implementation into standards [1-2]. It is generally recognized that current standards on fly ash do have some inadequacies with regard to performance prediction when included in concrete. Fineness requirements for fly ash for use in structural concrete (BS3892: Part 1) in the United Kingdom are currently being debated [2] with many workers suggesting that it would be possible to produce durable concrete with ashes which would not comply with the requirements of the standard [3].
Phase Characterization of Coal-Fueled Turbine Engine Deposits
Authors: Schields Paul J. , Spiro Clifford L. , Koch Edward F. 
Published: March 2011

ABSTRACTA major consideration in the development of a coal-fueled turbine engine is to minimize the deleterious effect of products of combustion (POC) on the engine components. Characterization of the POC phases is important for understanding and regulating combustion, emissions, deposition, corrosion and erosion behavior. POC phases deposited from the combustion of beneficiated bituminous coal in turbine simulators were characterized using x-ray techniques and electron microscopy. The phase assemblages include plagioclase feldspars, feldspathoids, spinels, anhydrite, hematite and noncrystalline material. The deposits had the form of a partially sintered powder and a slag. Differences in the phase composition of the powder and slag were determined by xray analysis and observed in the feldspar/spinel lattice parameters. The morphology, phase associations, compositional differences of the powder and slag, and heat treatment experiments indicate that the slag is largely formed by fusion of the powder. The hypothetical fusion process decomposes the CaSO4 in the powder and the released calcia is incorporated into the plagioclase solid solution powder phase. The additional alumina required for charge neutrality in the plagioclase comes from the powder's Al-rich spinel which transforms to an Al-poor spinel. These phase characterization results are useful for assessing and optimizing deposit remediation methods.
Is the Available Alkalitest A Good Durability Predictor for Fly Ash Concrete Incorporating Reactive Aggregate?
Authors: Smith Robert L. 
Published: March 2011

ABSTRACTThe available alkali test has been used for years as a method for preventing the use of a high-alkali fly ash in concrete containing reactive aggregate. This report presents data on fifteen good-quality Western ashes, both Class C and Class F, that are currently used in readymixed concrete. All fifteen ashes were effective in reducing the expansion due to the alkaliaggregate reaction. The reduction in mortar bar expansion (ASTM C 441) varied from 16% to 81%. Correlation of the percent reduction was made with available alkalies as Na2O, silica content, lime content, sulfur content, and the sum of silica, alumina and iron oxide. Surprisingly, the best correlation to percent reduction was with sulfur and the least was with available alkalies. This data indicates that most, if not all, fly ashes are effective in reducing the alkali aggregate reaction and that the available alkali test is not the best method for predicting the effectiveness of a fly ash in controlling this reaction.
The Effect of Blast Furnace Slag on the Microstructure of the Cement Paste/Steel Interface
Authors: Onabolu O. A. , Pratt P. L. 
Published: March 2011

ABSTRACTThe microstructures of steel reinforced ordinary Portland cement mortar samples, and those containing 40% and 70% slag as cement replacement, have been studied by electron optical techniques, after exposure to stagnant sea-water at 23°C for 320 days. Fracture surfaces along the interface with steel were examined using secondary electron imaging in the SEM. This revealed differences between the OPC and slag specimens as regards the morphology of the phases and the amounts of calcium hydroxide present. The microstructure at the interface with steel was studied by means of back scattered electron imaging combined with quantitative image analysis. Chloride concentrations at sections around the interface were determined by means of an EDXA facility linked to the SEM. Even after 320 days immersion in sea-water, there was some calcium hydroxide present in the interfacial zone.
Sample Preparation of Aluminum Bridge Test Vehicles for Tem In-Situ Crystallographic Studies of Electromigration
Authors: Rhoden W. E. , Maskowitz J. V. , Kitchen D. R. , Omlor R. E. , Lloyd P. F. 
Published: March 2011

IntroductionElectromigration in aluminum films has been identified as an increasing concern for integrated circuit reliability. Electromigration is the mass transport of atoms in a conductor under a current stress. Electromigration occurs in conductors experiencing current densities greater than 105 A/cm2 and is accelerated by high temperature. The damage to aluminum films manifests itself in the formation of voids, hillocks and whiskers along the conductor. This paper presents a test vehicle preparation procedure which can be used to investigate electromigration.