bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applications of Neutron Scattering to Problems in Materials Science
Authors: Weertman J. R. 
Published: March 2011

AbstractNeutrons possess a number of attributes which make neutron scattering a powerful technique for the investigation of problems in materials science. These properties are discussed with emphasis on their importance to materials characterization. A number of recent experiments using neutron scattering will be described. These studies include the areas of damage accumulation; residual stress; porosity in ceramics; polymer chain configurations; phase changes.
Investigation of the Homogeneity and Defect Structure in Semi-Insulating Lec GaAs Single Crystals by Synchrotron Radiation Double Crystal X-Ray Topography.
Authors: Barnett S J , Tanner B K , Brown G. T. 
Published: March 2011

AbstractThe high intensity and large beam size of a synchrotron radiation source have been exploited in order to obtain double crystal X-ray topographs of whole 2in. and 3in. slices of semi-insulating LEC GaAs single crystals. Exposure times, typically 30 minutes for high resolution topographs, are at least one order of magnitude down on those required when using a conventional source. Variations in relative lattice parameter and lattice tilt have been measured as a function of position on the slice. The defect structure has been imaged and dislocations are seen in cellular configurations, slip bands and linear arrays (lineage), the latter of which are shown to be associated with small lattice tilts, typically 30”. The defect structure revealed on the topographs has been correlated with 1μm infrared absorption micrographs which are believed to represent the concentration of the dominant deep level EL2.
Study of the Dynamic Behavior of Dislocations During the Melt Growth Process of Tin Crystal by Synchrotron X-Ray Topography
Authors: Nittono Osamu , Ogawa Taro , Gong Sheng Kai , Nagakura Sigemaro 
Published: March 2011

AbstractThe dynamic behavior of the melt growth process of Sn with low dislocation density has been investigated by means of synchrotron Laue topography using an X-ray sensing high resolution camera tube. No defect images are observed at the point where the melting begins. No dislocations are generated during the temperature rise to the melting point,although the dislocation configuration changes slightly. Most of dislocations which are contacting the melting interface do not propagate into a newly grown crystal part and the homogeneous solidification results in a nearly perfect crystal.Dislocations and slip bands are generated from a part where the solidification is completed. It was found that the growing interface appears atomically rough and extends through a considerably large number of layers.
Some Difficulties in the Assessment of Pore-Structure of High Performance Blended Cement Pastes
Authors: Marsh Bryan K. , Day Robert L. 
Published: March 2011

AbstractPartial replacement of cement by fly-ash allows the production of concretes with high strength and low permeability. The correct analysis and prediction of engineering behaviour requires a knowledge of the development of pore-structure of these materials. However, a study of the relationships between engineering and microstructural characteristics has revealed problems in the accurate assessment of pore-structure.Porosities of plain and blended pastes were analysed by both helium pycnometry and mercury porosimetry. Pastes showing pozzolanic reaction gave values of helium porosity whidh were different from the mercury porosity (measured on the same sample); pastes showing no pozzolanic reaction gave equal values for mercury and helium porosity. Also, significant differences in porosity and pore-size distribution were found for identical specimens when prepared by different techniques, namely direct oven-drying and solventreplacement; these differences occurred whether there was pozzolanic reaction or not.It is suggested that as well as experimental difficulties, there may be fundamental differences in the way pore-structure develops in plain and blended cement pastes.
Relation Between Strength, Pore Structure and Associated Properties of Slag-Containing Cementitious Materials
Authors: Roy Della M. , Idorn G. M. 
Published: March 2011

AbstractSubstantial increases of the strength of cement paste and mortars may be obtained in conventional processing by optimizing the materials components, the rheology and the curing, and thereby improving the microstructures. Cementitious materials with high proportions of granulated blast-furnace slag have been investigated. Higher strengths of ASTM C 109 mortars were obtained with 40 to 65% substitution of portland cement by slag, than with ordinary mix compositions and processing.For one set of mixtures, 28 day strengths ≥ 100 MPa (some as high as 240 MPa) were consistently attained after curing at temperatures ranging from 27 to 250°C. The slag substitutions developed finer pore structures as revealed by intrusion porosimetry measurements, than those with pure portland cement. This is believed to be a major reason for their enhanced durability. At each stage from 3 to 28 days, increase of curing temperatures from 27 to 90°C decreased porosity and increased the strength, reflecting an increased maturity.Implications for practice and suggestions for further work are discussed.
Production of High Strength Pastes, Mortars, and Concretes
Authors: Carrasquillo Ramon L. 
Published: March 2011

AbstractFor concrete, a grossly heterogeneous material, guidelines for selection of materials for its production, especially high strength concrete, should consider the interactions of its different components under load. Materials selection and production techniques for achieving concretes, mortars and cement pastes with strengths in excess of 10,000 psi are discussed. Emphasis is placed on the production of concretes having a compressive strength in the range of 10,000 to 15,000 psi using readily available materials and conventional production techniques. Emphasis is placed on the practical and technical significance of the factors involved in the selection of the materials and their proportions to achieve uniform, economical, high quality concrete. Selection of the concrete ingredients and their proportions is discussed in terms of their relative contribution to the compressive and flexural strength, elastic properties and observed failure mode of the paste, mortar and concrete. Production of concretes having compressive strengths in excess of 15,000 psi using exotic materials and special production techniques is also discussed.
Very High Strength Cfment-Based Materials – a Prospective
Authors: Diamond Sidney 
Published: March 2011

AbstractAn attempt is made to provide a prospective on new very high strength cement based materials. The mechanical properties of concrete and of conventional cement pastes are considered, and limitations on the behavior of paste set by the Griffith concept of a critical crack explored. Evidence is cited confirming that spherical air voids do indeed act as critical Griffith flaws in undried pastes; however it is suggested that shrinkage cracks dominate the behavior of cement paste exposed to drying. Very high strength systems.must avoid both large air voids and other pores and also be resistant to shrinkage cracking. Streams of development leading to “DSP” (Aalborg) and “MDF” (ICI) systems are described, and details of the functioning of the two classes of product are described. Current and potential commercial developments are briefly noted, and possible interrelations with the emerging areas of “high technology ceramics” mentioned. Finally, a brief summary of relevant mechanical properties is provided.
The Properties and Potential Applications of Macro-Defect-Free Cement
Authors: Alford N McN , Birchall J D 
Published: March 2011

AbstractThe properties of Macro-Defect-Free (MDF) cements are reviewed. Combinations of these properties place MDF cements in a unique position in the materials field, a position which makes direct replacement of current engineering materials such as metals plastics and ceramics a viable proposition. Perhaps of more importance is the invention of devices and components hitherto unavailable because of the property-restricted nature of available materials. Examples are given of unusual uses for cement. These include applications in the fields of cryogenics, ballistic protection, electromagnetic radiation screening and acoustics.
Slurry Infiltrated Fiber Concrete (SIFCON): Properties and Applications
Authors: Lankard David R. 
Published: March 2011

AbstractSteel fiber reinforced concretes (SFRC) are typically prepared by adding the fiber along with the other concrete ingredients in the mixing operation. At fiber contents in excess of 2 volume percent, the SFRC becomes difficult or impossible to mix and place. Inasmuch as improvements in concrete properties attributed to the fibers increase as a function of increasing fiber content, this situation places a limit on the ultimate property development in SFRC prepared using the premix approach. Recently, a procedure has been developed wherein steel fiber contents up to 20 volume percent have been provided. Slurry Infiltrated Fiber Concrete (SIFCCN) composites possess outstanding strength, ductility, and crack/spall resistant properties. Equally:important, the ability to construct with SIFCON has been demonstrated.
Microsilica Concrete: A Technological Breakthrough Commercialized
Authors: Radjy Farrokh F. , Loeland Kjell E. 
Published: March 2011

AbstractWith the advent of microsilica concrete, a new generation of high to ultra high strength and high durability concretes have become commercially feasible and are now being specified and used internationally. Microsilica concrete is produced by incorporating microsilica (beneficiated condensed silica fume) additives in conventional concrete mixes, using conventional materials and equipment. Flowing microsilica concretes with strengths as high as 17000 psi have become field realizable, also benefiting by durability improvements expressible by factors, not percents.Properties of microsilica concrete are reviewed, and property improvements qualitatively linked to a much refined micropore structure of the binder phase.Some recent and rapidly developing field and laboratory experience both in the U.S. and overseas are presented.
A Nuclear Reaction Analysis Technique to Determine The Penetration of Hydrogenic Species into Glasses Exposed to Leaching Solutions
Authors: Gignac L. M. , Altstetter C. J. , Brown S. D. 
Published: March 2011

AbstractNuclear reaction analysis is discussed as a method for determining the distribution of deuterium beneath the surfaces of glasses exposed to heavy water solutions for various times and temperatures. Limited examples of both conventional depth profiling for deuterium and a new technique for deuterium mapping are presented. The possible use of deuterium mapping for investigating the kinetics and mechanisms of the leaching of glasses is discussed.
International Waste Glass Study – Composition and Leachability Correlations
Authors: Wicks George G. , Rankin Duncan W. , Gore Sherry L. 
Published: March 2011

AbstractThe International Waste Glass Study found important similarities, based on correlations of composition and leaching performance, among many different defense and commercial waste glass compositions being studied worldwide. In addition, the beneficial effect of waste on glass performance was confirmed for the systems evaluated.
One-Year Leaching of Three SRL Glasses in Granite
Authors: Zhu Bing-Fu , Clark D. E. , Hench L. L. , Wicks G. G. , Werme Lars 
Published: March 2011

AbstractThree Savannah River Laboratory (SRL) simulated nuclear waste glasses were buried in granite boreholes 345 meters deep. Included in the same boreholes were other potential waste package components including stainless steel and bentonite. Samples were maintained at either ambient mine temperature (8–10°C) or 90°C. Differences in glass leaching performances were observed among the three compositions, with SRL 165 being more durable than SRL 131, both with 29.8% TDS waste. Likewise, the presence of some package components affected the leaching performances. Bentonite resulted in accelerated attack on the glass while the presence of stainless steel did not appear to have much effect. Results obtained through one year of burial are presented in this paper.
Electrokinetics, Adsorption and Colloid Study of Simulated Nuclear Waste Glasses Leached in Aqueous Solutions
Authors: Lee Cheng T. , Clark D. E. 
Published: March 2011

AbstractZeta potentials of SRL-131-29.8% TOS simulated nuclear waste glasses leached in D.I. water, Al, Ca, Mg, and Zn chloride solutions at 90°C were measured as a function of leaching time. For short term leaching, the adsorption of Ca, Mg, Zn and Al reverses the glass surface potential from negative to positive. Colloids were found to be stable in D.I. water and AICl3 solutions after leaching, presumably due to the electrostatic repulsion between the glass surface and similarly charged particles. Colloids were not found in Mg, Zn or Ca chloride solutions after leaching; instead, a relatively thick metasilicate surface layer was formed on glass surfaces leached in these solutions. The concentration of Si in solution is reduced by the formation of these surface layers.
Leaching Savannah River Plant Nuclear Waste Glass in a Saturated Tuff Environment
Authors: Bibler N. E. , Wicks G. G. , Oversby V. M. 
Published: March 2011

AbstractSamples of SRP glass containing either simulated or actual radioactive waste were leached at 90°C under conditions simulating a saturated tuff repository environment. The leach vessels were fabricated of tuff and actual tuff groundwater was used. Thus, the glass was leached only in the presence of those materials (including the Type 304L stainless steel canister material) that would be in the actual repository. Tests were performed for time periods up to 6 months at a SA/V ratio of 100 m−1. Results with glass containing simulated waste indicated that stainless steel canister material around the glass did not significantly affect the leaching. Based on Li and B (elements not in significant concentrations in the tuff or tuff groundwater), glass containing simulated waste leached identically to glass containing actual radioactive waste. The tuff buffered the pH so that only a slight increase was observed as a result of leaching. Results with glass containing actual radioactive waste indicated that tuff reduced the concentrations of Cs-137, Sr-90, and Pu-238 in the free groundwater in the simulated repository by 10–100X. Also, radiolysis of the groundwater by the glass (approximately 1000 rad/hr) did not significantly affect the pH in the presence of tuff. Measured normalized mass losses in the presence of tuff for the glass based on Cs-137, Sr-90, and Pu-238 in the free groundwater were extremely low, nominally 0.02, 0.02, and 0.005 g/m2, respectively, indicating that the glass-tuff system retained radionuclides well.
Nuclear Waste Glass Interfaces after 1 year Burial in Stripa
Authors: Werme L O , Hench L L , Lodding A 
Published: March 2011

AbstractInterface reactions between two nuclear waste borosilicate glasses and repository components have been studied in an in-situ burial experiment in Stripa mine, Sweden. Exposures up to one year have been analyzed and are reported.The results obtained up to date show an increased depth of attack ranging by: increased severity from the glass/granite interfaces, glass/glass interfaces to glass/bentonite interfaces. The rate and extent of surface attack is discussed in terms of ion exchange with species from the groundwater and leached from the repository components.
Effect of Temperature on the Sorption of Chelated Radionuclides
Authors: Maest Ann S. , Crerar David A. , Dillon Edward C. , Trehu Stephen M. , Rountree Tamara N. 
Published: March 2011

AbstractTemperature effects in the near-field radioactive waste disposal environment can result in changes in the adsorptive capacity and character of the substrate and the chemistry of the reacting fluids. This work examines the effect of temperature on 1) the kinetics of radionuclide sorption onto clays from 25°-75°C and 2) the degradation and metal-binding ability of two organic complexing agents found in chelated radioactive wastes and natural groundwaters. Clay-solution mixtures containing U, Co, Sr and Cs with kaolinite or montmorillonite were sampled over a 100-hour period for kinetic results at 25°, 50° and 75°C with and without EDTA. Three thermal degradation experiments with EDTA and oxalic acid were maintained at 250° for one week. Initial equilibrium concentrations were attained in the kinetics runs within 30 minutes in most cases. Possible sorption/retention mechanisms include ion exchange, physical adsorption and/or precipitation. EDTA decreased U and Co sorption, but slightly enhanced Sr and Cs sorption. Complexing of Al by EDTA may drive Sr and Cs to the clay surface to satisfy the resulting charge imbalance. Adsorption increased with increasing temperature for U, Co without EDTA and Sr, while Cs sorption decreased from 25°-75°C. Primary EDTA degration (at ∼200°C) products were mostly ethyl- and methyl-substituted amines with no metal-binding ability; therefore, to inhibit transport of low-level chelated radioactive wastes thermal or biological degradation is recommended. Interaction of high-level radioactive wastes with naturally-occurring organics in repository groundwaters may enhance migration of the actinides and 60Co.
Transport and Capture of Colloidal Particles in Single Fractures
Authors: Bonano E. J. , Beyeler W. E. 
Published: March 2011

AbstractIn this study, the transport and capture rates of colloidal particles were calculated for a parallel-plate channel simulating a single fracture. The steady-state convective diffusion equation was solved with the particle velocity normal to the walls of the channel being the sum of the external forces acting on the particles. The forces considered were the gravitational, London-van der Waals and electric-double layer forces. The effects of parameters governing these forces and particle production mechanism on the rates of particle capture and transport are determined. The dynamic balance between particle production and capture has a significant effect on the concentration of particles leaving the fracture. The average particle velocity, though higher than the average fluid velocity, seems to be insensitive to phenomena governing particle capture.
Behavior of Carbon-14 in Waste Packages for Spent Fuel in a Repository in Tuff
Authors: Konynenburg R. A. Van , Smith C. F. , Culham H. W. , Otto C. H. 
Published: March 2011

AbstractAnalysis of gas from a heated air-filled canister containing a spent fuel assembly before and after rupture of a fuel rod shows that about 1.5 mCi of 14C from the external surface of the assembly was rapidly oxidized and released as 14CO2 in excess oxygen at 275°C and 104rad/hr. After rupture, an additional 0.3 mCi was released, probably also from the external surface. The total 14C inventory in the entire 15×15 rod assembly including structural hardware is estimated to be 690 mCi. These measurements indicate that account will have to be taken of the time distribution of lifetimes of the canisters, and a broad definition of the “engineered system” may be necessary, in order to meet 1OCFR60 requirements with spent fuel in a repository in tuff.
Thermodynamically Coupled Mass Transport Processes in a Saturated Clay
Authors: Carnahan C. L. 
Published: March 2011

AbstractGradients of temperature, pressure, and fluid composition in saturated clays give rise to coupled transport processes (thermal and chemical osmosis, thermal diffusion, ultrafiltration) in addition to the direct processes (advection and diffusion). One-dimensional transport of water and a solute in a saturated clay subjected to mild gradients of temperature and pressure was simulated numerically. When full coupling was accounted for, volume flux (specific discharge) was controlled by thermal osmosis and chemical osmosis. The two coupled fluxes were oppositely directed, producing a point of stagnation within the clay column. Solute flows were dominated by diffusion, chemical osmosis, and thermal osmosis. Chemical osmosis produced a significant flux of solute directed against the gradient of solute concentration; this effect reduced solute concentrations relative to the case without coupling. Predictions of mass transport in clays at nuclear waste repositories could be significantly in error if coupled transport processes are not accounted for.
Extension of the EQ3/6 Computer Codes to Geochemical Modeling of Brines
Authors: Jackson Kenneth J. , Wolery Thomas J. 
Published: March 2011

AbstractRecent modifications to the EQ3/6 geochemical modeling software package [1–3] provide for the use of Pitzer's [4] equations to calculate the activity coefficients of aqueous species and the activity of water. These changes extend the range of solute concentrations over which the codes can be used to dependably calculate equilibria in geochemical systems, and permit the inclusion of ion pairs, complexes, and undissociated acids and bases as explicit component species in the Pitzer model. Comparisons of calculations made by the EQ3NR and EQ6 computer codes with experimental data confirm that the modifications not only allow the codes to accurately evaluate activity coefficients in concentrated solutions, but also permit prediction of solubility limits of evaporite minerals in brines at 25°C and elevated temperatures. Calculations for a few salts can be made at temperatures up to ∼300°C, but the temperature range for most electrolytes is constrained by the availability of requisite data to values ≤100°C. The implementation of Pitzer's equations in EQ3/6 allows application of these codes to problems involving calculation of geochemical equilibria in brines; such as evaluation of the chemical environment which might be anticipated for nuclear waste canisters located in a salt repository.
Rapid Increases in Permeability and Porosity of Bentonite-Sand Mixtures Due to Alteration by Water Vapor
Authors: Couture Rex A. 
Published: March 2011

AbstractPacked columns of canister packing material containing 25% bentonite and 75% quartz or basalt sand, were exposed to water vapor at temperatures of up to 260°C. The permeabilities of the columns were subsequently measured after complete saturation with liquid water in a pressurized system. Exposure to water vapor caused irreversible increases in permeability by factors of up to 105. After saturation with liquid water, the permeability was nearly independent of temperature. The increases in permeability were due to a large decrease in the ability of the bentonite to swell in water. Calculations suggest that swelling of bentonite exposed to water vapor at 250°C was not sufficient to fill the pore spaces. If the pore spaces are filled, the mixture will form an effective barrier against flow, diffusion, and transport of colloids.The results suggest that if bentonite-based canister packing material is exposed even briefly to water vapor at high temperatures in a high-level nuclear waste repository, its performance will be seriously impaired. The problem will be less severe if the proportion of bentonite is high and the material is highly compacted. Previous results show significant degradation of bentonite by water vapor at temperatures as low as 150°C. This suggests that in some repositories, backfill in tunnels and drifts may also be affected.