bluuebunny/crossref_metadata_2025_split huggingface dataset:
Processing of Low Alpha-Particle Emitting Ceramics
Authors: Morris P. A. , Handwerker C. A. , Coble R. L. , Gabbe D. R. , Howard R. T. 
Published: March 2011

AbstractThe raw materials and clean-room processing techniques required to produce a low alpha-particle emitting insulating material have been investigated with the goal of producing a dense fired alumina ceramic with a reproducible, low alpha-particle flux (≤ 0.01 α/cm2hr). Various sources of A12 O3, MgO, and SiO2, the primary constituents of the alumina body, were tested for the alpha-particle emitting elements, U and Th, and for total alpha-particle flux. Many materials contain U concentrations with corresponding alpha-particle fluxes of 0.01α/cm2hr. Die pressing, filter casting and isopressing have been used under class 100 clean-room conditions to process powder compacts and the benefits and problems of each were evaluated. Analysis of the material before, at various stages during processing, and after firing has shown that dense fired Al2O3 ceramics can be produced with no detectable increase above that of the source powder in the U and Th contents, or the alpha-particle flux.
Growth of thin Pb Layers on Cu(001)
Authors: Culbertson R. J. , Kuk Y. , Feldman L. C. 
Published: March 2011

AbstractThe growth of thin Pb layers (<12 monolayers) was studied in ultrahigh vacuum by high energy ion scattering/channeling, low energy electron diffraction (LEED)), and Auger electron spectroscopy (AES). Deposition and analysis were performed at 300 K and 140 K. The Pb coverage was determined quantitatively by ion scattering. The results indicated a clear transition in the growth mode as a function of temperature. At 300 K, two-dimensional island growth was observed up to 1.0 monolayer, followed by three-dimensional epitaxial growth of strained islands. Two-dimensional island growth was observed up to 5 monolayers at 140 K. The relative positions of the overlayer atoms relative to the substrate was studied to understand two-dimensional phase transitions above room temperature.
Diffraction Studies of the Atomic Structure of Grain Boundaries
Authors: Milkove K. R. , Lamarre P. A. , Schmückle F. , Vaudin M. D. , Sass S. L. 
Published: March 2011

AbstractThe application of diffraction techniques to study the atomic structure of grain boundaries is reviewed. The determination of the projected structure of a large angle [001] twist boundary is described. The influence of f.c.c. metal type and bonding type on boundary structure is examined. Generalizations are made concerning the structure of large angle [001] twist boundaries based on the results of the diffraction studies.
Characterization of Defects and Interfaces by the Ion Channeling Technique
Authors: Chu W. K. , Picraux S. T. 
Published: March 2011

AbstractChanneling of fast, light ions in crystals has been widely used as a tool for studying crystal defects. This subject has been reviewed earlier at MRS-1980. During MRS-1980, principles of ion channeling, and examples of channeling analysis on bulk defects and surface structures, lattice location of impurities, and clustering phenomena were given. In this review, we give a brief overview of defect studies by the channeling technique and then elaborate on recent developments in channeling analysis of interfacial structure. The ion beam channeling technique permits characterization of heteroepitaxial growth starting at monolayer coverages and allows quantitative measurement of the lattice strain in heteroepitaxial layers. The strain analysis has been developed for multilayer structures and, for example, the tetragonal distortions of strained-layer superlattices can be determined for lattice mismatches as low as 0.2% corresponding to lattice distortions of 0.01Å.
Perturbed Angular Correlation Measurements of Vacancy Trapping at Indium Atoms in Quenched Aluminum
Authors: Swanson M. L. , Wichert T. H. , Howe L. M. , Quenneville A. F. , Westcott O. M. 
Published: March 2011

AbstractThe perturbed angular correlation (PAC) method was used to study vacancy trapping at 111In atoms in quenched Al single crystals containing up to 10 ppm In. During annealing from 200–230 K, two different electric field gradients appeared, characterized by the interaction frequencies ν 01 = 67 MHz with asymmetry parameter η = 0.41, and νQ2 = 133 MHz with η = 0. The assignment of ν01 to a single vacancy-In atom pair is discussed. The results indicate that the migration energy of single vacancies in Al is = 0.55 eV.
On the Resolvability of Defect Ensembles with Positron Annihilation Studies
Authors: Fluss M. J. , Howell R. H. , Rosenberg I. J. , Meyer P. 
Published: March 2011

AbstractRecent advances in the use of positron annihilation to study defect ensembles in and on the surfaces of metals, are pointing the way towards studies where particular positron-electron annihilation modes may be identified and studied in the presence of one another. Although a great deal is understood about the annihilation of positrons in ostensibly defect free metals, much less is understood when the positron annihilates in complex defect systems such as liquid metals, amorphous solids, or at or near the vacuum-solid interface. In this paper the results of three experiments, all of which demonstrate means by which we can resolve various positron annihilation channels from one another, will be discussed.
The Influence of Pore-Strucrure on the Campressive Strength of Hardened Cement Paste
Authors: Yiun-Yuan Huang , Wei Ding , Ping Lu 
Published: March 2011

AbstractThe pore-structure strongly influences the carpressive strength of hardened cement paste (hcp) and other porous materials, as well as other mechanical properties. The simplest but most currently used expression representing the relationship between the pore-structure and compressive strength is fram Balshin: σ = σ0 (l-P)A, in which only the total porosity P is involved as a single parameter and σ0 and A are empirical constants. The influence of pore size distribution and pore shapes etc. are not considered.The authors introduce second parameter w - the factor of relative specific surface area of the pores other than the total porosity P into consideration and a new expression is proposed:σc=K11-p/1+2p(K2(1-p))K3w+K4 all the constants K1 - K4 can be determined experimentally. By using of this expression the new information relating the influence of pore-structure on the caopressive strength of hcp can be predicted.
Very High Strength Cement for Very High Strength Concrete
Authors: Aftcin Pierre-Claude , Bédard Claude , Plumat M. A. Sc. Marc , Haddad Gilbert 
Published: March 2011

AbstractDuring 1984 summer, an experimental concrete column was cast in a 26-story high-building using a 100 MPa silica fume concrete. Only the coarse aggregate was selected specifically for this concrete. The cement used was an ordinary type 1 Portland cement. The superplasticizer was a naphthalene base. The field conditions were among the most unfavourable, the transportation was about 3/4 of an hour. The placing lasted 15 minutes. However, after 1 h 00 the slump of this concrete having a water/cementitious ratio of 0.25 was still higher than 100 mm so that the concrete was placed without any problems.
High Strength Concrete and Mortars in High Temperature Environments
Authors: Williamson Robert B. , Rashed Ahmed I. 
Published: March 2011

AbstractA number of new materials are presently being introduced for application in high temperature environments. Though some of these are old materials fabricated with new methods or processes, many are actually new. This paper focuses on the use of high strength concretes or mortars for application to high temperature environments, such as furnaces or boilers for coal gasification and similar processes requiring high pressure and temperature. This paper reports the results of an investigation on the high.temperature performance of mortar of different strengths incorporating 0%, 8% and 16% of condensed silica fume (CSF). The experiments described have been carried out to compare the performance of different strength level mortars with different CSF contents. Generally speaking, it was found that low strength mortar with CSF is less susceptible to strength loss after high temperature exposure than mortar without CSF. On the other hand, high strength mortar with CSF seems to be more sensitive to high temperature than high strength mortar without CSF since it retains only 65% of its room temperature strength after heating to 3200C as compared to regular high strength mortar which retains 95% of its room temperature strength.Though there may be a possible practical problem in using high strength CSF concrete, this shown loss of strength in high strength CSF concrete upon heating may prove very important in giving us insight into the fundamental mechanisms of strengthening concrete with CSF. An explanation is hypothesized on the observed behavior of high strength CSF concrete, which will produce a theory for one of the ways in which CSF strengthens portland cement paste. It is theorized that the CSF touohens the portlandite in high strength paste, but after heating to 320 C, the CSF particles which have been converted to C-S-H have lost their ability to toughen the portlandite.
Microstructure of High Strength Cement Paste Systems
Authors: Regourd M. 
Published: March 2011

AbstractHigh strength cement pastes include hot pressed, autoclaved, impregnated low water/cement ratio, macrodefect free, ultrafine particles arrangement systems. The densification of the microstrucure is mainly related to a low porosity and to the formation of poorly crystalline hydrates. In composite systems like mortars and concretes, the interfacial bond between the cement paste and aggregates is moreover less porous and more finely crystallized than the normal “auréole de transition”.
Characterisation of Microstructure as a Systematic Approach to High Strength Cements
Authors: Scrivener Karen L. , Baldie K. D. , Halse Yick , Pratt P. L. 
Published: March 2011

AbstractUltimately the strength of cement is determined by the properties, amounts and distributions of the phases it contains and by the'way these are bonded together. Here an example is presented of the determination of the amount and distribution of calcium hydroxide, by BEI and quantitative image analysis, in a cement paste and cement/fly ash mixture which had previously been studied by TGA. Examination of crack paths on BEIs of polished cement surfaces gives some indication as to the importance of calcium hydroxide in determining the properties of the cement.
The Flexural Strength and Fracture Toughness of a Normal and a High Strength Polymer Modified Portland Cement
Authors: Eden N. B. , Bailey J. E. 
Published: March 2011

AbstractA model has been developed for the flexural strength of Portland cement pastes, based upon observed fracture behaviour of both normal and high strength pastes. Fibrillar or foil-like elements pull apart at a yield stress which is characteristic of the number of elements and interfacial shear strength. The former can be maximised by using a low water/cement ratio and the latter by inclusion of water-soluble polymer, followed by suitable drying. It is proposed that this is the mechanism by which high strength may be attained in Portland cement.
The Role of Boron in Monitoring the Leaching of Borosilicate Glass Waste Forms
Authors: Scheetz Barry E. , Freeborn W. Phelps , Smith Deane K. , Anderson Christine , Zolensky Michael , White William B. 
Published: March 2011

AbstractIn the absence of any identified solid phase host (other than the original glass), boron has been assumed to accumulate in the fluid during the reaction of borosilicate glass waste forms with aqueous fluids. Using this assumption, it is possible to define a boron index which can be used to monitor the amount of glass that has been dissolved and to provide a worst-case measure of the degradation of the primary glass waste form. Several boron-containing silicate phases have been identified thus invalidating the assumption that boron does not precipitate. The effect is apparently small and the assumption that boron release is a direct measure of degree of alteration of borosilicate glass is still probably a good one.
Leaching of Devitrified Glass Containing Simulated SRP Nuclear Waste
Authors: Jantzen Carol M. , Bickford Dennis F. 
Published: March 2011

AbstractTime-temperature-transformation curves have been determined for SRL-165 and SRL-131 waste glasses for all potential waste compositions. SRL-165 glasses, which contain less alkali, exhibit less complex devitrification and higher overall durability than SRL-131 waste glasses. Devitrification was found to have less effect on the durability of waste glasses than changes in composition. Non-uniform dissolution at the glass leached layer interface is observed. However, leached layers formed after 28 days shield the crystal interfaces from further dissolution.
Alterability of the French LWR Solution Reference Glass in Repository Conditions
Authors: Nogues J. L. , Vernaz E. Y. , Jacquet-Francillon N. , Pasquini S. 
Published: March 2011

AbstractThe disposal of glass blocks containing fission products in granitic geological formations is one of the options currently investigated in France. This paper discusses the major criteria selected to develop models of such repositories and gives the first results obtained with the corresponding experimental test. Five laboratory mockups corresponding to different alternatives regarding the fill materials were prepared. The following materials were used to encase the French LWR reference glass:- Test I : Granite, sand, stainless steel;- Test 2 : Granite, sand, illite, stainless steel;- Test 3 : Granite, sand, bentonite, stainless steel;- Test 4 : Granite, sand, Al2O3, ceramic, stainless steel;- Test 5 : Granite, sand, haitalloy C4.Samples were taken of the solutions obtained in the preconditioning cell and in contact with the glass to assess the glass corrosion behavior in each of these media. The experiments were completed by surface analyses designed to compare the morphology of the surface layers that develop with and without the environmental materials.
The Behavior of Actinide Containing Glasses During Gammirar Adiation in a Saturated Tuff Environment
Authors: Bates John K. , Oversby Virginia M. 
Published: March 2011

AbstractThe influence of gamma irradiation on the reaction of actinide doped SRL 165 and PNL 76–68 glasses in a saturated tuff environment has been studied in a series of tests lasting up to 56 days. The reaction, and subsequent actinide release, of both glasses depends on the dynamic interaction between radiolysis effects which cause the solution pH to become more acidic and glass reaction which drives the pH more basic. The use of large gamma irradiation dose rates to accelerate reactions that would occur in an actual repository radiation field may affect this dynamic balance by unduly influencing the mechanism of the glass-water reaction. Comparisons are made between the present results and data obtained by reacting the same or similar glasses using MCC-1 and NNWSI rock cup procedures.
Effect of Grande Ronde Basalt Groundwater Composition and Temperature on the Corrosion of Low-Carbon Steel in the Presence of Basalt-Bentonite Packing
Authors: Anantatmula R. P. 
Published: March 2011

AbstractThe Basalt Waste Isolation Project (BWIP) is being conducted for the U.S. Department of Energy (DOE) by Rockwell Hanford Operations. The effect of Grande Ronde Basalt groundwater composition and temperature on the corrosion rate of American Iron and Steel Institute (AISI) 1020 steel in basalt-bentonite packing was investigated as part of the Containment Materials Testing Program of the BWIP. The studies were based on a Plackett-Burman statistical screening design, the purpose of which is to identify the important variables affecting a process and to use this information to guide future investigative efforts. For the present studies, four anions (Cl−, F−, SO4−, and CO3−) and temperature were selected as the initial variables affecting corrosion. A minimum and a maximum value was chosen for each variable. The minimum value was 0 mg/L for the anions and 100 °C for the temperature. The maximum values were 780, 76, 576, and 120 mg/L, respectively, for Cl−, F−, SO4−, and CO3−, and 250 °C for the temperature. Analysis of the data revealed that temperature is the only statistically significant variable affecting corrosion of low-carbon steel in basalt groundwater in the composition range of the anions tested. Increasing the temperature from 100 °C to 250 °C decreased the total corrosion by a factor of seven to ∼5O mg/dm2 independent of the water composition. This is attributed to a strongly adherent layer of iron- and silicon-rich clay on the surface of the steel formed by a reaction of the steel surface with the packing material as observed in previous studies.
Corrosion Behavior of Carbon Steels Under Tuff Repository Environmental Conditions
Authors: McCright R. Daniel , Weiss H. 
Published: March 2011

AbstractCarbon steels may be used for borehole liners in a potential high-level nuclear waste repository in tuff in Nevada. Borehole liners are needed to facilitate emplacement of the waste packages and to facilitate retrieval of the packages, if required. Corrosion rates of low carbon structural steels AISI 1020 and ASTM A-36 were determined in J-13 well water and in saturated steam at 100°C. J-13 well water is representative of water which has percolated through the tuff horizon where the repository would be located. Tests were conducted in air-sparged J-13 water to attain stronger oxidizing conditions. A limited number of irradiation corrosion and stress corrosion tests were performed. Chromium-molybdenum alloy steels and cast irons were also tested. These materials showed lower general corrosion but were susceptible to stress corrosion cracking when welded.
Control of Oxidation Potential for Basalt Repository Simulation Tests
Authors: Jantzen Carol M. , Wicks George G. 
Published: March 2011

AbstractBorosilicate waste glass durability in simulated repository environments can be assessed by use of static tests in leach vessels fabricated of the representative geomedia. Control of the oxidation potential during the test simulates a basalt repository environment. Under very anoxic conditions (i.e. at negative Eh values), the interactions between basalt and SRP waste glass in silica-saturated basaltic groundwaters are the same as those of basalt and groundwater when no waste glass is present. The lack of significant leaching of ions from the waste glass and the lack of any significant changes in either the leached surfaces of glass or basalt under anoxic conditions suggests that the components of this system are at equilibrium when oxygen is absent.
Permeability Changes in Crystalline Rocks Due to Temperature: Effects of Mineral Assemblage
Authors: Morrow C. A. , Moore D. E. , Byerlee J. D. 
Published: March 2011

AbstractThe change in permeability with time of granite, quartzite, anorthosite and gabbro was measured while these rocks were subjected to a temperature gradient. The highest temperature (at the heat source) was fixed at 250°C, while low temperatures ranged from 60 to 111°C, depending on rock type. Permeability reductions of up to two orders of magnitude were observed, with the greatest reactions occurring in the quartzite. These changes are thought to be caused by dissolution of minerals at high temperatures, and redeposition of the dissolved material at lower temperatures. Quartz appears to be an important mineral in this self-sealing process. If very low permeability is desired around a nuclear waste repository in crystalline rocks, then a quartz-rich rock may be the most appropriate host.
Parametric Study of the Corrosion Behaviour in Static Distilled Water of Simulated European Reference High Level Waste Glasses
Authors: Iseghem Pierre Ph. Van , Timmermans W. , Batist R. De 
Published: March 2011

AbstractThe corrosion behaviour in distilled water of five simulated European reference high level waste glasses has been investigated for times up to 8 months. The glasses were chosen in accordance with the Joint European Community research programme on HLW form characterization: two French glasses (SON58, SON64), one British glass (UK209) and two glasses designed to incorporate HLW stored at the Eurochemic plant in Belgium (SM58 and SAN60). In the reference condition (90°C, SA.V−1 = 1 cm−1) the leaching was characterized mainly by diffusion processes and by the onset of saturation in the leachate (these saturation effects were found to depend on glass composition). In more dilute conditions (SA.V−1 = 0.1 cm−1), matrix dissolution was the rate controlling mechanism. Increasing the leachant temperature to 150°C and higher lead to pronounced surface crystallization and, at least for one glass (SAN60), to an increased corrosion.
Behavior of Nuclear Waste Elements During Hydrothermal Alteration of Glassy Rhyolite in an Active Geothermal System: Yellowstone National Park, Wyoming
Authors: Sturchio Neil C. , Seitz Martin G. 
Published: March 2011

AbstractThe behavior of a group of nuclear waste elements (U, Th, Sr, Zr, Sb, Cs, Ba, and Sm.d)u ring hydrothermal alteration of glassy rhyolite is investigated through geochemaical analyses of whole rocks, glass and mineral separates, and thermal waters. Significant enrichments of U, Sr, Sb, Cs, and Ba are found in altered rock relative to unaltered rock. Excess Sr, Cs, and Ba are concentrated in zeolites in altered rock. Excess U is associated with titanomagnetite surfaces. Th, Zr, and Sm are relatively immobile during alteration, and are strongly concentrated in celadonite.
The Salton Sea Geothermal Field as a Natural Analog for the Near-Field in a Salt High-Level Nuclear Waste Repository
Authors: Elders Wilfred A. , Moody Judith B. 
Published: March 2011

AbstractThe Salton Sea Geothermal Field (SSGF), on the delta of the Colorado River in southern California, is being studied as a natural analog for the near-field environment of proposed nuclear waste repositories in salt. A combination of mineralogical and geochemical methods is being employed to develop a three dimensional picture of temperature, salinity, lithology, mineralogy, and chemistry of reactions between the reservoir rocks and the hot brines. Our aim is to obtain quantitative data on mineral stabilities and on mobilities of the naturally occurring radionuclides of concern in Commercial High-Level Waste (CHLW). These data will be used to validate the EQ3/6 geochemical code under development to model the salt near-field repository behavior.Maximum temperatures encountered in wells in the SSGF equal or exceed peak temperatures expected in a salt repository. Brines produced from these wells have major element chemistry similar to brines from candidate salt sites. Relative to the rocks, these brines are enriched in Na, Mn, Zn, Sr, Ra and Po, depleted in Ba, Si, Mg, Ti, and Al, and strongly depleted in U and Th. However the unaltered rocks contain only about 2–3 ppm of U and 4–12 ppm of Th, largely in detrital epidotes and zircons. Samples of hydrothermally altered rocks from a wide range of temperature and salinity show rather similar uniform low concentrations of these elements, even when authigenic illite, chlorite, epidote and feldspar are present. These observations suggest that U and Th are relatively immobile in these hot brines. However Ra, Po, Cs and Sr are relatively mobile. Work is continuing to document naturally occurring radionuclide partitioning between SSGF minerals and brine over a range of temperature, salinity, and lithology.