bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solubility Effects in Waste Glass/Demineralized Water Systems
Authors: Fullam Harold T. 
Published: March 2011

ABSTRACTA study was carried out to determine the solubility limits of various elements found in waste glasses in demineralized water as a function of temperature. The work was sponsored by the Office of Nuclear Waste Isolation under contract to the Department of Energy. Solubility measurements were carried out at 35°, 65°, 95°, and 150°C using three nonradioactive waste glass compositions. Subsaturation and supersaturation methods were used to determine the solubility limits. The two methods gave markedly different values for most glass components. The results obtained indicate that it is difficult to assign solubility limits to most glass components without thoroughly describing the glass-water system. This includes not only defining the glass type, and system temperature, but also the glass surface area-to-water volume (S/V) ratio of the system and its thermal history.
Alpha Decay Self-Damage in Cubic and Monoclinic Zirconolite
Authors: Clinard F. W. , Land C. C. , Peterson D. E. , Rohr D. L. , Roof R. B. 
Published: March 2011

ABSTRACTSamples of primarily-monoclinic 238 Pu-doped zirconolite were stored at ambient temperature to allow accumulation of alpha decay self-damage to a dose of 6 × 1024 α/m3 (equivalent to a SYNROC age of ֮103 y). Bulk swelling reached 2.3 vol% with no tendency toward saturation, a damage response similar to that observed for cubic Pu-doped zirconolite. X-ray volumetric swelling at 4 × 1024 ֮/m3 was 1 vol%, considerably less than that for the cubic material. Changes in cell dimensions differed significantly from those reported by others for a monoclinic natural mineral. Extensive microcracking was observed, and is attributed at least partially to swelling differences between the matrix and minor phases.
Biological Intrusion of Low-Level Waste Trench Covers
Authors: Hakonson Thomas E. , Gladney Ernest S. 
Published: March 2011

ABSTRACTThe long-term integrity of low-level waste shallow land burial sites is dependent on the interaction of physical, chemical, and biological factors that modify the waste containment system. Past research on low-level waste shallow land burial methods has emphasized physical (i.e., water infiltration, soil erosion) and chemical (radionuclide leaching) processes that can cause waste site failure and subsequent radionuclide transport.The purpose of this paper is to demonstrate the need to consider biological processes as being potentially important in reducing the integrity of waste burial site cover treatments. Plants and animals not only can transport radionuclides to the ground surface via root systems and soil excavated from the cover profile by animal burrowing activities, but they modify physical and chemical processes within the cover profile by changing the water infiltration rates, soil erosion rates and chemical composition of the soil.One approach to limiting biological intrusion through the waste cover is to apply a barrier within the profile to limit root and animal penetration with depth. Experiments in the Los Alamos Experimental Engineered Test Facility were initiated to develop and evaluate biological barriers that are effective in minimizing intrusion into waste trenches. The experiments that are described employ four different candidate barrier materials of geologic origin. Experimental variables that will be evaluated, in addition to barrier type, are barrier depth and soil overburden depth. The rate of biological intrusion through the various barrier materials is being evaluated through the use of activatable stable tracers.
Hot-Pressed Barium Sulphate Ceramic Waste Forms for Direct Immobilisation of Medium Level Magnox Waste
Authors: Briggs A. , Jones D.V.C. , Cole G.B. 
Published: March 2011

ABSTRACTA possible method of treatment for Magnox cladding waste is by dissolution in nitric acid and precipitation of barium sulphate-based floc with which radioactive ions are co-precipitated. The floc could then be immobilised in a matrix material such as cement or bitumen to give the waste form, or alternatively can be converted directly into a waste form by hot pressing.This paper describes the direct conversion of barium sulphate floc, containing simulated radwaste, into a synthetic, ceramic version of the natural mineral barite by a hot-pressing route. By variation of the parameters pressure, temperature and time, optimum conditions for consolidation of the floc to > 90% theoretical density on a laboratory scale are found to be 22.5 MPa, 900°C for 10 minutes. Using a pressure of 15 MPa, at 900°C for 30 min., hot-pressed billets of BaSO4 have been made on a 5 kg scale. In going from the Magnox waste to the hot-pressed barium sulphate a volume reduction factor ∼ 18 is achieved. The principal phases in the product are found to be BaSO4 , MgO and Fe3O4, and the degree of consolidation achieved depends on the MgO content.The leaching behaviour of the hot-pressed materials in 100°C, 3 day Soxhlet tests also depends on the MgO content, and on the consequent level of open porosity. If there is porosity accessible to the leach water, MgO at the internal surfaces is converted to Mg(OH)2, which deposits within the pores, and a weight gain is registered in the Soxhlet test. If, however, there is no open porosity, a weight loss occurs, and leach rates ∼ 4 × 10−7 kg/m2/sec are found. In contrast, pure BaSO4, hot-pressed to similar densities, shows no variation in leaching behaviour over a wide range of o en porosities, and gives Soxhlet leach rates ∼ 8 × 10−8 kg/m2/sec.
Application of Ion Beam Techniques to the Study of Glass Durability: Enhanced Dissolution in Saline and Radiation Effects
Authors: Burman C. , Ke-Ming Wang , Lanford W.A. 
Published: March 2011

ABSTRACTNuclear reaction analysis, Rutherford backscattering and ion implantation techniques are applied to the study of the reaction between glass and aqueous solutions. The use of these techniques is described as are some of the results obtained. Solutions of NaCl are seen to etch some glasses several orders of magnitude faster than distilled water. Radiation damage created by high energy heavy ion bombardment is seen to have great effects on the penetration of hydrogen (water) into glass.
Point Defects and Microstructural Stability of Glasses Under Irradiation
Authors: Antonini Marcello , Buckley Samuel N. , Camagni Paolo , Gibson Peter N. , Manara Adriano 
Published: March 2011

ABSTRACTThe results of previous optical absorption experiments aiming to investigate the behaviour of atomic defects in silica based glasses irradiated with various types of particles have been extended to examine the effects of multiple irradiations which take place during long term storage of glasses containing HLW. In addition, point defect clustering phenomena have been investigated by means of high voltage transmission electron microscopy. It has been found that due to the large number of defects already present in amorphous silica prior to irradiations, the contributions of different bombarding particles to the total damage cannot be considered fully additive in terms of the relative number of displaced atoms, but some consideration has to be made of defect interactions and ionization damage. Clustering effects, while being absent in pure silica, are present in borosilicates at large dose rates (≳1022 electrons m−2 sec−1 ). At lower beam current densities and doses comparable to those achieved after 10–100 years of HLW storage, phase separation into a microcrystalline compound has been detected by transmission electron microscopy.
Radiation Effects in Radwaste Glasses : A Reappraisal of Alpha-Recoil Aging as Simulated by Ion Implantation.
Authors: Dran J.C. , Langevin Y. , Maurette M. , Petit J.C. 
Published: March 2011

ABSTRACTNew results on the etchability of lead implanted silicate glasses are presented which are satisfactorily accounted for by a Monte Carlo Model of etching. These results strongly support the radiation damage origin of the ion-induced modification of the chemical reactivity of glass. Major artefacts of ion implantation are then discarded as possible causes of the observed effects and consequently this technique is shown to be a valuable tool for the study of α-recoil aging in H.L.W. glasses.
Immobilization of High Level Nuclear Reactor Wastes in Synroc: A Current Appraisal
Authors: Oversby V.M. , Ringwood A.E. 
Published: March 2011

ABSTRACTResults are presented for leach testing at 95°C and 200°C of SYNROC containing 9% and 20% simulated high level radioactive waste, synthetic hollandite and pervoskite samples, and natural zirconolite and pervoskite samples. Single phase synthetic minerals show much higher leach rates than natural mineral samples and polyphase SYNROC samples. Natural zirconolite samples with low radiation damage have leach rates at 200°C based on U which are identical to those measured on SYNROC samples. Natural zirconolites with very large accumulated α dose and radiation damage have leach rates at 200°C which are only 5 times higher than those of low dose samples.
Ultraviolet Irradiation Induced Compaction and Photoetching in Amorphous, Thermal SiO2
Authors: Fiori C. , Devine R. A. B. 
Published: March 2011

ABSTRACTLaser irradiation (λ = 248 nm, E = 5 eV) of thermal, amorphous SiO2 is found to produce thermally reversible, linear compaction reaching a maximum of 16 % (accumulated, incident dose of ∼ 2000 J/cm2 followed by irreversible compaction and photoetching. Assuming the volume fluctuation to be ΔV/V = 3(Δ1/1)/(1+2σ) this corresponds to a maximum volume fluctuation of −36 %. An approximately linear refractive index versus ΔV/V relationship found in the linear compaction regime agrees with the predictions of the Lorentz-Lorenz law. Laser compaction results are found to be consistent with those obtained using hydrostatic pressure. That is argued by comparison with crystalline SiO2 polymporph, that compaction occurs via collapse of a high order ring structure into one having predominately 2 or 3 membered rings. Irreversible compaction/etching occurs when the lattice can no longer support a reduction in ring dimension and dangling bond defects are created. The presence of a large number of defects is sufficient for mechanism of superficial desorption and photoetching to become important.
The Electronic Structure of Doped Arsenic Triselenide
Authors: Barclay R. P. , Marshall J. M. , Main C. 
Published: March 2011

ABSTRACTWe have investigated the electronic properties of films of arsenic triselenide into which the transition metal nickel has been introduced by a co-sputtering technique. Measurement of d.c. conductivity, thermopower, optical absorption and photomobility have been performed to characterise the material. These measurements give new information concerning the influence of nickel on the optical gap, the position of the Fermi-level, and other aspects of transport in As2 Se3. In the most heavily doped sample the d.c. conductivity is increased by 11 orders of magnitude and the position of the Fermi-level is shifted by ΔEF∼0.6 eV. The results are explained in terms of a model in which an acceptor level is introduced into the valence band tail of a background density of states (DOS) obtained earlier for the undoped material. In contrast to the suggestion by previous workers that the incorporation of high concentrations of nickel can produce a transition to n-type conduction, we argue that the Fermi-level remains in the valence band tail and that hopping conduction of carriers close the Fermi-level yields a negative sign in thermopower.
Influence of Quenched Defects on Thermal Expansion and Glass Transition in Diopside (CaMgSi2O6)
Authors: Raman S. V. 
Published: March 2011

ABSTRACTThis study was conducted to investigate the possible occurrence of non-equilibrium defects and their influence on glass transition in a relatively depolymerized silicate structure. The glass of interest has an average bridging/non-bridging oxygen ratio of 1:2. It was prepared by fast quenching and was examined in the alumina pushrod dilatometer at heating rates of 5 and 15 ° C/min. The thermal expansion decreases with increase in the rate of heating although, the expansion coefficient is independent of heating rate at temperatures below the transition region. In the supercooled liquid region the expansion coefficient is higher at the higher heating rate. In the transition region it is both heating rate and temperature dependent. Three distinct temperatures are revealed in the transition region from temperature dependence of expansion rate. Their dependence on heating rate is described by a low activation energy of about 3Kcal/mol for transition. The single parameter fictive temperature is not in agreement with kinetics of relaxation due to a wide temperature interval of 600 to 750° C for the transition region. The transition kinetics is perhaps enhanced by the presence of defects whose annealing is impedded with increase in heating rate. Thus under the influence of higher defect concentration a spiked change in relaxation rate occurs and points to the presence of a critical temperature in the transition region. In the neighborhood of this temperature the relaxation rate of supercooled liquid is significantly lower than its solid analog. For short relaxation times in the supercooled liquid thermal expansion coefficient is relatively higher at the higher heating rate.
Theoretical Study of Semiconductor Interfaces
Authors: Walle Chris G. Van De , Martin Richard M. 
Published: March 2011

ABSTRACTWe perform self-consistent density functional calculations on semiconductor heterojunctions, using ab initio nonlocal pseudopotentials, and derive valence band discontinuities for many different lattice matched interfaces. Spin-orbit effects are included a posteriori. A comparison is made with previous calculations, which used empirical pseudopotentials, and with other heterojunction theories. We find reasonable agreement with reported experimental values, and derive some important conclusions about the nature of the lineups.
The Stony brook Multiprocessing Materials Simulator
Authors: Carleton Herbert R. 
Published: March 2011

ABSTRACTA parallel processing system with substantial computational power for the simulation of materials has been designed and constructed at Stony Brook. Although primarily designed to implement the molecular dynamics algorithm, the system is highly efficient in carrying out simulations that exhibit high degrees of local interaction. Our studies show that this system is capable of performance, for this application, which is comparable to the Cray-l at a small fraction of the cost.
Modelling of Thin Film Grain Structures and Grain Growth
Authors: Frost H. J. , Thompson C. V. 
Published: March 2011

ABSTRACTWe have generated two-dimensional grain structures by considering constant growth of regions which nucleate under various conditions. We have considered continuous nucleation at a constant rate, nucleation site saturation, continuous nucleation with nucleation-exclusion zones surrounding the growing regions, and decaying nucleation rates. The microstructures resulting from these varying conditions differ markedly in their topological and geometric properties.We have also developed a program which models grain boundary motion in structures resulting from nucleation and growth. Results from these models will be compared to observed microstructures in thin metallic and semiconductor films and should provide insight into the mechanisms of microstructural evolution and control.
Microscopic Phenomena of Macroscopic Conseouences:Interfaces, Glasses, and Small Aggregates
Authors: Landman Uzi , Barnett R. N. , Cleveland C. L. , Luedtke W. D. , Ribarsky M. W. , Scharf Dafna , Jortner Joshua 
Published: March 2011

ABSTRACTComputer simulations open new avenues in investigations of complex material systems and phenomena. The methodology, development and applications of molecular dynamics simulations are discussed and the wealth of microscopic information revealed via simulations of interphase-interfaces, liquid metals, metallic glasses and small aggregates are demonstrated.
The Solid-Liquid Interface: Theory and Computer Simulations
Authors: Laird B. B. , Haymet A. D. J. 
Published: March 2011

ABSTRACTWe present the results of computer simulations of body centered cubic (bcc)/melt interfaces, with particular emphasis on the “width” of the interface. Both static and dynamic properties of single crystal/liquid interfaces are examined. The implications for crystal growth near equilibrium are discussed. The results of these computer “experiments” are compared with an extended density functional theory of the solid-liquid interface.
High Sensitivity Auger Spectroscopy
Authors: Larson L. A. 
Published: March 2011

AbstractThe technique of Auger Electron Spectroscopy has been investigated for the purposes of detecting contamination levels in high dose ion implants. Historically, Auger sensitivities have been considered to be on the order of 1%. This is due to the rather large secondary electron background and the various combinations of electron beam and detector noise that may occur. In this study, it is shown that the use of background subtraction and integration of the resulting EN(E) Auger peak will result in considerably better sensitivities for the case of ion implants in silicon.
Sem-Based Characterization Techniques
Authors: Russell Phillip E. 
Published: March 2011

AbstractThe scanning electron microscope is now a common instrument in materials characterization laboratories. The basic role of the SEM as a topographic imaging system has steadily been expanding to include a wide variety of SEM-based analytical techniques. These techniques cover the range of basic semiconductor materials characterization to live-time device characterization of operating LSI or VLSI devices. This paper will introduce many of the more commonly used techniques, describe the modifications or additions to a conventional SEM required to utilize the techniques, and give examples of the use of such techniques. First, the types of signals available from a sample being irradiated by an electron beam will be reviewed. Then, where applicable, the type of spectroscopy or microscopy which has evolved to utilize the various signal types will be described. This will be followed by specific examples of the use of such techniques to solve problems related to semiconductor technology. Techniques to be emphasized will include: x-ray fluorescence spectroscopy, electron beam induced current (EBIC), stroboscopic voltage analysis, cathodoluminescence and electron beam IC metrology. Current and future trends of some of these techniques, as related to the semiconductor industry, will be discussed.
Sem-Ebic Characterization of Semiconducting and Semi-Insulating LEC-GaAs
Authors: Tokumaru Yozo , Okada Yasumasa 
Published: March 2011

AbstractWe have applied the SEM-EBIC technique (electron-beam-induced current method using a scanning electron microscope) to the characterization of both semiconducting and semi-insulating liquid encapsulated Czocralski (LEC) grown GaAs and have found this technique to be effective for semiinsulating materials as well as semiconducting ones. In semiconducting Si-, In- and undoped LEC-GaAs, growth striations were observed under usual measurement conditions. In semi-insulating undoped LEC-GaAs, clear EBIC images of individual dislocations and cell structures of dislocations were obtained by applying a high reverse bias voltage of about 10∼100 V to the specimens. We have also investigated nearly dislocation-free semiinsulating In-doped LEC-GaAs and found inhomogeneities which are different from those observed in undoped specimens. The spatial resolution of this technique is estimated to be 2–3 μm, which agrees with the experimental result
Characterization of Thin Film Dielectrics by FTIRS
Authors: Cox J. Neal 
Published: March 2011

AbstractThe silicon-oxygen chemical bond is the key building block for many of the dielectric thin films used in silicon MOS technology. High quality thermal silicon oxides serve as gate dieletrics. CVD silicon oxides, produced by a variety of deposition processes, are used as interlayer dielectrics and as passivating layers. These films may be stoichiometric or nonstoichiometric, or doped with boron and/or phosphorus to provide the most desirable film properties.Bandshape analysis of the Fourier Transform Infrared (FTIR) spectra of these films can provide information on the chemical bond strength, the homogeneity, and the optical dielectric function of various glasses. Spectral features are found to change characteristically, depending upon deposition conditions, subsequent processing (densification), the influence of dopants, stress, and the effects of overlying films. In comparing films [Bposited under different conditions, the primary Si-O stretching mode peak position shifts over a 30cm-1 range and has a FWHM that varies by as much as 50%. The FTIR technique can routinely resolve peak shifts in glasses as small as 2 cm-1, sufficient to detect the differences observed due to deposition or processing.
Micro-Reflection Spectroscopy Profiling of Interdiffusion in Epitaxial HgCdTe
Authors: Grimbergen M. , Szilagy A. 
Published: March 2011

AbstractComposition profiles of interdiffused epitaxial Hg1-xCdxTe have been determined using interband E1 microreflection spectroscopy. The technique provides a rapid, noncontacting method of compositional analysis using the near UV-visible spectral range. It measures alloy composition (x-value) over a sampling surface as small as 5 μm square to an accuracy better than 0.01. Profiles are measured by repeatedly etching small sampling wells in discrete steps. Profiles were measured on epitaxial Hg0.7Cd0.3Te films grown on Hg0.8Cd0.2Te substrates with and without extended anneal treatments. They were also calculated by numerically solving the diffusion equation using published composition dependent diffusion coefficients. The experimental and theoretical profiles are compared graphically. Calculated as-grown and annealed interdiffusion widths (9 and 13μm, respectively) differ from measured values by less than 15%. It is shown that Hg and Cd interdiffusion during both the growth and subsequent anneal is responsible for the observed interface widths.