bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Chemical Interactions in the Hydrated Layers of Nuclear Waste Glasses.
Authors: Sullivan Terrence M. , Machiels Albert J. 
Published: March 2011

ABSTRACTThe distribution of glass constituents within the hydrated layer is investigated through a mathematical representation of the fundamental processes that influence mass transport. A brief description of the models that are developed is presented. The resulting equations are implemented in a computer code named GELOH. The importance of the processes of network hydration and layer growth, alteration product formation, and dissolution is studied through the use of GELOH. The results of these studies are presented and interpreted in the light of the experimental evidence available on the aqueous corrosion of nuclear waste glass.
Dissolution of Technetium From Nuclear Waste Forms
Authors: Yasser Khalil M. , White William B. 
Published: March 2011

ABSTRACTThe immobilization of 99Tc in both ceramic and borosilicate glass waste forms and the mechanism of dissolution of technetium from these waste forms are complicated by the range of technetium valence states. Metallic Tc,ionic Tc4+ oxides, and volatile molecular species containing Tc7+ all occur within the stability field of water. Tc4+ will substitute readily for Ti4+ in titanatebased ceramics in such phases as perovskite (CaTiO3) and spinel (Mg2TiO4). Tc4+ can be homogeneously distributed in borosilicate glass by re-melting the glass under closed system conditions to prevent the re-oxidation of technetium. The dissolution of technetium from both glass and ceramic waste forms follow similar kinetic behavior although the dissolution rate from the titanate is two orders of magnitude lower. Dissolution under highly reducing conditions is too slow to measure on the time scale of the experiments.
Influence of Redox Condition in Iron, Silicon and Hydrogen Contents of Leached Glass Surface
Authors: Manara A. , Lanza F. , Della Mea G. , Rossi C. , Salvagno G. 
Published: March 2011

ABSTRACTSurface analysis has been conducted on samples leached in a Sochlet apparatus at 100°C in the presence and in the absence of air. The XPS technique was applied to analyse the content of iron and silicon while the nuclear reaction method was utilized to analyse the content of hydrogen. Samples leached in argon atmosphere have shown a smaller content of iron and silicon with respect to the samples leached in air atmosphere. The H concentration has shown the same behaviour. The results are discussed in terms of possible formation of iron compounds in the different redox condition and of their different stabilities and in terms of their efficiency in reducing exchange between Na+ and H+ ions.
Time Dependent Leaching in Two-Phase Composite Glasses
Authors: Montrose C. J. , Barkatt Aaron , Macedo P. B. 
Published: March 2011

ABSTRACTA model has been developed for the elemental leach rates as a function of time in the high-dilution limit for a two-phase composite glass material in which one phase exists as unconnected inclusions embedded within a major continuous phase. For those elements that are preferentially concentrated in this minor and presumed less durable phase, the leach rates are strongly time-dependent, decreasing significantly from the initial to the final steady-state value.
New Data on Ion-Induced Modifications of Aqueous Dissolution of Silicates
Authors: Della Mea G. , Dran J.-C. , Petit J.-C. , Bezzon G. , Rossi-Alvarez C. 
Published: March 2011

ABSTRACTThe ion-induced modifications of aqueous dissolution have been thoroughly investigated in several silicates (amorphous silica, quartz, soda-lime glass and albite) by applying depth profiling techniques (RBS and resonant nuclear reactions) for the characterization of leached surfaces. We show in particular that the H penetration after implantation and leaching is markedly increased when the ion dose exceeds a critical value comprised between 1013 and 1014 Pb.cm-2. This feature supports the radiation damage origin of the observed effects. Such experiments provide interesting clues about the aqueous dissolution of silicates and show that no important effect of α-decay is expected on the hydration of HLW glasses during disposal.
Laboratory and Field Data Needs for Site-Specific Repository Modeling
Authors: Apted M.J. 
Published: March 2011

ABSTRACTThe relative importance of material properties, geochemical processes, and environmental parameters affecting containment and release of radionuclides vary strongly as a function of time and spatial position within a nuclear waste repository located in basalt (NWRB). A simple matrix of spatial regions (Engineered-Barrier System, Disturbed-Rock Zone, Site System of the Controlled Access Zone) and time periods (Pre-emplacement, Containment, Isolation/Slow-release)can be used to identify the dominant processes that affect the containment, release, and migration of radionuclides. From this analysis, a directed and efficient program of field and laboratory studies can be conducted to obtain the data required to assess the feasibility of an NWRB and compliance with Federal regulatory criteria.
Predicting Amounts of Radiolytically Produced Species in Brine Solutions
Authors: Simonson S. A. , Kuhn W. L. 
Published: March 2011

ABSTRACTThe corrosion of iron overpack materials for nuclear waste forms in salt is highly dependent upon the species produced by the radiolysis of brines which may contact the metal. A computer code has been developed to predict the concentrations of the radiolytically produced species as a function of time using published values for radiation yields of species, chemical reaction rate constants, and parameters derived from experimental evidence.
Solubility Constraint: An Important Consideration in Safety Assessment of Nuclear Waste Disposal
Authors: Rai Dhanpat , Ryan Jack L. 
Published: March 2011

ABSTRACTSolubilities of key solid compounds that are either present in the waste form or can readily precipitate from waste package leachates under repository conditions can be used to set maximum limits on radionuclide concentrations expected in groundwater. This is because the solubility limited concentrations are independent of the release scenarios, hydrologic transport characteristics, and adsorption/desorption reactions. Some of the important factors that control solubilities are pH, pe, type of solid phase, and nature of complexing ligands in the ground waters. Most of the above factors are affected by radiolysis due to the inherent radiation field of the waste form. Experimental results pertaining to the solubilities of selected Am, U, Np, and Pu compounds and the effects of radiolysis are discussed. These results show that: 1) at expected repository pH and reducing conditions, solubility controlled concentrations of several actinides are low and near acceptable limits, 2) the redox conditions at the waste form-water interface may be very oxidizing due to radiolyticeffects, despite the fact that normal repository conditions are assumed to be reducing, 3) additional data on solubility limits and key thermodynamic parameters are needed.
Generation and Transport Properties of Colloidal Tri-And Tetravalent Actinide Species in Geologic Environments
Authors: Olofsson U. , Bengtsson M. , Allard B. 
Published: March 2011

ABSTRACTThe formation of colloidal particle fractions of triand tetravalent actinides (Am(III), Th(IV), Pu) has been studied in aqueous solutions under various conditions. (Variations of nuclide concentration 10-7-10-11 M; pH 3-12; salt medium 0.01-1.0 M NaCl04; storage time 6 h-6 months; temperature 5°C, 25°C, 70°C). A large fraction of the nuclides is sorbed on the vessel walls, but there is also a formation of centrifugable particles. For americium this fraction has two maxima, at pH 5-8 and at pH above 12. For thorium and plutonium this fraction is very small except at pH about 12. In the pH-range 7-9, which is expected in underground waste repositories, the particle fractions do not seem to be highly mobile. Plutonium behaves very similar to thorium in all studied systems, so it is probably tetravalent to a large extent.
The Behavior of Americium in Aqueous Carbonate Systems
Authors: Silva R. J. 
Published: March 2011

ABSTRACTThe solubilities of crystalline Am(OH)3and AmOHCO3were measured at 25° C in aqueous solutions of 0.1 M NaCl04by determination of the solution concentrations of Am. Prior to use in the measurements, the solid materials were characterized by their x-ray powder diffraction patterns. The solubility product quotients were calculated from the experimental data. The hydrolysis quotients of Am3+were also estimated from the hydroxide solubility data. Using the thermodynamic data derived from these experiments and the recently reported formation constants for the Am3+carbonate complexes, the solid phases and concentrations of solution species of americium in several aqueous carbonate systems were calculated using the computer code MINEQL.
Geochemical Studies of Columbia River Basalts
Authors: Brookins D. G. , Murphy M. T. , Wollenberg H. A. , Flexser S. 
Published: March 2011

ABSTRACTWe report our findings for two studies of Columbia River basalts that are relevant to United States radwaste disposal programs. A rhyodacite intrudes the Wanapum basalt and is exposed in a quarry along the Hood River, Oregon. Since the rhyodacite is different geochemically from the basalt, and was intruded at a high temperature, then this site can be used to evaluate the effects of the intrusion on the basalt. In such a study we assume the intrusive rock is a high temperature heat engine, and that cooling may be by convection, conduction, or both. Contact effects of the intrusion are not pronounced in the basalt, and are restricted to minor recrystallization within one meter of the contact, and to possibly some minor fracture filling. Traverses were made from the rhyodacite into the basalt, and samples at closely spaced intervals analyzed for K, U, Th by field and laboratory gamma spectrometry, and by neutron activation analysis for some 35 elements. Separate aliquots were analyzed by isotope dilution to inspect Sr isotopic variations. The chemical studies do not indicate migration of any elements from the rhyodacite into the basalt, nor for any in-basalt or in-rhyodacite migration. Despite a pronounced chemical gradient between the rocks, each has remained a closed, isochemical system. The Sr isotopic studies indicate that the rhyodacite possesses Sr (87/86) = 0.70407 ± 0.00008 while the intruded basalts possess Sr (87/86) = 0.7052 ± 0.0002. Even in samples of the contact, with intermingled rhyodacite and basalt, each rock preserves its own characteristic Sr (87/86) signature, thus again attesting to the closed system conditions. We conclude for this natural experiment that the Wanapum basalt is not readily penetrated by elements from a high temperature, molten source.
Progress on Radiometric Dating of Wolfcamp Brines Using 4He and 40Ar
Authors: Zaikowski A. , Kosanke B. J. , Hubbard N. 
Published: March 2011

ABSTRACTGround water samples (brines) from deep wells in the Palo Duro Basin, Texas are being analyzed for noble gases in an attempt to obtain radiometric ages for these brines. The brines contain radiogenic 4He and 40Ar produced from the radioactive decay of U, Th, and K. Consideration of hydrochemical data for the brines, various isotopic, chemical, and mineralogical data for the aquifer rocks and noble gas production rates allow estimating the age of the brines to be about 130 million years at two wells. At a third well interaquifer mixing has occurred and the age is presently indeterminate.
A Proposed Model for the Thermal Conductivity of Dry And Water-Saturated Tuff
Authors: Moss M. , Haseman G. M. 
Published: March 2011

ABSTRACTThe room-temperature thermal conductivities of two kinds of tuff from the Nevada Test Site have been measured on a linear-heat-flow thermal comparator. The results are the basis for an empirical model of the conductivity of these rocks in the dry and water-saturated conditions as a function of porosity. Tuff is one medium being considered for nuclear waste disposal. Devitrified, non-zeolitized tuffs with 6-22% porosity, and non-welded, zeolitized tuffs with 24-35% porosity were examined. The empirical geometric mean model is used to characterize the porosity-dependent thermal conductivity. We consider the rock matrix conductivity and the effective fluid conductivity as adjustable parameters in fitting the model to data for saturated and dehydrated samples, separately. For each rock type, the fitted value of matrix conductivity is the same in both the saturated and dehydrated cases; 2.3 and 1.1 W/(m.K) for the non-zeolitized and zeolitized tuffs, respectively. The fitted values for fluid conductivities are different for the the zeolitized and non-zeolitized tuffs, but the ratio of fitted water conductivity to fitted gas conductivity is very nearly the same for both rock types. This permits the use of a single equation to predict with good accuracy the ratio of saturated to dry rock conductivity.
Comparison of Batch And Autoradiographic Methods in Sorption Studies of Radionuclides In Rock And Mineral Samples
Authors: Pinnioja S. , Jaakkola T. , Miettinen J.K. 
Published: March 2011

ABSTRACTSorption of 89Sr, 58Co, 134Cs and 241Am in rock and mineral samples was determined by the batch method using crushed sanmples and by autoradiographic method using rock thin sections. The rock samples were tonalite and rapakivi granite, representing the Olkiluoto and Loviisa nuclear power plant sites, respectively. The autoradiographic method was found to be applicable sorption of radionuclides in rock and mineral samles. The 8orption order of nuclides in rock samples was: KaAM> KaCs>KaCo> KaSr the sorption order of the different minerals was biotite> hornblende >plagioclase> potassium feldspar> quartz. Distribution coefficients (Ka) obtained by the batch and autoradiographic methods were of the same order of magnitude. Ka-values of Sr, Co, Cs and Am for tonalite were 5, 20, 190 and 40 × 10-4 m3/m2 by the batch method and 1, 9, 130 and 170 × 10-4 m3/m2 by the autoradiographic method.
Selective Aluminum CVD for Sub-Micron VIA Plug Filling
Authors: Zhu N. , Jo S. K. , Freiler M. B. , Scarmozzino R. , Osgood R. M. , Cacouris T. 
Published: March 2011

ABSTRACTWe present a novel technique to metallize high-aspect-ratio, small-dimension contact holes and via plugs for application to integrated circuits and packaging. The technique uses a laser-assisted process to deposit a thin film of aluminum from DMA1H, which forms a seed layer for subsequent selective CVD. The resistivity of the deposited aluminum is nearly that of the bulk metal, the contact resistivity is good (∼0.03 μΩ-cm2), and the morphology of the deposited film is comparable to that obtained with physical vapor deposition. This process has been used to fill via holes in a SiO2 substrate, and small-diameter (0.7 μm), high-aspect-ratio (3:1), aluminum plugs have been repeatedly formed without the incorporation of voids. A custom-made via chain structure was used to determine the via resistance (plug and contact), which was found to be 0.1 -0.3 Ω. Our technique opens a new process window for void-free high-aspect-ratio via and contact hole filling, and is particularly interesting in that it offers the potential to use aluminum or aluminum-copper in plug metallization.
Self-Aligned Suicides for ULSI
Authors: Maex Karen , Schreutelkamp Rob 
Published: March 2011

ABSTRACTSince self-aligned suicides are beginning to be used routinely in integral ULSI processes, critical processing characteristics need to be investigated. In this paper, three relevant issues concerning processing are discussed, namely, the formation of ultra-thin suicides, the silicidation of laterally confined areas and the thermal stability of silicide/Si structures. The technological aspects of TiSi2 and COSi2 are discussed and related to their materials properties.
Investigation of an in-situ probe for phase transformations during RTP silicidation
Authors: Schreutelkamp R. J. , Vandenabeele P. , Deweerdt B. , Coppye W. , Vermeiren C. , Lauwers A. , Maex K. 
Published: March 2011

ABSTRACTIn-situ emissivity measurements at a wavelength of 2.4 μα were used to monitor RTP Co silicidation on crystalline and polycrystalline silicon substrates. The influence of various parameters influencing the silicidation reaction was extensively studied. It is shown that particularly the phase transformation from CoSi to the final suicide phase, COSi2, strongly depends on parameters such as background doping level and type of substrate. This is illustrated for As-doped substrates. The method is extremely sensitive for the in-situ detection of the thermal degradation of thin COSi2 films at high temperatures, which is demonstrated for 25 nm COSi2 layers on highly As-doped c-Si substrates.
Electrical Characterization of Phosphorus Doped Ion Beam Synthesised CoSi2/Si Schottky Barrier Diodes.
Authors: Spraggs R. S. , Pananakakis G. , Bauza D. , Reeson K. J. , Gwilliam R. M. , Hunt T. D. , Sealy B. J. 
Published: March 2011

ABSTRACTThe current/voltage characteristics of ion beam synthesised CoSi2/Si (n - type) Schottky barrier diodes implanted with phosphorus to doses between 5 × 1012 and 2 × 1013 ions cm-2are examined after annealing at temperatures in the range 400° - 1000°C. For each dose of implanted phosphorus, the effective barrier height of the CoSi2/Si interface is successively reduced as the anneal temperature increases. The results of Secondary Ion Mass Spectroscopy (SIMS) analysis indicate that these changes are due to an increase in the space charge density at the interface. For lower annealing temperatures the increase in space charge density is attributed to activation of the phosphorus in the tail of the dopant distribution which extends across the CoSi2/Si interface. For higher annealing temperatures larger increases in the space charge density are attributed to a modified dopant distribution resulting from phosphorus diffusion and activation at the interface. For doses of 1 × 1014 P* cm-2and 2×1015P*cm2, ohrnie characteristics are seen after annealing at temperatures of 1000°C and 500°C respectively.
Solid State Interaction and Nano-Scale Silicide Formation for Co/Ti Multilayers on Silicon
Authors: Hong Feng , Patnaik Bijoy K. , Rozgonyi George A. 
Published: March 2011

ABSTRACTThe formation of a 12nm thick, continuous and thermally stable COSi2 layer was described in our previous work [MRS Proc. 238, 587 (1992)]. Interdiffusion in the Co/Ti-Si multilayer system has been further studied and the initial Ti(O) thickness is shown to be a critical parameter in controlling its effectiveness as a diffusion barrier, and in modulating the Co-Si and Ti-Si compctctive reactions. Three Ti(O) and three Co layers with thickness from ∼5nm 20nm were deposited sequentially, with Ti(O) as the first layer, on Si-(100) substrates by dual source thermal evaporation. The morphology of the CoSix/Si interface was strongly influenced by Ti(O) thickness from ∼5nm to ∼10nm, and a 12nm thick uniform CoSi2 layer with ∼28μΩ-cm resistivity was produced as decribed previously. When the initial Ti(O) thickness was increased to ∼20nm and the Co thickness set at -10nm, Co diffusion was suppressed and Ti reacted with Si yielding an ∼10nm amorphous TiSix layer at 550°C. This amorphous layer transformed to a 15nm thick uniform C-54 TiSi2 layer after selective removal of upper layers and a 750°C plus 800°C annealing. A flat silicide/Si interface and a ∼58μΩ-cm resistivity were obtained. The significance of both thermodynamic and kinetic factors in the compctetive reactions is discussed.
Self-Aligned, Metal-Masked Dry Etch Processing of III-V Electronic and Photonic Devices
Authors: Pearton S. J. , Katz A. , Feingold A. , Ren F. , Fullowan T. R. , Lothian J. R. , Abernathy C. R. 
Published: March 2011

ABSTRACTElectron Cyclotron Resonance (ECR) plasma etching of a variety of III-V devices, including heterojunction bipolar transistors (HBTs), and lasers will be reviewed. In many of these devices, the metal contacts also perform as self-aligned, dry etch masks, so that mask erosion must be addressed. Sidewall smoothness is also an issue for most etched mesa lasers, and conditions for achieving the requisite smoothness will be discussed. The use of stencil masks for pattern transfer of large (∼100μm) features during cluster-tool, single wafer integrated processing raises the possibility of a completely in-situ fabrication technology without the need for lithography. The dry etching of a variety of ohmic and Schottky metallizations and also of dielectrics deposited in a low pressure, rapid thermal CVD system lays the foundation for integrated III-V device processing.
Junction Formation in Silicon Using a Phosphorus Vapor Source and Rapid Thermal Drive-In
Authors: White Eric R. , Ashok S. , Allara D. L. 
Published: March 2011

ABSTRACTn+-n and n+-p junctions were formed on n-type and p-type Si using a thin film of phosphorus obtained from a simple vapor source, and driving in the dopant atoms in a rapid thermal processing (RTP) system. The vapor treatment consisted of heating powdered red phosphorus in a nitrogen ambient and allowing the resulting phosphorus vapor to deposit on the Si samples. This was done in an inexpensive apparatus constructed from flasks and test tubes. Following the vapor treatment, an SiOxfilm was sputtered over the phosphorus coating in order to serve as a capping layer during subsequent RTP drive-in that forms the junction. The junction properties were characterized by spreading resistance and electrical (IV and CV) measurements after deposition of metal contacts layers.
A Study of the Copper Wire Ball Bonding Processes
Authors: Hongyuan Fang , Yiyu Qian , Yihong Jiang 
Published: March 2011

ABSTRACTCopper ball bonding is a new technology which is expected to replace the traditional gold ball bonding and paid attention in woled recently, the technology is very important to reduce cost and improve reliability of microelectronic components. In this paper, the copper wire ball bonding processes have been studied by means of the MW-EFO metal wire ball forming device and the JWYH-2 thermosonic ball bonder. The bond strength of the ball bond under varied ultrasonic power and bonding time have been tested. The tested results show that the maximal strength of copper ball bond can be over 20g, it has advantage over the gold wire ball bonding. In this paper, the deformation process of the copper ball bond has been analyzed and viewed by SME.
The Effect of Xe Ion Beam Treatment on the Interaction Between Gold and GaAs
Authors: Pécz B. , Radnóczi G. , Horváth Zs. J. , Barna P. B. , Jároli Erika , Gyulai J. 
Published: March 2011

ABSTRACTThe effect of the defective nature of the substrate on the alloying behaviour of Xe implanted Au(55 ran)/n-GaAs system was studied using cross sectional transmission electron microscopy.Low dose Xe implantation (700 keV, 1*1014 ions/cm2) caused the formation of about SO nm thick polycrystalline region of GaAs beneath the gold layer. Annealing the implanted sample at 450°C gold diffused through the polycrystalline GaAs region and formed large pits of Au(Ga) solid solution in the defective area of GaAs having stacking faults and twins. The formation of a regrown GaAs covering layer was observed on the top of the reacted metallization simultaneously.High dose implantation of Xe++ ions resulted in the formation of amorphous GaAs layer with a thickness of about 750 nm. Twinned regions of GaAs were observed at the amorphous - crystalline GaAs interface by high resolution electron microscopy. Ion beam caused phase transition was observed in this sample. The amorphous GaAs region recrystallized to single crystalline GaAs due to annealing at 400°C.