bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon-Nitride, Diamond-Like-Carbon and Silicon-Based Films Synthesized by Electron Cyclotron Resonance Chemical Vapor Deposition
Authors: Moran M. B. , Johnson L. F. 
Published: April 2011

AbstractCarbon-nitride and diamond-like-carbon films were deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) using carbon precursors in either a nitrogenor an argon-high-density plasma. The carbon precursors were tetrachloroethylene (C 2C14), ethylene (C2H4) and neopentane (C5H12). Electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared (FTIR) spectroscopy showed three distinct chemical compositions: chlorine-doped carbon nitride (CNx:Cl), hydrogenated carbon nitride (CNx:H) and hydrogenated amorphous carbon (a-C:H). FTIR spectroscopy revealed a fourth composition: chlorine-doped amorphous carbon (a-C:Cl). ESCA analysis of the a-C:Cl film was not performed. Microstructures ranging from amorphous to microcrystalline were observed using differential interference contrast (DIC) optical microscopy and atomic force microscopy (AFM). Plasma etching of the substrate prior to film growth and biasing of the stage during film growth strongly influence the resulting microstructure. 100-μm-size, stacked, pyramidal CNx:Cl crystallites were deposited onto a glass microscope slide through a combination of substrate preetching and rf-biasing of the stage during film growth. In later experiments, pulsed-dc-highvoltage biasing of the stage during the growth process resulted in the deposition of 1-jim-size, rectangular- and triangular-shaped CNx:Cl crystallites onto fused silica.Chlorinated instead of hydrogenated precursors were used to eliminate hydrogen incorporation during the growth of the ECR-CVD carbon nitride films. Chlorinated hydrocarbon precursors like trichloroethylene (C2HC13) and C2C14 reduce the amount of hydrogen in the plasma and make the formation of CN bonds more favorable. The results also show that doublebonded CC precursors are needed for N2 to react with carbon. However, when a hydrogenated precursor like C2H4 is used with a N2 plasma, hydrogen reacts with the CC double bond to form CH and NH bonds faster than N2 can react to form double- and single-bonded CN. The disadvantages of using chlorinated-carbon precursors are that the resulting CNx:Cl films contain a small amount of chlorine (Cl), are porous and are unstable with respect to moisture incorporation.It is much easier to obtain stable, dense films using chlorinated precursors if more conventional materials are deposited. Silicon dioxide (SiO2) and silicon nitride (Si3N4) films were deposited by ECR-CVD using trichlorosilane (SiHC13). The films showed no degradation or moisture incorporation after several months.
Low Temperature Synthesis of Si-C-N and C-N Films by IR-laser Assisted ECR-PECVD
Authors: Zhu Shen , White H. W. 
Published: April 2011

AbstractA new synthesizing method, IR-laser-assisted electron-cyclotron-resonance plasma-enhanced chemical vapor deposition (LA-ECR-PECVD), has been used to fabricate Si-C-N and C-N films on steel substrates at low temperatures (< 650 °C). Methane/nitrogen or carbon dioxide/nitrogen gases are dissociated to methane radicals and nitrogen plasma by the IR-laser and ECR to enhance the species' energy. An IR-laser beam (pulsed Nd:YAG laser, 1064 nm) was introduced into the growth chamber for two purposes: (1) to add Si atoms by ablating a Si target, and (2) to enhance the plasma concentration in the gas phase. An infrared vibration mode located at 1256 cm-l wavenumber was observed in Si-C-N and C-N films, although these films have an amorphous phase. The C-N film also has a Raman shift at 1276 cm-l. The AFM images reveal many islands with a size ranging from 50 nm – 150 nm in films.
Growth of Diamond on Sapphire by Pulsed Laser Ablation under Oxygen Atmosphere
Authors: Yoshimoto M. , Hishitani Y. , Maruta H. , Koinuma H. , Tachibana T. , Nishio S. , Kakihana M. 
Published: April 2011

AbstractWe examined the possibility of nucleation and growth of diamond via a hydrogen-free vapor phase route of pulsed laser ablation of a graphite target in a low-pressure pure oxygen atmosphere. The present evidences from microscopic, diffraction and spectroscopic techniques indicate that high-quality (111)-oriented diamond crystals could be nucleated and grown on ultra smooth sapphire (single-crystal α - A12O3)substrates at the temperatures lower than 600°C under the optimized growth conditions of oxygen pressure (around 0.15 Torn) and laser ablation (pulsed laser fluence of 3 x 108W/cm2at 5Hz).
Functionally gradient PECVD Ti(C,N) coatings
Authors: Shieh J. , Wang H. L. , Tsai M. S. , Hon M. H. 
Published: April 2011

AbstractTi(C,N) hard coating is well known as a suitable material for protecting substrate, and functionally gradient design is a method to improve the performance of it. In this study, functionally gradient Ti(C,N) coatings were performed by the technique of capacitive RF PECVD based on the investigation of Ti(C,N) monolayers with different C and N ratios. The results show that the composition and growth rate of Ti(C,N) monolayers are influenced by the nitrogen/methane ratio as other deposition parameters are fixed. A model is also proposed from the results obtained and is employed to calculate the reaction gas ratio and duration time needed for deposition in the gradient coating. The elements of Ti and N in the gradient coatings were analyzed by Auger electron spectroscopy (AES) and revealed that the composition changed linearly as designed. The residual stress of the gradient coatings was also measured to show that the gradient design provides the possibility for adjusting the stress distribution of PECVD hard coatings.
Oxidation of PECVD SiC Deposited from Trimethylsilane
Authors: DiFonzo Peter A. , Massuda Mona , Kelliher James T. 
Published: April 2011

AbstractThe stoichiometric composition and oxidation rates ( wet or dry ) of plasma enhanced chemical vapor deposited (PECVD) silicon carbide (SiC) films are effected by the deposition conditions of trimethylsilane (3MS) and carrier gas. We report the oxidation kinetics of SiC thin films deposited in a modified commercial PECVD reactor. A standard horizontal atmospheric furnace in the temperature range of 925–1100°C was used in the oxidation. Oxidized films were measured optically by commercially available interferometer and ellipsometer tools in addition to mechanically using a commercially available profilometer. Activation energies of the parabolic rates were in the range of 20.93 to 335.26 kJ/mol.
Improved Microstructures for Thermal Barrier Coatings Produced by Glancing Angle Deposition
Authors: Harris K. D. , Vick D. , Brett M. J. , Robbie K. 
Published: April 2011

AbstractA new approach to deposition of thin films for thermal barrier applications is described. During electron beam evaporation, the extreme shadowing effect that is present at highly oblique incidence is employed to introduce porosity into thin films of zirconia. Using controlled substrate motion a solid capping layer may be applied to these porous films. By depositing layers of porous material and capping in an alternating fashion a new structure is produced which warrants evaluation as an improved thermal barrier coating.
Sensitivity Analysis of Uranium Solubility Under Strongly Oxidizing Conditions
Authors: Liu L. , Neretnieks I. 
Published: April 2011

AbstractTo evaluate the effect of geochemical conditions in the repository on the solubility of uranium under strongly oxidizing conditions, a mathematical model has been developed to determine the solubility, by utilizing a set of non linear algebraic equations to describe the chemical equilibria in the groundwater environment. The model takes into account the predominant precipitation-dissolution reactions, hydrolysis reactions and complexation reactions that may occur under strongly oxidizing conditions. The model also includes the solubilitylimiting solids induced by the presence of carbonate, phosphate, silicate, calcium, and sodium in the groundwater. The thermodynamic equilibrium constants used in the solubility calculations are essentially taken from the NEA Thermochemical Data Base of Uranium, with some modification and some uranium minerals added, such as soddyite, rutherfordite, uranophane, uranyl orthophosphate, and becquerelite. By applying this model, the sensitivities of uranium solubility to variations in the concentrations of various groundwater component species are systematically investigated. The results show that the total analytical concentrations of carbonate, phosphate, silicate, and calcium in deep groundwater play the most important role in determining the solubility of uranium under strongly oxidizing conditions.
Effective Reactive Surface Area: an Anisotropic Property of Physically and Chemically Heterogeneous Porous Media
Authors: Smith Robert W. , Schafer Annette L. 
Published: April 2011

AbstractAlthough transport calculations are often formulated in terms of mass-based isotropic distribution coefficients, it is the abundance of reactive surface areas of subsurface materials that controls contaminant adsorption. In water-saturated homogeneous systems devoid of advective fluxes (e.g., batch experiments), the available reactive surface area is similar to the total surface area (as measured by conventional methods such as BET gas adsorption). However, in physically and chemically heterogeneous systems with advective fluxes, the effective reactive surface area (i.e., the surface area that a packet of advecting water interacts with) is smaller than the laboratory measured surface area and is a complex function of advective velocity and the correlation structures of the physical and chemical heterogeneities. Theoretical derivations for an important but simple type of heterogeneity (fine-scale horizontal layering) suggest that the effective reactive surface area is an anisotropic property of the medium and is inversely correlated with the anisotropy in hydraulic conductivity. The implications of reactive transport anisotropy include the concept that the retardation factor should be treated as a directional property rather than being treated as a constant. Furthermore, because of the inverse relationship between effective reactive surface area and hydraulic conductivity, batch adsorption experiments tend to overestimate the retention of contaminants relative to intact natural materials.
Radioiodide Sorption to Sediment Minerals
Authors: Kaplan D. I. , Serne R. J. , Parker K. E. , Kutnyakov I. V. 
Published: April 2011

AbstractLaboratory studies were conducted to quantify and understand the processes by which iodide (I−) sorbs to minerals found in subsurface arid sediments. Little or no I− sorbed to montmorillonite (Kd = −0.42 ± 0.08 mL/g), quartz (Kd = 0.04 ± 0.02 mL/g), vermiculite (Kd = 0.56 ± 0.21 mL/g), calcite (Kd = 0.04 ± 0.01 mL/g), goethite (Kd = 0.10 ± 0.03 mL/g), or chlorite (Kd = −0.22 ± 0.06 mL/g). A significant amount of I− sorbed to illite (Kd = 15.14 ± 2.84 mL/g).). Upon treating the iodide-laden illite with dissolved F−, Cl−, Br−, or 127I−, desorption (or isotopic exchange in the case of 127I) removed, respectively, 43 ± 3%, 45 ± 0%, 52 ± 3, and 83 ± 1 % of the I− originally adsorbed to the illite. The fact that such large amounts of I− could be desorbed suggests that the I− was weakly adsorbed, and not chemically bonded to a soft metal, such as mercury or silver, that may have existed in the illite structure as trace impurities. Finally, I− sorption to illite was strongly pH-dependent; the Kd values decreased from 46 to 22 mL/g as the pH values increased from 3.6 to 9.4. Importantly, I− sorbed to illite even under alkaline conditions. Together, these experiments suggest that illite removed I− from the aqueous phase predominantly by reversible physical adsorption to the pH-dependent edge sites. Illites may constitute a substantial proportion of the clay-size fraction of many arid sediments and therefore may play an important role in retarding I− movement in these sediments.
Development of a ceramic waste form for high-level waste disposal
Authors: Esh D. W. , Goff K. M. , Hirsche K. T. , Battisti T. J. , Simpson M. F. , Johnson S. G. , Bateman K. J. 
Published: April 2011

AbstractA ceramic waste form is being developed by Argonne National Laboratory* (ANL) as part of the demonstration of the electrometallurgical treatment of spent nuclear fuel [1]. The halide, alkaline earth, alkali, transuranic, and rare earth fission products are stabilized in zeolite which is combined with glass and processed in a hot isostatic press (HIP) to form a ceramic composite. The mineral sodalite is formed in the HIP from the zeolite precursor. The process, from starting materials to final product, is relatively simple. An overview of the processing operations is given. The metrics that have been developed to measure the success or completion of processing operations are developed and discussed. The impact of variability in processing metrics on the durability of the final product is presented. The process is demonstrated to be robust for the type and range of operation metrics considered and the performance metric (PCT durability test) against which the operation metrics are evaluated.
Migration of Plutonium in a Simulated Engineered Barrier System Consisting of Waste Glass and Ompacted Bentonite
Authors: Inagaki Y. , Saito R. , Furuya H. , Idemitsu K. , Arima T. , Banba T. , Maeda T. , Matsumoto S. , Tamura Y. , Kikkawa S. 
Published: April 2011

AbstractIn a simulated engineered barrier system consisting of a simulated HLW glass doped with Pu, a compacted bentonite and water under reducing conditions, migration tests of Pu from the glass into the bentonite through water were performed. The following results were obtained: (1) The presence of bentonite enhances the glass dissolution while it has no remarkable influence on the concentration of Pu dissolved species in the solution. (2) Only a small part of the leached Pu, which may correspond to the dissolved species, can diffuse into the bentonite with the apparent diffusion coefficient of 3×10−14m2/s. (3) Interactions between the glass and the bentonite have no remarkable influence on the diffusion of Pu.
Production And Characterization Of A Plutonium-238 Loaded Ceramic Waste Form For The Study Of The Effects Of Alpha Decay Damage
Authors: Steven M. , Frank Steven M. , Esh David W. , Johnson Stephen G. , Noy Marianne , O'Holleran Thomas P. 
Published: April 2011

AbstractArgonne National Laboratory has developed a glass-bonded sodalite ceramic waste form to immobilize fission products and plutonium that accumulate during the electrometallurgical conditioning of spent nuclear fuel. To investigate the effects of alpha decay damage on the structure and leaching characteristics of the ceramic material, 238Pu has been incorporated into the ceramic waste form. The 238pu,with its high specific activity, significantly increases the rate of alpha damage to the waste form. Long term studies have begun with periodic examination of the 238Pu loaded ceramic material. A number of characterization techniques are used to study the alpha decay damage on the structure of the waste form. In addition, PCT type leachate studies will be performed to determine the effect of alpha decay damage on the durability of the ceramic waste form. Preliminary results from this study are presented.
Radiolytic Gas Generation in Chemically-bonded Iron Phosphate Ceramic Forms used for Immobilization of Plutonium Ash Residues
Authors: Aloy Albert S. , Kolycheva T.I. , Knecht D. A. , Macheret Y. 
Published: April 2011

AbstractIron phosphate ceramic (IPC) samples were prepared with plutonium-238, and radiolytic gas generation was detennined for exposure times of up to 195 days. The specific activity of the synthesized IPC samples was 1.91 mCi/g. The composition of the generated gases was determined to contain mainly H, and lower amounts of O2, CO2 and CO. The molecular hydrogen G value (molecules of H2 per 100 eV absorbed dose) depended on the sample preparation methodology, ranging from 0.07 at 79 days for sample IPC-2 to 0.34 at 119 days for sample IPC-1. This difference could be due to different total amount (wt.%) of free water resulting in sample preparation. The leach rate data for radioactive and non-radioactive IPC samples obtained by the ANSI/ANS 16.1 procedure resulted in Leachability Indexes of 13.7 for Pu and 15.4 for Ce, above the NRC LLW acceptance minimum index of 6.
Radiological Properties of Heavy Liquid Metal Targets of Accelerator Driven Systems
Authors: Pankratov D. V. , Yefimov E. I. , Ignatiev S. V. , Levano V. I. 
Published: April 2011

AbstractThe long-lived radioactivity of lead-bismuth coolant (LBC) inside the targets of the accelerator driven systems (ADS) is estimated. It is determined by both spallation and fission products of lead and bismuth nuclides. Based on US safety standards the radiotoxicity of targets was calculated for different cooling down periods. In order to estimate the total radioactivity of 1-MW power target circuit (TC), which is developing now at IPPE, the contribution of its main components are preliminarily analyzed.
The Solubility Limited Source Term for Cement - Conditioned Wastes: A Status Report
Authors: Glasser F. P. 
Published: April 2011

AbstactAn important function of the cement backfill in a nuclear waste repository is to react with aqueous waste species and reduce their solubility. However, to quantify backfill performance it is first necessary to prove the existence and establish the nature of the chemical solubility controls. This can be done by characterising the solubility-limiting phases, determining their solubility and thermodynamic functions, and assessing their stability and persistence and solubility during backfill degradation. Much of the necessary data must be acquired experimentally. The title paper describes briefly the progresss of experimental work on selected species including nickel, chromium(III,VI), tin(IV) molybdenum(VI), uranium(VI), Ce(III,IV), thorium, actinide simulants (III, IV) and chloride. Data needs are assessed and although much experimental work remains to be done, methodologies have been developed which will expedite progress. The expectation of a more quantitative performance assessment of cement barriers is, therefore, attainable.
A model for Redox Control in A Cementitious Repository
Authors: Heath T. G. , Tweed C. J. 
Published: April 2011

AbstractCalculations have been performed to investigate long timescale redox control in a cementitious deep waste repository, once there has been significant corrosion of the steel containers in the near field. The methodology considers reaction of the porewater with redoxsensitive solids. The solids were selected based on considerations of the repository concept, the waste inventory and the processing of the waste into a form suitable for disposal. A number of factors that may affect the redox potential have been considered. Amongst these are the form of the redox-controlling solids, the effect of changes in pH, the effect of sorption onto the cementitious backfill, and the effect of the association of dissolved radionuclides with complexants arising from the degradation of organic wastes. The calculations suggest that for the United Kingdom Nirex Limited (Nirex) disposal concept and inventory, the redox system in the near field of the repository would be controlled by the iron(II)/iron(III) redox couple. This would maintain the redox potential in the repository near field at a low value for timescales in excess of 1 million years.
Ion Selective Resins: Development and Applications for Nuclear Waste Management
Authors: Czerwinski K. R. , Draye M. , Favre-Réguillon A. , Foos J. , Guy A. , Lemaire M. 
Published: April 2011

AbstractOrganic based ion selective resins have some similar attributes: case of synthesis, high metal ion complexation ability, and flexibility for different nuclear waste management applications. For most chelating polymers, the ligand is deemed to be of primary importance for the interaction with the targeted metal ion. The role of the polymer matrix is usually ignored. For ion specific resins, the polymer structure is formed to a specific metal ion. Using the molecular imprinting technique, resins can be formed with functional groups and cavities for a target metal ion. Ion selective resins have been developed for the separation of Cs. The methods and concepts used for the development of the Cs specific resins have been applied to the development of selective resins for Eu (a trivalent actinide model). The resulting resins are characterized by FTIR spectroscopy, moisture regain, and ion exchange capacity. The incorporation of 8-hydroxyquinoline into the resin increases selectivity for Eu over La. The results for the Eu study indicate ion specific resins can be developed for the separation of trivalent actinides from nuclear waste.
Development of Metal Recycling Process from Decommissioned Nuclear Power Plants
Authors: Ishikura T. , Abe S. , Sakai H. , Takahashi J. 
Published: April 2011

AbstractDismantling and demolition of a nuclear power plant generates a large amount of metal waste. Recycling of such waste for resource is important because of the limited capacity of the disposal site. Authors have developed metal recycling processes. It is found that pyrometallurgical separation techniques can effectively separate nickel and cobalt, which contain main contributors of radioactivity, from iron and chromium.
Optimization of immobilization of strontium and uranium by the solid matrix
Authors: Raicevic S. , Plecas I. , Lalovic D. I. , Veljkovic V. 
Published: April 2011

AbstractOne of the basic physical parameters which defines: (1) the capacity of the solid matrix for the incorporation (sorption) of the impurity and (2) the stability of the solid matrix -impurity system, is the ion-ion interaction potential, representing the main term of the cohesive energy. Using this parameter determined in the frame of the pseudopotential theory and pseudoatomic approximation we have investigated the systems HAP-Sr and HAP-UO2. In analysis, the hydroxyapatite (HAP, Ca10(PO4)6(OH)2) was selected as a model solid matrix since insoluble phosphates, phosphate ceramic and apatite-like materials are candidates for the immobilization of radionuclides. The substitution of calcium atoms by different impurities in HAP can be presented by the formula: Ca10-xMx(PO4)6(OH)2, where 0 ≤ x ≤ 10 and M = Sr2+, UO22+. It has been shown that (1) Sr can be safely immobilized by HAP, natural apatites and phosphate rocks in the whole range of its concentrations, and (2) that HAP is not an appropriate solid-matrix for immobilization of UO22+ because its incorporation in the low concentration results in a decrease of the matrix stability, stimulating formation of the inhomogeneous structure containing isolated clusters of the UO2- apatite solid phase.
Optimization of heat-liberating batches for ash residue stabilization
Authors: Karlina O. K. , Varlackova G. A. , Ojovan M. I. , Tivansky V. M. , Dmitriev S. A. 
Published: April 2011

AbstractOur study is concerned on development of a new stabilisation method of ash residue obtained after incineration of solid radioactive waste by means of heat liberating batches - compositions with redox properties. The results of optimisation of heat-liberating batches with the purpose of increasing process safety and obtained product quality of are discussed.