bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-plane Anisotropy in Hetero-Amorphous (CoFeB)-SiO2 Thin Films
Authors: Johnsson P. , Aoqui I. , Nötzold K. , Allebert J. , Munakata M. , Grishin A. M. 
Published: April 2011

ABSTRACTIn order to engineer materials suitable for micromagnetic inductor cores we have fabricated and investigated the properties of granular (CoFeB)-SiO2 amorphous thin films. The deposition method, synchronous triple-rf magnetron sputtering onto rotating substrates, induces anisotropy in the film plane. Here we present magnetic hysteresis loops, resistivity and magnetoresistance measurements of two of these films, with different amount of metallic content. Both films have anisotropic resistivity, which is higher for the film with less metallic content. The low-metallic-content film exhibits typical isotropic giant magnetoresistance (GMR), while the film with higher metallic content shows a mixture of GMR and anisotropic magnetoresistance (AMR). The AMR appears at fields below 500 Oe. We believe that this has not been observed before in amorphous samples. The behaviour of the resistivity versus temperature ρ (T) indicates that the sample with lower metallic content consists of isolated grains while the high-metallic-content sample consists of a percolated network. Experimental ρ (T) data for the low-metallic-content sample fit: to the variable-range hopping model at temperatures lower than 221 K and can be described by excitation of the carriers to the mobility edge at higher temperatures.
The Intermediate Phase in Ternary GexAsxSe1–2x Glasses
Authors: Qu Tao , Georgiev D.G. , Boolchand P. , Micoulaut M. 
Published: April 2011

ABSTRACTMelt-quenched AsxGexSe1–2x glasses over the composition range, 0 < x < 0.26, are examined in Raman scattering, T-modulated Differential Scanning Calorimetry (MDSC), and 119Sn Mossbauer spectroscopy measurements. The non-reversing enthalpy near Tg, ΔHnr(x), accessed from MDSC shows a global minimum (∼ 0) in the xc(1) = 0.09 < x < xc(2) = 0.16 range, and increases by an order of magnitude both at x < xc(1) and at x > xc(2). Raman mode frequency of corner-sharing Ge(Se1/2)4 tetrahedra studied as a function of x, also shows three distinct regimes (or power-laws, p) that coincide with ΔHnr(x) trends. These regimes are identified with mechanically floppy (x < xc(1)), intermediate (xc(1) < x < xc(2)), and stressed-rigid (x > xc(2)) phases. The Raman elasticity power-law in the intermediate phase, p1 = 1.04(3), and in the stressed rigid phase, p2= 1.52(5), suggest effective dimensionalities of d = 2 and 3 respectively.
Intermediate Range Order in Silicate Melts and Glasses: Computer Simulation Studies
Authors: Horbach Jürgen , Winkler Anke , Kob Walter , Binder Kurt 
Published: April 2011

ABSTRACTWe present the results of large scale computer simulations to discuss the structural and dynamic properties of silicate melts with the compositions (Na2O)(2·SiO2), (Na2O)(20·SiO2) and (Al2O3)(2·SiO2). We show that these systems exhibit additional intermediate range order as compared to silica (SiO2) where the characteristic intermediate length scales stem from the tetrahedral network structure. Furthermore we show that the sodium dynamics in the sodium silicate systems exhibits a very peculiar feature: the long–time decay of the incoherent intermediate scattering function can be described by a Kohlrausch law with a constant exponentβforq > qthwherebyqthis smaller than the location of the main peak in the static structure factor for the Na–Na correlations.
Actinide Migration in Granite Fractures: Comparison between In-Situ and Laboratory Results
Authors: Kienzler Bernhard , Römer Jürgen , Vejmelka Peter , Jansson Mats , Eriksen Trygve E. , Spahiu Kastriot 
Published: April 2011

ABSTRACTResults of migration experiments with fractured drill cores performed in laboratory and in the CHEMLAB 2 probe under in-situ conditions at Äspö HRL are presented. Drill cores for both experiments are prepared by the same method and provide similar hydraulic properties. As tracers, actinides Am(III), Pu(IV) and Np(V) are applied. Breakthrough of Np is found to be unre-tarded in comparison to inert HTO tracer. Recovery of Np amounts to less than 40%. Am and Pu are not eluted from the cores. Lower limits of the retardation factor of 135 are calculated for both Am and Pu. Post mortem investigations of the fractured cores are performed by cutting perpendicular to the cylinder axis and subsequent chemical and radiochemical analysis of abraded material and slices. Imaging of the slices reveals the geometry of the flow path. α-radiography of the slices shows similar distribution patterns of Np and Am. It is shown by TTA extraction that Np bound onto the slices is in the tetravalent state. Hence, Np(V) undergoes reduction during migration. Retention of Am and Np is attributed to different processes.
Results from burial experiments with simulated medieval glasses
Authors: Roemich Hannelore , Gerlach Sandra , Mottner Peter , Mees Florias , Jacobs Patric , Dyck Dirk van , Doménech Carbó Teresa 
Published: April 2011

ABSTRACTDuring several hundred years of burial in the soil, glasses, especially those with medieval compositions, develop heavily corroded surfaces, showing phenomena such as local pitting, laminated layers and browning effects. For this study the damage phenomena have been characterised for three original glasses, using conventional methods (light microscopy and SEM of the surface and cross sections) and microfocus X-ray computed tomography (mCT), a new non-destructive analytical technique.The degradation of glass in the soil depends on a variety of parameters, concerned with the glass itself and with the burial environment. Since synergetic effects may complicate any mechanistic studies, laboratory experiments have been carried out under controlled conditions.Humid soil environments with a pH of 6.5 to 7.5 lead to the development of local microcracks on the surface, whereas more alkaline soil conditions (pH 8.0 to 9.0) favour the formation of laminated structures. The conclusions of the paper focus on the effect of glass composition (model glasses and archaeological glasses), soil conditions (variation of pH) and exposure time (23 months versus several centuries).
Dynamic Behavior of Colloidal Silica in the Presence of Solid Phase
Authors: Chida Taiji , Niibori Yuichi , Tochiyama Osamu , Tanaka Koichi 
Published: April 2011

ABSTRACTSince silica undergoes polymerization, precipitation, and dissolution depending on the change in pH or temperature, the chemical behavior of silica would be much complicated when cement for the construction of geological disposal system greatly changes the pH (8 to 13) of groundwater. To clarify the dynamic behavior of silica in such an alkaline solution, the concentrations of silica in both soluble and colloidal form in the supersaturated solution in the presence of solid phase have been traced over a 40-day period. In the experiment, the concentration of silica in a soluble form was determined by the silicomolybdenum-yellow method, and the concentration of silica in soluble plus colloidal forms was determined by adjusting the pH of the solution to 13, where all the silica changes into a soluble form (mainly monomeric). In order to examine the dynamic behavior of colloidal silica with solid phase of silica, this study has used natural quartz and pure commercial amorphous silica, both in a size fraction of 74–149 μm, whose specific surface-area (BET, N2 gas) were respectively 1.0 m2/g and 400 m2/g. The Na2SiO3 solution (250 ml, pH>10, 298 K) was poured into a polyethylene vessel containing quartz or amorphous silica (0.1 g or 0.5 g), HNO3 and a buffer solution. The pH of the solution was set to 8. The silica initially in a soluble form at pH>10 (6.8×10-3 M or 1.2×10-2 M) became supersaturated and either deposited on the solid surface or changed into the colloidal form. The ratio of silica in those form depended both on the initial concentration of soluble-silica and the surface area of the solid. The concentration of colloidal-silica gradually decreased, where the logarithm of its concentration decreased linearly against time after the concentration of soluble-silica decreased to a metastable concentration slightly higher than the solubility of soluble-silica.
Incorporation of Radioactive Metals and Trace Metals into Phosphate “Anhydrous” Autunite: Thermodynamic Evaluation
Authors: Xu Huifang , Wang Yifeng 
Published: April 2011

ABSTRACTThe prediction of heavy metal solubility in the presence of phosphate is the key for designing a successful environmental remediation strategy or for the performance assessment of a nuclear waste repository. In order to evaluate the possibility for solubilities and incorporation of U and its fission products, such as Cs, Np, Pu, it is important to have the Gibbs free energies of formation of possible end-member phases. In this paper, we use a linear free energy relationship to calculate the Gibbs free energies of formation of divalent cation “anhydrous” autunite phases [M2+(UO2)2(PO4)2] and monovalent cation “anhydrous” autunite phases [M+2(UO2)2(PO4)2]. Based on predicted Gibbs free energies of formation for autunite phases, an equilibrium calculation indicates that it is feasible to incorporate NpO2+ into the autunite phases. If concentration of Cs+ is high, Cs+ will be incorporated into the autunite phases. However, it is not feasible to incorporate low concentration Cs+ released from spent fuel into the uranyl phosphate phases with layered structure and interlayer water (such as autunite phases, boltwoodite phases, and uranophane phases) as previously proposed. The predicted data can be considered as a first order approximation.
Characterization of α-Isosaccharinic acid: pKa-determination
Authors: Ekberg S. , Ekberg C. , Albinsson Y. 
Published: April 2011

ABSTRACTThe stability constant for isosaccharinic acid dissociation is of importance in complexation studies involving species present in radioactive waste. As there are very few stability constants reported in the literature, this study has determined stability constants at 22.8, 34.5 and 44.2° C, using potentiometric titrations in a 1 M NaClO4 solution. The stability constants were linear functions of the inverted temperature, thus allowing for a simple determination of the entropy and enthalpy of the reaction.
Dissolution of a Multiphase Waste Form
Authors: Lewis Michele A. , Dietz Nancy L. , Fanning Thomas H. 
Published: April 2011

ABSTRACTThe dissolution behavior of the ceramic waste form (CWF) is being investigated to support its qualification for disposal in the proposed repository at Yucca Mountain. The CWF consists of sodalite and glass phases and has been consolidated either by hot isostatic pressuring (HIP) or by pressureless consolidation (PC). In this paper we compare the dissolution behavior of the two materials using in MCC-1 type tests at 90°C in a simulated silicate groundwater. The test solutions were periodically exchanged limit feedback effects. The solid surface area to volume ratio was 10 m-1. Five types of samples were tested: (1) HIP CWF, (2) binder glass vitrified by HIP, (3) PC CWF, (4) binder glass vitrified by PC, and HIP sodalite. Boron releases were used to monitor glass dissolution; these were similar in tests with HIP CWF, HIP glass, and PC CWF, but about 3X higher in tests with PC glass. At the end of the tests, the surfaces of the reacted materials were examined with scanning electron microscopy for signs of preferential dissolution. Differences in the dissolution behaviors of the materials are described and the implications of the test results regarding the performance of the CWF in the disposal system are discussed.
Mobilization/Retention of Radionuclides during Corrosion of High Burnup Spent Fuel and Backfill Materials in Salt Brines
Authors: Loida Andreas , Kienzler Bernhard , Geckeis Horst 
Published: April 2011

ABSTRACTWith respect to the assessment of the long-term behavior of the waste form spent fuel it is of high importance to study the fuel alteration in contact with groundwater and near field materials. The aim of this work is to evaluate the impact of candidate backfill materials hydroxylapatite and magnetite on the overall corrosion behavior of this waste form in salt brine; both materials are used in corrosion tests together with spent fuel. The instant releases and the matrix dissolution rates appear to be similar in presence and in absence of any backfill material under study. However, Am,Np,Pu,U and Sr are retained at different ratios on the hydroxylapatite, on the magnetite and on the fuel sample, indicating possibly the formation of different radionuclide containing new solid phases.
Maintaining Chemically Reducing Waste-Package Conditions
Authors: Forsberg Charles W. , Dole Leslie R. 
Published: April 2011

ABSTRACTMost fission products and actinides in spent nuclear fuel (SNF) are trapped in the uranium dioxide (UO2) crystal structure and cannot escape until the UO2 is oxidized. Oxidation destroys the crystal structure, exposes the radionuclides to groundwater, and creates the potential for dissolution. For a repository in an oxidizing geochemical environment, the potential exists to delay the release of radionuclides for hundreds of thousands to millions of years by using a combination of excess depleted uranium dioxide and iron in the waste package (WP) to locally maintain chemically reducing conditions. This approach limits the rate of oxygen transport to the SNF after WP failure. Alternative methods of oxygen transport to the SNF were investigated, including transport by groundwater, diffusion through air, and diffusion through water.
Novel Functionalized Ceramic Getter Materials for Adsorption of Radioiodine.
Authors: Mattigod Shas V. , Fryxell Glen , Parker Kent , Kaplan Dan 
Published: April 2011

ABSTRACTA new class of getter materials has been synthesized for immobilization of long-lived radionuclides such as129I. These novel materials consist of nanoporous ceramic substrates with tailored pore sizes ranging from 2 – 20 nm. These high surface area (∼1000 m2/g) ceramic substrates have been functionalized with self-assembled monolayers consisting of soft cation-capped thiol-functionality. The resulting getter materials exhibit highly dense binding sites, and excellent selectivity for iodide. The effectiveness of these novel getter materials was evaluated using radioiodide-spiked samples of surface water and concrete leachate and adsorption performance was compared with natural sulfide mineral getter materials. The data indicated that the novel getter materials have very high affinity for radioiodide (Kd: 4 × 104– 3 × 105ml/g and 6 × 105ml/g in surface and concrete leachate respectively). Comparatively, the radioiodide Kdvalues for natural mineral getters were typically two to three orders magnitude less than the novel getters. The results indicated that the synthetic getter materials have the potential to immobilize and therefore retard the migration of129I in the subsurface environment. Additional studies are being conducted to evaluate thelong-term stability of these materials in waste disposal environments.
Cold Gas Dynamic Manufacturing – A new approach to Near-Net Shape Metal Component Fabrication
Authors: Morgan R. H. , Sutcliffe C. J. , Pattison J. , Murphy M. , Gallagher C. , Papworth A. , Fox P. , O'Neill W. 
Published: April 2011

ABSTRACTCold Gas Dynamic Manufacturing (CGDM) is a high-rate, direct deposition process capable of combining many dissimilar materials in the production of a single component. The process is based on Cold Gas Dynamic Spraying (CGDS) – a surface coating technology in which small, un-heated particles are accelerated to high velocities (typically above 500 m/s) in a supersonic gas jet and directed towards a substrate material. The process does not use a heat source (as with similar plasma and HVOF spray technologies), but rather employs the high kinetic energy of the particles to effect bonding through plastic deformation upon impact with the substrate or previously deposited layer. As a consequence it lends itself to the processing of temperature sensitive material systems such as oxidising, phase-sensitive or nano-structured materials. To achieve metallic bonding incident particles require velocities greater than a certain material-specific threshold value, such that thin surface films are ruptured, generating a direct interface. This bonding mechanism has been compared to explosive welding.This paper discusses the further development of the CGDS technique from surface coating technology into the basis for a novel Additive Fabrication process. The description of the apparatus is presented in addition to the basic processing conditions for the deposition of aluminium material. Particular attention is paid to the morphology of the deposited material, the microstructure and the interfacial boundary between splats.
Monolithic Three-Dimensional Integration of Micro-Fluidic Channels and Optical Waveguides in Fused Silica
Authors: Bellouard Yves , Said Ali , Dugan Mark , Bado Philippe 
Published: April 2011

ABSTRACTThis paper presents dramatic improvements in the micro-fabrication of three-dimensional microfluidic channels and high-aspect ratio tunnels within the bulk of a fused silica substrate. We also report the fabrication of optical waveguides within the same substrate, which is a major step towards the integration of sensing capabilities within microfluidic networks.This integrated device, which combines both fluidic channels and optical waveguides, opens new opportunities in bio- and chemical sensing. The flexibility of the improved manufacturing process offers substantial new design capabilities, especially for single channel probing and massively parallel processing and sensing.
Microwave Molecular Sieves Synthesis and Capillary Crystal Growth by Geometric Confinement.
Authors: Ogunwumi Steven B. , Wight John F. , Fajardo James C. 
Published: April 2011

ABSTRACTMicrowave heating is an alternate means for material processing. The technique is promising for the accelerated synthesis of new materials. Microwave molecular sieves synthesis is combined with capillary confinement as a novel synthetic method. It is successfully demonstrated in the preparation of small ZSM-5 crystals by microwave hydrothermal synthesis within 1–1.7 μm channels of a capillary bundle. The geometric and spatial confinement offered by the capillary is expected to define and control the resulting crystal size distribution and orientation.MCM-41, a mesoporous molecular sieve with a uni-dimensional regular array of hexagonal channels is investigated as a candidate for capillary confinement. The large porous channels of MCM-41(>35 å ) is attractive as a host for promoting inclusions of guest molecules or templates. The successful confinement of MCM-41 represents an important step towards the alignment of molecular sieves in a defined orientation within thin capillaries bundled (less than 5 μm channels). Ultimately, such an approach may be useful for the fabrication of new molecular sieve devices.
Dissipation Mechanisms in Thin-Film Silicon Microresonators on Glass Substrates
Authors: Gaspar J. , Chu V. , Conde J. P. 
Published: April 2011

ABSTRACTThe fabrication and characterization of thin-film silicon resonators processed at temperatures below 110°C on glass substrates is described. The microelectromechanical structures consist of surface micromachined bridges of phosphorus-doped hydrogenated amorphous silicon (n+-a-Si:H) deposited by plasma-enhanced chemical vapor deposition (PECVD) suspended over a metallic gate counterelectrode. The structures are electrostatically actuated. Resonance frequencies in the MHz range and quality factors as high as 5000 are observed in vacuum. The effect of the geometrical dimensions of the bridges and of the measurement pressure on the resonance amplitude and frequency is studied. The elementary energy dissipation processes in a-Si:H-based resonators are discussed. At atmospheric pressure, air damping dominates the energy dissipation. In vacuum, intrinsic mechanisms, such as clamping losses and surface losses, control the energy dissipation.
Cavitation Erosion and Friction Behavior of Stainless Steel as a Function of Grain Size
Authors: Bregliozzi Giuseppe , Ahmed Syed Imad-Uddin , Schino Andrea Di , Kenny Josè M. , Haefke Henry 
Published: April 2011

ABSTRACTResearch conducted on steels is motivated by a technological need to further improve their properties. Among the different steel types, austenitic stainless steels possess good corrosion resistance and formability. However, they also have a low yield strength. One way of increasing the yield strength is by grain refining. This work presents a study on the cavitation erosion and friction behavior of AISI 304 austenitic stainless steel characterized by two different grain sizes: 2.5 μm and 40 μm. The cavitation erosion behavior in water with different pH values and at room temperature has been studied by using a 20 kHz ultrasonic vibratory apparatus. The grain size of the steels has an important effect on the nature of damage produced on the surface of the samples. The resistance to cavitation erosion increases with decreasing grain size. It was also found that cavitation erosion resistance of the two steels is sensitive to variations in the pH value; decrease of this value produces an increase in surface damage. Using a precision microtribometer, with applied loads in the μN regime, it was found that capillarity plays a dominant role. At the same loads, in high humidity environments, both the fine and coarse grain steels exhibit high friction relative to measurements performed under dry conditions. At high loads (20 mN and above) a reversal in microfrictional behavior occurs in that friction is higher under dry conditions than under moist conditions.
Field Emission from the Carbon Nanotubes Grown over Cylindrical Surface
Authors: Sarangi D. , Karimi A. 
Published: April 2011

ABSTRACTCarbon nanotubes are excellent field emitters due to their high aspect ratios and small radii of curvature. These properties of the nanotubes offer tremendous possibilities for the realization of field emission devices. For the realization of the field emission devices controlled placement and alignment of the nanotubes over the substrate surface is desirable. Furthermore, field emission of the nanotubes in cylindrical geometry has added advantages over planar geometry. But, it is difficult to grow nanotubes uniformly over non-planar substrates such as long metallic cylinders by conventional CVD techniques. In the present investigation we have adopted a very simple technique called as Cold Plasma Chemical Vapor Deposition (CP-CVD) to grow carbon nanotubes over a catalyst-supported metallic wire by resistive heating in hydrocarbon atmosphere at about 750–C. The localized dissociation of the hydrocarbon gas over metallic wire allows well controlled growth of the nanotubes. The field emission performance of these nanotube coated wires was measured in a cylindrical geometry where the aluminum tube was used as an anode. Emission site density is found to be the most important parameter to control the field emission performance. Comparisons of the field emission properties were made using nanotubes grown in different hydrocarbon gases such as methane and acetylene. The effects of other parameters, such as growth time, was also investigated.