bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Deformable Fine Spinel Particles in High-Strain-Rate Superplastic Flow of Tetragonal ZrO2
Authors: Morita Koji , Hiraga Keijiro , Kim Byung-Nam , Sakka Yoshio 
Published: April 2011

AbstractThe role of MgAl2O4 spinel particle dispersion in high-strain-rate superplasticity (HSRS) of tetragonal ZrO2 was examined by characterizing microstructural changes during deformation. The dispersed spinel particles elongate with strain along tensile direction and the elongation tends to be pronounced with increasing strain rate. In the elongated spinel particles, intragranular dislocations lying along the elongated direction were observed, suggesting that the elongation relates to the dislocation motion. The flow behavior characterized by a stress exponent of ≈ 2.0 suggests that grain boundary sliding (GBS) is the predominant flow mechanism. The dislocation-induced plasticity in the spinel particles may assist the relaxation of stress concentrations exerted by GBS, leading to HSRS in tetragonal ZrO2.
Optimized screen-printing and SEM-FIB characterization of YSZ thin films for Solid Oxide Fuel Cells and gas sensors devices
Authors: Morata A. , Tarancón A. , Dezanneau G. , Peiró F. , Morante J. R. 
Published: April 2011

AbstractIn the present work, the screen printing technique has been used to deposit thick films of Zr0.84Y016O1.92 (8YSZ). In order to control the final porosity in view of a specific application (SOFCs or gas sensor), an experimental design based on analysis of variances (ANOVA) has been carried out. From this, we were able to determine the influence of several technological parameters on films porosity and grain size. The films obtained have been analysed with both Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) combined with SEM. We show that only the combination of experimental design and advanced observation technique such as Focused Ion Beam allowed us to extract significant information for the improvement of the deposition process.
The Influence of Environmental Conditions and Passive Film Properties on the MIC of Engineered Barriers in the Yucca Mountain Repository
Authors: Lloyd A.C. , Schuler R.J. , Noël J.J. , Shoesmith D.W. , King F. 
Published: April 2011

AbstractA combination of gamma radiation fields, the absence of moisture, and the high temperatures on the drip shield (DS) and waste package (WP) should combine to suspend microbial activity on the DS/WP surfaces for many tens of thousands of years. This lack of microbial activity, coupled with the corrosion resistance of the titanium Grade7 (Ti-7 drip shield) and the Alloy-22 (waste package) materials make microbially induced corrosion (MIC) of these engineered barrier materials extremely unlikely.
Material Analysis and Radioisotope Studies of Spent Nuclear Fuel found in the Marine Environment
Authors: Baikie I.D. , Dennis Frank , Crawford Ron , Scirea Massimo 
Published: April 2011

AbstractSand-sized particles of spent nuclear fuel have been found in the environment at Dounreay, north Scotland. These particles, believed to have been discharged during early stages of site operations in the 1960s, have been recovered from areas within the Site, coastal foreshore adjacent to the Site and offshore (marine) environments. As part of the Dounreay Site Restoration Plan, a significant program of work is being undertaken to establish the fate of the Dounreay particles in the marine environment. This program includes materials analysis of particles and particle analoguesThe diverse depositional environments, coupled to relatively long fuel-particle residence times, allow insight to be gained into the behaviour of the particles in the natural environment. This includes the effects of physical, chemical and mechanical processes such as particle erosion and corrosion, particle abrasion and particle-saltwater interaction. Using materials analysis techniques including Scanning Electron Microscopy, Energy Dispersive X-Ray Analysis, Electron Probe Microanalysis, together with 137Cs activity measurement we review the fuel-particle mechanical and chemical stability and current radio-isotope composition. These studies allows us to identify the fuel provenance, fuel treatment history and draw some general conclusions of the ultimate fuel particle residence time. We demonstrate that radioisotope modelling strongly indicates that particle break-up is limited by the chemical effects of the marine environment coupled with the native oxide films present on the metallic fuel. Particle transport and distribution are governed by environmental effects on the sediment and sediment transport mechanisms such as tidal currents and storm events.This study is unique in that it involves the potential effects of long-term saltwater and abrasion interactions with fuel matrixes containing both U-Al and U-Mo of which there is little literature available.
Application of A Monte Carlo Approach to Surface Complexation Modelling
Authors: Askarieh M.M. , Heath T.G. , Tearle W.M. 
Published: April 2011

AbstractA Monte Carlo-based approach has been adopted for development of a chemical thermodynamic model to describe the goethite surface in contact with sodium nitrate solutions. The technique involves the calculation of the goethite surface properties for the chemical conditions corresponding to each experimental data point. The representation of the surface was based on a set of model parameters, each of which was either fixed or was randomly sampled from a specified range of values. Thousands of such model representations were generated for different selected sets of parameter values with the use of the standard geochemical speciation computer program, HARPHRQ. The method allowed many combinations of parameter values to be sampled that might not be achieved with a simple least-squares fitting approach. It also allowed the dependence of the quality of fit on each parameter to be analysed. The Monte Carlo approach is most appropriate in the development of complex models involving the fitting of several datasets with several fitting parameters.Introduction of selenate surface complexes allowed the model to be extended to represent selenate ion sorption, selenium being an important radioelement in evaluation of the long-term safety of ILW disposal. The sorption model gave good agreement with a wide range of experimental sorption datasets for selenate.
Estimated Effects of Temperature-Relative Humidity Variations on the Composition of In-Drift Water in the Potential Nuclear Waste Repository at Yucca Mountain, Nevada
Authors: Browning Lauren , Fedors Randall , Yang Lietai , Pensado Osvaldo , Pabalan Roberto , Manepally Chandrika , Leslie Bret 
Published: April 2011

AbstractWe define four distinct thermohydrochemical environments for drip shield and waste package corrosion in the potential nuclear waste repository, referred to here as the Dry, Seepage + Evaporation, Seepage + Condensation + Evaporation, and the Seepage + Condensation environments. These environments are bounded by temperature and relative humidity conditions at drift wall and drip shield/waste package surfaces judged most likely to initiate fundamental changes in the quantity and/or chemistry of in-drift waters. The duration in which different environments might exist is evaluated by comparing simulated, time-dependent temperature and relative humidity curves for three different locations within repository drift 25. In-drift conditions and processes postulated to cause drip shield/waste package corrosion are evaluated within the context of the thermohydrochemical environments by various means, including analytical calculations and geochemical simulations. Of the four environments considered here, the Seepage + Evaporation environment presents the most significant potential for aqueous corrosion of drip shield and waste package materials, and may persist for approximately 500 years in center drift locations. The likelihood for corrosion in other thermohydrochemical environments is significantly lower, but may increase with the acquisition of new data or the demonstration of extenuating circumstances.
Corrosion Study of Actinide Waste Forms with Garnet-Type Structure
Authors: Yudintsev Sergey V. , Osherova Anna A. , Dubinin Alexander V. , Zotov Alexander V. , Stefanovsky Sergey V. 
Published: April 2011

AbstractGarnet-based ceramics doped with Gd, Th, and Ce as waste surrogates and compositions: (Ca1.5GdTh0.5)ZrFeFe3O12 (G3) and Ca2.5Ce0.5Zr2Fe3O12 (G21) were prepared at 1300 °C in air. Corrosion rates in deionized water measured using an MCC-2 procedure were found to be (in g × m-2 × day-1): 10-6 for Ce (G21), 3×10-5 for Gd and 10-6 for Th (G3). Corrosion rates of Ce, Gd, and Th in an acid solution (0.01 M HCl) were 2 × 10-1 (G21), 4 × 10-3 and 10-3 (G3), respectively. Chemical durability of the garnet ceramics is comparable to durability of titanate zirconolite and pyrochlore samples under similar conditions. Scanning electron microscopy has revealed no alteration of the sample surfaces after their contact with water, and the presence of newly formed iron-enriched phases of 1 to 3 micrometers in size, after interaction of the G21 sample with acid solution for 30 days. High leaching of the elements from the Ce-loaded garnet may be due to reduction of Ce in acid solution to Ce(III) or may be explained by lower stability of the structure of garnets (Ca2.5An0.5)Zr2Fe3O12 compared to (Ca1.5GdAn0.5)(ZrFe)Fe3O12, An = Ce4+ and Th4+. It was found that the (Ca2.5Ce0.5)Zr2Fe3O12 and (Ca2.5Th0.5)Zr2Fe3O12 garnets have distorted the elementary unit cell with decreasing lattice symmetry to tetragonal.
Experimental and Numerical Studies on Colloid-Enhanced Radionuclide Transport - The Effect of Kinetic Radionuclide Sorption onto Colloidal Particles -
Authors: Kurosawa Susumu , Ibaraki Motomu , Yui Mikazu , Ueta Shinzo , Yoshikawa Hideki 
Published: April 2011

AbstractNumerous studies have shown that colloidal particles in groundwater can facilitate radionuclide transport in subsurface environments. A series of laboratory experiments was conducted to investigate the effects of radionuclide sorption onto colloids and the surfaces of rock fractures. This research especially focused on the kinetic behavior of the sorption process. A mixed solution of Cs and clay colloids was injected into a single artificial fracture in a granite column. Simulations were also performed to analyze the experimental results using a numerical code, COLFRAC, which describes colloid-facilitated solute transport in discretely-fractured media. The code allows for either equilibrium or kinetic sorption onto the colloidal particles. The experimental and analytical results indicate that transport of Cs is facilitated by the colloidal particles, which can sorb Cs and transport through the fracture. The analyses also illustrate the importance of evaluating parameters that describe kinetic sorption onto colloids. Furthermore, radionuclide transport is likely to be retarded as colloidal particles that sorb radionuclides are filtered on the fracture surface.
Corrosion/Electrochemistry of Uranium Dioxide in Slightly Alkaline Hydrogen Peroxide Solutions
Authors: Goldik Jon S. , Noël James J. , Shoesmith David W. 
Published: April 2011

AbstractThe kinetics of H2O2 reduction have been studied in slightly alkaline (pH 9.7 NaCl) solution on 1.5 at.% SIMFUEL. Using cyclic voltammetric techniques, we have shown that the cathodic reduction of H2O2 is kinetically facile on UIVUVO2+x surfaces. Carbonate ions are found to have a significant effect on the kinetics of H2O2 reduction. Suppression of the reaction rate is observed at very cathodic potentials, and has been attributed to a competition between carbonate and hydrogen peroxide for catalytic sites on the electrode surface. A small enhancement of the reduction current occurs between –200 and +100 mV vs. SCE, which appears to be due to a surface adsorbed carbonate complex. The large values of the Tafel slopes for H2O2 reduction have been interpreted in terms of a chemical-electrochemical mechanism involving surface UV species. The results are discussed in terms of a mixed potential model for the prediction of nuclear fuel dissolution rates under permanent disposal conditions.
An Impact Study of the Implementation of a Materials Science and Engineering Module at the Fifth Grade Level
Authors: Zekri Souheil , Clayton LaNetra , Ferguson Emily , Okogbaa Geoffrey , Kumar Ashok , Das Tapas , Centeno Grisselle , Martin-Vega Louis 
Published: April 2011

AbstractAn impact study of the implementation of a newly developed Materials Science and Engineering Module was conducted as part of a National Science Foundation funded GK-12 project at the University of South Florida. The objective of GK-12 STARS (Students, Teachers and Resources in the Sciences) program is to foster systemic change in elementary by enriching math and science curricula and encouraging long-term professional development for teachers in the K-5 band. The program also aims to decrease the current educational gap in science and math curricula prevalent among certain schools within the same school district, which is reflected in the outcome of the Florida Comprehensive Assessment Test (FCAT). The module was developed for the purpose of enhancing existing textbook driven science instruction and creating a fundamentally sound scientific exposure in elementary school students. As part of this activity, students from three different schools (one private, one suburban, and one urban) were introduced to basic concepts in materials science and engineering through hands-on experiments, presentations, and field trips to the university's material research related laboratories (i.e. polymer chemistry, microelectronics, nanotechnology, geotechnics, corrosion, etc.) The developed module offered information ranging from basic definitions to newly discovered cutting edge phenomenon in the field of nanotechnology. Subsequently, pre and post test instruments were administered to assess student performance. Results from the pretest showed that students from all participating schools performed within the standard deviation. The post assessment test showed that the experimental group had twice as many correct answers, as the control group from each school.
Backside Storage Non-Volatile Memories: Ultra-Thin Silicon Layer on a Complex Thin Film Structure
Authors: Silva H. , Tiwari S. 
Published: April 2011

ABSTRACTBackside storage memories present an alternative to the conventional front-floating gate geometries by storing charge in defects on the back of a thin depleted silicon channel. This paper focuses on the fabrication of these devices using a modified Smart-Cut™ substrate preparation process followed by standard CMOS processing. The substrate is a complex silicon-on-insulator (SOI) substrate where instead of the buried oxide alone a charge trapping multi-layer stack of oxide-nitride-oxide (ONO) is used as the buried insulator. We demonstrate here the operation of these device structures at ultra-short length scales and summarize the characteristics of their operation.
Gold Langmuir-Blodgett deposited nanoparticles for non-volatile memories
Authors: Kolliopoulou S. , Tsoukalas D. , Dimitrakis P. , Normand P. , Paul S. , Pearson C. , Molloy A. , Petty M. C. 
Published: April 2011

ABSTRACTIn this work, we demonstrate a MISFET memory device that incorporates a monolayer of Langmuir-Blodgett (LB) deposited gold nanoparticles as floating gate charge storage elements. The FET device is fabricated on a SOI substrate using conventional silicon processing. The nanoparticle layer is separated from the channel area of the FET with a 5 nm thermal SiO2 layer and is isolated from Al gate contact with a LB-deposited organic insulator layer. The memory effect is tested using voltage pulses on the gate of the device and monitored through drain current measurements. The nanocrystals can be charged either from the channel through the thermal oxide layer by applying pulses smaller than 5 V or from the gate through the organic insulator for higher voltage depending on the pulse duration.
Dielectric and Optical Properties of Perovskite-type Artificial Superlattices
Authors: Harigai Takakiyo , Nam Song-Min , Kakemoto Hirofumi , Wada Satoshi , Saito Keisuke , Tsurumi Takaaki 
Published: April 2011

ABSTRACTBaTiO3/SrTiO3, BaTiO3/BaZrO3, and SrZrO3/SrTiO3 artificial superlattices were fabricated on SrTiO3 substrates by the molecular beam epitaxy (MBE) process. The stacking periodicity of each layer was varied from 1 unit cell to 40 unit cells, and the total thickness was fixed at 80 unit cells. In-situ reflection high-energy electron diffraction (RHEED) and x-ray diffraction (XRD) clearly shows the formation of the superlattice structure. Their lattice parameters obtained from the reciprocal space mapping measurement indicated that the lattice distortion was dependent on the stacking periodicity. The capacitance and the complex admittance of the superlattices were measured with interdigital electrodes by an impedance analyzer up to 110 MHz. It was found that the dielectric permittivity changed with the superlattice periodicity. The Q-V measurement results showed clear hysteresis curves and this suggested that ferroelectricity was induced into the SrZrO3/SrTiO3 superlattices despite a combination between paraelectrics/paraelectrics.
Artificially Induced Perturbations in Chirped Magneto-Optical Bragg Gratings
Authors: Jonsson Fredrik , Flytzanis Christos 
Published: April 2011

AbstractWe report on theoretical analysis of magneto-optically induced longitudinal perturbations in chirped magneto-optical Bragg gratings. The induced perturbations considered are of Lorentzian shape, with a spatial extent considerably larger than the spatial grating period but at least an order of magnitude less than the geometrical length of the grating. In the numerical simulation of the proposed device, we show on a high polarization state selectivity in the region of the perturbation, with resonance peaks of transmission for circularly polarized orthogonal components possessing a full width at half maximum as narrow as 0.18 nm, meanwhile being separated by 0.6 nm.
Novel Magneto-Optic Layers Based on Semiconductor Nanostructures for Kerr Microscopy.
Authors: Gourdon C. , Jeudy V. , Karczewski G. , André R. , Ivchenko E.L. 
Published: April 2011

ABSTRACTA novel type of magneto-optic layers based on CdMnTe quantum wells is used to image the magnetic flux pattern at the surface of type I superconductors. The magneto-optic layer is designed as an anti-reflecting optical cavity. The quantum wells are arranged in a Bragg structure and placed at maxima of the electric field in the cavity in order to enhance Faraday rotation.
Sodium Ion Conduction in Plastic Phases: Dynamic Coupling of Cations and Anions in the Picosecond Range
Authors: Wilmer D. , Feldmann H. , Lechner R.E. , Combet J. 
Published: April 2011

ABSTRACTResults of simple computer simulations and model calculations for ion conducting rotor phases are compared to quasi-elastic neutron scattering data from solid solutions of sodium orthophosphate and sodium sulphate, xNa2SO4 · (1 — x)Na3PO4. These materials are not only sodium fast-ion conductors in their high-temperature cubic phases but also show considerable dynamic reorientation disorder of their tetrahedral anions.At an elastic energy resolution of about 100 μeV, neutron spectrometry monitored oxygen scattering due to anion reorientation which occurs on the picosecond time scale. This thermally activated process exhibits activation energies between 0.184 eV (x = 0. 0) and 0.052 eV (x = 0.5). Analysis of the quasielastic intensities as a function of scattering vector Q gives clear evidence of the involvement of cations in the anion reorientation.Increasing the elastic resolution to about 1 μeV FWHM (thereby shifting the dynamic window to the nanosecond scale) allowed to examine sodium diffusion in x Na2SO4 · (1 — x)Na3PO4. This process consists predominantly of thermally-activated jumps between tetrahedrally coordinated sites, the activation energies ranging from 0.64 eV for x = 0.0 to 0.30 eV for x = 0.5.
Oxide-Ion Transport in Gadolinium Zirconate - Titanates under High Pressure
Authors: Takamura Hitoshi , Kakuta Hirofumi , Kamegawa Atsunori , Okada Masuo , Tuller Harry L. 
Published: April 2011

ABSTRACTThe oxide-ion conduction of gadolinium zirconate - titanates, Gd2(Ti1−xZrx)2O7 (GTZ), has been investigated under high pressure in the range of 2 to 6 GPa with the aid of a cubic-anvil-type apparatus. For these pyrochlore compounds, the oxide-ion conductivity at elevated temperatures in the range of 750 to 960 °C decreased with increasing pressure, indicating the presence of a positive activation volume, ΔV. The activation volumes ΔV of GZ (x = 1.0) and GTZ (x = 0.95) were 2.0 and 1.3 cm3/mol, respectively, at 750 °C and decreased with increasing temperature.
Exploration of Electrophoretic Deposition of YSZ Electrolyte for Solid Oxide Fuel Cells
Authors: Xu Zhigang , Rajaram Gukan , Sankar Jag 
Published: April 2011

ABSTRACTThe suspensions of yttria stabilized zirconia (YSZ) were prepared in pure acetylacetone and ethanol and their mixtures. In all of the suspensions, YSZ thin films were obtained using electrophoretic deposition technique on the substrates of stainless steel and porous strontium-doped lanthanum manganite (LSM) which is a typical cathode materials used in solid oxide fuel cells (SOFCs). The deposition behavior in the different suspensions was studied. The deposited films were dried at room temperature and then sintered at high temperature. Observation with scanning electron microscopy (SEM) showed the sintered YSZ were of high density.
Dye Sensitized Solar Cells Incorporating Polyelectrolyte Multilayer Composites
Authors: Lowman Geoffrey M. , Tokuhisa Hiroaki , Lutkenhaus Jodie L. , Hammond Paula T. 
Published: April 2011

ABSTRACTDye sensitized solar cells (DSSC's) are constructed using TiO2 electrodes synthesized by aqueous liquid phase deposition in combination with microcontact printing techniques or porous thin film template methods. Layer-by-layer deposition of polyelectrolytes is used to produce an ionic conducting solid-state electrolyte thin film, which is enhanced by post-processing in oligoethylene glycol diacid (OEGDA). The impact of TiO2 film architecture, as well as the thin film electrolyte, on device performance is discussed.
Nano-Columnar Mg Thin Films Created by Plasma Sputter Deposition for Improved Hydrogen Kinetics and Storage Properties
Authors: Zandbergen M. W. , Eijt S. W. H. , Legerstee W. J. , Schut H. , Svetchnikov V. L. 
Published: April 2011

ABSTRACTThe hydrogen storage properties of nanostructured Mg and MgH2 thin films were studied as created by Ar and Ar+H2 plasma sputter deposition. Columnar structures with typical widths of ∼120 nm are observed with their long columnar axis extending throughout the thickness of the films. Applying substrate bias voltages during deposition results in narrower columns. A concomitant reduction in hydrogen desorption temperature from 400 °C to 360 °C is observed. Capping the Mg films with a ∼100 nm thin Pd layer leads to significantly reduced hydrogen desorption temperatures of ∼200 °C induced by the catalytic activity of the Pd cap layer. Also, hydrogen permeation of the films is strongly improved. The rate-determining factor is found to be the dissociation of the hydrogen molecules. Optimum hydrogen loading conditions of the Pd/Mg films were obtained just above ∼200 °C at hydrogen pressures of 0.25–1.0 MPa, resulting in hydrogen storage capacities in the range of 4–7 wt%.