bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructures and properties of the tungsten wire/particle reinforced Zr57Nb5Al10Cu15.4Ni12.6 metallic glass composites
Authors: Choi-Yim Haein , Schroers Jan , Johnson William L. 
Published: April 2011

ABSTRACTTungsten wire or particle reinforced metallic glass matrix composites are produced by infiltrating liquid Zr57Nb5Al10Cu15.4Ni12.6 (Vit106) into tungsten reinforcements at 1150 K and at 1425 K. X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy are carried out to characterize the composite. The matrix of the composite processed at 1150 K is mostly amorphous, with some embedded crystals. During processing, tungsten dissolves in the glass-forming melt and upon quenching precipitates over a relatively narrow zone near the interface between the tungsten and matrix. In the composites processed at 1425 K, tungsten dissolves in the melt and diffuses through the liquid medium, and then reprecipitates upon quenching. The faster kinetics at this high temperature results uniform distribution of the crystals throughout the matrix. Mechanical properties of the differently processed composites containing wires and particles are compared and discussed. The composites exhibit a plasticity of up to 16 % without sacrificing the high strength to failure that is comparable to monolithic Vit 106.
Sorption of Pu(III-IV) Onto Tio2: A Preliminary Study
Authors: Olsson M. , Nilsson H. , Jakobsson A. M. , Albinsson Y. 
Published: April 2011

ABSTRACTA preliminary study of the sorption of reduced plutonium (III-IV) onto TiO2 has been done under anoxic conditions at varying pH and ionic strength. The first approach was to study tetravalent Pu, but the sorption decreases with time in this case. This is probably due to disproportionation of Pu(IV) at the TiO2 surface, which then acts as a catalyst. A further observation that supports this explanation is that the sorption of Pu(IV) onto the walls of the experimental equipment is in some cases higher than the sorption of (disproportioned) Pu onto the oxide.Pu(III) sorption onto the oxide was also investigated and showed similarities with the previously investigated sorption of Pm(III) in a similar system.
The Conservation of Ancient Glass
Authors: Paterakis Alice Boccia 
Published: April 2011

ABSTRACTGlass undergoes various corrosion mechanisms during burial. The state of deterioration and corrosion phenomena are deciding factors in the choice of conservation materials and techniques. Among the conservation treatments reviewed for ancient, archaeological glass are pre-treatment storage, cleaning, consolidation of weakened and de-vitrified glass, adhesives for reconstruction, and fill materials for restoration. The most recent materials and techniques used by conservators are presented. The concepts of permanence and reversibility with regard to conservation methods and materials are examined.
Cell Density Dependent Reduction Kinetics of Hexavalent Uranium byShewanella oneidensis
Authors: Mullen Lisa , Klepac Vanja , Pharino Chanathip , Czerwinski Ken , Polz Martin 
Published: April 2011

ABSTRACTShewanella oneidensisis a widely distributed species of bacteria and is known to utilize several elements such as iron, manganese and sulfur as electron acceptors. In an anoxic environment lacking more electrochemically favourable electron acceptorsS. oneidensisis shown to reduce uranium, changing its oxidation state from hexavalent to tetravalent, by the following reaction: H2+ UO22+→ 2H++ UO2. The uranyl solution concentration (U(VI)) was measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the reduction data were fit to first order. Several cell concentrations were examined and both the rate of uranyl reduction and the total amount of uranyl reduced are found to be dependent upon cell density. The largest rate constant was 0.7 hr-1corresponding to a cell density of 2.4*109cells/mL and an initial reduction rate of 1414 μM/hr. A cell concentration of 6.6*108cells/mL gave rise to an initial reduction rate of 400μM U(VI) per hour, and had, within a period of 72 hours approximately 98% of the original 2 mM uranyl acetate reduced, as opposed to only 87% for 2.4*109cells/mL.
Sand/Bentonite Barriers and Gas Migration: The GMT Large-Scale In-Situ Test in the Grimsel Test Site
Authors: Vomvoris S. , Lanyon B. , Marschall P. , Ando K. , Adachi T. , Fujiwara A. , Yamamoto S. 
Published: April 2011

ABSTRACTThe Gas Migration Test in the engineered barrier system (GMT) investigates the migration of waste-generated gas from low and intermediate level waste in a silo-type disposal concept. The EBS has now been emplaced and saturation was initiated in August 2001. The saturation patterns show heterogeneity within and between different layers of the EBS. Plans for the remaining test sequence are also presented.
Corrosion Behavior of Carbon Steel and Stainless Steel Materials under Salt Deposits in Simulated Dry Repository Environments
Authors: Yang Lietai , Pabalan Roberto T. , Browning Lauren , Dunn Darrell S. 
Published: April 2011

ABSTRACTIn-situ coupled multielectrode array sensors were used to measure the non-uniform corrosion of carbon steel and stainless steel materials under KCl salt deposit in simulated dry repository environments. It was found that the initiation of non-uniform corrosion occurs at a relative humidity that is 14% lower than the deliquescence relative humidity of the chloride salt. It was found also that once significant corrosion had occurred, the non-uniform corrosion process for the carbon steel material under the salt deposit continues at relative humidities as low as 27%.
Characterization of a Cerium-Rich Pyrochlore-Based Ceramic Nuclear Waste Form
Authors: Gieré R. , Segvich S. , BUCK E. C. 
Published: April 2011

ABSTRACTTitanate ceramics have been proposed as candidate materials for immobilizing excess weapons plutonium. This study focuses on the characterization of a titanate-based ceramic through X-ray diffraction (XRD), electron probe microanalysis, and electron energy-loss spectroscopy (EELS). Three distinct phases have been identified, and their volume fraction was determined from element distribution maps using Scionimage-NIH Analysis software. This analysis revealed that the pyrochlore-group phase betafite (A2Ti2O7) forms the matrix of the ceramic and occupies 90.4% of the volume. Uniformly distributed in this matrix are perovskite (A2Ti2O6) and Hf-enriched rutile (TiO2), which account for 6.4 vol% and 3.1 vol%, respectively. The studied ceramic exhibits a very low porosity (0.3 vol%), which is characterized by small (<6 μm), rounded and isolated voids. In the studied ceramic, A-site cations are represented by Ca, rare earth elements, and Hf. The powder XRD pattern of the ceramic allowed refining the unit cell parameters for the cubic betafite, which is characterized by a cell edge of 10.132±0.003Å. The EELS data indicate that Ce is present as both Ce3+ and Ce4+ in betafite, whereas in perovskite, all Ce is trivalent.
Hydration of Magnesium Oxide in the Waste Isolation Pilot Plant
Authors: Snider Anna C. 
Published: April 2011

ABSTRACTMagnesium oxide (MgO) is the only engineered barrier being emplaced in the Waste Isolation Pilot Plant (WIPP), a U.S. Department of Energy repository for transuranic waste. MgO will lower dissolved concentrations of actinides by consuming CO2 from possible microbial activity, by buffering the pH between 8.5 and 9.5, and by reducing the amount of free water in the repository. This paper discusses results from experiments measuring the hydration of MgO. Results suggest that periclase (MgO) hydrates rapidly to brucite (Mg(OH)2) in de-ionized water and 4 M NaCl solution at 90°C; the hydration rate decreases as temperature decreases. In ERDA-6, a NaCl-rich WIPP brine, MgO hydrates directly to brucite; in GWB, a high-Mg brine, periclase hydrates to magnesium chloride hydroxide hydrate(s) until the dissolved Mg2+ concentration decreases, and brucite becomes the stable phase. Under humid conditions MgO fully hydrates at higher humidities(> 50%). All data are consistent with diffusion-limited hydration reactions.
Radiolytic Modelling: Application To Spent Fuel Dissolution Experiments
Authors: Merino Juan , Cera Esther , Bruno Jordi 
Published: April 2011

ABSTRACTIn this work we describe our first efforts to simulate the chemical evolution of the spent fuel/water system in dissolution experiments using a radiolytic model. These experiments were carried out with spent fuel fragments in deionized water [1]. In order to build the radiolytic model, a set of reactions were selected, together with their kinetic constants, including the catalytic decomposition of H2O2 in the UO2 surface and a reaction mechanism for UO2 oxidation and dissolution. Averaged alpha and beta G-values were used, neglecting gamma radiation. Diffusion to the gas phase was treated thermodynamically assuming Henry's law. The computer code used in the simulations was CHEMSIMUL [9]. First attempts to simulate the experimental results were not successful and a sensitivity analysis was carried out. As a result of this, the kinetic constant of the reaction OH• + H2 → H• + H2O, the only reaction that consumes hydrogen in the system, was identified as a key parameter, together with the kinetic constants of the UO2 oxidation and dissolution reactions. Varying these parameters we were able to reproduce the experimental data. Although more simulations are needed, these results are encouraging because they give us more confidence in the use of radiolytic models as useful tools to predict the long-term alteration rate of the spent fuel under repository conditions, which is our ultimate goal.
Characterization and Modeling of Wafer and Die Level Uniformity in Deep Reactive Ion Etching (DRIE)
Authors: Sun Hongwei , Hill Tyrone , Schmidt Martin , Boning Duane 
Published: April 2011

ABSTRACTWafer and die level uniformity effects in Deep Reactive Ion Etching (DRIE) are quantitatively modeled and characterized. A two-level etching model has been developed to predict non-uniformities in high-speed rotating microstructures. The separation of wafer level and die level effects is achieved by sequentially etching wafers with uniformly distributed holes. The wafer level loadings range from 0.06% to 17.6%. Resulting wafer maps reflect the transition from an ion-limited region to a neutral-transport limited region. Additionally, long-range die-level interactions are also evaluated. Resulting die-level etching non-uniformities have a comparable magnitude to wafer-level effects. A model taking into account both the diffusion and reaction rate of neutrals is applied to predict the etching of up to 21 dies. Agreement between measurement and prediction support the hypothesis that the depletion of radicals is the main cause of die-level etch variation. The characterization and prediction methods are applied to etching a micro-scale turbine engine.
Electromechanical Behavior in Micromachined Piezoelectric Membranes
Authors: Robinson M. C. , Raupp J. C. , Demir I. , Richards C. D. , Richards R. F. , Bahr D. F. 
Published: April 2011

ABSTRACTPiezoelectric materials can convert mechanical and electrical energy, a particularly useful tool in developing micro and nanoscale systems. Characterizing the electromechanical behavior is essential to the design and optimization of the material's and device's performance. This paper examines the influence of boundary (clamping) conditions, relative thickness variations between the active one to two micron thick piezoelectric membrane and underlying passive support structure, and the electrode coverage on the electromechanical behavior. Membranes were fabricated with silicon and lead zirconate titanate (PZT) with a ratio of Zr to Ti of 40:60 that provide thickness ratios between 1:2 and 2:1 by depositing the PZT using sequential solution deposition. PZT films contain a tensile stress that accumulates during processing, therefore a compressive stressed layer of tungsten was sputtered on bulk micromachined membranes to produce a near zero net residual stress. A nonlinear finite element numerical simulation technique is utilized for the analysis of the composite thin film. A comparison between the behavioral trends determined by simulation and experimental methods will be discussed.
Thermophysical Properties of Ni Films for LIGA Microsystems
Authors: Borca-Tasciuc Diana-Andra , Nimbalkar Rajesh , Chen Gang , Graham Samuel , Borca-Tasciuc Theodorian 
Published: April 2011

ABSTRACTThis work reports temperature dependent thermophysical properties characterization of electrodeposited Ni and NiMn alloys intended for LIGA Microsystems applications. A steady-state method is used to determine the in-plane thermal conductivity. Anisotropic thermal diffusivity characterization is performed using a photothermoelectric technique. The measured thermal properties are dependent on the deposition method and also on subsequent temperature annealing steps. The thermal transport measurement results are correlated with scanning electron microscopy studies of the grain structure and measurements of the electrical transport properties.
Control of Stress in a Metal–Nitride–Metal Sandwich for CMOS-Compatible Surface Micromachining
Authors: Davies Rhodri R. , Combes David J. , McNie Mark E. , Brunson Kevin M 
Published: April 2011

ABSTRACTFurther to previous work, which demonstrated the ability to engineer the in- and out-of-plane stress components in PECVD silicon nitride, this paper reports on the control of stress in a metal-nitride-metal sandwich. The addition of a symmetric metallisation to the core nitride layer provides additional functionality by enabling electrical connectivity and electrostatic transduction. This represents a widely applicable structural layer for CMOS-compatible surface micromachining.The use of advanced test structures coupled with wafer curvature measurements has allowed for detailed analysis of the stress components within the metal-nitride-metal sandwich and enables predictive engineering of the mechanical properties of the structural layer. Relationships between the in- and out-of-plane stress components of the metal-nitride-metal sandwich as a function of the nitride RF deposition power are reported and discussed. In comparison to values measured for nitride-only, a -30MPa/μm stress gradient offset is observed. A mechanism for the decrease in the stress gradient with the addition of the metallisation is proposed and compares well to modelling.The optimised metal-nitride-metal sandwich can be repeatably engineered to realise low tensile in-plane stress (100MPa) and low out-of-plane stress gradient (0 ± 10MPa/μm). The effective Young's Modulus of the metal-nitride-metal sandwich was determined to be 150GPa; and a value of 195GPa was calculated for the nitride layer using analytical modelling. Work to further reduce the in-plane stress whilst maintaining low stress gradient is in progress by independently tuning the strain of the metal layers.
Assembly of nano-domain buildings blocks of copper oxalate with a cubic morphology
Authors: Soare L. C. , Bowen P. , Lemaître J. , Hofmann H. , Pijolat M. , Valdivieso F. 
Published: April 2011

ABSTRACTMetallic copper nanostructured particles were synthesised by thermal decomposition of a CuC2O4 precursor obtained via the precipitation reaction between Cu(NO3)2·6H2O and Na2C2O4 in the present of hydroxyl propyl methyl cellulose (HPMC). X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and thermogravimetric analysis (TG) were used to characterise the particles and their evolution during the transformation to metallic copper. We highlight the nanostructured nature of the oxalate precursor, which is made up of anisotropic nanosized buildings blocks (25nm by 40nm). These produce an anisotropy in the oxalate particle and influence the decomposition pathway. The results show the evolution of the nanostructure as a function of degree of reaction and a possible kinetic model is discussed.
Nanocomposite Material for Sensing of Halogenated Methanes: A Model Based on Charge Transfer Interaction for Selectivity
Authors: Sangoi Rajiv , Fuller L. , Santhanam K. S. V. 
Published: April 2011

ABSTRACTA unique nanocomposite of poly (3-methylthiophene) with functionalized multiwalled carbon nanotubes (MWNT) has been synthesized that shows selective sensing for halogenated methanes. The sensor has been found to give the highest response for chloroform and none for methane. A tentative model has been proposed for this selective sensing of halogenated methanes.
Theoretical studies of Electronic Structures and Optical Absorptions of Encapsulated Guest Alkali Metal Atoms in ITQ-4 Zeolite
Authors: Li Hong , Mahanti S. D. 
Published: April 2011

ABSTRACTAn ab-initio study of the electronic structures and optical absorption spectrum of the guest Cs and Na atoms absorbed in the pure silica ITQ-4 zeolite channels was carried out using density functional theory (DFT) and plane wave basis. Completely different geometries were found for doped Cs and Na in the channels. For Cs doping, a zig-zag chain was formed along the channel and a metallic band structure was obtained. However, a dimer structure around the channel center was found for Na doping and a narrow band gap semiconductor was observed for this system. Correspondingly, the calculated optical absorption spectrum also showed distinctive characters for Cs and Na dopings. Our theoretical results for Cs doping are compared with experimental measurements and previous DFT calculation with local orbital basis; better agreement with experiments has been reached than the previous calculation. For the Na doping, our theoretical predictions need to be confirmed by future experiments.
Pulsed Laser Deposition Parameter Optimization for Growth of Alumina (Al2O3) Thin Film on Silicon (100)
Authors: Wang Xinyu , Yarmolenko Sergey , Kumar Dhananjay , Xu Zhigang , Sankar Jagannathan 
Published: April 2011

ABSTRACTPulsed laser deposition (PLD) technique was used to grow alumina (Al2O3) thin films on (100) silicon substrate under different deposition conditions. The relationship between Al2O3thin film thickness, hardness, elastic modulus, surface morphology and PLD parameters such as laser energy and substrate temperature was investigated. The Film thickness was found to increase with an increase in laser energy and to decrease with an increase in substrate temperature. The film hardness and elastic modulus increases as substrate temperature increases. We have also shown that films are amorphous at lower substrate temperatures and transform to mixture of amorphous and crystalline phases. The ratio of amorphous to crystalline phases decreases with increase in temperature. The surfaces of Al2O3film grown using PLD was found very smooth with least root square roughness less than 2 nm.
Oxygen Diffusivity and Defect Transport in Pure and Yb Doped Nano-crystalline Ceria
Authors: Saraf Laxmikant , Shutthanandan V. , Thevuthasan S. , Wang C. M. , Koch K. T. , Andreasen J. A. , Marina O. , Zhang Y. 
Published: April 2011

ABSTRACTOxygen (18O) diffusivity in sol-gel synthesized nano-crystalline ceria films of average grain size of 3 nm and 7 nm, annealed at 300 °C and 450 °C for one hour respectively is examined by nuclear reaction analysis (NRA). Diffusivity and electrical transport properties measured by a. c. impedance spectroscopy were compared with microcrystalline ceria film of average grain size 38 nm annealed at 900 °C for one hour. Effect of enhanced oxygen diffusion along with reduced ionic transport in nano-crystalline ceria and reduced oxygen diffusion along with enhanced ionic transport in microcrystalline ceria are correlated to long range ordering, grain boundary scattering and defect density. Enhancement in the conductivity with reduction in activation energy from 1 eV to 0.5 eV in the case 4 atom% ytterbium (Yb) doped ceria compared to pure ceria is a result of increased oxygen vacancies taking part in the defect transport.
Mean Inner Potential of Nanostructured Noble Metal Catalysts - Pt/TiO2 Catalyst -
Authors: Ichikawa S. , Akita T. , Okazaki K. , Okumura M. , Tanaka K. , Kohyama M. 
Published: April 2011

ABSTRACTCatalytic properties of noble metal catalysts are often caused by their nanostructures. Gold catalysts are typical cases. It is especially interesting that the catalytic property of gold suddenly changes to resemble that of platinum when the mean size of gold dispersed on certain oxides is <2nm. This phenomenon should be owing to the change of the local electronic structure of the gold particle or the interface between the gold and the oxides, however its detail has not been cleared yet. We measured the mean inner potential of gold particles supported on TiO2 using electron holography and HREM, and found that the mean inner potential of gold depend largely on the size of the gold particles. When the size is >5nm, the mean inner potential is the same as the reported values of bulk gold (experimental: 21–23V, calculated: 25–30V). When the size is <5nm, it begins to increase >30V, and it begins to increase suddenly >40V at the size <2nm. It indicates that the electronic structure of the gold particle varies from that of the bulk state as the size of the gold reduces due to the nano-size effect or the interaction at the interface, since the mean inner potential is sensitive to the electronic state of the outer valence electron. On the other hand, the behavior of the platinum catalysts is different from that of gold catalysts. When the size of the platinum particle on the TiO2 support is >1.5nm, the mean inner potential of platinum is the same as that of the bulk (∼25V). In case of the particle with the size <1.5nm, it begins to increase and the increase rate is lower than that of the gold particles with the size <2nm. It is suggested to be due to the difference of the interaction with TiO2.
Hierarchically Ordered Multi-Component Block Copolymer/Particle Nanocomposite Materials
Authors: Bockstaller M. R. , Thomas E. L. 
Published: April 2011

ABSTRACTThis contribution reviews the structure formation processes that are observed in binary diblock copolymer/particle and ternary diblock copolymer/particle1/particle2 mixtures. The particle core size, the polymer domain spacing as well as the particle surface chemistry are shown to determine three distinct morphological types in particle/block copolymer composites, which is the preferential layer homogeneous distribution, the interfacial segregation and center alignment of the nanocrystals within one polymer domain. The different microstructural environments of the sequestered component that are implied by the respective particle distribution result in distinctively different optical properties of the composite and have important consequences for the prospects of metal nanocrystal/block copolymer composites as a platform for photonic crystal engineering. A detailed comparison between morphological studies and theoretical predictions will be presented that aims to better understand and control morphologies of structured cluster matter and its relation to the respective optical and mechanical properties of new microstructured composite materials.