bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atomistic Simulation of Displacement Cascades in Zircon
Authors: Devanathan R. , Weber William J. , Corrales L. Rene 
Published: April 2011

ABSTRACTLow-energy displacement cascades in zircon (ZrSiO4) initiated by a Zr primary knock-on atom have been investigated by molecular dynamics (MD) simulations using a Coulombic model for long-range interactions, Buckingham potential for short-range interactions and Ziegler-Biersack potentials for close pair interactions. Displacements are found to occur mainly in the O sublattice, and O replacements by a ring mechanism are predominant. Clusters containing Si interstitials bridged by O interstitials, vacancy clusters and anti-site defects are found to occur. This Si-O-Si bridging is considerable in ZrSiO4 quenched from the melt in MD simulations.
Precipitation of Crystalline NpO2 During Oxidative Corrosion of Neptunium-Bearing Uranium Oxides
Authors: Finch Robert J. 
Published: April 2011

ABSTRACTWe report crystallization of NpO2 during aqueous corrosion of unirradiated Np-bearing U3O8 under nominally oxidizing conditions. Powders of Np0.33U2.67O8 (Np:U = 1:8) were reacted in humid air at 90° and 150°c for several weeks in sealed stainless-steel vessels. Reacted solids were examined by scanning and transmission electron microscopies (SEM and TEM) and X-ray powder diffraction (XRD). Dehydrated schoepite, (UO2)O0.25–z(OH)1.5+2z (0 ≤ z ≤ 0.15), is the predominant U(VI) compound formed in these experiments and is a minor sink for Np (containing 2 wt.% Np, maximum). The primary sink for Np during corrosion of Np0.33U2.67O8 at 150°C is crystalline NpO2, which crystallized within 2 weeks of reaction in humid air. Corrosion of Np0.33U2.67O8 at 90°C resulted in crystallization of approximately equal proportions of crystalline NpO2 and Np2O5 during 16 weeks of reaction in humid air.
Nature and Effect of the Alteration Layer During Nuclear Waste Glass Dissolution
Authors: Gauthier A. , Coustumer P. Le , Thomassin J-H. 
Published: April 2011

ABSTRACTThe goal of this study is to understand the role of the interface developed during R7T7 glass alteration. This glass has been leached in two different aqueous media (pure water, silica rich water and phosphorous rich water). The lixiviation tests have been optimized to assess the role of the alteration layer developed on the surface of the glass. The solution and the solid have been characterized by ICP-MS and TEM/X-EDS respectively. The results put in evidence that a complex alteration layer is formed. Its texture, structure and chemistry are discussed with respect to the evolution of the solution during the tests. The alteration layer is always present on the surface of the glass and is considered to control (at short time) diffusion of the different species through the layer. Further study must be undertaken to assess the evolution and the stability of the interface for longer time periods.
Mechanism of Vapor Phase Hydration In High-Sodium Waste Glasses from Computer Simulations
Authors: Perez-Cardenas Fernando C. , Gan Hao , Lu Xiaodong , Pegg Ian L. 
Published: April 2011

ABSTRACTThe kinetics of vapor phase hydration (VHT) of high-sodium waste glasses often exhibits incubation, fast-rising, and final stages. The incubation stage is characterized by the slow and gradual appearance of transformed regions on the surface of the glass, signaling the initiation of the phase transformation. This is followed by a fast-rising stage, during which most of the transformation takes place. The final stage is characterized by the slower alteration of the remaining glass phase, which can have a duration orders of magnitude longer than those of the previous stages. While the Avrami equation provides a good representation of these features, the origin of the late-stage slow-down in the Avrami model is unrealistic for the VHT process. Computer simulations based on cell models have been used to investigate possible mechanistic origins. The models consider the formation of multiple alteration phases and simulate the complex interplay among the several microscopic mechanisms involved in the hydration process. The models assume that the transformation from the original pristine glass to the final stable altered phase occurs in two steps: from glass to a metastable phase, and then from a metastable to a stable phase. The results indicate that the late-stage slow-down can be reproduced as a result of the build-up of species that are incompatible with the stable phase or by the occlusion of the surface due to the growth of a surface phase that is less permeable to water. The simulation results are in good general agreement with the features of the experimental data.
A Glass-Encapsulated Ceramic Wasteform for the Immobilization of Chloride-Containing ILW: formation of Halite Crystals by Reaction Between the Glass Encapsulant and Ceramic Host
Authors: Donald I. W. , Metcalfe B. L. , Greedharee R. S. 
Published: April 2011

ABSTRACTWe have developed a calcium phosphate ceramic based on the mineral phases chlorapatite, Ca5(PO4)3Cl, and spodiosite, Ca2(PO4)Cl, which, on the basis of evidence from non-active simulant studies, is expected to provide an extremely effective host for immobilizing the chloride constituents resulting from the pyrochemical reprocessing of Pu. The immobilized product is in the form of a free-flowing, non-hygroscopic powder in which the chlorides are chemically combined within the mineral phases. In order to provide a monolithic wasteform suitable for long term storage, the feasibility of encapsulating this product in a compatible glass is being assessed. The final wasteform will be manufactured by a pressureless sintering route with sodium aluminophosphate based glasses currently being developed for this purpose. These glasses are of particular interest due to a combination of useful properties which include good sintering characteristics, together with excellent chemical durability. We have noted, however, that during sintering the Na present in the glass reacts with the chlorapatite and spodiosite phases to form a dispersion of halite crystals within the final wasteform. The formation of free halite within the wasteform is clearly undesirable, but can be minimized by careful control over the processing parameters, in particular the sintering temperature, or by reducing the chloride loading in the wasteform. The implications of these findings are highlighted and discussed.
The Replacement of Titanium by Zirconium in Ceramics for Plutonium Immobilization
Authors: Stewart M.W.A. , Begg B.D. , Vance E.R. , Finnie K. , Li H. , Lumpkin G.R. , Smith K.L. , Weber W.J. , Thevuthasan S. 
Published: April 2011

ABSTRACTZirconates and titanates, based on the nominal baseline composition developed for the Plutonium Immobilization Project (PIP), have been prepared with and without process impurities. The titanates form pyrochlore as the major phase and the zirconates form a defectfluorite. Little, if any, of each impurity is accommodated in the defect-fluorite and powellite, kimzeyite, a spinel and a silicate glass appear as extra phases in this ceramic. In the titanates the pyrochlore incorporates more impurities, with the remainder being accomodated in zirconolite and a small amount of silicate glass. At extremly high levels of impurities, traces of magnetoplumbite, perovskite, and loveringite were found. The defect-fluorite zirconate phase is more radiation damage resistant than the titanate pyrochlore, though the secondary phases in the zirconate will reduce the radiation damage resistance of zirconate monoliths. To produce a dense product the oxide-route zirconate required sintering temperatures of about 1550°C, 200°C higher than that required for the titanate. Silicate impurities reduce the sintering temperatures.
In Situ Isotopic Analysis of Uraninite Microstructures from the Oklo-Okélobondo Natural Fission Reactors, Gabon
Authors: Fayek Mostafa , Jensen Keld A. , Ewing Rodney C. , Riciputi Lee R. 
Published: April 2011

ABSTRACTUranium deposits can provide important information on the long-term performance of radioactive waste forms because uraninite (UO2+X) is similar to the UO2 in spent nuclear fuel. The Oklo-Okélobondo U-deposits, Gabon, serve as natural laboratory where the long-term (hundreds to billions of years) migration of uranium and other radionuclides can be studied over large spatial scales (nm to km). The natural fission reactors associated with the Oklo- Okélobondo U-deposits occur over a range of depths (100 to 400 m) and provide a unique opportunity to study the behavior of uraninite in near surface oxidizing environments versus more reducing conditions at depth. Previously, it has been difficult to constrain the timing of interaction between U-rich minerals and post-depositional fluids. These problems are magnified because uraninite is susceptible to alteration, it continuously self-anneals radiation damage, and because these processes are manifested at the nm to μm scale. Uranium, lead and oxygen isotopes can be used to study fluid-uraninite interaction, provided that the analyses are obtained on the micro-scale. Secondary ionization mass spectrometry (SIMS) permits in situ measurement of isotopic ratios with a spatial resolution on the scale of a few μm. Preliminary U-Pb results show that uraninite from all reactor zones are highly discordant with ages aaproaching the timing of fission chain reactions (1945±50 Ma) and resetting events at 1180±47 Ma and 898±46 Ma. Oxygen isotopic analyses show that uraninite from reactors that occur in near surface environments (δ18O= −14.4‰ to −8.5‰) have reacted more extensively with groundwater of meteoric origin relative to reactors located at greater depths (μ18O= −10.2‰ to −7.3‰). This study emphasizes the importance of using in situ high spatial resolution analysis techniques for natural analogue studies.
Human Spermatozoa on Nanostrucutured Ag Deposited on GaAs Surface
Authors: Quagliano Lucia G. 
Published: April 2011

ABSTRACTMotivated by the SERS (Surface Enhanced Raman Spectroscopy) sensitivity to very small amounts of material we are interested in the application of the SERS technique for studying complex biological systems, such as cells.Using nanometer-sized Ag particles deposited on GaAs surfaces as SERS-active substrate we have observed an enhancement of Raman signal from human spermatozoa. We have obtained structural information on extremely small amounts of biomaterials and at the same time evidence that the bio-systems are preserved on the surface.In our opinion, this kind of SERS-active substrates with nanometer-sized Ag particles on semiconductors might have promising application in nanoscale science and technology. In fact bio-molecules, cells and processes of their interfacing with Si, GaAs, silver and gold and other inorganic substrates, form the basis of bio-electronics a new emerging field at the crossing of molecular biology and nano-electronics with numerous electronic and biotechnological applications.
Electric field and Charged Molecules Mediated Self-Assembly for Electronic Devices
Authors: Lee Sang Woo , McNally Helen A. , Bashir Rashid 
Published: April 2011

ABSTRACTIn this paper we present techniques, utilizing dielectrophoresis and electrohydrodynamics, which can possibly be used for assembling devices suspended in a solution onto a binding site on a substrate. We explored the concepts using micro-scale negatively charged polystyrene beads and rectangular silicon blocks. Dielectrophoretic forces on devices in buffer solutions were examined as a function of frequency of the applied AC signal. The observed results can be explained by taking in account electro-thermal and AC electroosmotic effects. The study described in the paper can be used for placing and assembling micro and nano-electronic devices and objects at specific sites on various substrates, in combination with bio-inspired biological binding techniques such as DNA hybridization, antigen-antibody interactions, and ligand-receptor (avidin-biotin) interactions.
Control of inorganic morphologies by organic templates
Authors: Harding John H. , Duffy Dorothy M. 
Published: April 2011

ABSTRACTExperiments have shown that ordered monolayers of large organic molecules can control crystal nucleation and growth. The work of nucleation controls which morphology and phase will appear. We have used molecular dynamics to simulate the interfaces between stearic acid and a number of calcium carbonate surfaces. An important issue is the ionisation state of the acid which depends on the pH of the solution at the surface. We estimate this by solving the nonlinear Grahame equation for a calcium carbonate solution. The species in solution are chosen from geochemical models. The calculated interfacial binding energy between monolayer and material is often of the order of 1 Jm-2, suggesting that the nucleation rate is strongly enhanced.
ElectroTextiles - Technology to Applications
Authors: Ethridge Elana 
Published: April 2011

ABSTRACTElectroTextiles is a technology area that is in its formative stages of development. Over the past three years, several government and industrial workshops as well as international conferences have discussed and presented fundamental technical approaches and a few small companies are starting to offer commercial products. The combination electronics and textiles offer a new and unique way to fabricate novel large-area, flexible and conformable military and commercial systems. This paper will discuss the some of the challenges that need to be addressed for this technology to mature in the future.
Formation of Textile Structures for Giant-Area Applications
Authors: Seyam Abdelfattah M. 
Published: April 2011

ABSTRACTRecently, textile machine manufacturers introduced to the market significant technological advances. Examples of such advances are higher speeds, higher level of automation, new concept of jacquard weaving that enables control of individual warp threads, CAD systems, and wider machines than seen before. This paper reviews the new development of formation systems of textile structures with emphasis on technologies that enables the production of giant-area fabrics. The review includes broad range of technologies (weaving, knitting, needlepunching, hydroentanglement, meltblowing, etc.). Additionally, the paper sheds the light on the potential of the textile technologies to manufacture electrotextile fabric structures.
High Speed Response of Organic Light Emitting Diodes and Photo-Detectors Fabricated on a Polymeric Substrate for Polymeric Optical Integrated Circuits
Authors: Ohmori Yutaka , Kajii Hirotake , Taneda Takayuki , Kaneko Masamitsu , Fujiki Tsubasa , Takahashi Kazuya 
Published: April 2011

ABSTRACTOrganic electroluminescent diode (OELD) has been investigated for use as a light source of polymeric optical integrated devices. The OLED was fabricated by organic molecular beam deposition (OMBD) technique. The OLEDs were fabricated on both glass and polymeric substrates. The device fabricated on a polymeric substrate shows similar device characteristics to those on a glass substrate. Optical signals of faster than 100 MHz has been created by applying pulsed voltages directly to the rubrene doped OLED. Optical photo detectors (OPDs) utilizing superlattice structure phthalocyanines provide increased pulse response with input optical signals and the response was faster than 1 MHz.
Paper-Like Display Utilizing Organic Electroluminescent Diodes Fabricated on 10 Micron-Thick Polyimide Films
Authors: Ohmori Yutaka , Kajii Hirotake , Taneda Takayuki , Hikita Makoto , Takenaka Hisataka 
Published: April 2011

ABSTRACTAn organic light emitting device (OLED) has been successfully fabricated on a thin paper-like polyimide substrate (about 10 μm-thick), which is sandwiched between silicone oxide and silicone nitride films. The emission characteristics of the OLEDs, which consist of diamine derivative (α-NPD) and 8-hydroxyquinoline aluminum (Alq3), are similar to those fabricated on a conventional glass substrate. Since the substrates and the OLEDs are very thin like a paper, the devices can be applicable for paper-like displays.
Power Generation from Piezoelectric Lead Zirconate Titanate Fiber Composites
Authors: Mohammadi Farhad , Khan Ajmal , Cass Richard B. 
Published: April 2011

ABSTRACTPower generation from lead zirconate titanate (PZT) piezoelectric fibers in the form of 1–3 composites under application of an external force was investigated. Green fibers consisting of PZT powder dispersed in a cellulose binder were made by the Viscous Suspension Spinning Process (VSSP). The composites were made by firing sheets of parallel green PZT fibers at 1270 °C, and then laminating the sintered sheets in epoxy. Composites of several PZT fiber diameters (15, 45, 120, and 250 μm), with the fiber volume fraction fixed at ∼0.4, were investigated. Transducers comprised of electrode and poled plates of the composites, in which the plate thickness direction was in the fiber axis direction, were made. Power generation experiments were conducted by dropping a 33 g stainless steel ball onto the electroded face of each transducer from a height of 10 cm and recording the output voltage on an oscilloscope. A peak voltage of 350 V corresponding to 120 mW of peak power was obtained. The output voltage and power was the highest for the transducers made with the smallest diameter fibers (15μm) and increased with increasing of transducer thickness. The average piezoelectric coefficient, d33, of the transducers was about 300 pC/N and decreased with decreasing transducer thickness. In this paper, the power generation capability and dielectric properties of the laminated 1–3 fiber composites are discussed.
Current-voltage Characteristics of Single CdSe Colloidal Nanodots Measured by Conductive-tip Atomic Force Microscopy
Authors: Tanaka Ichiro , Kawasaki Eri , Ohtsuki O. , Uno K. , Hara M. , Asami H. , Murase T. , Kamiya I. 
Published: April 2011

ABSTRACTWe have investigated current-voltage characteristics of individual CdSe colloidal nanodots by conductive-tip atomic force microscopy (AFM). The colloidal nanodots were spun-coat and scattered on a self-assembled monolayer of thiophene molecules formed on Au (111) surfaces for single dot measurements. A thin SiO2 layer was deposited on the sample surface in order to prevent the dots being moved by the tip during measurement. We imaged the topography of isolated single dots by AFM operated in contact mode, and measured current-voltage characteristics with the conductive tip positioned on single dots; large conductivity changes which suggest resonant tunneling through a quantized energy level in the dot was observed even at room temperature.
Optical Properties of Semimagnetic Quantum Dots
Authors: Mackowski S. , Nguyen T. A. , Jackson H. E. , Smith L. M. , Kossut J. , Karczewski G. , Heiss W. 
Published: April 2011

ABSTRACTMeasurements of optical properties of epitaxially grown CdMnTe quantum dots are presented. Magnetic ions are incorporated into the structure by passivating the substrate surface with Mn prior the quantum dot deposition. As expected, the intensity of intra-Mn transition increases with the time of manganese passivation. The formation of magnetic quantum dots is evidenced by presence of single emission lines in the micro-photoluminescence spectrum. The width of single dot emission lines is much broader than observed for non-magnetic quantum dots. The broadening is caused by thermal fluctuations of magnetization in quantum dots. Resonant spectroscopy results indicate that the exciton-optical phonon scattering is the main energy relaxation mechanism in these structures. The measurements suggest that post-growth thermal processing offers the possibility of tuning the magnetic properties of these structures.
Quantitative Charge Imaging of Silicon Nanocrystals by Atomic Force Microscopy
Authors: Feng Tao , Atwater Harry A. 
Published: April 2011

ABSTRACTQuantitative understanding of charging and discharging of Si nanocrystals in SiO2 films on Si substrate is essential to their application in floating gate nonvolatile memory devices. Charge imaging by atomic force microscopy (AFM) or electrostatic force microscopy (EFM) can provide qualitative information on such system, while a further step is needed. We have developed a generalized method of images, which can solve Poisson equation for multiple dielectric layers, to simulate the charge imaging of Si nanocrystals by non-contact mode AFM under different sample geometries. Simulated images can be compared with experimental images thoroughly to estimate the total amount and distributions of trapped charges, which is also useful in the study of time evolution of charges or dissipation problems.
Equilibrium Analysis of Lattice-Mismatched Nanowire Heterostructures
Authors: Ertekin E. , Greaney P.A. , Sands T. D. , Chrzan D. C. 
Published: April 2011

ABSTRACTThe quality of lattice-mismatched semiconductor heterojunctions is often limited by the presence of misfit dislocations. Nanowire geometries offer the promise of creating highly mismatched, yet dislocation free heterojunctions. A simple model, based upon the critical thickness model of Matthews and Blakeslee for misfit dislocation formation in planar heterostructures, illustrates that there exists a critical nanowire radius for which a coherent heterostructured nanowire system is unstable with respect to the formation of misfit dislocations. The model indicates that within the nanowire geometry, it should be possible to create perfect heterojunctions with large lattice-mismatch.
New Nanocrystalline si Floating Gate Structue for Nonvolatile Memory Application
Authors: Wu L.C. , Shi J.J. , Chen K.J. , Xu J. , Li W. , Ma Z.Y. , Dai M. , Wu D. , Li A.D. , Huang X.F. 
Published: April 2011

ABSTRACTWe report a direct experiment evidence for holes and electrons charging in a new nanocrystalline Si (nc-Si) floating gate structure (SiO2/nc-Si/SiO2/c-Si) fabricated in-situ by plasma oxidation and layer by layer deposition technique in a plasma enhanced chemical vapor deposition (PECVD) system. In this nc-Si floating gate structures, the thickness of tunneling SiO2 layer is about 2 nm and the mean grain size of nc-Si is 6 nm obtained from Raman scattering and AFM measurements. The discrete quantum level and Coulomb charging energy for a single electron have been observed in large ensemble of nc-Si dots by frequency dependent capacitance spectroscopy, which demonstrates that the Coulomb blockade for electron in nc-Si dots is larger than size fluctuation effects on the quantum confinement for our nc-Si floating gate structure. Quantitatively, the experiment results of capacitance spectroscopy are in good agreement with the theoretical calculations. By contrasted with silicon single electron transistor memory made by using ultra fancy nanotechnology, nc-Si based memory can be fabricated with a minimum perturbation of conventional silicon technology and may be closest to industrial application.
Formation and Cathodoluminescence of Silicon Nanoclusters in Silica
Authors: Zamoryanskaya Maria V. , Sokolov Vladimir I. 
Published: April 2011

ABSTRACTThe process of formation of silicon nanoclusters in a silicate matrix by the focused electron beam of high power and their cathodoluminescent properties were studied in this paper. The size of the silicon clusters and their concentration depend on the electron beam power and on the properties of the silicate matrix (density, porosity, composition). In this paper we studied the evolution of cathodoluminescent properties in bulk silicon oxide, porous silicon oxide glass, silicagel (n·SiO2·m·H2O) and opal. The result of the modification of silica is the appearance of the CL bands at 2.3eV in green region, and the bands at 1.4 and 1.1eV. The CL intensity of these bands increases during the interaction with electron beam. The volt-ampere characteristics of the modified areas of the silica are non-linear and depend on the time of the interaction and the power of the electron beam. We relate the appearance of these new CL bands with formation of oxygen-deficit defects and silicon clusters.