bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of gas generation in matrices containing Ra-226 sources
Authors: Ojovan M. I. 
Published: April 2011

ABSTRACTSpent sealed radiation sources containing Ra-226 are immobilised either by the embedding into metal matrix materials or by welding enclosure in metal hermetic capsules. Encapsulation of sources ought provide safe conditions for storage for a long time period. Gaseous products (helium and radon) are generated due to the decay of Ra-226. The gas generation of Ra-226 sources can cause their rupture and consequent leakages of radionuclides. The higher the radioactivity of sources the higher the intensity of gas generation. The pressure of accumulated gas depends on many other factors therefore necessary limitations ought be determined for the encapsulation procedures. The process of gas generation is described herein in order to reveal the conditions of safe immobilisation of radium sources. A simple model describing immobilisation of sources in a metal host is proposed. Both helium and radon generation is considered followed by accumulation of gases near sources. Partial pressures of helium and radon are found depending on time. The diffusion of helium in the metal and decay of Rn-222 are taken into account. It is shown that the pressures of both radon and helium increase until some maximum values, after that the pressures slowly fall down. The maximum radon pressure being not very high is achieved during 65 days after immobilisation whereas helium increases its pressure during an extended period of time lasting for tens of years (137 years in the glass matrix) reaching very high magnitudes for powerful sources (137.5 MPa for a 100 GBq source in a glass capsule). Safe conditions of immobilisation of radium sources can be determined on the base of obtained data.
Analytical Electron Microscopy Study of Electron Radiation Damage in Iron Phosphate Glass Waste Forms
Authors: Sun K. , Wang L. M. , Ewing R. C. 
Published: April 2011

ABSTRACTA series of iron phosphate glass waste forms with compositions of 45Fe2O3-55P2O5, 20Fe2O3-80P2O5, and 20Fe2O3-20Na2O-60P2O5, namely FeP-1, FeP-2 and FeP-3, was studied by analytical electron microscopy (AEM). Transmission electron microscopy (TEM) bright-field (BF) imaging showed that under the electron irradiation, phase segregation occurred in both the FeP-1 and FeP-2 samples at high electron doses (3.84×1026 e/m2). In contrast, bubbles formed in the FeP-3 sample, even at a relatively low dose (2.88×1025 e/m2), which may be attributed to the migration of Na under irradiation as in the case in sodium borosilicate glass. Series electron energy-loss spectroscopy (EELS) analysis showed that the glass materials experienced mass-loss and composition variation. No obvious Fe valence state changes under irradiation were observed within the irradiation period.
Understanding the Behavior and Stability of Some Uranium Mineral Colloids
Authors: Mertz Carol J. , Fortner Jeff A. , Tsai Yifen 
Published: April 2011

ABSTRACTColloids are believed to be a dominant mode of transport for radionuclides in the unsaturated zone and thus the characterization of the attributes of the colloids is important for understanding and predicting subsurface transport. As uranium-based spent nuclear fuels will be prevalent at the high-level waste repository at Yucca Mountain, we have examined the colloidal properties of a mixture of two uranium minerals. This paper presents results of analyses on colloidal suspensions of meta-schoepite, (UO2)4)(OH)6·5H2O, and UO2+x, in 10 mM uranyl nitrate or J-13 groundwater (from Yucca Mountain, NV). A suite of techniques was used to characterize the colloids. The colloids detected by dynamic light scattering in the 10 mM uranyl nitrate solution exhibited a mean size of ∼200 nm and a colloid concentration on the order of 1012particles/L. Likewise, large 200 nm colloids of meta-schoepite and UO2+xwere dominant in the transmission electron microscopy analyses. The colloids detected in the J-13 groundwater exhibited a bimodal distribution; large globular 100–200 nm UO2+xcolloids and needle-like colloids of meta-schoepite were observed (with extremely fine microstructure exhibited for the meta-schoepite colloids). Electrophoretic mobility measurements of the meta-schoepite and UO2+xsuspension in 10 mM uranyl nitrate indicated that the colloids are not stable at pH values less than or equal to five. While at pH values ≥ 5.5, the colloids of meta-schoepite and UO2+xin 10 mM uranyl nitrate are stable, exhibiting zeta potentials of -30 to -60 mV. The results in this paper show that stable colloidal suspensions of uranium substrate colloids are possible under aqueous, oxidizing conditions.
As, Se, and Re Sorption by Mg-Al Layered Double Hydroxides
Authors: Bryan Charles R. , Wang Yifeng , Xu Huifang , Braterman Paul S. , Gao Huizhen 
Published: April 2011

ABSTRACTLayered double hydroxides (LDHs) have high anion exchange capacities and are easily synthesized in the laboratory, giving them considerable potential as adsorbents for anionic contaminants in the environment. In this study, sorption of arsenate, selenate, and perrhenate by uncalcined Mg-Al LDH (Mg:Al ratio 2.4:1) was evaluated. To investigate sorption mechanisms, the substrate was added to the solution both as a pre-wetted slurry (allowing 24 hours for rehydration), and as a dry powder. Sorption results varied for different anionic complexes. For selenate and perrhenate, an incubation time was required for the dry material to achieve the same Kd value as the pre-wetted material. For arsenate, however, both wetted and dry materials initially had high Kds, which decreased with time. These behaviors are attributed to the structural reconstruction of the calcined LDH material in solution. Se and Re are not highly sorbed by the phases present in the calcined material, but are incorporated as interlayer anions in the LDH structure upon hydration and reconstruction, while As may be sorbing onto the dehydration products, and being partially released during rehydration.
The Behavior or Light Water Reactor Fuel after the Cladding is Breached under Unsaturated Test Conditions
Authors: Cunnane J. C. , Fortner J. A. , Finch R. J. 
Published: April 2011

ABSTRACTExperiments were conducted to examine the corrosion behavior of fuel and cladding under test conditions selected to determine how fuel with breached cladding may behave under unsaturated repository conditions. The results discussed here were obtained from two test samples, each consisting of ∼3.5-in. segments of ATM103, a moderate-burnup (∼30 GWd/MtU) PWR fuel, exposed to humid air at 175°C. Visual examination of the samples after 540 days revealed that each had developed an axial crack that passed through a drilled hole in the cladding and ran the full length of the sample.Destructive examination of the fuel and cladding showed that the cladding had experienced extensive fuel-side corrosion. Metallographic examination of the cladding shows the hydride distribution near the drilled hole, the fracture surfaces, and the fuel-side corrosion products. Electron microscopy (SEM, TEM) and electron diffraction analyses were used to characterize the corrosion products. The results indicate that the fuel-side corrosion of the cladding and the specific volume increase associated with the formation of the corrosion products caused the hoop stresses that resulted in the observed axial splitting. The implications of these results for the expected evolution of the spent fuel cladding after the cladding is initially breached in an unsaturated repository are discussed.
Observation of Studtite and Metastudtite on Spent Fuel
Authors: McNamara Bruce , Buck Edgar , Hanson Brady 
Published: April 2011

ABSTRACTWe have characterized uranyl peroxide phases on commercial spent nuclear fuel (SNF) samples formed under immersion conditions. At short times, crystallites of metaschoepite were observed on the hydrated fuel particles. Over a two-year period, all evidences of metaschoepite disappeared and in many samples, the fuel particles appeared to be coated by a new alteration phase. Additionally, milligrams of corroded fuel aggregates were observed at the sample air-water interface in each sample. The corrosion phases on bulk fuel and on the suspended materials were examined by SEM, EDX, and XRD and were identified as studtite (UO4·4H20) and metastudtite (UO4·2H20), respectively. The reason for the partitioning of the two phases is unclear at this time. SEM micrographs of the bulk powders indicated extensive surface corrosion and fragmentation of particles.
Programmable Technologies for Micro- and Nano-Scale Pattern and Material Transfer and Possible Applications for Control of Self-Assembly
Authors: Nagel David J. 
Published: April 2011

ABSTRACTProgrammable methods for transferring materials to surfaces in patterns can produce structures with micrometer and nanometer scale features. All such technologies involve combinations of information, materials and energy. The materials in additive technologies can originate in the vapor phase, as liquids or suspensions, or as solids. The energy can come from laser, electron or ion beams, or the pressures used in writing, dispensing, jetting or flow methods. Many of the programmable techniques do not require high temperatures, so they can be used to make fine-scale structures of organic and bio-materials, and even live biologicals. Quantitative comparisons of both additive and subtractive programmable methods show that only a few, based on electron or ion beams, or on proximal probes, are capable of making nanometer-scale structures. Assembly methods, notably self- and directed-assembly, should prove to be central to the realization of manufacturable nanotechnology. Programmable deposition technologies may be used to supply materials for, and otherwise control self-assembly processes. The four sets of technologies, namely masked lithography, direct-write techniques, self-assembly and directed-assembly, provide a versatile and powerful toolbox for making micro-and nano-meter scale devices and systems.
Developing Nanoscale Materials Using Biomimetic Assembly Processes
Authors: Bachand George D. , Rivera Susan B. , Boal Andrew K. , Bauer Joseph M. , Koch Steven J. , Manginell Ronald P. , Liu Jun , Bunker Bruce C. 
Published: April 2011

ABSTRACTThe formation and nature of living materials are fundamentally different from those of synthetic materials. Synthetic materials generally have static structures, and are not capable of adapting to changing environmental conditions or stimuli. In contrast, living systems utilize energy to assemble, reconfigure, and dismantle materials in a dynamic, highly non-equilibrium fashion. The overall goal of this work is to identify and explore key strategies used by living systems to develop new types of materials in which the assembly, configuration, and disassembly can be programmed or “self-regulated” in microfluidic environments. As a model system, kinesin motor proteins and microtubule fibers have been selected as a means of directing the transport of molecular cargo, and assembly of nanostructures at synthetic interfaces. Initial work has focused on characterizing and engineering the properties of these active biomolecules for robust performance in microfluidic systems. We also have developed several strategies for functionalizing microtubule fibers with metal and semiconductor nanoparticles, and demonstrated the assembly of composite nanoscale materials. Moreover, transport of these composite assemblies has been demonstrated using energy-driven actuation by kinesin motor proteins. Current work is focused on developing mechanisms for directing the linear transport of microtubule fibers, and controlling the loading/unloading of nanoparticle cargo in microfluidic systems.
Non-impact electrostatic micromanipulation by voltage sequence for time
Authors: Saito Shigeki , Takahashi Kunio , Urago Masataka 
Published: April 2011

ABSTRACTThis paper proposes how to determine a voltage sequence for time to realize a non-impact electrostatic micromanipulation by kinetic control of a detached particle. The system consists of a manipulation probe, a spherical microparticle, and a substrate plate. These objects are all conductive. The particle initially sticks to the probe tip due to adhesional force and is detached by the applied voltage. The force on the particle, which is generated by electrostatic interaction, is evaluated through a boundary element method. Although the numerical method is used, all the parameters are normalized. Based on the evaluation, we propose the simple method by accelerating and decelerating voltage, and clearly express the conditions of voltage and time by considering the total work to the particle during its flight. The discussion about the time reveals the feasibility of the method from the viewpoint of the through-rate of a power-source.
Ellipsometry Measurement Accuracy of Gate Oxides under Polysilicon
Authors: Jiang Gary , Pelcher Don , Kwon Daewon , Clerico Jana , Collins George 
Published: April 2011

ABSTRACTPrecisely controlling the thickness of ultrathin silicon dioxide (SiO2) gate dielectric films is critical for high yield advanced generation semiconductor manufacturing. Advanced methods for producing ultrathin gates deposit both the gate dielectric and the polysilicon (poly-Si) gate electrode in a single cluster tool. This avoids the opportunity for adsorption of molecular airborne contamination (MAC) between deposition of the two layers, but necessitates measuring gate oxide thickness through a thick poly-Si layer.Variations in poly-Si grain size, amorphous silicon content, and roughness, make it very difficult to model the optical feedback in the visible spectral range to resolve ultrathin (10–20 Å) gate oxides with sufficient accuracy and repeatability for process control.This paper studies the optical behavior of the poly-Si/dielectric filmstack from 190 nm to 900 nm and the physical properties of the poly-Si layer. A more accurate modeling method is proposed to characterize the poly-Si and its top roughness layer using effective medium approximation (EMA) models. Using the new model, both a spectroscopic ellipsometer (SE) and a multi-angle multi-wavelength laser ellipsometer (MWLE) were employed to measure wafers with different poly-Si and gate oxide thicknesses. TEM was used to characterize the film thickness while roughness was determined using AFM. Good correlation was obtained between the TEM, AFM, and ellipsometry results. Excellent repeatability (0.04 Å 1σ on a 15 Å gate oxide for 10 days) and across the wafer uniformity (0.2 Å 1σ for a 49-point map) were also achieved when measuring gate dielectric films under the poly-Si with the MWLE.
Effects of Softbake Parameters on a Benzocyclobutene (BCB) Adhesive Wafer Bond
Authors: Pascual Daniel N. 
Published: April 2011

ABSTRACTThis study explores the effects of softbake parameters including temperature and duration on the homogeneity and toughness of a Benzocyclobutene (BCB) adhesive bond. Experiments were initially performed on silicon wafer pieces and then verified using quartered wafers bonded on a different machine. A four-point bend delamination test was employed to quantitatively measure interface toughness while uniformity was analyzed visually. A softbake temperature of 150 °C for 10 minutes yielded strong void-free bonds with an interface toughness of 23 J/m2.
Adhesion force and Nanotribological Characteristics of Chemical Vapor Deposited Fluorocarbon Films
Authors: Kim Nam-Kyun , Kim Tae-Gon , Park Jin-Goo , Kim Woon-Bae , Shin Hyung- Jae 
Published: April 2011

ABSTRACTIn this study, Adhesion force and Nanotribological Characteristics of fluorocarbon (FC) films on Al deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) were evaluated. The contact angle of FC thin films on Al was measured to be around 110°. The surface energy was calculated to be 15 dynes/cm from the measurements of contact angles of polar and nonpolar solutions on surfaces. The contact angle hysteresis, which is an indicator for the surface heterogeneity, was lower than 30°. The friction force of FC films coated surfaces was three times lower than bare Al. The adhesion force of bare Al was measured to be around 9.6nN. The presence of FC films on Al reduced it to below 4nN. Fourier transform infra-red (FTIR) spectra showed the presence of fluorocarbon groups such as –CFn- and =CF=CF2.
Measurement of shape and deformation of MEMS at the wafer level
Authors: Furlong Cosme , Ferguson Curtis F. , Melson Michael J. , Pryputniewicz Ryszard J. 
Published: April 2011

ABSTRACTOne of the approaches to fabrication of MEMS involves surface micromachining to define dies on single crystal silicon wafers, dicing of the wafers to separate the dies, and electronic packaging of the individual dies. Dicing and packaging of MEMS accounts for a large fraction of the fabrication costs, therefore, nondestructive evaluation at the wafer level, before dicing, can have significant implications on improving production yield and costs. In this paper, advances in development of optoelectronic holography (OEH) techniques for nondestructive, noninvasive, full-field of view evaluation of MEMS at the wafer level are described. With OEH techniques, quantitative measurements of shape and deformation of MEMS, as related to their performance and integrity, are obtained with sub-micrometer spatial resolution and nanometer measuring accuracy. To inspect an entire wafer with OEH techniques, measurements of overlapping regions of interest (ROI) on a wafer are recorded and adjacent ROIs are stitched together through efficient 3D correlation analysis algorithms.
Single Osteoblast Chemical Sensor via Non-invasive Bio-Electronic Interface
Authors: Yang Mo , Zhang Xuan , Kohr Bonnie , Morgan Andre , Ozkan Cengiz S 
Published: April 2011

ABSTRACTThe broad-spectrum sensitivity of cell based biosensors offers the capability for detecting known and unknown chemical/biological agents. One cellular parameter that is often measured is the extracellular potential of electrically active cells. Membrane excitability in osteoblasts plays a key role in modulating the electrical activity in the presence of chemical agents. However, the complexity of this signal makes interpretation of the cellular response to a chemical agent difficult to interpret. By analyzing shifts in the signal's power spectrum, it is possible to determine a frequency spectrum also known as Signature Pattern Vectors (SPV) specific to a chemical. We used a 5x5 multiple microelectrode array system to spatially position osteoblast cells, by using a gradient AC field. Fast Fourier Transformation (FFT) analyses were used to extract information pertaining to the frequency of firing from the extracellular potential.
Kinetics and Mechanism of Nucleation, Growth and Stabilization of Metal Oxide Nanoparticles
Authors: Tannenbaum Rina , King Scott , Hyunh K. , Zubris Melissa , Dan Nily 
Published: April 2011

ABSTRACTReactive metallic fragments that are formed by the decomposition of organometallic complexes, undergo a nucleation and growth process that gives rise to the formation of nanocrystals. In the absence of stabilizing molecules, the aggregation process is restricted mainly due to the decreasing mobility of the particles and their declining diffusional rates as a function of their increasing size. On the other hand, in the presence of a polymer in the reaction medium, the growing metallic particles are stabilized by the surface adsorption of the polymer chains, thus lowering their surface energy and creating a barrier to further aggregation. Studies of the nucleation and aggregation kinetics of metallic particles formed from the decomposition of organometallic precursors have been used to shed light on the mechanism of their formation. In these studies, the rate of decomposition of the precursor organometallic complexes used has been considered to represent the overall rate of the process. Moreover, it has been implicitly assumed that the formation kinetics of the metal nanoclusters directly coincides with the decomposition kinetics of their precursors. In this study, we attempt to decouple the kinetic characteristics of the various steps that comprise the overall nucleation and aggregation process cobalt oxide nanoclusters. A combination of infrared and x-ray photoelectron spectroscopies, and particle size determination by dynamic light scattering, are used to identify the individual contribution of each step to the overall mechanism of metal nanocluster formation.
Characterizing the Dopant Behavior of Functionalized Carbon Nanotubes in Conducting Polymers
Authors: Hughe Mark , Snook Graeme A. , Chen George Z. , Shaffer Milo S. P. , Fray Derek J. , Windle Alan H. 
Published: April 2011

ABSTRACTThe electrochemical polymerization of conducting polymers, such as polypyrrole, generally requires the incorporation of an anionic dopant to balance the positive charge on the oxidized conducting polymer chains. The susceptibility of multiwalled carbon nanotube (MWNT) surfaces to functionalization makes them exciting candidates for a new class of dopant for conducting polymers. In this work, the doping of polypyrrole with functionalized MWNTs is investigated using a combination of electrochemical impedance spectroscopy, scanning electron microscopy, and quartz crystal microbalance work. The findings described here are particularly relevant in light of recent reports indicating that carbon nanotube-conducting polymer composites hold great promise for use in electrochemical capacitors, also known as supercapacitors [1,2].
Carbon Nanotubes and Nanofibers Grown by Microwave Plasma Enhanced Chemical Vapor Deposition on a Nickel Substrate
Authors: Belay K. G. , Jackson J , Xin Yan 
Published: April 2011

ABSTRACTBoth carbon nanotubes and carbon nanofibers were grown on a thick nickel substrate by means of microwave plasma enhanced chemical vapor deposition (MPECVD) process using 20% CH4 and 80% H2 at a temperature of 750°C and a pressure of 50 Torr. The substrate was pre-abraded with 1.0μm diamond powder and 15.0 μm diamond paste to increase the rate of nucleation. When the substrate is taken out of the reactor the film detaches itself completely from the nickel. Unusual outgrowth structures appear jutted on one section of the substrate in a symmetrical manner. These structures were very hard and, when analyzed using environmental scanning electron microscope (ESEM), Raman microscopy and transmission electron microscope (TEM), micro-trees and an abundance of multi wall carbon nanotubes (MWCNTs) and nanofibers were observed. An attempt to measure the hardness of the film using a nano-indenter was inconclusive due to the extreme hardness of the material produced.
Proton Conducting Nano Hybrid Membranes Synthesized from Temperature Tolerant Polydimethylsiloxane (PDMS) Polymers
Authors: Kim Je-Deok , Honma Itaru 
Published: April 2011

ABSTRACTFlexible and temperature tolerant nano-hybrid membranes consisting of zirconium (titanium) oxides and polydimethysiloxane (PDMS) with the different molecular mass of 4500 and 600 have been synthesized by sol-gel processes. The membrane of zirconium/PDMS=2 (in molar) showed enhanced thermal stability and flexibility up to 300 °C due to the presence of cross-linkable inorganic nano-phase in the hybrid macromolecular matrix. The membrane becomes proton conducting polymer electrolyte when doped with 12-phosphotungstic acid (PWA). The proton conducting properties of the hybrid membranes with various PWA concentration were measured in the temperature range from room temperature to 150°C under saturated humidity conditions. A maximum conductivity of 2×10-2 S/cm was obtained at 150°C when the PDMS/zirconium oxides hybrid matrix was changed to gel state due to the higher water activity at elevated temperatures.