bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Single Crystal Zircon, (Zr,Pu)SiO4, Doped with238Pu
Authors: Hanchar John M. , Burakov Boris E. , Anderson Evgeniy B. , Zamoryanskaya Maria V. 
Published: April 2011

ABSTRACTSingle crystals of238Pu doped zircon (from 0.3 to 3.5 mm in size) were successfully grown for the first time ever using a Li-Mo flux synthesis method. The incorporation of Pu ranged from 1.9 to 4.7 wt. % el. (with approximately 81 wt.% of238Pu isotope). The crystals obtained were pink-brown, and then over a period of five months changed to a brown color, and glow in the dark. The intensity of the CL emission in the Pu doped crystals is correlated with the Pu content, and the CL emission showed no change 141 days after the initial CL measurements were made. Single crystal X-ray diffraction results obtained 141 days after synthesis indicate unit cell parameters (in angstroms): a = 6.6267(15), c = 5.9992(10) and a cell volume of 263.41(10). Radiation damage calculations indicate that after only a short period of time, six months (∼3.3 ×1014α-decay events per milligram), these zircon crystals have already accumulated significant α-induced radiation damage.
Role of Naturally Occurring Organic Matter on Thorium Transport in a Wetland
Authors: Kaplan Daniel I. , Knox A. S. 
Published: April 2011

ABSTRACTA wetland located on the Savannah River Site in Aiken, South Carolina has become contaminated by a number of radionuclides as a result of operating a pilot-scale nuclear test facility. Sediment Th-232 concentration at the site exceed 700 mg/kg, whereas background concentrations are ∼7 mg/kg. The Th is relatively mobile, having moved >300-m since 1958 and greatly exceeding contaminant transport model predictions. Studies were initiated to determine the chemical cause for the enhanced transport of Th. Particle-size fractionation studies showed that colloids alone were not likely responsible for all of the enhanced transport of Th. Sediment sequential extraction data showed that >80% of the Th was associated with the sediment organic fraction. In an experiment in which varying soil amendments resulted in the release of dissolved organic carbon (DOC) to the aqueous phase, a significant correlation (r = 0.91; p ≤ 0.01, n = 8) was calculated between aqueous Th and DOC. Pore water Th partitioning to hydrophobic resins suggested that 33% of the aqueous Th was associated with organic matter. Together, these results provide indirect evidence support the notion that enhanced mobility of Th at the site may in part be due to the presence of Th-DOC complexes.
Effect of β-Radiation on the Non Irradiated UO2(s) Dissolution
Authors: Clarens F. , Giménez J. , Pablo J. de , Casas I. , Sevilla M. , Dies J. 
Published: April 2011

ABSTRACTIn this work, we studied the effect of β radiation (Sr90 source with an activity of 7 mCi) on the dissolution of non irradiated UO2, as a chemicalanalogue of the spent nuclear fuel, in different leaching solutions.The experiments were carried out using a specifically designed continuous flow-through reactor and in nitrogen atmosphere to avoid oxygen contamination. The solid used was a non irradiated uranium dioxide with a particle size of 100–320 μm, which specific surface are was determined by the BET method. The experiments were carried out in NaCl media at different pH values. Both pH and redox potential of the solutions were continuously monitored. In all the cases, blank experiments were performed in parallel.Dissolution rates obtained under the effect of β radiation were compared with dissolution rates determined in the presence of hydrogen peroxide (the main oxidizing species radiolitically formed by the β radiation according to the CHEMSIMUL code) and with electrochemically determined UO2 corrosion rates found in the literature.
Materials for Freeform Fabrication of GHz Tunable Dielectric Photonic Crystals
Authors: Clem Paul G. , Carroll James F. , Niehaus Michael K. , Cesarano Joseph , Smay James E. , Lewis Jennifer A. , Lin Shawn-Yu 
Published: April 2011

ABSTRACTPhotonic crystals are of interest for GHz transmission applications, including rapid switching, GHz filters, and phased-array technology. 3D fabrication by Robocasting enables moldless printing of high solid loading slurries into structures such as the “woodpile” structures used to fabricate dielectric photonic band gap crystals. In this work, tunable dielectric materials were developed and printed into woodpile structures via solid freefrom fabrication (SFF) toward demonstration of tunable photonic crystals. Barium strontium titanate ceramics possess interesting electrical properties including high permittivity, low loss, and high tunability. This paper discusses the processing route and dielectric characterization of (BaxSr1-XTiO3):MgO ceramic composites, toward fabrication of tunable dielectric photonic band gap crystals.
Carbon Nanotube Modification Using BaF2 Vapor in Ultra-High Vacuum Environment
Authors: Santiago Francisco , Gehman Victor H. , Long Karen , Boulais Kevin A. 
Published: April 2011

ABSTRACTCarbon nanotubes have attracted significant attention in the scientific community due to their unique properties and potential applications. One of the most promising applications is a carbon-nanotube transistor. The motivation of this work is to find ways to connect carbon nanotubes directly to silicon using Ba as a chemical link. We studied chemical interactions between carbon nanotubes and BaF2 vapors using x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Surfaces of silicon wafers were chemically modified to allow the epitaxial growth of BaF2 using molecular beam epitaxy (MBE). Samples containing 2D single crystal islands of BaF2 were covered with carbon nanotubes with an average coverage of 10 nanotubes per um2. The samples were transferred to an outgasing station inside the MBE system and heated to 900°C for two hours in a pressure of 10-9 mbar. XPS C1s data before and after heat show a major change in the nature of the carbon nanotube electronic states. In addition XPS shows formation of a Ba-C “carbide like” bond and no presence of fluorine. AFM images of the same region taken before and after heat exposure show remarkable changes in the surface morphology of the carbon-nanotube wall.
Direct Writing of 3D Microstructures Using a Scanning Laser System
Authors: Yu Hui , Grüntzig Alexander , Zhao Yi , Sharon André , Li Biao , Zhang Xin 
Published: April 2011

ABSTRACTIn this paper, a new revolutionary 3D manufacturing approach to rapid processing of 3D microstructures in both soft (SU-8) and rigid (Si) materials is introduced. This technique facilitates very fast prototyping without the need of masks, resulting in a low-cost, short-turnaround flexible fabrication process.
Fabrication of Micro-Contact Probe Using Mo-Cr Spring with Au Plating Bump
Authors: Kaneshiro Chinami , Hohkawa Kohji 
Published: April 2011

ABSTRACTIn this paper, we report a new technology for fabricating interconnects and/or contact probes for LSI fabrication. We used a Mo-Cr spring wire as a lead wire. To reduce the resistance of the lead wire, we applied a Au plating bump to the tip of a Mo-Cr spring covered with Au thin film. Experimental results showed that contact resistance was lowered by forming an Au plating bump on the Mo-Cr spring wire, which was plated under controlled conditions.
Micromechanical Characterization of Gasb by Microbeam Deflecion and Using Nanoprobe and Finite Element Analysis
Authors: Ospina M. , Vangala S. R. , Yang D. , Sherwood J. A. , Sung C. , Goodhue W. D. 
Published: April 2011

ABSTRACTThe commercial development of low-power electronics and electro-optics based on antimonides demands a better understanding of the mechanical properties of ternary and quaternary thin-film alloys fabricated from the InGaAlAsSbP material system. Of particular importance is the determination of Young's modulus of these materials. In this paper, a technique for studying the mechanical behavior of these thin films was developed by using microbeam bending and finite element modeling. The technique was successfully applied to investigate the mechanical properties of GaSb. A test structure consisting of an array of gallium antimonide microbeams was fabricated with lengths ranging from 50 to 500 μm long. The microbeams were deflected using a calibrated nanoprobe, thereby generating load-displacement curves. Young's modulus was then extracted from the data using beam bending theory and a finite element simulation of the structures under load. A total of five microbeams with the same trapezoidal cross-section and lengths of 80, 85, 200, 250 and 500 μm were tested to study the technique applicability and size scaling effects on the mechanical properties. It was observed that the 80 and 85 μm beams exhibited linear elastic behavior and the 200, 250, and 500 μm microbeams exhibited non-linear elastic behavior.
Statistical Thermodynamics of Two-Dimensional Fluids of Solid Nanoparticles
Authors: Pozhar Liudmila A. , Maguire John 
Published: April 2011

ABSTRACTThe second virial coefficient-based statistical thermodynamics of a diluted fluid of rigid particles of regular polygonal shape is discussed. Analytical expressions for the second virial coefficient, surface tension, isothermal compressibility and isothermal speed of sound are derived in this approximation. The obtained results provide analytical guidelines for numerical simulations and modeling studies of two-dimensional (2D) particulate fluids (thin films) widely used in processing of model (nano)composite materials and other technological processes.
Multiscale modelling of Carbon nanotubes
Authors: Hamm Marc , Elliott James A. , Smithson Huw J. , Windle Alan H. 
Published: April 2011

ABSTRACTA comprehensive understanding of nanotube materials requires the ability to link different carbon nanotube models, which were developed to work at different length scales. Here we describe the mapping of a molecular dynamics (MD) model for single-wall carbon nanotubes onto a wormlike chain. This mapping employs a mode analysis of the bending fluctuations of the nanotube, similar to those used in experiments [1]. The essence of this mapping is to find an appropriate bending stiffness for the wormlike cha in in order to represent the nanotube on a coarsened scale. We find that this mapping will only work well, if the wavelength probing the nanotube stiffness is sufficiently large. For single-wall (9,9) armchair nanotubes vibration modes with node distances of 3 nm underestimate the long wavelength limit of the bending constant by about 50%. This mismatch tends to increase for tubes with larger radii.
Exploring Space Groups for Three Dimensional Photonic Band Gap Structures Via Level Set Equations: The Face Centered Cubic Lattice
Authors: Maldovan Martin , Ullal Chaitanya K. , Carter Craig W. , Thomas Edwin L. 
Published: April 2011

ABSTRACTA level set approach was used to study photonic band gaps for dielectric composites with symmetries of the eleven face centered cubic lattices. Candidate structures were modeled for each group by a 3D surface given by f(x,y,z)-t=0 obtained by equating f to an appropriate sum of structure factor terms. This approach allows us to easily map different structures and gives us an insight into the effects of symmetry, connectivity and genus on photonic band gaps. It is seen that a basic set of symmetries defines the essential band gap and connectivity. The remaining symmetry elements modify the band gap. The eleven lattices are classified into four fundamental topologies on the basis of the occupancy of high symmetry Wyckoff sites. Of the fundamental topologies studied, three display band gaps--- including two: the (F-RD) and a group 216 structure that have not been reported previously.
Nanodisperse Many-Particle-Systems: Concept, Structure-Property Relationships and Characterization Strategy
Authors: Oleshko Vladimir P. 
Published: April 2011

ABSTRACTNanodisperse many-particle-systems (MPS), often forming compact matter, consist of atomic/molecular nano-sized building units, which interact with each other. The interactions among clusters and with the embedding matrix mainly determine the macroscopic properties of the material. The functional properties of nanostructured matter depend on a number of parameters that describe the single cluster (structure, chemical composition, size and shape), the near-order and far-order effects of a given cluster and which can be modeled using the concept of MPS. The specified parameters have to be considered in a detailed multilevel ultramicroscopic and analytical characterization, and several can be manipulated to tailor new materials with desired optical, electronic or catalytic properties. Such approach provides logical synergism between modeling, engineering and characterization of disperse composite nanomaterials by the combination of analytical electron microscopy and image analysis techniques, as illustrated by examples utilizing chemically stabilized “giant” clusters of noble metals and multifractal percolation nanostructures of Ag filaments.
Nanoporous thermosets via Reactive Encapsulation of a Chemically Inert Solvent versus Free Radically Polymerized and Phase Separating Systems
Authors: Raman Vijay I. , Palmese Giuseppe R. 
Published: April 2011

ABSTRACTNanoporous thermosets are used as polyelectrolytes in fuel cells, separation membranes, and sensors and actuators, etc. Design of nanoporous thermosets for such applications entails controlling permeability by tailoring the pore size and pore chemistry. Usually free radically polymerizing and simultaneously phase separating systems are used to synthesize porous thermosets. A novel method of synthesizing nanoporous polymeric materials is employed in this work. This technique involves the synthesis of nanoporous thermosets by reactive encapsulation of an inert solvent using step-growth crosslinking polymerization reaction carried out until completion without phase separation into macroscopic phases. Key structural features of the porous materials synthesized by the reactive encapsulation technique were investigated by Scanning Electron Microscopy (SEM) after extraction and supercritical drying using carbon dioxide. Micrographs of the materials synthesized using the reactive encapsulation technique showed that the porous materials of pore size less than 100nm are obtained. Micrographs also showed that the reactive encapsulation technique can be employed to synthesize nanoporous polymeric materials of desired porosity and pore size by changing the solvent content. In addition, porous thermosets were also synthesized using free radical chemistry and phase separating system. The differences in the porous morphology of both these systems were enunciated using SEM micrographs.
Synthesis and Characterization of Novel Vanadium Dioxide Nanorods
Authors: Chen Wen , Mai Liqiang , Jiang congsheng , Peng Junfeng , Xu Qing , Zhu Quanyao 
Published: April 2011

ABSTRACTVanadium dioxide nanorods (B phase) have been synthesized, for the first time, using cetyltrimethylammonium bromide (CTAB) as structure-directing template in hydrothermal condition. Morphology and structure of the sample were characterized by XRD, SEM, HRTEM, XPS, TG-DTA and redox titration. The results show that the products are VO2 (B) nanorods and they are 1∼2 μm in length. HRTEM micrographs reveal that they indeed form bundles of agglomerated smaller filaments with diameters ranging from 20 to 40 nm. This filament-like shape in the nanoscale dimension leads to the exposure of a large fraction of the atoms to the surface. Thus, these materials are promising candidates for the development of new functionalized materials. TG investigation shows that there are a weight loss of 2.21 % between 250∼400 °C corresponding to removal of the organic residuals and a weight gain at about 430 °C corresponding to oxidation of vanadium with low oxidation state. The simplicity of hydrothermal process, cheapness, and availability of raw materials are advantages favoring the scaling-up of nanorods.
High-Resolution Analytical Electron Microscopy Investigation of Metastable Tetragonal Phase Stabilization in Undoped, Sol-Gel Derived Zirconia Nanoceramics
Authors: Oleshko Vladimir P. , Howe James M. , Shukla Satyajit , Seal Sudipta 
Published: April 2011

ABSTRACTThe mechanisms underlying stabilization of the metastable tetragonal (t)-phase in sol-gel derived, nanocrystalline ZrO2 were studied by high-resolution analytical electron microscopy, utilizing parallel electron-energy loss (PEEL) and energy-dispersive X-ray spectroscopies. The powders were synthesized by hydrolysis of Zr (IV) n-propoxide at ratios of molar concentration of water to Zr n-propoxide, R=5 and 60, respectively, followed by calcination at 400°C. Dense particles of the as-precipitated ZrO2 (R=5) revealed 4–11 nm-sized nanocrystals embedded in the amorphous matrix that may serve as nuclei for the t-phase during calcination. The calcined particles consist of 10–100 nm–sized t-crystals. For as-precipitated ZrO2 (R=60), week aggregates (50–100 nm) of largely amorphous 4–20 nm-sized particles after calcination yield a mixture of t-and monoclinic (m-) nanocrystals. PEELS fingerprints of the band structure with the intensity threshold matching the expected position of a direct bandgap at 4–5 eV allow to differentiate between the amorphous and nanocrystalline ZrO2. Stabilization of t-phase (R=5) with sizes up to 16 times larger than reported earlier is likely due to strain-induced confinement from surrounding growing grains, which suppress the volume expansion associated with the martensitic t-m transformation. For R=60, loose nanoparticle agglomerates cannot suppress the transformation. In this case, the t-phase may be partially stabilized due to a crystal size effect and /or to the presence of m-phase.
Synthesis of Hydroxyapatite – Hyaluronic acid Nano Composite Sol under Well-Controlled Condition
Authors: Ishikawa Yuko , Senna Mamoru 
Published: April 2011

ABSTRACTHydroxyapatite (HAp) – Hyaluronic acid (HYA) nano composite sol was prepared at room temperature, at pH 8, by a coprecipitation method from CaCl2 or Ca(CH3COO)2 and H3PO4. These soluble Ca sources were used in order to increase the number of nucleation sites for HAp on HYA. Starting materials were supplied by two kinds of processes to give solution(s) of only PO43- or, PO43- and Ca2+ simultaneously into HYA solution containing Ca2+. Morphology of the aggregates and crystallite size as well as lattice parameters of the HAp were examined by TEM and XRD data with Rietveld refinement. We observed needle like aggregates of crystallites of HAp. Supplying methods of Ca sources controlled the aspect ratio of the aggregates and HAp crystallite. Lattice parameters of the samples prepared from CaCl2 shifted towards those of chloroapatite. Those from Ca(CH3COO)2, however, correspond to the literature values of single crystal HAp. The results of FT-IR spectra and the changes of rheological property indicate the electrostatic interactions between negatively charged functional groups of HYA and HAp.
Achieving electrical percolation in polymer-carbon nanotube composites
Authors: Rahatekar Sameer S. , Hamm M. , Shaffer Milo S. P. , Elliott James A. 
Published: April 2011

ABSTRACTThe addition of carbon nanotubes (CNTs) to a polymer matrix is expected to yield improvements in both mechanical and electrical properties. The focus of this paper is to give a snapshot of our current work on CNT-filled thermoplastic polymer textile fibers and the enhancement of their electrical properties. The challenge is to determine the type and size of nanotubes that are most effective for a given application, and how they should be dispersed or modified to interact with the polymer. The objective of this work is to develop an understanding of how the processing methods and properties of nanotube polymer composites are related to the geometry of the nanotubes used, their orientation, and their loading fraction. It will then be possible to design desired composite properties by controlling the relevant process variables.The research described in this paper primarily involves mesoscale simulations (dissipative particle dynamics) of packed assemblies of oriented CNTs suspended in a polymer matrix. Computer simulations have been carried out to study the effect of processing conditions, aspect ratio of CNTs and effect of electric field on electrical conductivity. The percolation threshold required to achieve an electrically conductive polymer-CNT fiber can be predicted for given set of process variables. The model predictions are compared with the predictions of classical percolation theory, and with experimental data from measurements of bulk resistivity from CNTs dispersed in thermoplastic polymers.
Bramble-like Mesostructured Nickel Oxide Fiber Clusters
Authors: Cao Jieming , Wang Jun , Liu Jinsong , Chang Shuquan , Fang Baoqing , Ma Xianjia , Chang Xin , Xu Guoyue , Tao Jie 
Published: April 2011

ABSTRACTBramble-like mesostructured nickel oxide/surfactant fibers were synthesized by using anionic surfactants (sodium dodecylsulfonate or sodium dodecylsulfate: SDS) as templates, and nickel salts as inorganic precursors, via the “S-I+” route in alkaline condition. The as-prepared samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetry-differential thermal analysis (TG/DTA) techniques. Such form of mesostructure nickel oxide is found for the first time and is believed to have potential applications in catalysis, host-guest chemistry, and electrochemical devices.
Spherulitic Morphology and Thermal Stability of PP/ZnO Nanocomposites
Authors: Razdan Sandeep , Patra Prabir , Kim Yong , Warner Steve 
Published: April 2011

ABSTRACTPolypropylene nanocomposites were prepared using zinc oxide as the filler by melt mixing process. Nanocomposites were also prepared using maleic anhydride grafted polypropylene and methylated-zinc oxide using the same method. The samples were analyzed for observing changes in morphology and thermal stability using various characterizing instruments. The results showed that zinc oxide induced changes in the morphology and thermal stability of polypropylene, though by varying amounts depending on the type of nanocomposite prepared. The nanocomposites prepared from g-PP and methylated zinc oxide showed significant changes in crystallization temperature, decomposition temperature and residue formed upon decomposition, as compared to the rest of the composites or control samples. This was attributed to higher degree of interaction existing at the interphase between the organic and inorganic phases for these nanocomposites.
Creeping friction on amorphous polymers: Dissipation through molecular relaxation
Authors: Overney René M. , Sills Scott 
Published: April 2011

ABSTRACTThe dissipation mechanisms of nanoscale friction between a scanning force microscopy (SFM) tip and amorphous polystyrene are found to reside solely within the polymer's intrinsic molecular mobility, and are discussed with respect to the glass transition temperature. In both the glassy and the rubbery states, lateral force microscopy friction results revealed the dissipative behavior as activated relaxation processes with potential barrier heights of 7 kcal/mol and 83 kcal/mol, respectively. These values correspond to hindered phenyl (side chain) rotation and to the α-relaxation, respectively. The velocity relationship with friction, F(v), was found to satisfy simple fluctuation surface potential models with F ∝const -ln(v) and F ∝const -ln(v)2/3. Within ∼27 K above the glass transition temperature, friction displayed a shear thinning type behavior, also found in materials that exhibit multiple phases.