bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Iron and pH on Glass Dissolution Rate
Authors: Jeong Seung-Young , Ebert William L.
Published: April 2011

Short-term static tests were conducted with a surrogate high-level waste glass to measure the effects of pH and dissolved iron on the glass dissolution rate. The tests were conducted to determine if a term to account for the effects of dissolved iron is needed in the glass degradation model developed for Total System Performance Assessment (TSPA) calculations for the Yucca Mountain disposal system license application. The glass degradation model includes terms for dependencies on temperature, pH, and chemical affinity. A series of tests was conducted at 90 °C in various pH solutions without iron and with added FeCl3, Fe2O3, Fe3O4, and FeOOH. Tests were conducted at glass surface area/solution volume (S/V) ratios about 2 and 10 m-1for between 2 and 21 days. Solution concentrations of boron were used to measure the extent of reaction and calculate the glass dissolution rates. Similar rates were measured in tests conducted with and without iron at each pH. Both the results of the tests with and without iron showed V-shaped pH dependence curves with minima at near-neutral pH values. The pH dependencies (η) are about 0.44 in basic solutions and –0.49 in acidic solutions, based on the combined results of tests with and without iron. These are within the range of values for the pH dependence in the TSPA model for site recommendation.
Structural characterization of polycrystalline (Nd,Al)-substituted zirconolite
Authors: Loiseau Pascal , Caurant Daniel , Baffier Noël , Fillet Catherine
Published: April 2011

Zirconolite (formally CaZrTi2O7) is a crystalline phase particularly well adapted to actinide immobilization because of its excellent long-term behavior and its good containment capacity. Most of the French studies on zirconolite deal with minor actinides that are mainly responsible for the long-term radiotoxicity of high-level radioactive wastes. For these kind of studies, trivalent minor actinides (Am3+, Cm3+) can be simulated by a lanthanide ion with an ionic radius similar to that of Nd3+. Thus, several materials having the composition Ca1-xNdxZrTi2-xAlxO7 (0 ≤ x ≤ 0.8) were prepared by solid state reaction. These polycristalline materials were first characterized by X-ray diffraction and scanning electron microscopy associated with energy dispersive X-ray analysis in order to determine the nature of the crystalline phases formed. For low neodymium content (x ≤ 0.1), electron spin resonance of Nd3+ ions revealed that a significant proportion of these ions entered into trace amounts of perovskite. Nevertheless, all Ca1-xNdxZrTi2-xAlxO7 samples with x ≤ 0.6 can be considered as almost single phase zirconolite-2M. Structure refinement by the Rietveld method of Ca0.7Nd0.3ZrTi1.7Al0.3O7 showed that Nd3+ and Al3+ ions mainly entered respectively into the calcium site and into the split five-fold coordinated titanium site. Structural characterization of Ca0.3Nd0.7ZrTi1.3Al0.7O7 and Ca0.2Nd0.8ZrTi1.2Al0.8O7 samples confirmed that these compositions led to the crystallization of almost single phase zirconolite-3O, an orthorhombic polytype of zirconolite, whose structure was also refined by the Rietveld method. Results concerning neodymium location in Ca0.7Nd0.3ZrTi1.7Al0.3O7 and Ca0.3Nd0.7ZrTi1.3Al0.7O7 were qualitatively confirmed by optical absorption spectroscopy at low temperature.
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

Single 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

A 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

In 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

Photonic 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

Carbon 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

In 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

In 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

The 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

The 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

A 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

A 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

Nanodisperse 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

Nanoporous 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

Vanadium 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

The 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

Hydroxyapatite (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

The 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

Bramble-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

Polypropylene 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

The 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.
Mechanical Properties of Polyethylene Containing Defunctionalized Single Wall Carbon Nanotubes
Authors: Shofner Meisha L. , Peng Haiqing , Gu Zhenning , Khabashesku Valery N. , Margrave John L. , Barrera Enrique V.
Published: April 2011

To take advantage of the benefits of chemical functionalization and the desirable properties of unfunctionalized SWNTs, this research studies the effect of removing functional groups from SWNTs dispersed in a polymer matrix. Chemical functionalization of single wall carbon nanotubes (SWNTs) is a method for disrupting rope structure and adding reactive species to the nanotube to improve interfacial bonding and load transfer in composites, but changes to the nanotube hexagon structure caused by chemical modifications are expected to have a detrimental effect on the SWNTs' intrinsic mechanical properties. Thus, composites containing defunctionalized SWNTs and polyethylene are analyzed to evaluate the effect of functional group removal on the mechanical properties. The mechanical properties are measured using tensile tests. Issues of defects in the SWNT structure, polymer degradation, and changes in the fiber/matrix bonding as a result of functionalization removal are studied using Raman spectroscopy, thermogravimetric analysis, infrared spectroscopy, and dynamic mechanical analysis.
Synthesis and mechanical characterisation of Fe-based bulk metallic glasses and mixed amorphous/crystalline phases
Authors: Castellero Alberto , Lindsay Greer A. , Reza Yavari A. , Inoue Akihisa
Published: April 2011

Fully amorphous and mixed amorphous/crystalline bulky (Fe77+yGa3P9.5-yC4.5B3.5Si2.5)(100-x)/100Fex alloys were prepared varying Fe and Fe-P contents. The effect of the compositional changes on glass forming ability (GFA), stability of the amorphous phase and mechanical properties was studied. When y = 0 and x is enhanced from 0 to 2, the stability of the supercooled liquid region decreases of 10 K. For x = 0 and y = 3.5 the glass forming ability is drastically reduced leading to a mixed structure consisting of bcc-Fe, Fe3(P,C,B) and a small fraction of amorphous phase.

During compression test at room temperature the deformation of fully amorphous samples (y = 0) is dominated by the initiation and propagation of shear bands with consequent nil or small plastic deformation (0.2 % at 3000 MPa) for the alloys with x = 2 and x = 0 respectively. Embrittlement of (Fe77Ga3P9.5C4.5B3.5Si2.5)0.98Fe2 was observed after partial and full devitrification.

A higher Young modulus and a maximum strength of 3300 MPa were shown by the as cast partially crystalline Fe80.5Ga3P6C4.5B3.5Si2.5 alloy; also in this case, no yielding was detected.

Finally, compression tests at high temperature for fully amorphous Fe77Ga3P9.5C4.5B3.5Si2.5 showed inhomogeneous deformation up to 402°C. Homogeneous non-Newtonian plastic deformation was detected at 427°C. Newtonian homogeneous flow at 452°C is limited by the crystallisation of the superliquid and consequent final failure.
On the Wear Assessment of Multilayer Nanocrystalline Diamond Coated Implants of the Temporomandibular Joint
Authors: Papo Malesela J. , Catledge Shane A. , Machado Camilo , Kashef Somaieh , Eberhardt Alan E. , Vohra Yogesh K.
Published: April 2011

We deposited multilayer Nanocrystalline Diamond (NCD) thin films on Ti-6Al-4V substrates that were machined to imitate the shapes of the condyle and fossa of the temporomandibular joint (TMJ). We performed low stress wear assessment experiments on condyle/fossa pairs mounted in a custom-built mandibular movement simulator (MMS) for 5 x 105 loaded cycles at 1.2 Hz, which is equivalent to 4.4 years of clinical use. Analysis of wear surfaces on the control and the NCD-coated pairs indicated that no film delamination occurred on the NCD-coated condyle/fossa couple and that wear damage was extensive on the uncoated condyle/fossa pair. The high stress wear tests performed using the Ortho-POD machine at loads of 80 and 165 N showed that loss of film on the condyle specimens occurred after 3300 and 341 cycles, respectively. A subsequent evaluation of the influence of condyle curvature on wear by articulating a multilayer condyle/disk pair at a load of 50 N and 250 000 cycles at 1.2 Hz, showed that film delamination on the condyle occurred after 12500 cycles and no loss of film was observed on the disk after 250 000 cycles of articulation. Our results show that the observed lower film lifetimes on the condyles at high stresses are not related to intrinsic stresses in the film but probably due to lower film adhesion on the curved surfaces of the condyle.
Space Environment Effect on Fluorinated Polymers
Authors: Chipara M. , Edwards D. L. , Zaleski J. , Hoang B. , Przewoski B. , Balascuta S.
Published: April 2011

The effects of the space environment on polytetrafluorethylene and some fluorinated polymers, copolymers, and blends are critically reviewed. It is shown that in low altitude orbits such as Low Earth Orbit and Geostationary Orbit the presence of both ionizing radiation and atomic oxygen triggers a synergetic degradation of materials based on fluorinated polymers. The behavior is due to the lability of the in-chain alkyl radical to oxygen attack. It is concluded that fluorinated polymers should not be used as materials for space applications, as long as the mission implies low Earth orbits.
Coupling between order parameter and compositional fluctuations in the irradiation induced monoclinic to tetragonal phase transition in pure zirconia.
Authors: Simeone D , Baldinozzi G , Gosset D. , Dutheil M.
Published: April 2011

Zirconia, oxidation product of Zircaloy cladding elements of nuclear plants, exhibits an unusual behaviour under irradiation. Impinging ions and neutrons induce a monoclinic to tetragonal phase transition at room temperature in this solid. To understand this modification of the positions of the stability lines in such a solid under irradiation, we have studied the monoclinic to tetragonal first order phase transition versus temperature in pure micrometric and nanometric zirconia samples. From these works, it was possible to understand the behaviour of this material under irradiation pointing out the key role of defects induced irradiation on its phase diagram.
NMR study of proton beam irradiated TlH2PO4
Authors: Kim Se Hun , Lee Kyu Won , Jang Jae Won , Lee Cheol Eui
Published: April 2011

We have investigated proton beam irradiation effects on TlH2PO4 (TDP) showing an antiferroelectric phase transition and a ferroelastic phase transition. The sample was irradiated by 1 MeV proton beams to a dose of 1015 ions/cm2 and studied by means of 1H NMR measurements. The NMR rotating-frame spin-lattice relaxation time was measured as a function of temperature, and analyzed in order to understand the proton motions and the order parameter reflecting the structural changes caused by the proton irradiation.
Irradiation Effect of Nitrogen Ion Beam on Carbon Nitride Thin Films
Authors: Aizawa Shinichiro , Nasu Yuka , Aono Masami , Kitazawa Nobuaki , Watanabe Yoshihisa
Published: April 2011

Irradiation effect of low-energy nitrogen ion beam on amorphous carbon nitride (a-CNx) thin films has been investigated. The a-CNx films were prepared on silicon single crystal substrates by hot carbon-filament chemical vapor deposition (HFCVD). After deposition, the CNx films were irradiated by a nitrogen ion beam with energy from 0.1 to 2.0 keV. Irradiation effect on the film microstructure and composition was studied by SEM and XPS, focusing on the effect of nitrogen ion beam energy. Surface and cross sectional observations by SEM reveal that the as-deposited films show a densely distributed columnar structure and the films change to be a sparsely distributed cone-like structure after irradiation. It is also found that 2.0 keV ions skeltonize the films more clearly than 0.1 kev ions. Depth profiles of nitrogen in the films observed by XPS show that nitrogen absorption into films is more prominent after irradiation by 0.1 keV nitrogen ions than 2.0 keV ions.
Destruction of Multiwall Carbon Nanotubes under the Influence of Ion Bombardment
Authors: Brzhezinskaya Mariya M. , Baitinger Eugen M. , Shnitov Vladimir V.
Published: April 2011

In this paper, the results of experiments on irradiation of the multiwall carbon nanotube (MWNT) samples by argon ions with energy of 1 keV are presented. They were obtained by energy loss spectroscopy of reflected electrons and Auger electron spectroscopy.

It was found that ion irradiation of MWNTs decreases the characteristic energy and increases the full width at the half of the maximum (FWHM) of the π-plasmon peak. The plasmon relaxation time was found.
Nanostructural Fluctuation in Radiation-Amorphized Alloys
Authors: Watanabe Seiichi , Takahashi Heishichirou , Lam Nghi Q.
Published: April 2011

Spatio-temporal nanostructural fluctuations brought about by transient, metastable atom-cluster formation and the manifold nature of inherent atomic ordering in electron-irradiation-amorphized NiTi were investigated by using a combination of in situ observations inside a high-resolution high-voltage electron microscope (HR-HVEM) and image analyses of molecular-dynamics-simulated atom configurations. Nanometer-sized clusters were found to appear and disappear in the irradiated region. The random formation and annihilation of such nanoclusters are believed to be responsible for nanostructural fluctuations which appear to be related to transitions among manifold inherent structural states, involving multirelaxation processes. Temporal fluctuations in the amorphized structure were manifested through the dose-dependent local amorphization parameter, potential energy, volume, and inherent cluster bonding. The observed fluctuations obey a universal power law. Within the framework of the multi-Lorentzian picture, the resultant power law describes the distribution of multirelaxation times or cluster lifetimes. In addition, a unified relation for the temporal autocorrelation function for such fluctuation phenomena has been determined.
Silicon Micro-Photonic Structure for Ultra-Sensitive Biosensing
Authors: Schmidt Bradley , Almeida Vilson , Manolatou Christina , Preble Stefan , Lipson Michal
Published: April 2011

We demonstrate a micron-size planar silicon photonic device that is able to detect low concentrations of metal nano-particles approaching single particle detection. This sensitivity is achieved by using strong light confining structures that enhance the extinction cross-section of metal nano-particles by orders of magnitude. Structures were fabricated and measurements of the transmission spectra of the devices demonstrate the detection of 10 nm diameter gold particles resting on the device with a density of fewer than 2 particles per 104 nm2 (the area of the sensing region surface). Using such a device, in a fluidic platform, one could detect the presence of a single metal nano-particle specifically bound to various analytes, enabling ultrasensitive detection of analytes including DNA, RNA, proteins, and antigens.
Three-Dimensional Lithography for Rutile TiO2 Single Crystals using Swift Heavy Ions
Authors: Awazu Koichi , Fujimaki Makoto , Ohki Yoshimichi , Komatsubara Tetsuro
Published: April 2011

We have developed a nano-micro structure fabrication method in rutile TiO2 single crystal by use of swift heavy-ion irradiation. The area where ions heavier than Cl ion accelerated with MeV-order high energy were irradiated was well etched by hydrofluoric acid, by comparison etching was not observed in the pristine TiO2 single crystal. Noticed that the irradiated area could be etched to a depth at which the electronic stopping power of the ion decayed to a value of 6.2keV/nm. We also found that the value of the electronic stopping power was increased, eventually decreased against depth in TiO2 single crystal with, e.g. 84.5MeV Ca ion. Using such a beam, inside of TiO2 single crystal was selectively etched with 20% hydrofluoric acid, while the top surface of TiO2 single crystal subjected to irradiation was not etched. Roughness of the new surface created in the single crystal was within 7nm with the atomic forth microscopy measurement.
Very large plasmon band shift in strongly coupled metal nanoparticle chain arrays.
Authors: Sweatlock L. A. , Penninkhof J. J. , Maier S. A. , Polman A. , Atwater H.
Published: April 2011

30 MeV silicon ion irradiation of silica glass containing 10 nm silver nanocrystals causes alignment of the nanocrystals in closely spaced linear arrays along the ion tracks. Optical transmission measurements show a 1.5 eV splitting of the surface plasmon resonant absorption bands for polarizations longitudinal and transversal to the arrays. The resulting material is a highly anisotropic glass that absorbs blue light of one polarization, and near-infrared light of the orthogonal polarization. Finite-difference time domain simulations are used to explore the effects of interparticle spacing and total array length on the absorption properties.
Optical Properties of Dielectric and Magnetic Photonic Crystals in the Low-Frequency Limit
Authors: Krokhin Arkady , Arriaga Jesús , Reyes Edgar
Published: April 2011

We consider the long-wavelength limit for two-dimensional photonic crystals - periodic arrangement of magneto-dielectric rods with dielectric and magnetic constant εa and μa embedded in a magneto-dielectric background (εb,βb). Using the Fourier expansion method in the low-frequency limit (ω → 0 ) we develop an effective medium theory and give a rigorous proof that, in this limit, a periodic medium behaves like a homogeneous one. We derive compact analytical formulas for the effective index of refraction of a 2D photonic crystal. These formulas are very general, namely the Bravais lattice, the cross-sectional form of cylinders, their filling fractions and the dielectric and magnetic constants are all arbitrary. For non-magnetic materials, μa = μb = 1, we show how to introduce index ellipsoid and demonstrate that the E-mode is an ordinary wave and the H -mode is an extraordinary wave. For magnetic materials the both modes turn out to be extraordinary. This unusual property is unknown for natural crystals.
Growth and Optical Properties of 2D Photonic Crystals Based on Hexagonal GaAs/AlGaAs Pillar Arrays by Selective-Area Metalorganic Vapor Phase Epitaxy
Authors: Motohisa J. , Takeda J. , Inari M. , Fukui T.
Published: April 2011

We report on the growth of GaAs and GaAs/AlGaAs heterostructured hexagonal pillar arrays using selective area (SA) metalorganic vapor phase epitaxy (MOVPE) for the application of two-dimensional photonic crystals (2D-PhCs). SA-MOVPE was carried out on SiO2 masked (111)B GaAs substrates with circular or hexagonal hole openings. Extremely uniform array of hexagonal GaAs/AlGaAs pillars consisting {110} vertical facets with their diameter of order of 200 nm were obtained. Unexpectingly strong intense light emission was observed for the room temperature photoluminescence measurement, which suggests low surface nonradiative recombination and enhancement of the light extraction efficiency of the pillar arrays.
Dispersion Properties of Photonic Crystal Fibers - Issues and Opportunities
Authors: Lægsgaard J. , Barkou Libori S. E. , Hougaard K. , Riishede J. , Larsen T. T. , Sørensen T. , Hansen T. P. , Hansen K. P. , Nielsen M. D. , Jensen J. B. , Bjarklev A.
Published: April 2011

The dispersion, which expresses the variation with wavelength of the guided-mode group velocity, is one of the most important properties of optical fibers. Photonic crystal fibers (PCFs) offer much larger flexibility than conventional fibers with respect to tailoring of the dispersion curve. This is partly due to the large refractive-index contrast available in silica/air microstructures, and partly due to the possibility of making complex refractive-index structures over the fiber cross section. We discuss the fundamental physical mechanisms determining the dispersion properties of PCFs guiding by either total internal reflection or photonic bandgap effects, and use these insights to outline design principles and generic behaviours of various types of PCFs. A number of examples from recent modeling and experimental work serve to illustrate our general conclusions.
Imaging, Manipulating, and Analyzing with Nanometer Precision: Application of the Nanoworkbench
Authors: Guise Olivier , Ahner Joachim , Levy Jeremy , Yates John T.
Published: April 2011

We report the development of novel nanometer-scale manipulative and analytical devices for imaging, chemically analyzing and manipulating nanometer-scaled materials. Two different versions of the nanoworkbench are operating currently at the Surface Science Center of the University of Pittsburgh and at the Seagate Research Center in Pittsburgh. The instrument at Seagate consists of a modified commercially available high resolution scanning electron microscope (lateral resolution ∼1 nm at 10 kV) in combination with a set of four unique nano-manipulators, operating in the pressure range from 102 to 10−7 mbar. At the University of Pittsburgh a home-built UHV version of the nanoworkbench is in operation. In this UHV-instrument, several inter-connected UHV chambers allow in-situ deposition of thin-films and conventional surface analysis. The resolution of the SEM of the UHV system is limited to about 50 nm. We report the first results obtained by using both versions of the nanoworkbench, where we succeeded in writing patterns of ultra-small carbon-containing dots (8nm in diameter) with high position accuracy (<5nm) by electron-beam-induced deposition of carbon-containing background gases. Additionally, four-point probe measurements were performed on a SiGe system.
Affinity Rate Law Failure to Describe Sodium Borosilicate Glass Alteration Kinetics
Authors: Frugier P. , Gin S. , Jégou C.
Published: April 2011

Simplified glass compositions were chosen to improve our knowledge of the alteration kinetics of complex glasses dedicated to the confinement of high-level waste. Since 1998, the sodium borosilicate glass system is at the center of a passionate debate between an affinity-based kinetic rate law and a protective surface layer theory. All the authors who have investigated ternary 68/14/18 SiO2–B2O3–Na2O glass agree on the fact that the affinity law cannot satisfactorily account for its alteration kinetics. Some authors explained that these discrepancies between classical kinetic rate law and experimental findings could be due to macromolecular amorphous separation in the 68/14/18 sodium borosilicate system and that this simplified glass could be divided into 90% reedmergnerite (NaBSi3O8) and 10% diborate (Na2O–2B2O3). This article provides evidence of the homogeneity of ternary 68/18/14 SiO2–B2O3–Na2O glass at nanometric scale and shows that even phase separation at less than nanometric scale could not explain the inability of hydrated glass-solution affinity laws to describe its alteration. The relative simplicity of the SiO2–B2O3–Na2O chemical system allows a critical examination of the macroscopic alteration laws developed over the last twenty years based only on the hydrated glass-solution chemical affinity without taking into account the formation and reactivity of the gel or its passivating properties.
Interactions of Simulated High Level Waste (HLW) Calcine with Alkali Borosilicate Glass
Authors: Morgan S. , Hand R. J. , Hyatt N. C. , Lee W. E.
Published: April 2011

This study looks at the interactions between simulated calcined high level waste from fuel reprocessing and mixed alkali borosilicate glass frit in the early stages of melting, and the possibility of the formation of yellow phase during these stages. Simulant “calcine” from a full scale inactive trial (Magnox: oxide “blend” 25:75) was pre-mixed with alkali borosilicate glass, to achieve a 25wt% waste loading, and melted at 1050°C at various times. It is shown that dissolution occurs in two separate stages; the first involves formation of a low density CsLiMoO4 fluid, which separates and forms a yellow/green layer on the surface of the melt, accompanied by some dissolution of rare- earth elements (Nd, Ce, Gd) and Zr from the waste into the glass matrix. The second stage entails more extensive migration of these rare-earth elements into the glass, and the disappearance of the surface layer on the melt. The glass appears more homogenized at the later stages of melting, but still contains undissolved particles of calcine after 16 minutes.
Using Acoustic Emission in Quality Control of Glass and Ceramics for Radioactive Waste Immobilization
Authors: Belov V. Z. , Aloy A. S. , Khlopin V. G.
Published: April 2011

Laboratory scale unit for registration of acoustic emission (AE) signals was used for integrity control of glass granules and ceramic bodies. AE waveform recorded in course of the temperature changes has been shown to allow for an unambiguous interpretation and may be used for nondestructive quality control of glass and ceramics bodies.