bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phases Formation and Elements Partitioning in the CaO-Gd2O3(UO2)-MnO-TiO2 System: Application to Rare Earth - Actinide Waste Immobilization
Authors: Kirjanova Olga I. , Stefanovsky Sergey V. , Yudintsev Sergey V. 
Published: April 2011

ABSTRACTCeramics within the compositional series Ca4-xGdxMn2Ti7O20+x/2 (x = 0, 1, 2, 3, 4) and a sample with Ca2U2Ti7O20 formulation were studied as promising matrices for immobilization of rare earth (RE) and actinide (An) constituents of high level waste (HLW). The samples were prepared by cold pressing of oxide mixtures in pellets at 200 MPa followed by their sintering at 1400 °C or melting at 1500 °C and examined with X-ray diffraction, scanning and transmission electron microscopy. At x=0 and x=1 a perovskite – pyrophanite assemblage occurred. The sample with x=2 consisted of murataite and perovskite. Murataite was a major phase in the sample with x=3 (pyrochlore and perovskite were minor phases) and the only phase in the sample with x=4 prepared under oxidizing conditions (in air). The latter was composed of two murataite varieties with seven- and five-fold fluorite unit cells. The sample with the same formulation but synthesized under reducing conditions contained pyrochlore as an extra phase. Coupled substitution 2 Gd3+ = Ca2+ + U4+ resulted in formation of pyrochlore as the major phase. Mu-rataite and perovskite are considered as the host phases for rare earths and actinides mainly trivalent, including Pu(III), Am(III), and Cm(III), and corrosion products (Mn, Fe, Al) whereas pyrochlore is the host phase for rare earths and tetravalent actinides (U(IV), Np(IV), Pu(IV)). This makes the system of calcium, gadolinium, manganese, and titanium oxides prospective for immobilization of RE – An fraction of HLW containing minor corrosion products (iron group elements).
Zirconolite-based glass-ceramics for actinides immobilization: Effects of glass composition and of actinides simulant nature
Authors: Loiseau Pascal , Caurant Daniel , Bardez Isabelle , Majerus Odile , Baffier Noël , Fillet Catherine 
Published: April 2011

ABSTRACTZirconolite (CaZrTi2O7) based glass-ceramics, in which the crystalline phase (aimed at preferentially incorporating minor actinides or Pu) is embedded in a durable calcium aluminosilicate glassy matrix, can be envisaged as good waste form candidates. In this study, the effect of parent glass composition – and particularly of TiO2, ZrO2, CaO and Al2O3 amounts -on the microstructure and the structure of the glass-ceramics obtained after controlled devitrification (nucleation + crystal growth) is reported. It clearly appears that the volume percentage of zirconolite crystals and their nucleation rate in the bulk of the glass strongly depends both on (CaO + ZrO2 + TiO2) and Al2O3 amounts in parent glass. Neodymium is mainly used to simulate trivalent minor actinides whereas several samples were also prepared with other lanthanides (Ce, Eu, Gd, Yb) in order to investigate the effect of simulant field strength in glass on the nature and the composition of the crystals formed. The effect of partial or total molar substitution of ZrO2 by HfO2 in parent glass composition was also studied in order to prepare Ca(Zr1-xHfx)Ti2O7 (0 < × ≤ 1) based glass-ceramics which could be interesting in order to minimize criticality problems.
Neptunium Speciation in Humic Acid-rich Clay Water upon Interaction With Radioactive Waste Glass Samples
Authors: Pirlet V. , Van Iseghem P. 
Published: April 2011

ABSTRACTOrganic complexes of actinides are known to occur upon interaction of high level waste glass and Boom Clay which is a potential host rock formation for disposal of high level waste in Belgium. The solubility and mobility of237Np, one of the most critical radionuclides, can be affected by the high dissolved organic carbon content of the Boom Clay porewater through complexation with the humic substances. The influence of humic substances on the Np behaviour is considered through dissolution tests of Np-doped glasses in Boom Clay water and through fundamental study of the specific interaction between Np(IV) and the humic acids using spectroscopic techniques. High Np(IV) concentrations are found in the glass dissolution tests. These concentrations are higher than what we should expect from the solubility of Np(OH)4, the solubility limiting solid phase predicted under the reducing conditions and pH prevailing in Boom Clay. Studying the specific interaction of Np(IV) with humic acids in Boom Clay porewater, high soluble Np concentrations are also measured and two main tetravalent Np-humate species are observed by UV-Vis spectroscopy. The two species are interpreted in terms of mixed hydroxo-humate complexes, Np(OH)xHA with x = 3 or 4. These species are the most likely species that can form according to the pH working conditions. Using thermodynamic simplified approaches, high complexation constants, i.e. log β131and log β141respectively equal to 46 and 51.6, are calculated for these species under the Boom Clay conditions.Comparing the spectroscopic results of the dissolution tests with the study of the interaction of Np(IV) with humic substances, we can conclude that the complexation of Np(IV) with the humic acids may occur and increases the solubility of Np(OH)4upon interaction of a Np-doped glass and the Boom Clay porewater.
MTU Laser-Based Direct-Write Techniques: Recent Development and Nanoparticles Patterning Results
Authors: Nadgorny Edward M. , Zhou Changgong , Drelich Jaroslaw , Zahn Randy 
Published: April 2011

ABSTRACTTwo laser-based direct-write techniques to guide particles from a mist source to a target substrate by laser beams were recently developed at Michigan Tech. The laser-guided direct-write (LGDW) technique uses a hollow optical fiber, while the laser-guided microsensor patterning (LGMP) technique uses a micrometer-sized aperture. The techniques are suggested to be utilized for patterning microstructures made of nanoparticles that are either crystallized from liquid precursors or directly deposited from nanoparticle-in-liquid suspensions. The computational results based on the paraxial Fraunhofer approximation of a Gaussian beam diffracted by a circular aperture and experimental measurements of corresponding deposition rate under different conditions suggest several factors for setup optimization of LGMP. The results indicate that among the most important factors are the aperture size relative to the laser beam-waist size and the divergence of the beam near the aperture. Examples of gold-thiolate, protein-coated polystyrene, and carbon-polymer composites deposition are presented.
Scanning Probe Characterization of Localized pH Changes on a Sapphire Surface in the Presence of an Applied Field
Authors: Bullard Joseph W. , Kershner Ryan J. , Cima Michael J. 
Published: April 2011

ABSTRACTSingle crystal sapphire substrates were lithographically patterned with a system of parallel platinum electrodes, which were used to manipulate 1.58μm silica particles inplane, in the presence of an aqueous solution. Observation of the motion of these particles revealed the adhesion of some of them to the sapphire surface near the platinum working electrode, even in the range of pH where the zeta potentials of silica and sapphire are of the same sign. This phenomenon suggests the existence of localized differences in pH, attributable to the presence of potential determining ions produced in the faradaic processes occurring at the electrodes during the electrophoretic manipulation of silica particles. Atomic force microscopy (AFM) was used to corroborate this hypothesis, measuring the forces between a silica particle and a sapphire substrate in the presence of an applied field. The resultant force-distance curves demonstrate a change in the interaction forces between particle and substrate as a function of distance from the electrode. Variations in this interaction correspond to localized differences in the zeta potential of the substrate, which, in turn, are related to localized differences in pH. Quantification of these spatial variations in pH as a function of time yields further information about the diffusion of these faradaically produced potential determining ions across the substrate.
Controlling the position and morphology of nanotubes within a polymer thin film
Authors: Lahiff Emer , Minett Andrew I. , Curran Seamus , Ryu Chang Y. , Blau Werner J. , Ajayan Pulickel M. 
Published: April 2011

ABSTRACTWe introduce a new method of producing polymer/nanotube composites where the morphology of nanotubes within the composite can be controlled. The thickness of the composite thin film can also be altered as required. Carbon nanotubes are grown from organo-metallic micro-patterns. The morphology of the tubes is determined by the conditions under which the tubes are grown and also, the type of catalyst used. These periodic nanotube arrays are then incorporated into a polymer matrix by spin-coating a curable polymer film on the as-grown tubes. The density and position of conduction channels through the thin film composite can be easily pre-determined by controlling the morphology of the embedded nanotubes. This technique of producing freestanding nanotube/polymer composite films represents a more efficient method of combining these materials for potential flexible electronic applications in an inexpensive and scalable manner.
Ceramic Microfabrication Techniques for Microdevices with Three-Dimensional Architecture
Authors: Nair Balakrishnan , Wilson Merrill , Akash Akash , Crandall Joe , Lewinsohn Charles , Cutler Raymond , Flinders Marc 
Published: April 2011

ABSTRACTThe term “microfabrication” has been used primarily as an acronym for silicon-based device fabrication. Recent developments in ceramic processing technology have resulted in cost-effective, scalable options of ceramic microfabrication that offer the potential for fabrication of devices with a number of advantages over silicon-based microdevices for specific applications. These advantages include the ability to fabricate devices with three-dimensional architecture, high-temperature operation up to 1200°C, porous layers for gas diffusion, and textured substrate properties for specific applications through wider materials selection. Processing routes for these ceramic microdevices with three-dimensional architecture include established processes such as tape casting, laser machining, lamination and sintering, or new processes such as reaction bonding and lost-mold techniques. The ability to fabricate three-dimensional feature geometries allows the application of these ceramic microfabrication techniques for device fabrication targeted at a number of applications such as point-of-use high purity gas generation, microchannel devices, microreactors, fiber-optic connectors and heat-pipes for microelectronics.
Gas Adsorption Evidence of Single-Wall and Multi-Wall Carbon Nanotube Opening
Authors: Babaa Moulay-Rachid , McRae Edward , Dupont-Pavlovsky Nicole , Delpeux Sandrine , Beguin Francois , Valsaque Fabrice , Ghanbaja Jaafar 
Published: April 2011

ABSTRACTCarbon nanotubes offer a surface very similar to that of graphite, a reference substrate in physisorption experiments aimed at studying substrate-adsorbate interactions. The curvature, however, introduces new questions. What are the effects of this on condensation pressures or heats of adsorption? Can one experimentally distinguish between different adsorption sites? In this study, we compare adsorption isotherms of several simple gases (Kr, Xe, CCl4) on singlewall (SWNTs) and multi-wall carbon nanotubes (MWNTs), before and after opening. For mechanically opened SWNTs, the accessibility of the adsorption sites and the molecular arrangements of the adsorbed gases are discussed. With the much bigger, well-defined MWNTs, the “cutting method” called upon a nitric acid treatment followed by a CO2 oxidation. TEM investigations and physisorption studies clearly revealed tube opening and that the inner channels became accessible to Kr molecules.
Molecule Derived Nanomaterials: Chemical Concepts for Composition, Morphology and Particle Size Control
Authors: Mathur Sanjay 
Published: April 2011

ABSTRACTConventional material synthesis procedures rely on the intrinsic chemical behaviours (e.g., different hydrolysis rates of the reactants in solution phase reactions or different vapour pressure or thermal stability in the gas phase reactions) of the different components, which make the material properties susceptible to inaccuracies due to an increased number of process variables. As a consequence, phase separation and element segregation are present at the nanometer scale, although the global stoichiometry of the product may correspond to the desired composition. In this context, the use of well-defined molecular precursors is a promising approach to grow extended solid-state structures from atomic constituents.
On Molecular Dynamics Simulation of Metal Clusters and Their XRD and ELNES Spectra
Authors: D'Agostino G. , Gusso M. 
Published: April 2011

ABSTRACTWe report on molecular dynamics calculation of few selected metal clusters by means of classical many-body potential. Despite simplicity of the approach, structural and thermodynamic properties have been achieved, such as an estimation of melting temperature lowering with size. As expected, coexistence ranges are observed instead of a single temperature transition. Phonon spectra have been also evaluated. Thermal atomic displacements at low temperature have been, in turn, estimated by means of Bose statistics.This work is intended as a step toward computer aided interpretation of cluster characterization by X-ray's or electron beams. Therefore, X-rays diffraction patterns and near edge electron energy loss have been simulated for different model structures in order to provide insights on those characterization technique capabilities.
Quaternary–matrix, nanocomposite self-lubricating PVD coatings in the system TiAlCN-MoS2 – structure and tological properties
Authors: Spassov V. , Savan A. , Phani A. R. , Stueber M. , Haefke H. 
Published: April 2011

ABSTRACTNowadays the demands placed upon the tooling in processes such as cutting, drilling, milling, stamping, bending, etc. are constantly growing and restrictive. On one hand, productivity, cost efficiency and quality all require high-speed processes to be developed. On the other hand, environmental safety requires very little or no lubricant to be used (dry cutting or minimized spray-lubrication). When combined, these two considerations mean: the tool should wear very little, withstand high temperatures and the friction between the tool and the work piece should be minimized. An apparent approach to simultaneously satisfying such requirements is coating the tools with self-lubricating hard coatings. Quaternary TiAlCN is a rapidly developing hard coating suitable for a number of cutting applications. The well-known wear-resistant coating TiN has been demonstrated to have improved high-temperature oxidation resistance when aluminum is included, i.e. TiAl N. Addition of yet a fourth element, carbon, has the primary effect of lowering the high friction coefficient occurring between the ceramic coating and steel. The high hardness, toughness, heat resistance and low friction coefficient of TiAlCN make it the ideal candidate for applications such as milling, hobbing, tapping, stamping and punching. MoS2 is a well-known solid lubricant widely used as tribological coatings, especially for applications working in vacuum or dry environment. Combining the wear resistance of the quaternary TiAlCN matrix with the lubricating properties of MoS2 has an extremely beneficial effect in further improving the tribological performance of the resulting composite. The coatings were deposited on hardmetal (WC-Co) and Si (100) substrates using reactive magnetron sputtering. The structure of the coatings is studied by plain-view TEM and XTEM, electron diffraction and ED X. The tribological properties were examined by Pin-on-Disk (PoD) tribometer. The adhesion was estimated by scratch test, and the hardness was measured by nanoindentation. All the coatings examined had a very low friction coefficient (typically below 0.09) and volumetric wear rate against 100Cr6 steel (AISI 52100) of 7.10-7 mm3/N/m. The relation of deposition parameters to structure to properties is discussed. To the authors knowledge, this is the first paper describing quaternary TiAlCN matrix with inclusions of MoS2.
Oxidative Dehydrogenation of Ethylbenzene to Styrene Over Graphite Nanofibers
Authors: Xu Xuejun , Terry R. , Baker K. 
Published: April 2011

ABSTRACTTubular and platelet graphite nanofibers were used as catalysts for the oxidative dehydrogenation of ethylbenzene to produce styrene at temperatures between 350 and 577 °C in packed bed tubular quartz flow reactors. The performances of GNF catalysts were evaluated in terms of conversion, selectivity and styrene yield. Tubular GNF showed higher activity than platelet GNF, but the latter showed higher selectivity than the former material. Both types of GNF exhibited significantly better performance than a commercial catalyst when operated under the same conditions.
On the development of the <111> fiber texture in nanocrystalline gold during growth and annealing
Authors: Andreasen Klaus P. , Schell Norbert , Jensen Thomas , Petersen Jakob H. , Jensen Martin S. , Chevallier Jacques , Bøttiger J. 
Published: April 2011

ABSTRACTThe evolution during growth and subsequent annealing of the <111> fiber texture in magnetron-sputtered nanocrystalline Au films has been studied experimentally using X-ray diffraction with synchrotron radiation. To quantitatively investigate this fiber texture, grain orientation distributions were recorded in situ during growth and during subsequent annealing using Bragg-Brentano geometry. The (111) diffraction intensity was measured as a function of the sample tilt χ, the tilt axis lying at the intersection of the film surface and the scattering plane. As a quantitative measure of the texture, we used the width of the orientation distributions. The grain-orientation distributions narrowed during annealing. The activation energy for the process behind this texture change was found to be 0.64 ± 0.05 eV, close to the activation energy for grain boundary self-diffusion in nanocrystalline Au. This and the narrowing of the grain orientation distributions led us to suggest that the observed changes in texture originated from grain rotations and not from grain growth. Grain growth did not take place at the lower temperatures, where changes in orientation distributions were observed.
Growth of Single Crystal Tungsten Nanorods by Oblique Angle Sputter Deposition
Authors: Karabacak Tansel , Wang Pei-I , Wang Gwo-Ching , Lu Toh-Ming 
Published: April 2011

ABSTRACTWe report the creation of single crystal tungsten nanorods with unusual simple cubic β-phase. These novel nano-structures were grown by oblique angle sputter deposition with substrate rotation through a shadowing effect. Transmission electron microscopy (TEM) diffraction patterns from individual nanorods clearly show the single crystal structure. It is evident from TEM diffraction measurements, during the oblique angle deposition, both β-phase W(100) and α-phase W(110) islands exist at the initial stages of growth. However, at later stages of the growth the β-phase structure dominates. This is in contrast to the sputter deposition at normal incidence where only the thermodynamically stable bcc α-phase W(110) polycrystalline films were formed when the film grew to a certain thickness. We explain our results by using the shadowing and adatom mobility mechanisms: At the initial stages of growth, the β-phase W(100) islands grow taller due to the lower adatom mobility on these islands. The taller β-phase W(100) islands survive in the competition during oblique angle growth and form isolated nanorods in the later stages, while the shorter α-phase W(110) islands stop growing due to the shadowing effect. In addition, our Monte Carlo simulation results agree well with the experimental measurements.
Photoluminescence of Si/SiO2, RE2O3/Si/SiO2and RE2O3/Si/Al2O3(RE = Er, Nd, Tm) Sputtered Thin Films
Authors: Rozo C. , Fonseca L. F. , Resto O. , Weisz S. Z. 
Published: April 2011

ABSTRACTSi/SiO2, RE2O3/Si/SiO2and RE2O3/Si/Al2O3films were sputtered. Si/SiO2films were annealed to 1100°C for 30 min in Ar. RE2O3/Si/SiO2films were annealed to 700°C, 1000°C, or 1100°C for 30 min in Ar. RE2O3/Si/Al2O3films were annealed to 700°C for 30 min in Ar. Raman spectra and photoluminescence (PL) obtained for the Si/SiO2films show relation between Si nanocrystal (nc) presence, Si nanoparticle (np) PL and Si target area. Nd2O3co-sputtered films presented PL for the (4F5/2,2H9/2) →4I9/2,4F3/2→4I9/2,4F3/2→4I11/2, and4F3/2→4I13/2transitions. Er2O3co-sputtered films presented PL for the4I11/2→4I15/2, and4I13/2→4I15/2transitions. Tm2O3co-sputtered films presented PL for the3H4→3H6transition. Different spectral shapes were observed for the infrared (IR) PL of the Er3+ions and of the Nd3+ions for the RE2O3/Si/Al2O3films with respect to the RE2O3/Si/SiO2films.
Vanadium Oxide Nanofibers and Vanadium Oxide Polyaniline Nanocomposite: Preparation, Characterization and Electrochemical Behavior
Authors: Lutta Samuel T. , Dong Hong , Zavalij Peter Y. , Whittingham M. Stanley 
Published: April 2011

ABSTRACTThe sol gel reaction of NH4VO3 and polymethylmethacrylate (PMMA) template followed by hydrothermal treatment formed (NH4)xV2O5-Δ.nH2O rods. TGA, SEM, XRD and FTIR characterized this compound. Heating (NH4)xV2O5-Δ.nH2O in oxygen and nitrogen at 250 °C and 300 °C respectively resulted in the formation of vanadium oxides nanofibers of V3O7 and V2O5. Performance of these compounds as cathode in rechargeable lithium battery was investigated in a LiPF6/mixed carbonate electrolyte. The materials show good cycling with capacity greater than 130mAh/g, which translates to the insertion of 0.5 moles of Li+ per vanadium of the active material.
Tapping-mode AFM - Force Measurement Capabilities on Compliant Surfaces
Authors: Nnebe Ijeoma M. , Schneider James W. 
Published: April 2011

ABSTRACTWe investigate the feasibility of tapping-mode atomic force microscopy (TM-AFM) as a force measurement tool for compliant surfaces. For quantitative extraction of the tip-sample interactions, numerical modeling of the cantilever dynamics is required using a defined form for the interaction, with the results compared to experiment. Through TM force measurements on silicon, we illustrate that a forced damped harmonic oscillator model sufficiently represents the motion of the cantilever. Particularly for liquid operation, distance-dependent dissipation must be included in the model for accurate quantification of the tip-sample interactions and for successful reproduction of experimental force curves. This dissipation is not due to damping from the bulk viscous medium, but is likely frictional in origin. This investigation shows that TM force measurement in liquid is feasible and could be particularly advantageous for the measurement of intermolecular interactions from soft and easily deformed molecular layers.
Carbon Nanotube and Nanofibre Reinforced Polyamide-12 Fibres
Authors: Shaffer M. S. P. , Sandler J. K. W. , Pegel S. , Windle A. H. , Gojny F. , Schulte K. , Cadek M. , Blau W. J. , Lohmar J. , van Es M. 
Published: April 2011

ABSTRACTA range of multi-wall carbon nanotubes and carbon nanofibres were mixed with a polyamide-12 matrix using a twin-screw microextruder, and the resulting blends used to produce a series of reinforced polymer fibres. The aim was to compare the dispersion and mechanical properties achieved for nanofillers produced by different techniques. A high quality of dispersion was achieved for all the catalytically-grown materials and the greatest improvements in stiffness were observed using aligned, substrate-grown, carbon nanotubes. The use of entangled multi-wall carbon nanotubes led to the most pronounced increase in yield stress. The degrees of polymer and nanofiller alignment and the morphology of the polymer matrix were assessed using X-ray diffraction and calorimetry.