bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer-Coated Ultra-Fine Particles
Authors: Brousseau Patrick , Dubois Charles 
Published: April 2011

AbstractUltra-fine metallic particles have demonstrated recently their potential in tailoring the performance of energetic materials. DRDC Valcartier has explored methods to create controllable nanometric coatings on metallic particles and has opted to use polymers to treat the particles. Those coatings can have multiple positive effects. For example, in the case of aluminium, small particles are very reactive and tend to cause interations with the surrounding media. One example is the ageing of aluminium nanoparticles in the presence of air and humidity. Ultra-fine particles age much faster than micron-size particles. The long-term stability of energetic material mixes containing ultra-fine particles will be affected by this reactivity, and coatings would help to solve this problem. Another example is the interaction of aluminium nanoparticles with nitramines that causes gassing. Three coating methods will be presented: by thermoplastics using a Ziegler-Natta reaction, by thermosets through a polycondensation reaction initiated at the surface of the particles, and in-situ coating of particles by on-line polymerization during the plasma production of powders. The results of coating experiments using those methods will be presented. It will be shown that, for aluminium particles, adequate dispersion is a challenge and affects the results of the coating experiments. To assess the performance of the coating methods, ageing tests were carried out on coated and uncoated nanoparticles. The results of ageing tests with those methods will be presented and compared. It will be shown that the polymer coatings reduce significantly the loss of active metal content during accelerated ageing tests. Since the purpose of the powders is to be used in energetic materials, a study on the rheological effects of the coated particles in polymeric solutions will be presented as well. Coated particles increase the relative viscosity of HTPB-Al solutions by a factor of 100 at low shear rates, but much less with PPG.
Inorganic Nanoparticles for Gun Propellants
Authors: Baschung Barbara 
Published: April 2011

AbstractThe possibility of increasing the burning rate of solid rocket propellants by adding nanoparticles of aluminum into the propellant formulation has already been well-known for many years. This paper deals with micron- and nanoparticles embedded in gun propellants. The objective is to increase the gun performance. The burning behavior of solid propellants based on ultra-fine aluminum powder was investigated in a high pressure range which is reached in a gun tube. The burning rate of such a propellant is much higher (nearly two orders of magnitude) than for the similar propellant with the micron-sized aluminum. This paper presents a review of burning experiments with propellants based on the nano- and micron-sized particles of aluminum. The burning behavior of NENA solid propellants based on nano-scale aluminum was studied as a function of the portion of aluminum in the mixture. The burning of these propellants follows Vieille's burning law. The burning rate increases by augmenting the aluminum portion in the propellant. Theoretical models are reviewed in order to understand these experimental burning results. An advanced propellant coated with appropriate nanoparticles is presented in the conclusion. With this propellant and a special ignition by microwaves it should be possible to ignite solid propellants by using high loading densities (> 1.2 g/cm3).
Hot Spots from Dislocation Pile-up Avalanches
Authors: Grisé William 
Published: April 2011

AbstractThe model of localized adiabatic heating associated with release of a dislocation pile-up avalanche is described and re-evaluated. The model supplies a fundamental explanation of shear banding behavior in metal and non-metal systems. Now, a dislocation dynamics description is provided for more realistic assessment of the hot spot heating, for both straight dislocation pile-ups and circular loop pile-ups. Such a localized heating effect was overestimated in the earlier work, in part, to show the dramatic enhancement of the work rate, and the corresponding temperature build-up, potentially occurring in the initial pile-up release, say, at achievement of the critical dislocation mechanics-based stress intensity for cleavage. Proposed applications are to potentially brittle metal, ionic, and energetic material systems.
A Study of Shock-Wave Propagation in Single Crystallinefcc-Al and α-Fe2O3and an Interface between Two Such Phases Using MD Simulations
Authors: Tomar Vikas , Zhou Min 
Published: April 2011

AbstractThis research focuses on shock wave propagation in <100>, <110>, and <111> oriented single crystalline Al, <0001> oriented single crystalline Fe2O3, and an interface between the {100} surface of Al and the {0001} surface of Fe2O3. An interatomic potential is developed to describe interatomic interactions in the Fe+Al+Fe2O3+Al2O3material system. The potential is capable of describing the behaviors of Fe, Al, Fe2O3, and Al2O3as well as of composites consisting of any combination of these components. The analyses in single crystals focus on the relationships between the shock wave velocity (US) and the particle velocity (UP) as a function of single crystalline orientation. Calculations also focus on the formation and propagation of defects. The analyses reveal that the US-UPrelationship as well as the type and the extent of deformation strongly depend on the crystallographic orientation. The interfacial shock wave propagation analyses focus on the change in atomic structure near the interface as a function of UP. Calculations show that there is a threshold UPvalue above which the atomic structure on both sides of the interface undergoes significant changes which are accompanies by enhanced increase in temperature and pressure relative to what is seen in both phases when they are deformed alone. This observation suggests a possibility that this threshold may represent the onset of a shock-induced reactive structural change.
Free Recovery Effects of Shape-Memory Polymers for Cardiovascular Stents
Authors: Yakacki Christopher Michael , Shandas Robin , Lanning Craig , Gall Ken 
Published: April 2011

AbstractThe shape-memory effect was examined in polymer stents intended for cardiovascular applications. Four polymer networks were synthesized from poly(ethylene glycol) dimethacrylate and tert-butyl acrylate with 10 wt% and 20 wt% crosslinker, and with glass transition temperatures (Tg) of 52°C and 55°C. Solid and 50% porous stents were manufactured and tested for free strain recoverability at temperatures at or just above 37°C. Stents with lower glass transition temperatures and a higher degree of crosslinking recovered faster than their counterparts. Lower deformation (packaging) temperatures and higher recovery temperatures induce more rapid recovery. The presence of geometrical features, such as pores, initiated recovery sooner, but had negligible influence on overall recovery.
Nanoparticle Ring Structures based on Protein Assemblies
Authors: Behrens Silke , Habicht Wilhelm , Wagner Kerstin , Unger Eberhard 
Published: April 2011

AbstractThe bottom-up wet-chemical synthesis of inorganic materials provides tools for generating nanostructures from particles to one-dimensional structures, but these conventional chemical techniques usually offer little control over the deposition of metals or metal particles into nanosized ring structures although interesting properties and applications, e.g., Aharonov-Bohm rings are expected. Our results provide a straightforward and rapid wet-chemical synthesis to ring-like metal particle arrays. Applying appropriate conditions, tubulin dimers, proteins of 4-5 nm diameter and a length of 8 nm, self-assemble by specific recognitions capabilities into defined superstructures. Ca2+ ions, e.g., direct the assembly of tubulin into 50 nm sized, ring-like structures. In our approach, these ring-like protein assemblies serve as a functionalized scaffold where the metal particles are generated in situ and deposited into spiral-shaped particle arrays, reflecting the arrangement of the protein subunits within the assembly. The resulting size and crystalline structure of the materials were examined using transmission electron microscopy and scanning force microscopy.
Millimeter-scale surface nano-structuring using focused ion beam milling
Authors: Dovidenko Katharine , Potyrailo Radislav A. , Le Tarte Laurie A. 
Published: April 2011

AbstractNew patterning schemes for a variety of applications including sensors and photonics are explored. We present here a comprehensive study of using focused ion beam (FIB) milling to modify surfaces over millimeter-scale areas with nano-patterns of dimensions down to 30 nm. A typical example of a pattern is 40 nm diameter × 40 nm depth wells with a 200 nm pitch. Typical sample materials are metals, but polymer patterning is possible. We have also evaluated the surface of the patterned materials to ensure there are no negative effects of these patterning schemes on the future device performance.
Effects of Dielectrophoretic Parameters on Fabrication and Electronic Properties of Single-Walled Carbon Nanotube Devices
Authors: Dong Lifeng , Youkey Steven , Bush Jocelyn , Lo Jennifer , Jiao Jun , Dubin Valery M , Chebiam Ramanan V 
Published: April 2011

AbstractWe recently developed a novel floating-potential dielectrophoretic method to selectively position individual single-walled carbon nanotubes between two floating electrodes while the bundles of nanotubes and impurities were attracted into the region between two control electrodes. In this study, we investigated effects of several process parameters including electric field distribution, electric field frequency, and solution media in order to understand the physical mechanisms of this dielectrophoretic process and to improve its efficiency. Results showed that both the magnitude and the direction of electrical force applied onto the nanotubes can be tailored by changing these process parameters. It was found that a 1 wt% sodium dodecyl sulfate in deionized water is an efficient solution for separating bundles of nanotubes into individual nanotubes and aligning individual nanotubes with a clean surface between two electrical contacts in comparison to N,N-dimethylformamide, 1,2-dichloroethane, 1,2-dichlorobenzene, 1,1-dichloromethane, ethanol, and isopropanol solutions. The fabricated carbon nanotube devices exhibit electronic properties comparable to nanotube transistors and interconnects fabricated by other methods.
How to realize ultimate spatial and temporal resolutions by laser-combined scanning tunneling microscopy?
Authors: Shigekawa Hidemi , Takeuchi Osamu , Aoyama Masahiro , Terada Yasuhiko , Kondo Hiroyuki , Oigawa Haruhiro 
Published: April 2011

AbstractBy combining scanning tunneling microscopy (STM) and the optical pump-probe technique using a femtosecond pulse laser, we have developed a new microscopy, shaken pulse-pair-excited STM (SPPX-STM), that enables us to observe the dynamics of electronic structures with the ultimate spatial and temporal resolutions.
Rolling behavior of cylindrical micro-object analyzed by finite element method
Authors: Ochiai Toshihiro , Saito Shigeki , Takahashi Kunio 
Published: April 2011

AbstractAnalyzing the rolling behavior of micro-object is necessary for the realization of the micro-manipulation technique by mechanical-method. Thus in this paper, we obtain the rolling resistance of an isotropic elastic cylindrical micro-object in adhesive contact to a rigid surface.In order to estimate the rolling resistance, we assume this adhesive contact to be the plane strain problem, and calculate the total energy of this system as the numerical function of the contact area using finite element method (FEM). The total energy of this system is defined as the sum of the next three terms: the elastic energy of the cylindrical micro-object, the interface energy within the contact area, and the mechanical potential energy that depends on the external moment applied to the cylindrical micro-object. A careful consideration of the energy balance of the system clarifies that the rolling resistance has the value of 0.1 [10-12Nm] for the polystyrene (where a work of adhesion = 0.1[N/m]) cylindrical micro-object with the radius and thickness. Hence, we establish the procedure of the calculation for the rolling resistance of the micro-object based on the principle of the energy balance by finite element method.
Nanocones- a different form of carbon with unique properties
Authors: Heiberg-Andersen Henning , Helgesen Geir , Knudsen Kenneth , Pinheiro Jean Patrick , Svåsand Eldrid , Skjeltorp Arne 
Published: April 2011

AbstractIt is possible to make perfect conical carbon nanostructures fundamentally different from the other nanocarbon materials, notably buckyballs and nanotubes. Carbon cones are realized in five distinctly different forms. They consist of curved graphite sheets formed as open cones with one to five carbon pentagons at the tip with successively smaller cone angles, respectively. The nucleation and physics of nanocones has been relatively little explored until now. We present here the key facts and latest results on this “5’th form of carbon”.
NiSi Nanowires and Nanobridges Formed by Metal-Induced Growth
Authors: Kim Joondong , Lee Dongho , Anderson Wayne A 
Published: April 2011

AbstractNickel monosilicide (NiSi) nanowires (NWs) were fabricated by metal-induced growth at 575 °C. The solid-state reaction of Ni and Si provides linear grown NWs. The parallel grown NW forms a nanobridge (NB) across a trench, patterned with a simple optical lithography and metal lift-off method. The Ni pads gave a good Ohmic contact without affecting the I-V transport characteristics through a NB. The metallic NB, 2.73 µm in length and 50 nm in diameter, gave a low resistance of 148 . The self-assembled nanobridge can be applied to form nanocontacts at relatively low temperatures. The MIG NB is a promising 1 dimensional nanoscale building block to satisfy the need of ‘self and direct’ assembled ‘bottom-up’ fabrication concepts.
Atomistic Study of the Mechanical Properties of One-Dimensional Nanomaterials
Authors: Shintani Kazuhito , Kameoka Shunji , Sato Shuhei , Kometani Yusuke 
Published: April 2011

AbstractThe mechanical properties of Au nanowires under a uniaxial load are investigated by molecular-dynamics simulation. The modified embedded-atom method (MEAM) potential is employed to calculate the interactions between Au atoms. Ten kinds of model nanowires with different cross-sections and axis directions are prepaired. The structural dependence and size effect of the Young’s moduli of Au nanowires are discussed.
Selective Chemical Vapor Growth of Carbon Nanotubes for Application of Electronic-Measuring Nano-Probes
Authors: Okuyama Hiroki , Iwata Nobuyuki , Yamamoto Hiroshi 
Published: April 2011

AbstractSelectively grown carbon nanotubes (CNTs) and/or vertically aligned CNTs (VACNTs) on patterned metal electrodes have been prepared for applications to a novel electronic-measuring nano-probe. We propose newly a position-controlling method of CNTs by controlling not only a position of catalysts but also the thickness of metal underlayers for the catalysts. The selective growth of CNTs was achieved at edges of the metal pattern by thermal chemical vapor deposition. The width of selectively grown CNTs was minimized, about 2.6 µm. The width was about 80 times as small as that of the metal pattern. VACNTs were synthesized by a plasma enhanced CVD method in which the high electric field in a cathode dark space was applied to the substrates. The VACNTs grew up, however, all over the metal pattern.
Formation of Large Bulk [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4 Glassy Alloy by Flux Melting and Water Quenching
Authors: Bitoh Teruo , Makino Akihiro , Inoue Akihisa , Greer A. Lindsay 
Published: April 2011

AbstractThe large bulk glassy [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4 alloy specimens with the diameters up to 7.7 mm have been prepared by water quenching the melt immersed in the molten flux of B2O3. The maximum diameter of the obtained specimens is approximately 1.5 times as large as the pre-vious result for copper mold casting should be cooled at the higher rate than the of water quenching. The flux melting improves the glass-forming ability by the elimination of oxides and other inclusion in the molten metal which act as heterogeneous nucleation sites for crystallization.
Multi-paradigm multi-scale modeling of dynamical crack propagation in silicon using the ReaxFF reactive force field
Authors: Buehler Markus J. , van Duin Adri C.T. , Goddard III William A. 
Published: April 2011

AbstractWe report a study of dynamic cracking in a silicon single crystal in which the ReaxFF reactive force field is used for ∼3,000 atoms near the crack tip while the other 100,000 atoms of the model system are described with a simple nonreactive force field. The ReaxFF is completely derived from quantum mechanical calculations of simple silicon systems without any empirical parameters. Our results reproduce experimental observations of fracture in silicon including details of crack dynamics for loading in the [110] orientations, such as dynamical instabilities with increasing crack velocity. We also observe formation of secondary microcracks ahead of the moving mother crack. We conclude with a study of Si(bulk)-O2 systems, showing that Si becomes more brittle in oxygen environments, as known from experiment.
Deviation of the mechanical response of Wall-patterned (001) GaAs Surface: a central-plastic-zone criterion
Authors: Le Bourhis Eric , Patriarche G. 
Published: April 2011

AbstractWall-patterned GaAs surfaces have been elaborated by photolithography and dry etching. Different surfaces were produced in order to change the aspect ratio of the walls formed at the substrate surface. The mechanical behaviour of individual walls was investigated by nanoindentation and the responses were compared to that of a standard bulk reference (flat surface). Deviation from the bulk response is detected in a load range of 0.1-25 mN depending on the aspect ratio of the walls. A central-plastic-zone criterion is proposed in view of TEM images of indented walls and allows predicting the response deviation of a given wall knowing its width. The application of substrate patterning for optoelectronic devices is proposed in the perspective of eliminating residual dislocations appearing in mismatched structures.
Solution-Processed ZnO Nanowire Network Thin Film Transistors for Transparent Electronics
Authors: Bakhishev Teymur , Volkman Steven , Subramanian Vivek 
Published: April 2011

AbstractWe describe a process to grow ZnO nanowires in aqueous solution of Hexamine and Zinc Nitrate to obtain a network of nanowires 0.5-1.5μm long. The growth was initiated on ZnO nanoparticles spun-cast onto thermal SiO2. We demonstrate bottom-gate FET structures formed using these nanowire networks as channel layers with gold (Au) and aluminum (Al) source/drain pads. Resulting transistors are well-behaved with on-off ratios >104 and mobility >10-2 cm2/V-s, calculated without accounting for actual surface coverage of nanowires. Actual nanowire mobility is therefore substantially higher, attesting to the potential for this technique as a method for realizing low-cost, high-brightness displays.
In Situ HREM Observation of Phase Transformation Process in FePt and FePtCu Nanoparticles
Authors: Nakanishi Masatoshi , Furusawa Gen-ichi , Waki Kokichi , Hattori Yasushi , Kamino Takeo , Sasaki Katsuhiro , Kuroda Kotaro , Saka Hiroyasu 
Published: April 2011

AbstractThe processes of phase transformation in individual nanoparticles of FePt and FePtCu synthesized by the reverse micelle method, which are chemically homogeneous and monodisperse, have been investigated by an in-situ HREM observation in a FE-TEM. Polycrystalline FePt particles, initially of chemically disordered face-centered cubic phase (A1) were reconstructed into A1 single crystals between 25 °C and 650 °C, followed by phase transformation from A1 to chemically ordered face-centered tetragonal phase (L10) which began between 650 °C and 680 °C. The coalescence began concurrently with phase transformation, i. e., between 650 °C and 680 °C. They turned to be a round-shaped L10 particle between 680 °C and 720 °C. The single crystal formation, the phase transformation from A1 to L10, the coalescence and the round-shaped particle formation were also observed in the FePtCu nanoparticles. The temperatures of single crystal formation, phase transformation (and coalescence) and round-shaped particle formation of the FePtCu nanoparticles were between 25 °C and 500 °C, between 550 °C and 600 °C and between 600 °C and 650 °C, respectively. These temperatures were substantially lower than those for the FePt nanoparticles.
In-situ Microscopic Study of Cu Intragranular Electromigration
Authors: Chen Kuan-Chia , Liao Chien-Neng , Wu Wen-Wei , Chen Lih-Juann 
Published: April 2011

AbstractElectromigration (EM) in unpassivated copper lines at room temperature has been investigated in ultra-high vacuum by in-situ transmission electron microscopy (TEM). The electric current induced atomic migration in a (211)-oriented Cu grain has been successfully recorded in real-time video. The atomic image of the (211) grain was found to vanish directionally when applying an electric current density of 2 × 106 A/cm2 through the Cu line. The results suggested that the combination of {111} planes and <110> directions to be the easiest EM path in crystalline copper. By performing selective area diffraction (SAD) analysis on a single Cu grain with (111) crystal orientation, some unusual electron diffraction patterns appeared after passing an electric current through the Cu line. It is believed that the EM-induced Cu twinning may be held responsible for the unique diffraction patterns
Carbon Nanotube Growth from Nanoscale Clusters Formed by Ion Implantation
Authors: Choi Yongho , Oakley Jennifer Sippel , Rinzler Andrew , Ural Ant 
Published: April 2011

AbstractWe have demonstrated that iron ions implanted into silicon dioxide thin films form nanoscale clusters which can act as catalyst for carbon nanotube growth. We have implanted iron ions with an energy of 60 keV and three different doses (1014, 1015, and 1016 cm-2) into silicon dioxide thin films thermally grown on silicon substrates. We then used chemical vapor deposition (CVD) to grow carbon nanotubes on these ion implanted substrates with methane as the precursor gas. We studied the effect of ion implantation dose on the structural properties of the nanoscale clusters, as well as the carbon nanotubes nucleated from these clusters. The nanoscale clusters and grown nanotubes were characterized by Atomic Force Microscopy and Raman spectroscopy. The electrical characteristics of the as-grown nanotubes were also characterized. We found that growth of low density, horizontal, and small diameter carbon nanotubes on silicon dioxide is possible using this nucleation technique.
Enhanced Biocompatibility of GPC by Ion Implantation and Deposition
Authors: Zimmerman Robert Lee , Gürhan Ismet , Muntele Claudiu I. , Ila Daryush , Özdal-Kurt Feyzan , Sen B. H. 
Published: April 2011

AbstractBiocompatible Glassy Polymeric Carbon (GPC) is used for artificial heart valves and in other biomedical applications. Although it is ideally suited for implants in the blood stream, tissue that normally forms around the moving parts of a GPC heart valve sometimes loses adhesion and creates embolisms downstream. Here we compare silver ion implantation and silver deposition, each of which strongly inhibits cell attachment on GPC. Inhibition of cell adhesion is a desirable improvement to current GPC cardiac implants. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that traces of silver can favorably influence the surface of GPC for biomedical applications.