bluuebunny/crossref_metadata_2025_split huggingface dataset:
TEM 3D Tomography of Noble Metal Nanowires Growth Inside SiO2 Mesoporous Aggregates
Authors: Arbiol J. , Rossinyol E. , Cabot A. , Peirò F. , Cornet A. , Morante J. R. 
Published: April 2011

AbstractThe use of bright-field transmission electron microscopy 3-D tomographic reconstruction allowed us to localize the synthesized nanostructures within the pores of mesoporous nanotemplates. Using this technique, we found that noble metal impregnation resulted in the inclusion of metal nanostructures within the SBA-15 mesoporous silica hexagonal pores (from nanoclusters to nanowires). The method allowed corroborating if the nanostructures were synthesized inside the pores or if they were alternatively on the nanotemplate aggregates exterior surface.
Defect Formation in Surface Modified TiO2 Nanostructures
Authors: Prokes S.M. , Gole James L. 
Published: April 2011

AbstractThe defect formation in surface modified TiO2 has been studied. Anatase TiO2 structures in the 3-20 nm range formed by a wet chemical technique were surface modified and nitridation of the highly reactive TiO2nanocolloid surface was achieved by a quick and simple treatment in alkyl ammonium compounds. The nitriding process was also accompanied by a metal surface coating process using electroless plating techniques, resulting in a thin metal surface layer on the modified TiO2 nanostructures. The crystal structure of the resultant TiO2-xNx nano-colloids remained anatase and the freshly prepared samples exhibited a strong light emission near 560nm (2.21 eV), which red shifted to 660 nm (1.88 eV) and dropped in intensity with aging in the atmosphere. This behavior was also evident in some of the combined nitridized and metal coated TiO2 nano-colloids. Electron Spin Resonance performed on these samples identified a resonance at g = 2.0035, which increased significantly with nitridation. This resonance is attributed to an oxygen hole center created near the surface of the nanocolloid, which correlates well with the observed optical activity.
Synthesis of Co@Au Core-Shell Nanoparticles in Non-Aqueous Solution and their Characterization
Authors: Ban Zhihui , O'Connor C. J. 
Published: April 2011

AbstractA homogeneous non-aqueous solution reactions method has been developed to prepare gold-coated cobalt (Co@Au) nanoparticles. After the sample was washed with 8% HCl, XRD (X-Ray Diffraction), TEM (transmission electron microscopy), and magnetic measurements SQUID (Superconducting Quantum Interference Device) are utilized to characterize the nanocomposites. XRD shows the pattern of sample, which is responding to gold and cobalt, no cobalt oxide was found. TEM results show that the average size of Co@Au nanoparticles is about 10 nm and we can find core-shell structure of the sample. SQUID results show that the particles are ferromagnetic materials at 300K. So the gold- coated cobalt nanoparticles (Co@Au) can be successfully prepared by the homogeneous nonaqueous approach. This kind of core-shell materials is stable in acid condition, which would give many opportunities for bio- application.
Finite-Size Effects and Surface-Enhanced Raman Scattering in Noble-Metal Nanoparticles
Authors: Pustovit Vitaliy N. , Shahbazyan Tigran V. 
Published: April 2011

AbstractWe study the role of a strong electron confinement on the surface-enhanced Raman scattering from molecules adsorbed on small noble-metal nanoparticles. We describe a novel enhancement mechanism which originates from the different effect that confining potential has on s-band and d-band electrons. We demonstrate that the interplay between finite-size and screening efects in the nanoparticle surface layer leads to an enhancement of the surface plasmon local field acting on a molecule located in a close proximity to the metal surface. Our calculations show that the additional enhancement of the Raman signal is especially strong for small nanometer-sized nanoparticles.
Growth of Co Nanoclusters on SiC Honeycomb Templates
Authors: Chen Wei , Loh Kian Ping , Xu Hai , Wee A.T.S. 
Published: April 2011

AbstractA honeycomb-like SiC reconstructed surface with regular, periodic porosity in the nano-scale range has been used as an effective template for the formation of monodispersed Co nanoclusters. In-situ scanning tunneling microscopy (STM) was used to study the nucleation process of the Co nanoclusters on this template. The deposition of Co at different substrate temperature was investigated by STM. It is found that the failure in the deposition of Co nanoclusters on the SiC honeycomb template with substrate temperatures higher than room temperature (RT) might be due to the high desorption rate of the adsorbed Co atoms.
Atomistic Simulations of fcc Pt75Ni25 and Pt75Re25 Cubo-octahedral Nanoparticles
Authors: Wang Guofeng , Van Hove M.A. , Ross P.N. , Baskes M.I. 
Published: April 2011

AbstractWe have developed interatomic potentials for Pt-Ni and Pt-Re alloys within the modified embedded atom method (MEAM). Furthermore, we applied these potentials to study the equilibrium structures of Pt75Ni25 and Pt75Re25 nanoparticles at T=600 K using the Monte Carlo method. In this work, the nanoparticles are assumed to have disordered fcc cubo-octahedral shapes (terminated by {111} and {100} facets) and contain from 586 to 4033 atoms (corresponding to a diameter from 2.5 to 5 nm). It was found that, due to surface segregation, (1) the Pt75Ni25 nanoparticles form a surface-sandwich structure: the Pt atoms are enriched in the outermost and third atomic shells, while the Ni atoms are enriched in the second atomic shell; (2) the equilibrium Pt75Re25 nanoparticles adopt a core-shell structure: a Pt-enriched shell surrounding a Pt-deficient core.
Molecular-Dynamics Study of the Structural Dependence of the Young Modulus of Au Nanowires
Authors: Kameoka S. , Shintani K. 
Published: April 2011

AbstractThe deformation of Au nanowires of helical multi-shell (HMS) structures and the fcc structure under a tensile external force is addressed by molecular-dynamics simulation. The modified embedded-atom method (MEAM) potential is employed for calculating the interaction between Au atoms. At first, a model nanowire is equilibrated at a specified temperature. Next, the external force in the axial direction is imposed on the Au atoms at the ends of the nanowire. We conclude that the Young modulus of a Au nanowire depends on its atomic structure.
Room-Temperature Lasing Characteristics of Zinc Sulfide Single Nanoribbons
Authors: Zapien J. A. , Jiang Y. , Meng X.-M. , Chen W. , Lifshitz Y. , Lee S.-T. 
Published: April 2011

AbstractWe present a study of the photoluminescence and lasing characteristics of individual single-crystal zinc sulfide nanoribbons. We show that ZnS presents optical gain at the near band gap emission of ∼338 nm. Optical gain together with the optical cavity defined by the perfect crystallographic structure with a rectangular cross section results in lasing activity at optical pumping power densities of ∼ 50 kW/cm2. Small collection angle measurements show that nanoribbons form excellent optical cavities and gain medium with record (FWHM<0.1nm) lasing modes free of PL background. Large collection angles (as previously employed for nanowire measurements) add a broad, non-resonant PL component and obscure the original high-quality lasing of the nanowires/nanoribbons.
Controlling the Growth Direction of ZnO Nanowires on c-Plane Sapphire
Authors: Nikoobakht Babak , Davydov Albert , Stranick Stephan J. 
Published: April 2011

AbstractWell oriented vertical ZnO nanowires (NWs) are grown on c-plane sapphire via a vapor- phase transport process using an Au thin film as a catalyst. This new finding is unexpected due to the fact that the lattice mismatch between the zinc oxide and the underlying substrate is 18%. X- ray diffraction (XRD) analysis shows that single-crystal, wurtzite NWs grow in the [0001] direction normal to the basal sapphire plane, which proves that a-plane sapphire is not essential for growth of vertical ZnO NWs, as has been previously stated.[1] We have found that by controlling the thickness of the Au-film and pre-growth annealing of the Au/sapphire substrate NWs can be grown either tilted or vertical. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies on Au films with thicknesses ranging from 1 to 10 nm show that in the absence of film annealing, NWs can be grown 32° tilted from the surface normal, whereas pre-annealed Au films result in growth of NWs in the surface normal direction. We attribute the formation of the normal and tilted growth directions to the surface concentration of O and Al ions on sapphire.
Targeting Magnetic Nanoparticles in High Magnetic Fields for Drug Delivery Purposes
Authors: Asmatulu Ramazan , Claus Richard.O. , Riffle Judy S. , Zalich Michael 
Published: April 2011

AbstractBiodegradable magnetic nanoparticles were synthesized using Poly(L-Lactic Acid) and magnetite nanoparticles (∼14 nm) at different dosages, and then these nanaoparticles (nanocomposites) and pure magnetic particles were targeted in external magnetic fields by changing the test parameters. The magnetic field test results showed that magnetic saturation, fluid speed, magnetic field distance and particle size were extremely effective for a magnetic guidance system that is needed for an effective drug delivery approach. Thus, it is assumed that such nanoparticles can carry drugs (chemotherapy) to be able to cure cancer tumors as well as many other diseases.
Carbon Nanotube-Based Permeable Membranes
Authors: Holt Jason K. , Park Hyung Gyu , Bakajin Olgica , Noy Aleksandr , Huser Thomas , Eaglesham David 
Published: April 2011

AbstractA membrane of multiwall carbon nanotubes embedded in a silicon nitride matrix was fabricated for use in studying fluid mechanics on the nanometer scale. Characterization by fluorescent tracer diffusion and scanning electron microscopy suggests that the membrane is void-free near the silicon substrate on which it rests, implying that the hollow core of the nanotube is the only conduction path for molecular transport. Assuming Knudsen diffusion through this nanotube membrane, a maximum helium transport rate (for a pressure drop of 1 atm) of 0.25 cc/sec is predicted. Helium flow measurements of a nanoporous silicon nitride membrane, fabricated by sacrificial removal of carbon, give a flow rate greater than 1×10-6 cc/sec. For viscous, laminar flow conditions, water is estimated to flow across the nanotube membrane (under a 1 atm pressure drop) at up to 2.8×10-5 cc/sec (1.7 μL/min).
Integrating Carbon Nanotubes For Atomic Force Microscopy Imaging Applications
Authors: Ye Qi , Cassell Alan M. , Liu Hongbing , Han Jie , Meyyappan Meyya 
Published: April 2011

AbstractCarbon nanotube (CNT) related nanostructures possess remarkable electrical, mechanical, and thermal properties. To produce these nanostructures for real world applications, a large-scale controlled growth of carbon nanotubes is crucial for the integration and fabrication of nanodevices and nanosensors. We have taken the approach of integrating nanopatterning and nanomaterials synthesis with traditional silicon microfabrication techniques. This integration requires a catalyst or nanomaterial protection scheme. In this paper, we report our recent work on fabricating wafer-scale carbon nanotube AFM cantilever probe tips. We will address the design and fabrication considerations in detail, and present the preliminary scanning probe test results. This work may serve as an example of rational design, fabrication, and integration of nanomaterials for advanced nanodevice and nanosensor applications.
Novel Chemical Approach to Achieve Advanced Soft Lithography by Developing New Stiffer, Photocurable PDMS Stamp Materials
Authors: Choi Kyung M. , Rogers John A. 
Published: April 2011

AbstractRecent advances in microfabrication technology allow us to develop a number of novel devices with high performance. In microfabrication technology, a new development, ‘soft lithography’, is widely used by making stamps, molding, and microcontact-printing due to the low cost and easy processability. The resolution of soft lithography significantly relies on the performance of stamping materials. However, pattern transfers using commercially available PDMS stamp materials often end up with mechanical failures such as collapse or sag due to their low physical stiffness. Additionally, most of those commercial PDMS materials are thermally curable systems, which results in significant thermal deformations. These limitations have motivated us to start this work, which demonstrates a ‘chemical approach’ to overcome those limits by developing new stiff, photocurable PDMS stamp materials with attached designed functionalities. Molecular modification of PDMS materials results in advanced soft lithography, which produces enhanced physical toughness, lower polymerization shrinkage, and photopatterning capability.
A Multi-layer Technology for Biocompatible Polymer Microsystems with Integrated Fluid and Electrical Functionality
Authors: Moss Eileen D. , Han Arum , Frazier A. Bruno 
Published: April 2011

AbstractA method to fabricate biocompatible polymer microfluidic systems with integrated electrical and fluid functionality has been established. The process flow utilizes laser ablation, microstenciling, and heat staking as the techniques to realize multi-layered polyimide based microsystems with microchannels, thru and embedded fluid / electrical vias, and metallic electrodes and contact pads. As an application of the fabrication technology, a six layer multi-functional cellular analysis system has been demonstrated. The electrophysiological analysis system contains fluid microchannel / via networks for cell positioning and chemical delivery as well as electrical detectors and electrodes for impedance spectroscopy and patch clamping studies. Multiple layers of 50.8µm thick Kapton® sheets with double-sided polyimide adhesive layers were used as the primary material-of-construction. Microchannels with widths of 400µm as well as thru hole vias with 3.71µm diameters (aspect ratios of over 12:1) were laser ablated through the polyimide sheets using an excimer laser and a CO2laser. Electrical traces and contact pads with features down to 20µm were defined on the flexible polyimide sheets using microstenciling. The patterned layers were bonded using heat staking at a temperature of 350°C, a pressure of 1.65MPa for 60 minutes. This multi-layer technology can be used to create microfluidic devices for many application areas requiring biocompatibility, relatively high temperature operation, or a flexible substrate material.
Tuning the Mechanical Properties of Poly-silicon Film by Surface Modification Using Plasma Treatment
Authors: Su Wang-Shen , Fang Weileun , Tsai Ming-Shih 
Published: April 2011

AbstractThe mechanical properties of thin film are very critical for the performance of MEMS devices. Since Poly-silicon film is of great use in MEMS, this study investigates the surface modification by various plasma treatments to finely tune the chemical and mechanical properties of poly-silicon film. Various plasma treatments, including H2, O2, and NH3, were implemented to modify the original Si-Si film bonding, Young's modulus, and hardness of poly-silicon film. These were significant Si-O, Si-OH/Si-H and Si-NH2/Si-N bonds formed after O2, H2 and NH3 plasma treatment, respectively. According to the H analysis from SIMS depth profile of, the thickness of surface modified layer would be ranged from 50 to 120 nm. In summary, the surface modification with H2 plasma can reduce the elastic modulus of poly-silicon film for about 32.3%; moreover, the following vacuum annealing will further reduce the elastic modulus for about 60.2%. Therefore, surface modification with an adequate plasma treatment would be an effective method to change the chemical and mechanical properties of poly-silicon film.
Fabrication of Ordered Sub-Micron Topographies on Large-Area Poly(Urethane Urea) by Two-Stage Replication Molding
Authors: Milner Keith R. , Balmer Mallory , Donahue Henry J. , Snyder Alan J. , Siedlecki Christopher A. 
Published: April 2011

AbstractIt has been established that material surface topography can have a significant effect on biological cell adhesion, in the absence of changes in surface chemistry. Such investigations were typically performed using surface features with size on the order of microns, comparable to the dimensions of the cells. It has been demonstrated that sub-micron sized topographies that cannot be created via contact lithography also influence cell behavior. The ability to affect cell adhesion is a prime consideration in the development of novel biomaterials. This study reports a two-stage replication molding process for fabricating ordered sub-micron sized features over a large area of biomedical polyether(urethane urea). Such a technique has great applicability in the area of long-term implantable materials as a method for influencing cell-material interactions.
Formation of Three Dimensional Ni Nanostructures for Large Area Catalysts
Authors: Carey J. D. , Henley S. J. , Mendoza E. , Giusca C. E. , Adikaari A. A. D. T. , Silva S. R. P. 
Published: April 2011

AbstractThe formation of Ni nanostructures to act as catalysts in the growth of carbon nanotubes is reported. The changes in the surface morphology of Ni produced by three methods - thermal evaporation and annealing of thin films, pulsed laser ablation and annealing of Ni, and the use of metal containing macromolecules - have been investigated by atomic force microscopy and scanning electron microscopy. In the case of thermal annealing of thin metal films in the temperature range 300-500°C we observe an increase in the mean diameter of the islands formed, accompanied by a reduction in the mean island density with increasing temperature. We attribute this effect to mass transport of weakly bound individual Ni atoms and/or small island clusters across the surface to form larger isolated islands, in a process similar to Ostwald ripening. Using a pulsed KrF excimer laser for ablation of a Ni target we show that nanometre smooth Ni thin films can be produced provided a sufficient number of laser shots is used. The surface morphology of these smooth films can then be altered by laser annealing to form Ni droplets. It is found that the mean diameter of the Ni droplets depends not only on the initial Ni thickness but also the laser fluence. It is also found that the nanostructuring of the film depends on the presence of an oxide under layer, with a higher fluence required on thinner oxides and no nanostructuring observed on bare Si. Finally, we show that Ni nanostructuring can be formed by suitable annealing of a Ni containing aqueous dendrimer solutions.
Debonding Under Fatigue Loading at Polymer/Inorganic Interfaces
Authors: Sharratt Bree M. , Dauskardt Reinhold H. 
Published: April 2011

AbstractThe mechanisms associated with cycle-by-cycle damage accumulation resulting in fatigue crack propagation between a highly constrained polymer layer and an adjacent elastic substrate are explored. Specifically, cyclic fatigue-induced crack growth between a bisphenol F model epoxy system and a passivated silicon substrate under Mode I loading is reported. Preliminary findings regarding the effects of fatigue load ratio on interfacial crack growth rates are presented. While intermediate crack growth rates were significantly accelerated under cyclic loading, the near-threshold crack growth behavior under cyclic and monotonic loading was surprisingly similar.
Testing Multiwall Carbon Nanotubes on Ion Erosion for Advanced Space Propulsion
Authors: Yap Yoke Khin , Menda Jitendra , Vanga Lakshman Kumar , Kayastha Vijaya , Wang Jiesheng , King Lyon B. , Dimovski Svetlana , Gogotsi Yury 
Published: April 2011

AbstractAre carbon nanotubes more resistant than diamonds against ion erosion? Here, we report an evaluation of multiwall carbon nanotubes (MWNTs) as the protective coating against plasma erosion in advanced space propulsion systems. We have compared polycrystalline diamond films with MWNTs, amorphous carbon (a-C) and boron nitride (BN) films. Two types of MWNTs were investigated including vertically aligned (VA) MWNTs, and those horizontally laid on the substrate surfaces. Only diamond films and VA-MWNTs survived erosion by 250 eV krypton ions of a flight-quality Hall-effect thruster. VA-MWNTs are found to bundle at their tips after ion erosion.
Twin Boundaries and Stacking Faults in Monazite (Monoclinic LaPO4)
Authors: Hay Randall S. 
Published: April 2011

AbstractMonazite (LaPO4) was indented at room temperature. Deformation twin boundaries and stacking faults were characterized by high resolution transmission electron microscopy. Kinked deformation twins were also characterized and analyzed. Three types of stacking faults associated with climb-dissociated partial dislocations were observed. Two were found on twin boundaries, and a third in the lattice. Formation mechanisms are discussed. The superimposition of stacking faults along twin boundaries during deformation twinning and the glide of climb-dissociated partial dislocations allowed by stacking fault migration are discussed. The possible relationship between the formation mechanisms for these defects and the low- temperature recrystallization and self-annealing of defects in monazite is considered.
The Mechanical Properties in the Vicinity of Grain Boundaries in Ultrafine-Grained and Polycrystalline Materials Studied by Nanoindentations
Authors: Schweitzer E. , Durst K. , Amberger D. , Göken M. 
Published: April 2011

AbstractThe strength of structural materials strongly depends on the structure and properties of grain boundaries. Interfaces usually act as barriers to dislocation motion and therefore strengthen materials with decreasing grain size, quantitatively described by the well-known Hall-Petch relation. However, interfaces in nanocrystalline materials are often covered with impurities or second phases, which may influence the mechanical properties. With nanoindentation testing it is now possible to probe the strength of interfaces like grain boundaries directly on a nanometer scale. Therefore this method was used to investigate the properties in the vicinity of grain boundaries in polycrystalline materials with conventional grain size and in ultrafine-grained metals prepared by equal channel angular pressing (ECAP), where no impurities are introduced during processing. Measurements on an austenitic steel clearly show a decreasing hardness close to the interface opposite to the general expected behavior of strengthening. In this case segregation effects strongly influence the mechanical properties near the boundaries. The nanoindentation investigations on ultrafine-grained Al and Cu show a strong strain rate sensitivity. Inelastic effects are also found between unloading-loading segments during indentations.
Bimodal Microstructures in Nanocrystalline Al and Al-Mg Alloy Powders Prepared by Cryogenic Ball Milling
Authors: Zhou F. , Lee Z. , Lavernia E. J. , Nutt S.R. 
Published: April 2011

AbstractThe microstructures of nanocrystalline Al and Al-7.6 at% Mg alloy powders processed by cryogenic ball milling (i.e., cryomilling) and subsequent thermal annealing were characterized using transmission electron microscopy. The as-milled samples primarily consisted of equiaxed grains with average sizes of ∼ 26 nm. The annealing treatments at elevated temperatures resulted in bimodal grain-size distributions, with sub-micrometer-sized grains embedded in a matrix of nanocrystalline (<50 nm) grains. The bimodal microstructures were formed during the processes of recovery and recrystallization.