bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fatigue Microdamage in Bovine Cortical Bone Imaged by Micro-Computed Tomography Using a Barium Sulfate Contrast Agent
Authors: Leng Huijie , Wang Xiang , Niebur Glen L , Roeder Ryan K 
Published: April 2011

AbstractAccumulation of microdamage during fatigue can lead to increased fracture susceptibility in bone. Current techniques for imaging microdamage in bone are inherently destructive and two-dimensional. A non-destructive, three-dimensional technique is needed to measure the spatial density of microdamage accumulation. Therefore, the objective of this study was to image microdamage accumulation in cortical bone during fatigue using micro-computed tomography (micro-CT) with a barium sulfate (BaSO4) contrast agent. Bovine cortical bone beams were loaded under four-point bending fatigue. Two symmetric notches were machined on the tensile surface in order to generate damage at the stress concentrations during loading. Specimens were loaded to a specified number of cycles or until one notch fractured, such that the other notch exhibited accumulated microdamage just prior to fracture. Microdamage ahead of the notch was stained by precipitation of BaSO4 and imaged using micro-CT. Reconstructed images showed a distinct region of bright voxels around the notch tip or along propagating cracks due to the presence of BaSO4, which was verified by backscattered electron imaging and energy dispersive spectroscopy. The stained region exhibited a characteristic kidney shape perpendicular to the notch tip, which was correlated to principal strain contours calculated by finite element analysis. The area of stained regions was positively correlated with the number of loading cycles.
Electrochemical Dip-Pen Nanolithography of Conductive Wires
Authors: Zhang Fapei , Yamada Ryo , Tada Hirokazu 
Published: April 2011

AbstractWe have explored the fabrication of conductive nanowires on different types of substrates by electrochemistry-assisted DPN (E-DPN) with an atomic force microscope. Various parameters of E-DPN were examined systematically including the effects of coating methods and the types of the tips on the electrodeposition behavior. It was found that a chemically-modified Si AFM tip is very suitable for E-DPN. Platinum and polyaniline nanowires with a line width of ca.100 nm to sub- 100 nm were prepared on the metallic (Au) and semiconducting (Si) surfaces. The parameters indispensable for E-DPN of metal and polymer nanowires on an insulating SiO2 surface will also be discussed.
Synthesis of Hybrid Colloids Through the Growth of Polystyrene Latex Particles onto Methacryloxy methyl triethoxysilane - Functionalized Silica Particles
Authors: Perro Adeline , Reculusa Stéphane , Bourgeat-Lami Elodie , Duguet Etienne , Ravaine Serge 
Published: April 2011

AbstractOne area of particular effort recently is the use of colloidal particles as precursors in engineering new materials. Nevertheless, these particles are nearly always spheres. This places limitations on the structures that can be built, especially in making photonic-bandgap materials. Therefore, it is a great challenge to create new colloids with an original shape, i.e. different from the sphere, in a controllable manner.We present here an original approach to create hybrid organic-inorganic colloidal particles with a perfect controlled shape. The synthetic route of these structures, which are composed of spherical silica spheres surrounded by a varying number of polystyrene beads, consists in the emulsion polymerization of styrene in presence of silica particles, which had been surface-modified by a coupling agent containing polymerizable groups.The influence of the size of the silica particle and of the nature of the coupling agent on the resulting colloidal particles morphologies was carefully analyzed. We show in particular that the number of growing polystyrene beads varies homogeneously with the diameter of the mineral spheres. A main advantage of this technique is also that we can precisely control the reaction time, allowing us to tune the final morphology of the hybrid structures. These colloidal assemblies are original building blocks for the elaboration of new functional materials.
Production and Properties of Glass Fibre-Reinforced Polymer Composites with Nanoparticle Modified Epoxy Matrix
Authors: Wichmann Malte H.G. , Gojny Florian H. , Sumfleth Jan , Fiedler Bodo , Schulte Karl 
Published: April 2011

AbstractIncreasing the mechanical performance, e.g. strength, toughness and fatigue properties of composites is the objective of many ongoing research projects. Nanoparticles, e.g. carbon nanotubes (CNTs) and fumed silica provide a high potential for the reinforcement of polymers. Their size in the nanometre regime make them suitable candidates for the reinforcement of fibre reinforced polymers, as they may penetrate the reinforcing fibre-network without disturbing the fibre-arrangement.In this work, glass fibre-reinforced epoxy composites with nanoparticle modified matrix systems were produced and investigated. GFRPs containing different volume fractions of the nanofillers were produced via resin transfer moulding. Matrix dominated mechanical properties of the GFRP laminates could be improved by the incorporation of nanoparticles. The addition of only 0.3 wt.% CNTs to the epoxy matrix increased the interlaminar shear strength from 33.4 to 38.7 MPa (+16%). Furthermore, the application of electrically conductive nanoparticles enables the production of conductive nanocomposites. This offers a high potential for antistatic applications and the implementation of functional properties in the composite structures. The effects of different filler types and volume fractions on the electrical properties of the GFRPs were investigated. GFRPs containing 0.3 wt.% of CNTs, for example, exhibit an anisotropic electrical conductivity. Furthermore, an electrical field was applied to the composites during curing. The effects on the resulting electrical and mechanical properties are discussed.
Self-assembled Nanoline Template for Growth of Nanoparticles and Nanowires on Si(001)
Authors: Owen James Hugh Gervase , Miki Kazushi 
Published: April 2011

AbstractLong, straight self-assembled nanolines of Bismuth are used as an atomic-scale non-lithographic template for the deposition of different metals. The Bi nanolines are 15 Å wide and can grow to lengths exceeding 1μm, limited only by the substrate terraces. We describe the method of formation of these templates, and demonstrate strongly preferential adsorption of different metals. We observe both wetting behaviour, in which elongated metal islands form nanowires along the template, and nonwetting behaviour, in which arrays of metal clusters of uniform size are produced.
Metal Organic Chemical Vapor Deposition Growth of GaN and GaMnN Multifunctional Nanostructures
Authors: Gupta Shalini , Kang Hun , Kane Matthew , Fenwick William E , Li Nola , Strassburg Martin , Asghar Ali , Dietz Nikolaus , Ferguson Ian T 
Published: April 2011

AbstractQuantum dots (QDs) have been shown to improve the efficiency and optical properties of opto- electronic devices compared to two dimensional quantum wells in the active region. The formation of self-assembled GaN nanostructures on aluminum nitride (AlN) grown on sapphire substrates by Metal Organic Chemical Vapor deposition (MOCVD) was explored. This paper reports on the effect ofin-situactivation in nitrogen atmosphere on MOCVD grown GaN nanostructures. The effect of introducing manganese in these nanostructures was also studied. Optically active nanostructures were successfully obtained. A blue shift is observed in the photoluminescence data with a decrease in nanostructure size.
Reflectance spectroscopy of single photonic crystal island fabricated by ink-jet printing
Authors: Wang Dake , Park Minseo , Park Jungho , Moon Jooho 
Published: April 2011

AbstractA micro-reflectance spectroscopy was performed on a single island of photonic crystal array. An array of islands of photonic crystal with colloidal polystyrene beads was assembled on Si using ink-jet printing. The polystyrene colloids with three different sizes (190 nm, 210 nm, and 270 nm in diameter) were used and the polystyrene colloidal particles were self-assembled to form fcc lattices with three different lattice spacing. It was observed from the reflectance spectra that the position of the optical stop band shifts as the size of the colloidal particle changes. Effective medium approximations were used to model the dielectric properties of the colloid/air composite. The theoretically expected reflectance peak position agrees well with those of the experimentally observed peaks. The effect of finite size of the photonic crystal island on its reflectance spectroscopy was investigated by comparing the reflectance spectra collected from four different photonic crystal islands assembled from the same polystyrene colloidal particles, but with different lateral size for each island. It was found that the primary reflection peak was broadened and its intensity was reduced when the lateral size of the island was decreased.
Engineering Three Dimensional Nanotextured Opal-Like Silica Foams
Authors: Carn Florent , Massé Pascal , Ravaine Serge , Backov Rénal 
Published: April 2011

AbstractNovel meso-/macroporous SiO2 monoliths have been reached by applying a nanotectonic pathway within a confined geometry, i.e. a non-static air-liquid foam patterning process. Final scaffolds are a very close transcription of the tailored periodic air-liquid foam template while coalesced silica particles are texturing the as-synthesized foam walls. The interconnected nanoparticles and associated void space between adjacent particles allow generating intrinsic mesopores, thereby defining hierarchically organized porous scaffolds. The good control over both the air-liquid foam’s water volume fraction and the bubble size allow a rational tuning of the macropore shape (diameter, Plateau border’s width). In contrast with previous study, closed-cell structures can be reached, while the opal like scaffold structure is maintained with thermal treatment, avoiding thus strong shrinkage associated to the sintering effect.
Submicrometer-Sized Polystyrene Particles Packing on Silicon Microfabricated Substrate
Authors: Tanaka Manabu , Shimamoto Naonobu , Tanii Takashi , Ohdomari Iwao , Nishide Hiroyuki 
Published: April 2011

AbstractThe Packing of submicrometer-sized polystyrene particle within micro-boxes; micrometer-sized squarely recessed pits, was achieved using silicon microfabricated substrates and a simple dipping and pulling-up process. A special phenomenon, cubic packing structures of the particles, was observed when using a micro-box substrate with a few times larger side-length than the particle diameters. Several particle packing structures within different sized micro-boxes were demonstrated, and the relationship between the particle packing structures and micro-box sizes were discussed.
Properties of Chemically Modified Carbon Nanotubes
Authors: Kumashiro Ryotaro , Ohashi Hirotaka , Akasaka Takeshi , Maeda Yutaka , Takaishi Shinya , Yamashita Masahiro , Maruyama Shigeo , Izumida Takeshi , Hatakeyama Rikizo , Tanigaki Katsumi 
Published: April 2011

AbstractElectric transport properties of chemically modificated carbon nanotubes (CNTs) using Si-containing organic molecules were investigated by means of the field effect transistors (FETs) technique. From the results of FET measurements, it was shown that p-type semiconducting CNTs can be converted to n-type ones by exohedral silylation. It is suggested that the electron carrier are doped into CNTs from the additional silyl groups, that is, the electronic properties of CNTs can be controlled by chemically modifications of outer surface.
An atom probe tomography study of grain boundary segregation in nanocrystalline Ni-W
Authors: Detor Andrew , Miller Michael K. , Schuh Christopher A. 
Published: April 2011

AbstractAtom probe tomography is used to observe the solute distribution in electrodeposited nanocrystalline Ni-W alloys with three different grain sizes (3, 10, and 20 nm) and the results are compared with atomistic computer simulations. The presence of grain boundary segregation is confirmed by detailed analysis of composition fluctuations in both experimental and simulated structures, and its extent quantified by a frequency distribution analysis. In contrast to other nanocrystalline alloys, the present Ni-W alloys exhibit only a subtle amount of solute segregation to the intergranular regions. This finding is consistent with quantitative predictions for these alloys based upon a thermodynamic model of grain boundary segregation.
Dislocation Instability in Nanoscale Particles
Authors: Carlton Christopher , Ferreira Paulo 
Published: April 2011

AbstractUnderstanding the mechanical behavior of nanoparticles has become a key factor for the success of many engineering applications. Classically, for polycrystalline materials one would expect an increase in the yield strength for smaller grain sizes according to the empirical Hall-Petch equation. However, at the nanoscale, this mechanism seems to break down. Despite the number of interesting papers published on this topic, controversy persists and consensus is still lacking. While this discussion is of great interest for polycrystalline nanoparticles, contemporary models for strengthening are inappropriate for single-crystal nanoparticles, which, altogether, pose a very different problem: the absence of grain boundaries to inhibit dislocations. In this context, we present a new model wherein the change in Gibbs Free Energy of an edge dislocation in a single-crystal particle provides a driving force for dislocation motion. These results show that dislocations become unstable and are spontaneously ejected from the particles below a certain critical size.
Mechanical Behavior of Multi-Principal-Element Fe0.71Cr1.48Al0.38Ni1.42Co Alloy
Authors: Wang Woei-Ren , Chen Hung-Cheng , Lai Jiun-Hui , Tu Chin-Pang , Sheu Tsing-Shien 
Published: April 2011

AbstractThe conventional concept of alloy design is based on the principal metallic element (>40 at.%); therefore, it is novel and challenging for a new alloy design to synthesize several (5∼7) principal elements (each <35 at.%), i.e. equal or near-equal molar ratio. With the design concept of multi-principal-element alloy, this paper will present the mechanical behaviors and workability of this alloy, Fe0.71Cr1.48Al0.38Ni1.42Co in molar ratio. The alloy possessed the simple FCC crystal structure even though these elements come from three categories of crystalline structures, FCC, BCC and HCP. The hardness can also reach 367(Hv) after precipitated treatment at 700°C for 24 Hr.. Meanwhile, the ultimate tensile strength (UTS) of Fe0.71Cr1.48Al0.38Ni1.42Co can be elevated to 1112 MPa as almost triple as the original sample, and the elongation rate can be kept at 20%.
A Mother-Daughter Mechanism of Mode I cracks: Supersonic Crack Motion Along Interfaces of Dissimilar Materials
Authors: Buehler Markus J. , Gao Huajian 
Published: April 2011

AbstractIn this paper we summarize recent progress in applying large-scale atomistic studies of crack dynamics along interfaces of dissimilar materials. We consider two linear-elastic material strips in which atoms interact with harmonic potentials, with a different spring constant in each layer leading to a soft and a stiff strip. The two strips are bound together with a weak potential whose bonds snap early upon a critical atomic separation. An initial crack serves as initiation point for the failure. We will focus on the maximum speed of mode I loaded cracks along such a biomaterial interface. Upon nucleation of the crack, it quickly approaches a velocity a few percent larger than the Rayleigh-wave speed of the soft material. After a critical time, we observe that a secondary crack is nucleated a few atomic spacings ahead of the crack. This secondary crack propagates at the Rayleigh-wave speed of the stiff material. If the elastic mismatch is sufficiently large, the secondary crack can be faster than the longitudinal wave speed of the soft material, thus propagating supersonically. Supersonic crack motion is clearly identified by two Mach cones in the soft material. This suggests that mother-daughter mechanisms, formerly only reported in mode II cracks in homogeneous materials, play an important role in interfacial mode I crack dynamics. The studies reported in this paper exemplify the usage of large-scale atomistic simulation to investigate the physics of fracture.
Unit Shearing Events in Plasticity of Amorphous Silicon
Authors: Demkowicz Michael J. , Argon Ali S. 
Published: April 2011

AbstractPlasticity in amorphous silicon (a-Si) as modeled by the Stillinger-Weber (SW) potential was investigated using structure relaxation by potential energy minimization. Irreversible stress drops in the observed mechanical response are the source of plastic deformation in this model directionally bonded material. Every such stress drop was found to be accompanied by atomic rearrangements that give evidence of the existence of unit inelastic shearing events that are characteristic of a-Si and account for plasticity in this material.
Fractal Dimension for Ceramic Fracture Surface
Authors: Bielecki Jerzy , Kotowski Piotr 
Published: April 2011

AbstractAn investigation of an influence of loading parameters on fractal dimension of electrotechnical ceramics fracture has been presented. Investigation objects were samples made of C110 and C130 ceramics. Specimens were breaking under cyclic and static loading conditions. To estimate fractal characteristics a method used for metals fracture had been adapted. Fractal dimensions were estimated for profiles obtained by the vertical cross section method. Obtained results show that fractal dimension does not characterises the material. That dimension does not characterises loading conditions, as well.
Indentation Crystallization and Phase Transformation of Amorphous Germanium
Authors: Patriarche G. , Le Bourhis E. , Khayyat M.M. , Chaudhri M.M. 
Published: April 2011

AbstractIt has been known for about 15 years that when a Vickers indenter is loaded on to a crystalline semiconductor, such as silicon, a semiconductor to metallic phase transition occurs during indenter loading and on removal of the indenter the material within the residual indentation becomes amorphous. Here we report on a completely opposite effect: when a Berkovich or Vickers diamond indenter is loaded on to a submicrometre thick film of amorphous germanium, it densifies, crystallizes and undergoes structural phase transitions. These observations are based on transmission electron microscopy and Raman scattering investigations. It has also been shown that the indentation-induced crystallization and phase transitions occur close to the indenter tip, where the plastic strains are the highest.
Deformation Mechanisms in Refractory Rare-Earth Phosphates
Authors: Hay Randall , Mogilevsky Pavel 
Published: April 2011

AbstractA method for prediction of deformation twin modes from analysis of the necessary atomic shuffles was developed for monazite (monoclinic LaPO4). This method is applied to scheelite (tetragonal CaWO4), xenotime (tetragonal YPO4), and zircon (tetragonal ZrSiO4). The predictions are compared to observations in these materials. Merit of the predictive method is discussed.
Nanoscale Measurements in Organic Memory Devices from C60 in Insulating Polymers
Authors: Kanwal Alokik , Chhowalla Manish 
Published: April 2011

AbstractFollowing our pervious works demonstrating all-organic memory devices based on a nanocomposite material consisting of C60 molecules dispersed in an insulating polymer. In this paper, we will report on conducting atomic force microscopy (c-AFM) measurements from nanosized regions on memory devices. The c-AFM nanoscale measurements show a hysteresis of high and low conductance states, in agreement with our previous reports on macroscopic memory devices. The c-AFM measurements were verified by 30nm gap cell devices fabricated via e-beam lithography, which also showed similar current values. Analysis of our data reveals that the conduction mechanism switches from direct tunneling to Fowler-Nordheim tunneling above a threshold voltage.
Two-Dimensional Carbon Nanotube Networks: A Transparent Electronic Material
Authors: Gruner George 
Published: April 2011

AbstractThe random, two-dimensional network formed of electrically conducting nanoscale wires, called carbon nanotubes, is a transparent electronic material that can be fabricated using room-temperature printing or spraying technologies. Depending on the network density, networks with both metallic- and semiconducting-like attributes can be fabricated. Both display high conductivity, high carrier mobility and optical transparency. The networks also have high mechanical flexibility, robustness and environmental resistance. Application opportunities range from lightweight, transparent conducting films, to electrically conducting fabrics, to active electronic devices and sensors.
Free-standing Diamond Single Crystal Film for Electronics Applications
Authors: Yang Jie , Huang Weixiao , Chow T. P. , Butler James E. 
Published: April 2011

AbstractHigh quality single crystal diamond film is an excellent transparent semiconductor material. Combined with its good electrical, optical, thermal and chemical properties, diamond-based semiconductor devices offer the potential of operation at very high voltages (>10 kV), power levels, and temperatures (>400°C) and under extreme radiation conditions.In this paper, we exploit the optical transparent property of MPCVD single crystal diamond films to correlate the quality of the epi-layers with the performance of Schottky barrier diodes fabricated on the layer. We used optical microscopy to observe stress induced birefringence caused by defects/dislocations in the material and micro- Raman/photoluminescence to detect relative amounts of non-diamond carbon and color centers (nitrogen and silicon atom complexes with lattice vacancies) in the material. High structural quality (low stress) is correlated with the properties of Schottky barrier diodes fabricated in the material. Vertical devices made from a 20 µm homo-epi-layer have been shown high breakdown fields of 1.85 MVcm-1 (BV = 3.7 kV) and conduction of 0.6 A/cm2 at 20V forward drop at 290 °C. Through device failure analysis, we can conclude that the 1.85 MVcm-1 field is only a lower limit for the material. Local stresses (dislocations) and point defects appear to be the main reasons for the high voltage failure of our single crystal diamond rectifiers.
Four-probe Magnetoresistance of Current-perpendicular-to-plane Structures
Authors: Zhou Hua , Covington Mark W. , Seigler Michael A. 
Published: April 2011

AbstractThe resistance and magnetoresistance (MR) of three-dimensional current-perpendicular-to-plane (CPP) structures have been calculated via numerical finite element solutions of the Laplace equation. This model accounts for the non-uniform current paths in a four-probe geometry that can yield MR that differs from the intrinsic MR of the isolated CPP pillar with spatially uniform current flow. We calculated the four-probe MR for various geometries and resistivities of both the normal metal leads and the magnetoresistive pillar. From a single, unified approach, we are able to consistently account for the disparate behavior that has been previously published. In particular, we identify conditions that produce four-probe MR that differs from the intrinsic MR of the CPP pillar and highlight those situations where the four-probe resistance is negative. Finally, we present a simple analytical formula for the MR ratio that is applicable to narrow CPP pillars with wide, thin leads.