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Lattice distortion in single crystal rare-earth arsenide/GaAs nanocomposites
Epitaxial single crystal nanocomposites comprised of rare-earth arsenide nanoparticles embedded in GaAs (001) layers produce a larger change in lattice parameter than expected from the lattice parameters of relaxed films. Despite similar cubic structures and lattice parameters, elongation of the interfacial bond length between the two materials induces additional strain causing an expansion in the nanocomposite lattice. The interface bond length is material dependent with an average atomic layer spacing at the ErAs:GaAs interface of 1.9 Å while the spacing at the ScAs:GaAs interface is only 1.4 Å. Implications for lattice matching various single crystal epitaxial nanostructures in semiconductors are discussed.
The influence of pressure on the phase stability of nanocomposite Fe{sub 89}Zr{sub 7}B{sub 4} during heating from energy dispersive x-ray diffraction
Nanocomposite materials consisting of small crystalline grains embedded within an amorphous matrix show promise for many soft magnetic applications. The influence of pressure is investigated by in situ diffraction of hammer milled Fe{sub 89}Zr{sub 7}B{sub 4} during heating through the {alpha}{yields}{gamma} Fe transition at 0.5, 2.2, and 4.9 GPa. The changes in primary and secondary crystallization onset are described by diffusion and the energy to form a critical nucleus within the framework of classical nucleation theory.
Flexible and Conductive MXene Films and Nanocomposites with High Capacitance
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Tunable core-shell single-walled carbon nanotube-Cu 2 S networked nanocomposites as high-performance cathodes for lithium-ion batteries
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Processable conductive graphene/polyethylene nanocomposites: Effects of graphene dispersion and polyethylene blending with oxidized polyethylene on rheology and microstructure
Poor dispersion of graphene in non-polar polymer matrices creates composites with limited applications. A method to improve the dispersion of graphene in polyethylene (PE) via blending PE with oxidized PE (OPE) is examined. Graphene was produced by simultaneous thermal exfoliation and reduction of graphite oxide. Nanocomposites of graphene with PE as well as graphene with PE/OPE-blends were prepared by solvent blending. Improved dispersion of graphene in PE/OPE blends substantially decreases percolation from both rheological (0.3 vol%) and electrical (0.13 vol%) measurements compared to neat PE nanocomposites (1 and 0.29 vol%), respectively. A universal Brownian dispersion of graphene in polymers was concluded similar to that of nanotubes, following the Doi-Edwards theory. Micromechanical models, such as Mori-Tanaka and Halpin-Tsai models, modeled the mechanical properties of the nanocomposites. The nanocomposites microstructure, studied by small angle x-ray scattering, confirmed better dispersion of graphene at lower loadings and the formation of surface fractals in the blend/graphene nanocomposites; whereas only mass fractals were observed in neat PE/graphene nanocomposites.
Atomistic modeling of defect-induced plasticity in CuNb nanocomposites
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Enhancement in performance of polycarbazole-graphene nanocomposite Schottky diode
We report formation of polycarbazole (PCz)–graphene nanocomposite over indium tin oxide (ITO) coated glass substrate using electrochemical technique for fabrication of high performance Schottky diodes. The synthesized nanocomposite is characterized before fabrication of devices for confirmation of uniform distribution of graphene nanosheets in the polymer matrix. Pure PCz and PCz-graphene nanocomposites based Schottky diodes are fabricated of configuration Al/PCz/ITO and Al/PCz-graphene nanocomposite/ITO, respectively. The current density–voltage (J-V) characteristics and diode performance parameters (such as the ideality factor, barrier height, and reverse saturation current density) are compared under ambient condition. Al/PCz-graphene nanocomposite/ITO device exhibits better ideality factor in comparison to the device formed using pure PCz. It is also observed that the Al/PCz-graphene nanocomposite/ITO device shows large forward current density and low turn on voltage in comparison to Al/PCz/ITO device.
Electrical and mechanical tuning of 3D printed photopolymer–MWCNT nanocomposites through in situ dispersion
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Synthesis and enhanced light absorption of alumina matrix nanocomposites containing multilayer oxide nanorods and silver nanoparticles
Highlights: {yields} Multilayer oxide nanorods (nanocables) were obtained via chemical processing. {yields} Ag nanoparticles were deposited between the core and shell layers of the nanorods. {yields} The structure and composition of the nanorods were analyzed by SEM and TEM. {yields} CoO nanorods and Ag nanoparticles enhance light absorption of the nanocomposites. -- Abstract: In this paper, multilayer oxide nanorods were deposited in the nanopores of anodic aluminum oxide (AAO) via solution infiltration followed by heat treatment. The nanorods have a core-shell structure. First, the shell (nanotube) with the thickness of about 40 nm was made of TiO{sub 2} through the hydrolysis of (NH{sub 4}){sub 2}TiF{sub 6}. Second, silver nanoparticles with the diameter of about 3 nm were added into the TiO{sub 2} layer through thermal decomposition of AgNO{sub 3} at elevated temperatures. Then, cylindrical cores (nanorods) of CoO and ZnO with 200 nm diameter were prepared, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the structure and composition of the nanorods. UV-vis light absorption measurements in the wavelength range from 350 to 1000 nm were performed to study the effect of nanorod and nanoparticle addition on the light absorption property of the alumina nanocomposites. It is found that CoO nanorods increase the light absorption of the alumina matrix composite in the wavelength range from 500 nm to 800 nm, but the TiO{sub 2} shell does not increase the light absorption much. The ZnO nanorods do not change the light absorption either. However, the addition of silver nanoparticles significantly enhances light absorption of both AAO/TiO{sub 2}/Ag/CoO and AAO/TiO{sub 2}/Ag/ZnO nanocomposites. This increase in the visible light absorption reveals that there exists surface plasmon around the fine silver nanoparticles in the nanorods.
Electronic structure of the SiN x /TiN interface: A model system for superhard nanocomposites
Not Available
Persistence of crystal orientations across sub-micron-scale "super-grains" in self-organized Cu-W nanocomposites
We use precession electron diffraction to investigate the crystallographic character of copper (Cu)-tungsten (W) nanocomposites fabricated via physical vapor co-deposition at 400 oC. We observe sub-micron-scale regions, where apparently disconnected Cu and W grains have near identical crystallographic orientations. This persistence of grain orientations suggests Cu and W grains within these regions are interconnected in 3-D when they first form and may be considered as intercalated, sub-micron-scale "super-grains". Indeed, atom probe tomography provides direct evidence of 3-D interconnectivity of W domains. Our findings shed light on the structure and self organization mechanisms of nanocomposites formed by spontaneous phase separation of co-deposited metals.
A novel rapid synthesis of Fe{sub 2}O{sub 3}/graphene nanocomposite using ferrate(VI) and its application as a new kind of nanocomposite modified electrode as electrochemical sensor
Highlights: • A novel rapid synthesis of rGO–Fe{sub 2}O{sub 3} nanocomposite was developed using Fe(VI). • Fe(VI) as an environmentally friendly oxidant was introduced for GO synthesis. • Synthesized rGO–Fe{sub 2}O{sub 3} nanocomposite was applied as electrochemical sensor. • A non-enzymatic sensor was developed for H{sub 2}O{sub 2}. - Abstract: In this study, a novel, simple and sensitive non-enzymatic hydrogen peroxide electrochemical sensor was developed using reduced graphene oxide/Fe{sub 2}O{sub 3} nanocomposite modified glassy carbon electrode. This nanocomposite was synthesized by reaction of sodium ferrate with graphene in alkaline media. This reaction completed in 5 min and the products were stable and its deposition on the surface of electrode is investigated. It has been found the apparent charge transfer rate constant (ks) is 0.52 and transfer coefficient (α) is 0.61 for electron transfer between the modifier and glassy carbon electrode. Electrochemical behavior of this electrode and its ability to catalyze the electro-reduction of H{sub 2}O{sub 2} has been studied by cyclic voltammetry and chronoamperometry at different experimental conditions. The analytical parameters showed the good ability of electrode as a sensor for H{sub 2}O{sub 2} amperometric reduction.
Achieving 3-D Nanoparticle Assembly in Nanocomposite Thin Films via Kinetic Control
Nanocomposite thin films containing well-ordered nanoparticle (NP) assemblies are ideal candidates for the fabrication of metamaterials. Achieving 3-D assembly of NPs in nanocomposite thin films is thermodynamically challenging as the particle size gets similar to that of a single polymer chain. The entropic penalties of polymeric matrix upon NP incorporation leads to NP aggregation on the film surface or within the defects in the film. Controlling the kinetic pathways of assembly process provides an alternative path forward by arresting the system in nonequilibrium states. Here, we report the thin film 3-D hierarchical assembly of 20 nm NPs in supramolecules with a 30 nm periodicity. By mediating the NP diffusion kinetics in the supramolecular matrix, surface aggregation of NPs was suppressed and NPs coassemble with supramolecules to form new 3-D morphologies in thin films. The present studies opened a viable route to achieve designer functional composite thin films via kinetic control.
Multiphase Resistivity Model for Magnetic Nanocomposites Developed for High Frequency, High Power Transformation
New power conversion systems that offer promise to transform electricity grids into unified interactive supply networks require high-resistivity soft-magnetic materials to allow for switching of magnetic materials at frequencies approaching 100 kHz for power transformation in the megawatt range. Amorphous and nanocomposite soft-magnetic materials, which represent the state of the art in terms of high power densities and low losses at high frequencies, have resistivities that depend on the structures and spatial distributions of multiple phases in thin ribbons. We present a multiphase resistivity model applicable to nanocomposite materials by considering an equivalent circuit approach considering paths through an amorphous, crystalline, and growth inhibitor shell phase. We detail: (a) identification of amorphous, crystalline, and shell phases; (b) consideration of the role of the morphology of each phase in an equivalent circuit model for the resistance; (c) a two-band model for the Fe/Co composition dependence of the resistivity in crystalline and amorphous phases; (d) a virtual bound state model for resistivity to explain increased resistivity due to early transition-metal growth inhibitors in the shell surrounding the nanocrystalline phase; and (e) disorder effects on amorphous phase resistivity. Experimental design and results for systems of interest in high-frequency power transformation are discussed in the context of our model including: (a) techniques for measurements of cross-section and density, (b) four-point probe and surface resistivity measurements, and (c) measurements in Fe- and Co-rich systems comparing amorphous and nanocomposite materials.