Core-leaf onion-like carbon/MnO2 hybrid nano-urchins for rechargeable lithium-ion batteries

A hybrid nano-urchin structure consisting of spherical onion-like carbon and MnO2 nanosheets is synthesized by a facile and environmentally-friendly hydrothermal method. Lithium-ion batteries incorporating the hybrid nano-urchin anode exhibit reversible lithium storage with superior specific capacity, enhanced rate capability, stable cycling performance, and nearly 100% Coulombic efficiency. These results demonstrate the effectiveness of designing hybrid nano-architectures with uniform and isotropic structure, high loading of electrochemically-active materials, and good conductivity for the dramatic improvement of lithium storage.

Atmospheric-pressure discharges for the fabrication of surface-based metal nanostructures

Various reactor configurations for generating atmospheric-pressure discharges were tested, and several types of nanostructures, including Mo nanoflakes, were successfully synthesized. Here, we present photographs of the discharges, as well as SEM images of representative nanostructures.

Plasma/ion-controlled metal catalyst saturation : enabling simultaneous growth of carbon nanotube/nanocone arrays

It is shown that the simultaneous saturation of Ni nanoparticles used as catalyst for vertically aligned carbon nanotube and nanocone arrays can be improved in low-temperature plasma- or ion-assisted processes compared with neutral gas-based routes. The results of hybrid multiscale numerical simulations of the catalyst nanoarrays (particle sizes of 2 and 10 nm) saturation with carbon show the possibility of reducing the difference in catalyst incubation times for smallest and largest catalyst particles by up to a factor of 2. This approach is generic and provides process conditions for simultaneous nucleation and growth of uniform arrays of vertically aligned nanostructures. © 2008 American Institute of Physics.

Atmospheric-microplasma-assisted nanofabrication : metal and metal–oxide nanostructures and nanoarchitectures

In this paper, we report on the fabrication of Mo-oxide nanostructures and nanoarchitectures using an atmospheric-microplasma (AMP) system. This AMP system shows a high degree of flexibility and is capable of producing several different nanostructures and nanoarchitectures by varying the process parameters. The low-cost and simplicity of the process are important characteristics for nanomanufacturing, and AMPs offer such advantages. In addition, AMPs have shown the ability of promoting self-organization of nanostructures. © 2009 IEEE.

Plasma-controlled metal catalyst saturation and the initial stage of carbon nanostructure array growth

The kinetics of the nucleation and growth of carbon nanotube and nanocone arrays on Ni catalyst nanoparticles on a silicon surface exposed to a low-temperature plasma are investigated numerically, using a complex model that includes surface diffusion and ion motion equations. It is found that the degree of ionization of the carbon flux strongly affects the kinetics of nanotube and nanocone nucleation on partially saturated catalyst patterns. The use of highly ionized carbon flux allows formation of a nanotube array with a very narrow height distribution of half-width 7 nm. Similar results are obtained for carbon nanocone arrays, with an even narrower height distribution, using a highly ionized carbon flux. As the deposition time increases, nanostructure arrays develop without widening the height distribution when the flux ionization degree is high, in contrast to the fairly broad nanostructure height distributions obtained when the degree of ionization is low.

Nonlinear effects of ionization on surface waves on a plasma-metal interface

Nonlinear effects associated with density modulation caused by wave-induced ionization in magnetized plasmas were studied. The ionizing surface waves propagate at the interface between the plasma and a metallic surface. It is shown that the ionization nonlinearity can be important for typical experimental conditions.

A model of a large-area planar plasma producer based on surface wave propagation in a plasma-metal structure with a dielectric sheath

A theoretical model of a large-area planar plasma producer based on surface wave (SW) propagation in a plasma-metal structure with a dielectric sheath is presented. The SW which produces and sustains the microwave gas discharge in the planar structure propagates along an external magnetic field and possesses an eigenfrequency within the range between electron cyclotron and electron plasma frequencies. The spatial distributions of the produced plasma density, electromagnetic fields, energy flow density, phase velocity and reverse skin depth of the SW are obtained analytically and numerically.

Monoclinic β-MoO3 nanosheets produced by atmospheric microplasma : application to lithium-ion batteries

Porous high surface area thin films of nanosheet-shaped monoclinic MoO 3 were deposited onto platinized Si substrates using patch antenna-based atmospheric microplasma processing. The films were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and electrochemical analysis. The electrochemical analysis shows original redox peaks and high charge capacity, and also indicates a reversible electrochemical behaviour particularly beneficial for applications in Li-ion batteries. SEM shows that the films are highly porous and consist of nanosheets 50-100 nm thick with surface dimensions in the micrometre range. HRTEM reveals that the MoO3 nanosheets consist of the monoclinic beta phase of MoO3. These intricate nanoarchitectures made of monoclinic MoO3 nanosheets have not been studied previously in the context of applications in Li-ion batteries and show superior structural and morphological features that enable effective insertion of Li ions.

Heating mechanism of self-interaction of surface polaritons at n-type semiconductor-metal interface

The influence of electron heating in the high-frequency surface polariton (SP) field on the dispersion properties of the SPs considered is investigated. High frequency SPs propagate at the interface between an n-type semiconductor with finite electron pressure, and a metal. The nonlinear dispersion relation for the SPs is derived and investigated.

Growth of carbon nanocone arrays on a metal catalyst: The effect of carbon flux ionization

The growth of carbon nanocone arrays on metal catalyst particles by deposition from a low-temperature plasma is studied by multiscale Monte Carlo/surface diffusion numerical simulation. It is demonstrated that the variation in the degree of ionization of the carbon flux provides an effective control of the growth kinetics of the carbon nanocones, and leads to the formation of more uniform arrays of nanostructures. In the case of zero degree of ionization (neutral gas process), a width of the distribution of nanocone heights reaches 360 nm with the nanocone mean height of 150 nm. When the carbon flux of 75% ionization is used, the width of the distribution of nanocone heights decreases to 100 nm, i.e., by a factor of 3.6. A higher degree of ionization leads to a better uniformity of the metal catalyst saturation and the nanocone growth, thus contributing to the formation of more height-uniform arrays of carbon nanostructures.

Excitation of surface plasmon-polariton waves at a semiconductor-metal interface

The excitation of surface plasmon-polariton waves propagating across an external magnetic field (Voigt geometry) in a semiconductor-metal structure by means of the attenuated total reflection method is investigated. The phase matching conditions for the surface waves excitation in the Kretchmann configuration are derived and analyzed. The effect of different nonlinearities on the excitation of the surface waves is studied as well.

Self-interaction of surface polaritons at the narrow-gap n-type semiconductor metal interface

The non-linear self-interaction of the potential surface polaritons (SP) which is due to the free carriers dispersion law where nonparabolicity is studied. The SP propagate at the interface between n-type semiconductor and a metal. The self interaction of the SP is shown to be different in semiconductors with normal and inverse zone structures. The results of the SP field envelope evolution are given. The obtained nonlinear frequency shift has been compared with shifts which are due to another self-interaction mechanisms. This comparison shows that the nonlinear self-interaction mechanism, which is due to free carriers spectrum nonparabolicity, is especially significant in narrow-gap semiconductor materials.

Dispersion properties of surface waves in a two-layer plasma structure bounded by a metal

The effect of the nonuniformity of the electron density on the dispersion properties of surface waves propagating in a direction transverse to an external magnetic field is studied for the model of a two-layer plasma structure bounded by a metal. It is shown that the spectra of the waves can be effectively controlled by varying the degree of nonuniformity of the density and the dimensions of the layers.

Self-interaction of magnetoplasma surface waves at a plasma-metal boundary

We investigate nonlinear self-interacting magnetoplasma surface waves (SW) propagating perpendicular to an external magnetic field at a plasma-metal boundary. We obtain the nonlinear dispersion equation and nonlinear Schroedinger equation for the envelope field of the SW. The solution to this equation is studied with regard to stability relative to longitudinal and transverse perturbations.

Azimuthal surface waves in a coaxial semiconductor structure with metal walls

The dispersion properties and topography of the fields of azimuthal surface wave (ASW) in a coaxial semiconductor structure with metal walls, placed in an external magnetic field, are investigated analytically and numerically. It is shown that an ASW phase-shifting device can be realized in the proposed structure. The conditions are indicated for which wave perturbations exist having frequencies that depend on the direction of phase change.