Microwave hybrid synthesis of silicon carbide nanopowders

Nanosized silicon carbide powders were synthesised from a mixture of silica gel and carbon through both the conventional and microwave heating methods. Reaction kinetics of SiC formation were found to exhibit notable differences for the samples heated in microwave field and furnace. In the conventional method SiC nanopowders can be synthesised after 105 min heating at 1500 °C in a coke-bed using an electrical tube furnace. Electron microscopy studies of these powders showed the existence of equiaxed SiC nanopowders with an average particle size of 8.2 nm. In the microwave heating process, SiC powders formed after 60 min; the powder consisted of a mixture of SiC nanopowders (with two average particle sizes of 13.6 and 58.2 nm) and particles in the shape of long strands (with an average diameter of 330 nm).
The powders were prepared by a sol-gel process. Dielectric constants (ϵ′) and dielectric loss tangents (tanδ) were measured within the microwave frequency range from 4 to18 GHz. Both ϵ′ and tanδ of pure SiC nanopowder are much higher (ϵ′=40–50, tanδ=0.6–0.7) than for the doped ones over the frequency range. The dielectric parameters decreased with increasing aluminum and nitrogen contents. Infrared (IR) spectra were measured in the range from 500 to 4000 cm−1, showing that the background of pure SiC nanopowder is also much higher than for the doped ones. The possible mechanisms of these promising features of undoped SiC nanopowder are discussed.
By a simple and controlled method, that is, by electroless plating, nickel has been deposited on the surfaces of Silicon Carbide Nanopowders Energy dispersive spectrometry (EDS) spectra show that pre-treatments of the silicon carbide nanoparticles have an important influence on the effect of electroless nickel plating. Transmission electron microscopy images and EDS spectra of silicon carbide nanoparticles before and after electroless nickel plating reveal that nickel has been deposited on the surface of silicon carbide nanoparticles and the deposited nickel and silicon carbide nanoparticles are bound tightly.

The Extinction Spectra of Silver Nanopowders Arrays

Influence of Array Structure on Plasmon Resonance Wavelength and Width
We use high-quality electrodynamics methods to study the extinction spectra of one-dimensional linear chains and two-dimensional planar arrays of spherical Silver Nanopowders, placing emphasis on the variation of the plasmon resonance wavelength and width with array structure (spacing, symmetry), particle size, and polarization direction. Two levels of theory have been considered, coupled dipoles with fully retarded interactions and T-matrix theory that includes a converged multipole expansion on each particle. We find that the most important array effects for particles having a radius of 30 nm or smaller are captured by the couple dipole approach.

Our calculations demonstrate several surprising effects that run counter to conventional wisdom in which the particle interactions are assumed to be governed by electrostatic dipolar interactions. In particular, we find that for planar arrays of particles with polarization parallel to the plane the plasmon resonance blue shifts as array spacing D decreases for D larger than about 75 nm and then it red shifts for smaller spacings. In addition, we find that the plasmon narrows for D > 180 nm but broadens for smaller spacings.

The results can be rationalized using a simple analytical model, which demonstrates that the plasmon wavelength shift is determined by the real part of the retarded dipole sum while the width is determined by the imaginary part of this sum. The optimal blue shifts and narrowing are found when the particle spacing is slightly smaller than the plasmon wavelength, while red shifts and broadening can be found for spacings much smaller than the plasmon wavelength at which electrostatic interactions are dominant. We also find that the array spectrum does not change significantly with array symmetry (square or hexagonal) or irradiated spot size (i.e., constant array size or constant particle number).

The application of metal nanowires

Metal nanowires can have a variety of forms. Sometimes they appear in the order to non crystal, such as five symmetrical or helix. Electronic in the Pentagon pipe and spiral pipe winding.

This lack of crystal order is because the nanotubes in only one dimension (Zhou Xiang) reflect cyclical, while in other dimensions can have any order to the law of energy. For example, in some cases, nanowires can show five fold symmetry, this symmetry cannot be observed in nature, but can be found in a small amount of atoms contributing to clusters. The five fold symmetry equivalent atoms cluster twenty fold symmetry: Twenty surface body is low energy states of a cluster of atoms, but because the surface of the body twenty can not be repeated indefinitely in all directions and fill the whole space, this order is not observed in the crystal.

In electronic, optoelectronic and nano electronic and mechanical devices, nano wires may play an important role. It also can be used as in the synthesis of additives, quantum devices in the line, field emitters and biological molecular nano sensor.

Metal nanowires can be natural sunlight came together in a very small area in the crystal, light gathering ability is 15 times the average light intensity. Because of the wavelength diameter is smaller than the incident solar light nanowire crystals, can cause the nanowires inside the crystal and the surrounding light intensity of resonance. The study participants, just to get the doctor degree of research on Niels Pohl Peter Klogstrup explained that the photons through resonance emit more concentrated (solar energy conversion is realized in the process of dissemination in the photon), which helps to improve the conversion efficiency of solar energy, so that the solar cell technology nanowires get real ascension based on the.

Nano silicon semiconductor light-emitting materials research

By changing the quantity of silicon rich, annealing conditions, size and density control oxidation of silicon in silicon Silicon Carbide Nanopowders. Literature that the critical temperature of silicon nanocrystals is 1000oC, and we tested to determine the critical annealing temperature for 900oC nanocrystals. On the right is via the 900oC annealing silicon rich silicon was about high resolution electron microscopy images of 30% silicon rich silicon oxide. Can clear the silicon nanocrystals. On the left corner of the electron diffraction pattern it is.

First observed by Au/ (Ge/SiO2) /p-Si superlattice structure electroluminescence. Right out of high resolution electron microscopy figure four cycle Ge/SiO2 superlattices. The bright line for the SiO2, 2.0nm thickness, Ge thickness of 2.4nm.

The growth of nano SiO2/Si/SiO2 double barrier by magnetron sputtering technique on silicon substrate (NDB) single well potential sandwich structure, the first realization of visible photoluminescence of Au/NDB/p-Si structure. Discovery of electroluminescence peak position, intensity with the nanometer silicon layer thickness (W) changes as synchronous oscillations, as shown on the right. Further tests and analyses show that the oscillation period is equal to the deBroglie wavelength of 1/2 carrier. Lighting model is explained by our group proposed electroluminescence.

For the first time based on SiO2:Si:Er film growth by magnetron sputtering has been achieved on the 1.54 m wavelength as (optical communication window) Er electroluminescence.