Mechano-optical wavelength tuning in a photonic crystal microcavity with sub-1 V drive voltage

A micro-bimorph cantilever with self-aligned nanotips is monolithically integrated with a photonic crystal based device using optical and deep UV lithography techniques. Upon electrostatic actuation, the dielectric nanotips perturb the optical field, providing electromechano-optical modulation of light. Static tuning of the optical transmission spectra by more than 600 pm is measured with a sub-1 V drive voltage, resulting in a modulation as high as 21 dB. The observed strong electromechano-optical effect may find application in power efficient devices for optical communication networks, such as wavelength routing elements.     

The synthesis of few-walled carbon nanotubes by the catalytic pyrolysis of methane and the kinetics of their accumulation

The kinetic dependences of the accumulation of carbon during pyrolysis of CH₄ mixed with H₂ on an Mo-Co/MgO catalyst with the atomic ratio Mo: Co: Mg = 3: 1: 76 at atmospheric pressure, temperature 900°C, and various CH₄ and H₂ partial pressures were determined by direct thermogravimetric measurements in combination with electron microscopic examination. The main solid pyrolysis products were found to be carbon nanotubes with two to five walls. The outside diameter of nanotubes changed from ～3 to 9 nm. A kinetic model of the accumulation of carbon was suggested. The model took into account the formation of two products, nanotubes and carbon deposited on their surface, process reversibility, and catalyst deactivation by nanotubes formed.     

Study of size-fractionated coal-combustion aerosols using instrumental neutron activation analysis

The chemical composition of aerosols emitted during coal combustion was studied as a function of particle size down to 0.01 m. The aerosol collections were carried out in a 81 MW capacity boiler that burned Venezuelan coal in a circulating fluidized bed combustion chamber. The samples were analyzed with upstream of the electrostatic precipitator using a Berner low-pressure impactor, which was quipped with a cyclone pre-cutter to avoid overloading of the first impaction stages. The samples were analyzed by INAA for up to about 40 elements. The elemental concentrations in the particulate matter for each impaction stage were plotted as a function of stage number (particle size). For the elements Na, Al, K, Ca, Sc, Ti, V, Ga, La and Sm, the concentration variation was limited to a factor of 2 to 4, and the concentrations of these elements were lower for the initial and final impactor stages than for the intermediate particle sizes. The variations were also limited to a factor of 2–4 for Mn, Fe, As, Sb and Th, butall these elements showed increasing concentrations with decreasing particle size. Still other elements, such as Ni, Cr, Co, Za, W, Mo and the halogens, were highly enriched (up to 20–100 fold) in the fine particles when compared with the coarse particles.     

Synthesis of nanoparticles using vapor-phase decomposition of copper(II) acetylacetonate

Experimental data on the synthesis of crystalline Cu, Cu₂O, and CuO nanoparticles obtained earlier by the vapor-phase decomposition of copper(II) acetylacetonate (Cu(acac)₂) were systematized and generalized. Studies were performed using a laminar flow reactor at atmospheric pressure within the ranges of precursor partial vapor pressure P _prec = 0.06–44 Pa and reactor temperature from 432 to 1216°C. The decomposition of Cu(acac)₂ was studied in an inert nitrogen atmosphere and in the presence of various reagents (water vapors, H₂, O₂, and CO). The composition of synthesized particles varied from pure copper to its oxides (Cu₂O and CuO) depending on experimental conditions and used reagents. A semi-empirical kinetic model was proposed for describing the product dynamics. The hypothesis on the predominant role of copper dimers in a particles growth was stated. It was established that the composition of products is determined by the surface reactions on growing particles and is dependent on the ratio between the concentrations of the gaseous reagents. Calculated phase diagrams of the products of Cu(acac)₂ decomposition in the presence of various reagents were in good agreement with experimental data. The proposed method of construction of the phase diagram of decomposition products can be employed for other systems. It was established that, upon the Cu(acac)₂ decomposition in the presence of CO, carbon nano-onions were formed in addition to copper nanoparticles.Translated from Kolloidnyi Zhurnal, Vol. 67, No. 1, 2005, pp. 5–25.Original Russian Text Copyright © 2005 by Nasibulin, Shurygina, Kauppinen.     

Synthesis of boron nitride multi-walled nanotubes by laser ablation technique

Carbon nanotubes are known as prospective material for the optoelectronics, vacuum electronics, non-linear optics and for the composite material synthesis. Boron nitride nanotubes (BNNTs) were obtained only recently. It is expected that these nanotubes possess the unique properties. BN is much more chemically inert than carbon. Its oxidation temperature is above 1000°C as the graphite is totally oxidized already at 650°C. BNNTs are wide-gap semiconductors with the 6 eV gap. In case of the introducing of the carbon atoms into the BN nanotube wall its bandgap may be varied in wide range. This property is important for the UV optics.     

The ν9 + ν11 − ν11, ν10 + ν11 − ν11 hot band system in allene-d4

The hot band system ν₉ + ν₁₁ ? ν₁₁, ν₁₀ + ν₁₁ ? ν₁₁ in allene-d₄ was studied at a resolution near 0.010 cm^?1. About 1500 partly overlapped hot band rotational lines were assigned and fitted to a model taking into account z-Coriolis resonance between the combination levels ν₉ + ν₁₁ and ν₁₀ + ν₁₁ as well as vibrational l-type resonances within these levels. Upperstate constants have been derived from an analysis in which the constants for the ν₁₁ level were constrained. A detailed study of rotational as well as vibrational l-type doublings occurring in the KΔK = ?1 subband is presented, and the sign of vibrational l-type doubling constants for the ν₁₀ + ν₁₁ level is determined. A localized (x, y)-Coriolis resonance between ν₁₀ + ν₁₁ and ν₄(B₁) + ν₁₁ is discussed and the interaction parameter is obtained as well as some constants for ν₄ + ν₁₁.     

ν7 and ν9 bands of formic acid near 16 μm

The ν₇ and ν₉ fundamental bands of formic acid were studied by Fourier transform spectroscopy with a resolving power of 0.020 cm^?1. Band centers obtained are ν₇ = 626.158 cm^?1 and ν₉ = 640.722 cm^?1. It was possible to determine rotational and centrifugal distortion parameters for both vibrational states v₇ = 1 and v₉ = 1 and also the two first-order Coriolis interaction parameters along z and x axes and the second-order Coriolis parameter along z axis. The stability of rotational and distortion parameters compared to ground state values confirms that a Watson type Hamiltonian is well adapted to such a problem.