Optics and Spectroscopy - We study the photocatalytic activity of nanocomposites based on θ-phase alumina (Al2O3) with different TiO2 concentrations for heterogeneous photocatalysis and... 相似文献
Thermal transformations in systems formed by interaction of Zn and Na nitrates with Y, X, and A zeolites were studied by TG—DTA technique. Temperature regions of existence of adsorbed water, water of crystallization, and decomposition of NO3– anion were determined. These intervals depend on the composition, structure, method of preparation, and pre-treatment conditions of zeolite systems. The extent of NO3– decomposition depends not only on the zinc and sodium content but also on the presence of ammonia involved in NO3– reduction. The zeolite matrix strongly stabilizes the occluded NO3– anions. A portion of zinc oxide formed by zinc nitrate decomposition is probably localized inside the zeolite cavities as the [Zn—O—(ZnO)n—Zn]2+ particles. The latter compensate charges of the isolated [AlO4]– tetrahedra. 相似文献
Kinetics and Catalysis - The catalytic properties of supported Mn/carrier catalysts (carriers: Al2O3, SiO2, SiO2–Al2O3) in the ozone-assisted oxidation of volatile organic compounds (using... 相似文献
The results of numerical modeling of two-phase electrolyte thermo-and hydrodynamics in the working space of a separate electrolyzer
cell with vertical electrode arrangement are presented. The problem is solved in a self-consistent formulation taking into
account the electric current, Joule heat evolution, gas evolution, gas and liquid flows, and electric conductivity of the
disperse phase. Within the framework of the proposed two-liquid approach, near-wall bubbly flow is calculated using a model
of expanding gas plume, which is based on the introduction of an effective force acting upon the gas phase. The results of
several variants of such calculations are compared. The numerical solution is also compared to approximate analytical solutions
of the problem. The results of this study can be used to calculate estimations of the electrical and thermal regimes of vertical
electrolyzers. 相似文献
A deamination method was proposed for pretreatment before biological treatment of process nitrogen-containing wastewater from caprolactam production. 相似文献
Microcrystalline ZnO films presenting well-defined and tunable orientation were obtained by spin coating of alcoholic sols by two different approaches, based on controlled hydrolysis-condensation of Zn-ethanolamine complexes. As-deposited films are formed by amorphous zinc oxide-acetate submicronic particles, which are transformed into oriented ZnO after thermal treatment. The orientation of ZnO depends on the synthesis method, and the solvent. While in ethanol and [Zn] = 0.05 mol·L–1, films consist of rectangular platelets oriented with the (100) planes parallel to the substrate (a//n), the orientation of the particles changes to (c//n) for systems in 2-methoxyethanol (2-ME) and [Zn] = 0.75 mol·L–1. A study of chemical factors that influence the orientation (precursor, solvent, MEA/Zn ratio, concentration, coating parameters, heat treatment) is presented. 相似文献
We have carried out experiments of two-photon excitation of vapor phase H2O and D2O molecules at atmospheric pressure. A narrow-band tunable UV OPO laser is used in the experiments. Transient
B1 → B1 emission from the excited predissociating state is seen in both cases. The complete
B1 ← A1 fluorescence excitation spectrum in the spectral range of 245-250 nm is measured and compared with theory. It is shown that
the predissociation rate increases with the rotational quantum number K'a > 2 more strongly than with K′2a. No perturbation effects on the measured LIF spectra are observed at a laser power density below 2 GW/cm2. Experimental results indicate a negligible contribution from both molecular association and collisions with atmospheric
gases. Only an extremely weak vibrational progression belonging to the second positive system of N2 has been observed, which appears to be due to energy and charge transfer in N+2* + H2O collisions.
Received 25 January 2002 / Received in final form 27 May 2002 Published online 4 March 2003 相似文献
New experimental data on antiparallel-beam holograms recorded in LiNbO3, temperature fixation of the recorded holographic gratings, and the spectral characteristic of a narrow-band (0.01 nm) interference filter are reported. The effects of asymmetry in the diffraction efficiency and the emergence of satellites in the transmission spectrum of the filter are observed. These effects are explained using the birefringence properties of the crystal and the ability of holograms to transfer power between the beams in the course of recording. 相似文献
We present a study on the chemical and structural transformations in highly porous monolitic materials consisting of the nanofibrils of aluminum oxyhydroxides (NOA, Al2O3·nH2O) in the temperature range 20–1700 °C. A remarkable property of the NOA material is the preservation of the monolithic state during annealing over the entire temperature range, although the density of the monolith increases from ~0.02 up to ~3 g/cm3, the total porosity decreases from 99.3 to 25% and remains open up to 4 h annealing at the temperature ~1300 °C. The physical parameters of NOA monoliths such as density, porosity, specific area were studied and a simple physical model describing these parameters as the function of the average size of NOA fibrils—the basic element of 3D structure—was proposed. The observed thermally induced changes in composition and structure of NOA were successfully described and two mechanisms of mass transport in NOA materials were revealed. (i) At moderate temperatures (T?≤?800 °C), the mass transport occurs along a surface of amorphous single fibril, which results in a weak decrease of the length-to-diameter aspect ratio from the initial value ~24 till ~20; the corresponding NOA porosity change is also small: from initial ~99.5 to 98.5%. (ii) At high temperatures (T >?800 °C), the mass transport occurs in the volume of fibrils, that results in changes of fibrils shape to elliptical and strong decrease of the aspect ratio down to ≤?2; the porosity of NOA decreases to 25%. These two regimes are characterized by activation energies of 28 and 61 kJ/mol respectively, and the transition temperature corresponds to the beginning of γ-phase crystallization at 870 °C.
First results on femtosecond laser 3D-microstructuring are reported in a novel class of organic-inorganic hybrid materials based on titanium oxide gels. Transparent optical-grade polished hybrid samples demonstrate strong photosensitivity assigned to electrons trapped as Ti3+ centers. Two different regimes of the microstructuring are observed: reversible and irreversible. In tight-focusing conditions using “on-the-fly” technique the single-pulse microstructuring is achieved with nanojoule laser pulses. The process thresholds have been studied on the surface and into the bulk of the material with irradiation by 1, 2, 10, and 100 laser pulses. A reduction of the damage threshold fluence by a factor of 2.5 is observed when increasing exposure from 1 pulse (1.2 J/cm2) to 100 pulses (0.5 J/cm2). PACS 42.62.-b; 40.70.-a; 78.66.Sq 相似文献