Kinetics of concentrating and ultrapurifying dichlorosilane by batch distillation with periodical withdrawals

The results of theoretical and experimental studies for the kinetics of separating dichlorosilane from a mixture of volatile chlorosilanes and ultrapurifying the dichlorosilane concentrate by batch distillation are reported. A mathematical model of the process is proposed. It is shown that the model and computational algorithm adequately describe both processes. The obtained experimental and theoretical data made it possible to design a concentration and ultrapurification process with a maximal productivity at a specified product purity.     

Oscillations in a bounded volume of reacting gas suspensate

Sverdlovsk. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 1, pp. 82–88, January–February, 1991.     

Grain orientation effects on copper enrichment and oxygen generation during anodizing of an Al-1at.%Cu alloy

Anodizing of solid-solution Al-1at.%Cu alloy in ammonium pentaborate electrolyte is shown to develop two distinct types of amorphous film. On alloy grains of {1 0 0} orientation, the alumina film is of uniform thickness and relatively featureless. For other grains, the film is of non-uniform thickness and contains oxygen bubbles. In both cases, copper species are distributed throughout the film. Copper is enriched in the alloy to ∼5.8×10¹⁵ Cu atoms cm⁻² for bubble-free grains, with similar or slightly lower levels for other grains. Evidently, copper enrichment alone does not lead to generation of oxygen. Other factors suggested to be involved, each dependent upon grain orientation, are the structure of the enriched alloy layer, the cyclic nature of the oxidation of copper, and the generation of modulated film compositions.     

Laser-Printed Plasmonic Metasurface Supporting Bound States in the Continuum Enhances and Shapes Infrared Spontaneous Emission of Coupled HgTe Quantum Dots

In order to advance the development of quantum emitter-based devices, it is essential to enhance light-matter interactions through coupling between semiconductor quantum dots with high quality factor resonators. Here, efficient tuning of the emission properties of HgTe quantum dots in the infrared spectral region is demonstrated by coupling them to a plasmonic metasurface that supports bound states in the continuum. The plasmonic metasurface, composed of an array of gold nanobumps, is fabricated using single-step direct laser printing, opening up new opportunities for creating exclusive 3D plasmonic nanostructures and advanced photonic devices in the infrared region. A 12-fold enhancement of the photoluminescence in the 900–1700 nm range is observed under optimal coupling conditions. By tuning the geometry of the plasmonic arrays, controllable shaping of the emission spectra is achieved, selectively enhancing specific wavelength ranges across the emission spectrum. The observed enhancement and shaping of the emission are attributed to the Purcell effect, as corroborated by systematic measurements of radiative lifetimes and optical simulations based on the numerical solution of Maxwell's equations. Moreover, coupling of the HgTe photoluminescence to high quality factor modes of the metasurface improves emission directivity, concentrating output within an ≈20° angle.     

Supported palladium nanomaterials as catalysts for petroleum chemistry: 1. Specifics of palladium diacetate reduction with hydrogen on silica gel in catalyst synthesis

The reduction reaction of Pd(II) diacetate, a precursor in nanocatalyst synthesis, with molecular hydrogen on silica gel has been studied. A kinetic model involving the autocatalytic mechanism of Pd(II) reduction to Pd(0) and adequately describing the experimental data has been proposed. Similarities and dissimilarities in the mechanism of this process on silica gel and carbon have been revealed. On the basis of quantum-chemical simulation data, it has been suggested that the differences are due to both a high bond energy of the precursor with the support and modifications in geometry of various Pd(II) diacetate species adsorbed on the surface. The controllable reduction of the precursor makes it possible to manufacture materials with a metal particle size of 1.7–2.8 nm according to transmission electron microscopy data. The materials catalyze the reaction of phenylacetylene hydrogenation to styrene with a high activity and selectivity at 25°C and 1 atm of hydrogen.     

Peculiar electric properties of polarized layer in alkaline silicate glasses

Broadband dielectric spectroscopy (BDS) was applied to study polarization phenomena in alkaline silicate glasses, in particular, properties and structure of subsurface (anodic) polarized layers forming in poling with deposited film electrodes of different structures. A model of poled glasses which does not contradict experimental data is proposed. In accordance with the model, a poled glass is presented as two resistor-capacitor circuits in a series connection, one of which is the polarized layer and another is the rest of the sample. It is found that the electric properties of the layers essentially depend on the structure of the anodic electrode used in glass poling. It is also shown that the dielectric response of poled glass samples is mainly determined by the electric properties of the submicron polarized layers and this gives an opportunity to reveal specific properties of the layers rather than ones of the glass sample bulk. Revealed temperature dependence of DC conductivity of the polarized layers obeys Arrhenius's law, and determining activation energy does not depend on the electrode. Finally, it is noted that today above-mentioned information about polarized layers can be obtained only by BDS.     

Fire-resistant polymer nanocomposites based on metal oxides and hydroxides

The fire-resistant properties of polymer nanocomposites based on polyvinylchloride and nanoparticles of metal compounds were studied. The investigation of nanoparticles and the determination of their sizes were carried out using scanning electron microscopy (SEM). The size of the nanoparticles of magnesium hydroxide was equal to 50–100 nm; iron oxide, 25–50 nm; and zinc oxide, 50–100 nm. Another type of fire retardant used in the work was aminotrimethylenephosphonic acid ammonium salt (AMPAS); however, the total content of the different additives did not exceed 15%. The nanocomposites obtained were investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC); in addition, the parameters of the oxygen index (OI) and carbon residue (CR) were measured for them. The lowest combustibility was exemplified by the composite material containing as the fire retardants a mixture of AMPAS and ZnO.