Effect of nanosized titania on the structure and properties of the composites based on butadienenitrile rubber

Nanocomposites based on butadienenitrile rubber (butadiene copolymer with 28% acrylonitrile) with functional titania nanoparticles of different nature have been obtained, and their complex study by X-ray diffractometry, small-angle X-ray scattering, scanning electron microscopy, electron probe X-ray microanalysis, and X-ray energy-dispersive spectroscopy has been performed. Differences in the morphology and composition of the surface and transverse cuts of nanocomposites in dependence of nanoparticle characteristics are established. It is found that the nanocomposites with the largest crystallite sizes have the lowest viscosity. It is also revealed that the nature of titania nanoparticles barely affects the vulcanization kinetics, and that the optimal vulcanization time for the composites is 25 min. Uniaxial extension tests have shown that nanocomposites with the best properties can be fabricated by introducing amorphous titania into the polymer (butadienenitrile rubber).     

Phase transitions of native celluloses from evolutionarily different sources into polymorph IV

A procedure was suggested for preparing cellulose polymorph IV by dissolution of native celluloses from evolutionarily different sources in trifluoroacetic acid to molecularly dispersed state, followed by regeneration and treatment under hydrothermal conditions.     

Study of structural order in porphyrin-fullerene dyad ZnDHD6ee monolayers by electron diffraction and atomic force microscopy

The structure of porphyrin-fullerene dyad ZnDHD6ee monolayers formed on the surface of aqueous subphase in a Langmuir trough and transferred onto solid substrates has been studied. The data obtained are interpreted using simulation of the structure of isolated molecules and their packing in monolayer and modeling of diffraction patterns from molecular aggregates having different sizes and degrees of order. Experiments on the formation of condensed ZnDHD6ee monolayers are described. The structure of these monolayers on a water surface is analyzed using π-A isotherms. The structure of the monolayers transferred onto solid substrates is investigated by electron diffraction and atomic force microscopy. The unit-cell parameters of two-dimensional domains, which are characteristic of molecular packing in monolayers and deposited films, are determined. Domains are found to be organized into a texture (the molecular axes are oriented by the [001] direction perpendicular to the substrate). The monolayers contain a limited number of small 3D domains.     

Study of polyelectrolyte complexes of chitosan and sulfoethyl cellulose

The complexing of polycation chitosan and polyanion sulphoethyl cellulose during the formation of polyelectrolyte simplex membranes using the layer-by-layer deposition of a solution of one polyion on a gel-like film of another one has been studied. The structural characteristics of the multilayer composites and their components have been analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray microanalysis. A technique is proposed for studying the structure of surface layers of thin polymer films (15–20 μm) using a portable DIFREI-401 diffractometer. It is shown that the sequence of layer deposition during the formation of membrane films does not affect their structural characteristics. The interaction between positively charged chitosan groups (-NH ₃ ⁺ ) and negatively charged sulfoethyl cellulose groups (-SO ₃ ^? ) during the growth of polyelectrolyte complexes results in a packing of chitosan chains in the multilayer film.     

Formation and x-ray and electron diffraction study of Cds and Pbs particles inside fatty acid matrix

Langmuir-Blodgett films of lead and cadmium stearate were treated by exposure to H₂S atmosphere. Such treatment lead to formation of CdS and PbS particles and protonation of stearic acid head-groups. The process was studied by small-angle X-ray scattering. The reaction was shown to be completed after 5 hours of treatment.     

Low-Voltage Scanning Electron Microscopy and Energy-Dispersive X-Ray Microanalysis of the Interface of Multilayer Polymer Composite

The morphology of the layer of polyelectrolyte complex, which is formed in the composite based on chitosan and sulfoethyl cellulose during the contact of a solution of one of them with a gel film of the other one, has been investigated by the low-voltage (≤3 kV) scanning electron microscopy. A technique for eliminating the effects related to charge accumulation on the dielectric film surface is proposed.     

Analysis of the induced photothermal conduction in the Mn4Si7-Si〈Mn〉-Mn4Si7 and Mn4Si7-Si〈Mn〉-M heterojunctions

The kinetics of photocurrent is studied in the presence of the intrinsic irradiation at hν ≥ 1.12 eV in the Mn₄Si₇-Si〈Mn〉-Mn₄Si₇ and Mn₄Si₇-Si〈Mn〉-M heterojunctions at relatively high applied voltages. It is demonstrated that photocurrent, scattered power, and temperature at the reverse-biased contact of the heterojunction depend on time at dc applied voltage, low temperature, and irradiation at hν ≥ 1.12 eV. The analysis of the temperature dependences of the photocurrent growth with time is used to demonstrate that the photocurrent pulses consist of two fragments: the first one corresponds to a slowly increasing relatively low current with a slope of (2–4) × 10^?4 A/s and the second fragment is characterized by a sharp increase in the current with a slope of 0.1–1.0 A/s. Based on the slopes, the heating rates (β₁ = 42 deg/s and β₂ = 3 × 10³ deg/s) and temperature gradients across the transient layer that corresponds to the Mn₄Si₇-Si〈Mn〉 interface (ΔT/Δx = 6.3 × 10⁶ K/cm for β₁ = 42 deg/s and ΔT/Δx ≥ 1.5 × 10⁸ K/cm for β₂ = 3 × 10³ deg/s) are estimated. It is demonstrated that the Joule self-heating allows relatively high heating rates in the reverse-biased contact of heterojunction, which provides rapid heating similar to the rectangular step excitation that is equivalent to the activation of the long-wavelength (extrinsic) irradiation.     

High-resolution transmission electron microscopy for crystallographic study of nanomaterials

The potential of high-resolution transmission electron microscopy (including the quantitative computer processing of images and computer simulation) in a local analysis of nanomaterials is discussed. A number of examples of the application of fast Fourier transform and simulated high-resolution electronmicroscopy images in the identification of nanophases and the crystallographic study of nanocrystals and nanoparticles are considered. The role that B.K. Vainshtein played in the development of a unified approach for determination of the structure of materials using short-wave diffraction is indicated.     

Role of the surface layer of aqueous subphase in the self-organization mechanism of metal sulfide textures under a Langmuir monolayer

The structural self-organization mechanism of the axial textures of the metal sulfide nanocrystals from an aqueous subphase under a condensed Langmuir monolayer of fatty acid molecules, with allowance for the existence of a thin structured water surface layer on the aqueous subphase surface, is considered.