Simulation of structural and electrical parameters of СdS thin films

Based on the calculations from the first principles, we obtained the distributions of valence electron densities and electron energy spectra for a CdS film with different oxygen concentrations. According to the results of calculations, it is established that during the adsorption of oxygen atoms on the surface of CdS, oxygen taking electrons from the surface atoms of the CdS film, increases its catalytic activity. The oxygen concentration should not exceed 12.5%.

Optical properties of semiconductor “anisotropic” quantum dot

The optical properties of an “anisotropic” semiconductor nanodot – a nanoscale object in the form of a rectangular parallelepiped - with sides a ≠ b ≠ c are considered. Such dimensions are closely related to the values of the effective masses of the electron. The analysis of the spectral dependence of the absorption coefficient a(w) under different degrees of "anisotropy" and under different polarizations of the electromagnetic wave is carried out. The cases of the most intense optical transitions, i.e. between electronic states separated by the Fermi level, are analyzed. The obtained results indicate that 1) a(w) is of line structure, and 2) the positions of the peaks of a(w) in identical optical transitions in the isotropic nanodot and in the “anisotropic” ones coincide qualitatively. However, different masses in the “anisotropic” nanodot lead to a shift to the left or right of the peaks relative to identical peaks in the isotropic nanodot with simultaneous splitting of its degenerate peaks. Such shifts and their magnitudes are determined both by the degree of anisotropy (i.e. by the ratio between the effective masses), and by the polarization of light. It is pointed out that modern achievements in the creation of ordered semiconductor materials with nanoobjects of different shapes and sizes in nanostructures allows us to consider polarized electromagnetic wave as an effective factor in achieving the desired physical characteristics.

Percolation phenomena in the polymer composites with conducting polymer fillers

The electrical properties of polymer nanocomposites based on dielectric polymer matrices of different types and electrically conductive polymer fillers – polyortotoluidine, polyorthoanisidine and polyaniline have been studied. It is shown that the concentration dependence of the specific conductivity on the content of fillers has a percolation character with a low “percolation threshold”, which depends on the nature of the polymer matrix and polyaminoarene and is 1.7-10.0 vol.%. The calculated critical parameters of electroconductivity are characteristic of the formation of an infinite 3-dimensional cluster of conductivity and indicate a significant influence of the nature of the components and morphology of the material on the charge transfer processes in such systems.

Regularities of Stress-Corrosion Cracking of Pipe Steel 09G2S at Cathodic Polarization in a Model Soil Environment

Peculiarities of corrosion-mechanical fracture of 09G2S pipe steel samples in the conditions of cathodic protection were investigated. It was established that depending on the level of protective potential, stress-corrosion cracking of pipe steel of a ferrite-pearlite class 09G2S can occur by different mechanisms. The range of protective potentials was determined, at which the anodic dissolution and hydrogen embrittlement occur simultaneously during the fracture of steel, namely from -0.85 V to -1.0 V. The existence of the above mechanisms is confirmed by the change in the strength and viscosity properties of the steel and the morphology of the fractures. For steels of other manufacturing technology and grades, these potential areas may differ.

Rapid formation methods of arrays of randomly distributed Au and Ag nanoparticles, their morphologies and optical characteristics

By the method of rapid radiation heating (at a speed of 20-25 K/s) of Au and Ag films with a thickness of 4-35 nm to temperatures of 573-693 K in air and in the process of vacuum deposition of silver on heated (up to 700 K at a heating rate of 10 K/s ) glass substrates formed Au and Ag NPs arrays with nanoparticle sizes from several tens to hundreds of nanometers, the position λSPR of which is in the range of 520-597 nm for Au NPs and 424-509 nm for Ag NPs. It is established that the average size of nanoparticles depends on the thickness of gold and silver films and the annealing temperature. The results testify that glass substrates with arrays of randomly distributed gold NPs can be used as effective SERS-substrates for the investigation of Raman spectra of nanosized (50-100 nm) chalcogenide films.

Zn-doped CoFe2O4Nanoparticles Synthesized Using Ginkgo Biloba Extract: Cation Distribution, Mossbauer Studies and Application for Water Treatment

The cobalt-zinc ferrites Zn1-xCoxFe2O4 (where x=0; 0.2; 0.4; 0.6; 0.8; 1.0) were obtained by green synthesis using Ginkgo Biloba extract as reductant and fuel. The cation distribution of the spinel ferrites has been investigated by means of X-ray diffraction and Mossbauer spectroscopy. The surface morphology and elemental composition were analyzed by SEM and EDS. The crystallite size decrease with increasing Co2+ content calculated from Scherrer equation and Williamson-Hall method. Adsorption properties of the spinel system were investigated using Congo Red (CR) dye as model pollutant. It is concluded that the adsorption of Congo red dye molecules can occur due to electrostatic and donor-acceptor interactions with the adsorbent surface containing various amount of active centers.

Cross-linked composite proton conductive membranes

Using UV-curing technique the proton conductive polymer materials based on acrylic monomers: 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylic acid (AA) and acrylonitrile (AN), cross-linked by varying amounts of N,N'-methylene(bis)acrylamide (MBA), and the hybrid polymer/inorganic membrane of the same content with addition of sol-gel system (SGS) based on 3-methacryloxypropyl trimethoxysilane (MAPTMS) and tetraethoxysilane (TEOS) were synthesized. The obtained materials were characterized by analysis of thermal, mechanical and morphological properties. Proton conductivity and water uptake were found to depend on the level of cross-linking of the materials. The value of proton conductivity of the hybrid membrane was sufficiently high reaching 3.46 × 10-2 S cm-1.

Investigation of the Effect of Agarose Gel Concentration and Culture Period on Bio and Mechanical Properties of Chondrocyte Tissue Engineering

As a gel scaffold for chondrocyte tissue engineering, agarose concentration plays a significant role in the relationship between porosity and nutrition. In this work, the effect of concentration and period cultured on Glycosaminoglycan (GAG) and mechanical properties have been studied. A bovine chondrocytes have been isolated and seeded in different agarose gel scoffed concentrations, about 4% and 6%, for different period cultured, 0 and 7 days. The MTS machine and Spectrophotometric with calibration curve method were used to measure mechanical properties, and GAG concentration of the prepared samples, respectively. The results of mechanical tests and GAG contents shown that there are a wide range of dispersion in the most of the samples, which attribute to different factors. For mechanical properties, these factors could be attributed to anisotropic of the produced chondrocyte with agarose scaffolds, insufficient cells' dispersion within the gel scaffold during seeding and cultured time, and some test procedure condition, such as EBSS hydration. While for GAG results, those factors could be the differences of the cell growth environment between in-vitro and in vivo media.

Solar cells based on CdTe thin films

An analysis of the use of semiconductor solar cells based on thin-film cadmium telluride (CdTe) in power engineering is carried out. It is shown that the advantages of thin-film technology and CdTe itself as a direct-gap semiconductor open up the prospect of large-scale production of competitive CdTe solar modules. The physical and technical problems of increasing the efficiency of CdS/CdTe heterostructure solar cells, which are significantly inferior to the theoretically possible value in mass production, are discussed. The state of CdTe thin-film solar cells, which make CdTe a suitable material for ground-based photoelectric conversion of solar energy, the historical development of the CdTe compound, the application of CdTe thin films, the main methods and strategies of device production, device analysis and fundamental problems related to the future development of thin-film modules based on cadmium telluride.

Phase equilibrium diagram of the Hf-Fe-Sn system at 1070 K

Experimental studies of the phase equilibrium diagram of the Hf-Fe-Sn ternary system at 1070 K were performed by X-ray powder diffractometry, scanning electron microscopy and electron probe microanalysis techniques in the whole concentration range. At annealing temperature four ternary compounds are realized: Hf6FeSn2 (K2UF6 structure type, space group P-62m), Hf1.8Fe5Sn3.8 (Hf1.82Fe5Sn3.82 structure type, space group Cmmm), Hf3Fe4Sn4 (Zr3Fe4Sn4 structure type, space group Pnma), and Hf9Fe3.7Sn10.3 (Hf9Fe4Sn10 structure type, space group Cmc21). An existence of the Hf1-xFe2+x-ySny solid solution formed by substitution of the iron atoms by tin in the Hf1-xFe2+x (MgZn2-type) binary compound up to 19 at. % Sn was found. Solubility of Fe in the Hf5Sn3 binary (Mn5Si3-type) extends up to 10 at. % (a=0.8363(2)-0.8324(4), c=0.5726(1)-0.5686(4) nm).