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The morphology, structure, and elemental composition of hybrid materials based on polyelectrolyte complexes of chitosan with nickel and cobalt oxides formed on the surface of stainless steel are studied by using asymmetric alternating current. The X-ray phase analysis has shown that cobalt hydroxyisocyanate is the main phase of these hybrid materials. These hybrid materials are shown to be promising as the electrodes in supercapacitors with alkaline electrolyte, their specific capacitance reaching 479 F g‒1 at the current density of 1 A g–1. The antimicrobial activity of hybrid materials with respect to gram-positive (S. aureus) and gram-negative (E. coli) bacteria is revealed. The corrosion-protective properties of the hybrid materials are studied in 3.5 mass % NaCl solution. They are shown to shift the corrosion potential in the positive region as compared with unprotected steel. [ABSTRACT FROM AUTHOR]

Antibacterial drugs when used for a long time are known to cause antibiotic resistance in bacteria. Rapid development of resistance to modern antibacterial drugs by microorganisms makes it necessary to look for new therapeutic methods. The use of metal nanoparticles and their oxides as a basis for creating new generation antimicrobial agents is a promising alternative, which makes it interesting to study the methods for metal nanoparticles synthesis as well as their physical, chemical and pharmacological properties. The review discusses how antibiotic resistance develops in biofilms and possible ways to overcome it in the case of nanosize metal particles, describes the synthesis and nature of action of silver, copper and zinc cation-containing nanoparticles, and provides the results of assessing the effects of metal nanoparticles on antibiotic sensitivity in Gram-positive and Gram-negative bacteria as well as fungi as compared to the known dosage forms. Cu2+ cations and Zn2+ cations have a marked antibacterial effect towards Staphylococcus aureus and Pseudomonas aeruginosa. Ag+ cations showed the highest activity against S. aureus, Escherichia coli, Klebsiella pneumoniae and Candida albicans. [ABSTRACT FROM AUTHOR]

The possibility of forming hybrid coatings based on cobalt and nickel oxides immobilized in a chitosan polymer matrix on the surface of AISI 304 stainless steel using the non-steady-state electrolysis method is shown. The study of the morphology and surface structure of the coatings developed is carried out using scanning electron microscopy. According to X-ray spectral microanalysis, the main elements of the hybrid coatings are O, C, Co, and Ni. The formation of polyelectrolyte complexes and the immobilization of metal oxides in a chitosan polymer matrix are proven by infrared (IR) spectroscopy. Studying the phase composition of the hybrid coatings developed is carried out using X-ray diffraction and transmission-electron-microscopy methods. Identification of the X-ray diffraction patterns is difficult because of the amorphous structure and high dispersion of the coating substance. Therefore, the structure and most probable main phases of the hybrid coatings developed are established using transmission electron microscopy. It is established that oxide compounds of the coating represent particle agglomerates. It is shown that the results of structural investigation of hybrid coatings obtained using different physical-chemical methods are correlated and complementary. [ABSTRACT FROM AUTHOR]

We demonstrate the feasibility of fabricating hybrid coatings based on manganese, molybdenum, cobalt, iron and tungsten oxides on carbon-fiber cloth by transient electrolysis. The structure and surface morphology of the developed coatings are characterized by scanning electron microscopy. Electron-probe microanalysis shows that Mn, Mo, Co, Fe, and W are the major elements in the hybrid coatings. The charge state of elements in the surface layers of the hybrid oxide coatings is established by X-ray photoelectron spectroscopy, which also shows that oxygen is present in the coatings in quantities sufficiently high for the metals to be in the form of their highest oxides. For molybdenum, the predominant oxidation state is +6, iron is at +2 and +3, and manganese is +3 or higher. The formation of an intermediate layer of tungsten oxides on the surface of carbon-fiber cloth during the surface preparation stage is also demonstrated. [ABSTRACT FROM AUTHOR]

The effect of the parameters of micro-arc oxidation (MAO)—pulse repetition rate and pulse width—on the composition and properties of the coatings obtained by micro-arc oxidation of aluminum alloy D16T as well as on the productivity of the MAO process is explored. It is found that the pulse repetition frequency in the range from 100 to 500 Hz significantly increases the rate of the MAO coating deposition. Changes in composition and properties of the MAO coatings are observed at pulse width from 50 to 200 μs. Starting with a pulse width of 50 μs and a frequency of 400 Hz, the γ-Al2O3 crystal phase is detected in the coating and the elemental composition changes significantly along with morphology and microhardness of the coating. [ABSTRACT FROM AUTHOR]

Transient electrolysis based on polarization with alternating asymmetric current of industrial frequency is used in this work to obtain bismuth-ferrite hybrid materials on a support from aqueous solutions of electrolytes. X-ray phase analysis showed that the materials formed on the surface of the steel are multiphase systems. The influence of the heat-treatment temperature on the elemental and phase composition and the surface morphology of the hybrid materials is studied. The charge state of bismuth and iron in the surface layers and over the depth of ion etching of the hybrid material is studied with X-ray photoelectron spectroscopy, and layer-by-layer deposition of the components of the hybrid material is found. [ABSTRACT FROM AUTHOR]

Nanocrystalline bismuth titanates Bi2Ti4O11 (115±5 nm), Bi4Ti3O12 (60±5 nm), Bi2Ti2O7 (105±5 nm), Bi8TiO14 (82±5 nm), and Bi12TiO20 (102±5 nm) were synthesized by heat treatment of the coprecipitated composition. It was revealed that the crystallite sizes of the target materials are determined by the minimum crystallite size of the first phase to crystallize in the reaction system. The process parameters of the synthesis and of the sintering of the materials were found to depend on the melting point of the surface (nonautonomous) phase. It was shown that the formation of the materials is mainly influenced by the kinetic factor, and the influence of the structural features is less pronounced. [ABSTRACT FROM AUTHOR]

Formation of nanocrystalline bismuth titanate Bi2Ti2O7 with pyrochlore structure obtained via thermal decomposition of a co-precipitated product has been studied. The onset of vigorous formation of Bi2Ti2O7 has been shown to correlate with the melting point of the surface phase based on bismuth oxide. The upper temperature limit of the region of nanocrystalline Bi2Ti2O7 stability has been found. Technological parameters of synthesis of Bi2Ti2O7 with average crystallite size of 75–130 nm have been determined. [ABSTRACT FROM AUTHOR]

A material based on lanthanum orthophosphate LaPO4 with inclusion of particles of lanthanum metaphosphate LaP3O9 was synthesized. The influence of the process parameters of the synthesis on the structure and properties of the material was determined. Heat treatment of the coprecipitated lanthanum phosphates at 700°C leads to the formation of a nanopowder with the LaPO4crystallite size of approximately 17 nm. Heat treatment of the nanopowder at temperatures from 1100 to 1500°C yields compact materials based on the LaPO4-LaP3O9 system. The heat treatment of the nanopowder at 1100°C leads to a sharp decrease in the porosity of the material (to ~5%) at insignificant grain growth (200-400 nm); under these conditions, the thermal conductivity [λ(25°C) = 3.2 W m-1 K-1], microhardness [Hv(25°C) = 4.6 ± 0.4 GPa], Young's modulus [E(25°C) = 132 ± 9 GPa], and cracking resistance [K1c(25°C) = 1.6 ± 0.1 MPa m1/2] pass through maxima. The thermal expansion coefficient of the material depends on the heat treatment conditions only slightly and amounts to (8.2 ± 0.2) × 10-6 K-1. [ABSTRACT FROM AUTHOR]

The review is devoted to microarc (or plasma-electrolytic) oxidation (MAO) of carbon-graphite materials with the purpose of protecting their surfaces from oxidation, primarily, high-temperature oxidation. It is found that the formation of protective coatings on graphite under certain conditions occurs in accordance with trends similar to the formation of oxide layers on valve metals. The phenomenological model of the mechanism of formation of MAO coatings on graphite is given. In particular, the results of our own studies are described, as well as the data on the achieved level of characteristics of obtained MAO coatings are given. [ABSTRACT FROM AUTHOR]

The results of studies of composite electrochemical coatings modified by nano- and microparticles of various natures are presented. Functional properties (hardness, wear resistance, friction coefficient, corrosion resistance, etc.) and structural features of main types of composite coatings are considered. [ABSTRACT FROM AUTHOR]