Irina Kurzina

Selective oxidation of alcohols over Si3N4-supported silver catalysts

Silver-containing catalysts supported on ceramic silicon nitrides and modified with Zr or Al are considered. The catalytic activities of the catalysts in the dehydrogenation and oxidative dehydrogenation of ethanol into acetaldehyde are compared. The introduction of oxygen into the reaction mixture decreases the temperature of 100% ethanol conversion to 270°C and increases the acetaldehyde selectivity to 95% for all of the catalysts. According to temperature-programmed reduction data, the simultaneous presence of Fe and Ag on the catalyst surface enhances the activity of the supported catalysts. It is hypothesized that the Ag/Fe interface plays the key role in the formation of active sites on the catalyst surface.

Modification of Polymer Materials by Electron Beam Treatment

Electron beam processing is one of the effective methods for modification of surface material properties. Influence of electron beam irradiation on the structure of polymeric materials such as polyvinyl alcohol and polylactic acid was investigated. Electron beam processing was carried out at 8 kV accelerating voltage and a pressure of 3 x 10-2 Torr, the emission current was from 25 to 40 A, the pulse duration was from 150 to 300 μs and the pulse number was from 1 to 10. The elemental composition and the structural state of the surface of irradiated polymer materials were studied by infrared spectroscopy (IR-spectroscopy), X-ray photoelectron spectroscopy (XPS), scanning-electron microscopy (SEM) and atomic-force microscopy (AFM) methods. It was established that certain chemical processes take place and some physicochemical properties change under electron treatment.

Effect of ultrafine powders on the structural formation processes and mechanical properties of Al–7%Si alloy

The multi-component system interaction mechanisms associated with ultrafine powders (TiO2 and ZrO2) and fluorine-containing salts (K2ZrF6, Na3AlF6 and Na5Al3F14) with the Al–7%Si melt are studied. The formation of a multi-phase system with a high concentration of crystallization centres (N ≈ 7 · 1012 U/cm3) was identified. We experimentally show that the injection of an ultrafine powders modifying mixture containing refractory metal oxides and fluorine-containing salts into a Al–7%Si melt leads to a significant reduction in the a silicon plate size (by 1.5 times) and the Fe-containing phases (by 4 times). An equal distribution of the eutectic phase (α-Al + β-Si) is established in the Al– 7%Si alloy. As a result of microstructural changes when the modifying mixture was injected, a factor of 2 increase in the Al–7%Si alloy ductility was observed.

Synthesis and investigation of physico-chemical, antibacterial, biomymetic properties of silver and zinc containing hydroxyapatite

In the work we carried out microwave synthesis of modified hydroxyapatites (HA) with different content of ions. A solid solution based on HA remains a single-phase sample when the calcium ions are substituted by silver and zinc ions up to 5 % by weight (0.5 mole fraction). The microstructure parameters, morphology and the particle powders size were studied by X-ray diffraction analysis, IR spectroscopy, and scanning electron microscopy (SEM). It is shown that the modification of НA by silver (AgHA) and zinc (ZnHA) ions increases the size of its particles, the degree of crystallinity, and the pore sizes of the samples while reducing their specific surface and uniformity of their forms. Elemental analysis and distribution of elements over the surface of HA, AgHA, and ZnHA powders were performed by X-ray spectral microanalysis (RSMA). The ratio of Ca/P is within the range of 1.66-1.77 and corresponds to the ratio of Ca/P in stoichiometric HA and the HA entering bone tissue. The ability of AgHA- and ZnHA-subs...

Preparation of Biocompatible Composites based on Poly-L-Lactide/Hydroxyapatite and Investigation of their Anti-Inflammatory Activity

Relevance of the work is due to the need for new materials that are used in medicine as a substitute for natural bone tissue injuries, fractures, etc. The aim of the work is to obtain composites with improved biocompatible properties based on poly-L-lactide (PLA) and hydroxyapatite (HA) and to perform pilot analysis of interaction PLA, HA, composite PLA-HA with primary human monocytes-derived macrophages in vitro. The pilot experiments using human primary monocytes cultivated on the surface of the samples demonstrated that PLA-HA can stimulate release of anti-inflammatory cytokines that indicates the presence of potential anti-inflammatory properties of the composites

The preparation of the Ti-Al alloys based on intermetallic phases

This article deals with a method of obtaining materials in the Ti-Al system. Research was carried out in accordance with the phase diagram of the system state. It was established, that both single-phase and multiphase systems, containing finely dispersed intermetallic compositions of phases Ti3Al, TiAl and TiAl3, are formed. Additionally, it was found that the pure finely dispersed (coherent-scattering region (CSR) up to 100 nm) intermetallic compound TiAl3 is formed at molar ratio of Ti:Al = 1:3. Experimentally proved the possibility of produce the complex composition of alloys and intermetallic compounds and products based on them.

Effect of ultradisperse TiO2, ZrO2, and cryolite powders on high-chromium cast iron hardening

The quantitative parameters of structural-phase state of Fe–27% Cr–2% Ni–2.8% C cast iron are determined via X-ray diffraction and transmission electron microscopy before and after adding ultradisperse TiO2, ZrO2 and cryolite powders. The contributions from individual physical mechanisms in increasing the yield stress of cast irons are quantitatively assessed. It is established that the main contribution to the durability of modified Fe–27% Cr–2% Ni–2.8% C cast iron come from solid-solution, dispersion, and grain-boundary mechanisms of hardening.

Grain size effect on yield strength of titanium alloy implanted with aluminum ions

The paper presents a transmission electron microscopy (TEM) study of the microstructure and phase state of commercially pure titanium VT1-0 implanted by aluminum ions. This study has been carried out before and after the ion implantation for different grain size, i.e. 0.3 µm (ultra-fine grain condition), 1.5 µm (fine grain condition), and 17 µm (polycrystalline condition). This paper presents details of calculations and analysis of strength components of the yield stress. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a different effect on the yield stress. So, both before and after the ion implantation, the increase of the grain size leads to the decrease of the alloy hardening. Thus, hardening in ultra-fine and fine grain alloys increased by four times, while in polycrystalline alloy it increased by over six times.

Influence of the Composition, Structure, and Physical and Chemical Properties of Aluminium-Oxide-Based Sorbents on Water Adsorption Ability

Interaction between the water adsorption ability of aluminium-oxide-based sorbents and their chemical composition, acid-base properties of the surface, and textural characteristics has been analysed. Alumina desiccants were synthesized with the centrifugal–thermal activation of gibbsite followed by the hydration of the gibbsite under mild conditions. It was demonstrated that the multicyclic adsorption regeneration of samples under realistic conditions results in structural transformations and changes in the acidity of their surfaces and water adsorption ability. The modification of pseudoboehmite with alkali ions increases surface basicity and the dynamic capacity of adsorbents relating to water vapours. Equations have been presented that describe the adsorption and desorption processes taking place during water vapour adsorption with the materials studied.

Structural-phase state and surface properties of composite materials based on polylactide and hydroxyapatite

The phase composition and unit cell parameters were determined for composites based on polylactide and hydroxyapatite with the polylactide/hydroxyapatite weight ratios of 90/10, 80/20, 70/30, and 60/40. As the polylactide content of the composites is increased, they become less hydrophilic, and the surface energy σS-G increases from 29.13 to 74.35 mJ m–2. The sample with the component weight ratio of 70/30 is characterized by the maximal roughness, and the Ca2+ and Mg2+ ions from simulated body fluid are actively adsorbed onto its surface, as proved by SEM examination of the composites.