Svetlana Lugovskoy

Production of hydroxyapatite layers on the plasma electrolytically oxidized surface of titanium alloys.

Hydroxyapatite (HA) is a bioactive material that is widely used for improving the osseointegration of titanium dental implants. Titanium can be coated with HA by various methods, such as chemical vapor deposition (CVD), thermal spray, or plasma spray. HA coatings can also be grown on titanium surfaces by hydrothermal, chemical, and electrochemical methods. Plasma electrolytic oxidation (PEO), or microarc oxidation (MAO), is an electrochemical method that enables the production of a thick porous oxide layer on the surface of a titanium implant. If the electrolyte in which PEO is performed contains calcium and phosphate ions, the oxide layer produced may contain hydroxyapatite. The HA content can then be increased by subsequent hydrothermal treatment. The HA thus produced on titanium surfaces has attractive properties, such as a high porosity, a controllable thickness, and a considerable density, which favor its use in dental and bone surgery. This review summarizes the state of the art and possible further development of PEO for the production of HA on Ti implants.

Effect of time on the formation of hydroxyapatite in PEO process with hydrothermal treatment of the Ti-6Al-4V alloy

A titania layer containing calcium and phosphate with rough and porous structure was prepared by plasma electrolytic oxidation (PEO) and hydrothermal treatment (HT) at different time treatment. The most corresponding to the stoichiometry of hydroxiapatite ratio of Ca: P in the oxide layer can be achieved by the optimization of the electrolyte composition and the main parameters of PEO. While at the stage of PEO hydroxiaptite precursors are formed with only residual quantity of the hydroxyapatite, the subsequent hydrothermal treatment results in the formation of a much more pronounced hydroxyapatite phase.

Physical and Chemical Characterization of Raw and Mechanochemically Treated Humine and Humic Acid from Brown Coals

Comparable analysis of the morphology of surface, IR-spectra and X-ray spectroscopy of source and mechanochemical dispersed samples of humic acid and humine of Kara-Keche coal has been made. Selective adsorption of ferricinium cation from water solutions of perchloric acid on the source and mechanochemical dispersed samples of humic acid and humine of Kara-Keche coal has been established.

Mathematical Modeling of High Energy Ball Milling (HEBM) Process

In the present study the modeling of the HEBM process is presented. The impact velocity, impact angle, rotation speed, mass of balls, ball-to-powder weight ratio and time of milling have been taken into account in order to calculate the energy transferred from the balls to the powder. Two different systems, namely, TiN-AlN and polysalicylic acid were experimentally investigated in order to confirm the validity of the model. The calculation results are in a reasonable agreement with the results of experimental research.

Solvation Excess of Urea over Water in Humic Acid in Three-Component Solutions Saturated with the Biopolymer

Humic acids were extracted from brown coals of the Kara-Keche deposit (Kyrgyzstan) and characterized. The solubility of humic acid in aqueous urea solutions was studied. The solvation excess of urea over water on humic acid in solution was calculated. The possibility of simultaneous binding of urea molecules on three independent centers of humic acids was shown. An estimation of humic acid molecular dimensions in aqueous urea solutions is given.

Modifying the Sorption Capacity of Biopolymers by the Mechanochemical Activation

Mechanochemical activation (MCA) of electrode lignin was performed and the activated lignin was studied by IR-spectroscopy for different activation times. The activated lignin was tested for the ability of binding Cr2O72-, Cu2+, Ni2+ ions. It was established that structure deformation, which does not distort the stronger hydrogen bond lattice, but leads to the formation of highly developed surface with active functional groups, occurs in the course of MCA. Weaker inter-layer bonds are broken in the activation process and quickly recovered after the load release. The comparison of the sorption capacity of Cr2O72-, Cu2+, Ni2+ ions by the MCA treated vs. inactivated lignin for different activation times was performed.