Fabrication of Coatings on the Surface of Magnesium Alloy by Plasma Electrolytic Oxidation Using ZrO2 and SiO2 Nanoparticles

Results of investigation of the incorporation of zirconia and silica nanoparticles into the coatings formed on magnesium alloy by plasma electrolytic oxidation are presented. Comprehensive research of electrochemical and mechanical properties of obtained coatings was carried out. It was established that the polarization resistance of the samples with a coating containing zirconia nanoparticles is two times higher than that for the sample with base PEO layer. One of the important reasons for improving the protective properties of coatings formed in electrolytes containing nanoparticles consists in enhanced morphological characteristics, in particular, the porosity decrease and increase of thickness and resistivity (up to two orders of magnitude for ZrO2-containing coating) of porousless sublayer in comparison with base PEO layer. Incorporation of silica and zirconia particles into the coating increases the mechanical performances. The layers containing nanoparticles have greater hardness and are more wear resistant in comparison with the coatings formed in the base electrolyte

Composite Coatings of AMg3 Alloy Formed by a Combination of Plasma Electrolytic Oxidation and Fluoropolymer Spraying

This paper presents the results of an investigation of the changes in the corrosion, wear resistance, and wettability of composite coatings formed on the AMg3 alloy through plasma electrolytic oxidation (PEO) and subsequent spraying with an organofluorine polymer. The evaluation of the electrochemical properties of the composite layers revealed a decrease in the corrosion current density compared with the PEO coating (from 3.8 × 10−8 to 3.1 × 10−11 A/cm2). The analysis of the wear resistance of composite coatings established that the application of this type of coating reduced the wear of the samples by two orders of magnitude when compared with the PEO layer. Using the contact-angle measurement, it was found that with an increase in the number of polymer spray applications, the wettability of coatings decreased, so the contact angle for the composite coating with triple fluoropolymer application increased by 134.3° compared to the base PEO coating

Electronic Structure, Optical and Magnetic Properties of Oxygen-Deficient Gray TiO_2–δ(B)

The gray-colored oxygen-deficient TiO2–δ(B) nanobelts have been synthesized through a combination of the hydrothermal method followed by an ion exchange process and vacuum annealing. Electron paramagnetic resonance reveals an existence of F-centers in the form of electron-trapped oxygen vacancies within the anionic sublattice of the gray bronze TiO2 that induces its colouration. The diffuse reflectance spectroscopy showed that the formation of oxygen vacancies into TiO2(B) significantly increases its absorption intensity in both visible and near infrared ranges. The band gap of TiO2(B) with anionic defects is equal to 3.03 eV (against 3.24 eV for white TiO2(B) treated in air). Room temperature ferromagnetism associated with the defects was detected in gray TiO2–δ(B), thus indicating it belongs it to the class of dilute magnetic oxide semiconductors. It was found that in the low-temperature range (4 K), the magnetic properties of vacuum annealed TiO2(B) do not differ from those for TiO2(B) treated in air. We hope that the findings are defined here make a contribution to further progress in fabrication and manufacturing of defective TiO2-based nanomaterials for catalysis, magnetic applications, batteries, etc

Bone Tissue Condition during Osteosynthesis of a Femoral Shaft Fracture Using Biodegradable Magnesium Implants with an Anticorrosive Coating in Rats with Experimental Osteoporosis

Today, osteoporosis has become a major global health issues. The World Health Organization declares that 320 billion people have osteoporosis now, and more than 1.5 billion osteoporosis traumatic events occur every year. Bones become fragile and fracture risk is high; thus, it is crucial to choose the right biodegradable implants in order to minimize reoperations of patients with systemic osteoporosis. This investigation aimed to carry out a morphological assessment of the state of bone tissue with osteosynthesis of a femoral fracture in rats, using a model of osteoporosis with the installation of magnesium alloy implants coated with hydroxyapatite and sealed with polytetrafluoroethylene. According to this study, the indicators of angiogenesis and bone formation in experimental animals were significantly higher when an implant coated with hydroxyapatite sealed with polytetrafluoroethylene was used, compared to an implant coated only with hydroxyapatite and in rats without an implant. Based on the data obtained, it is possible to consider a magnesium implant coated with hydroxyapatite and sealed with polytetrafluoroethylene as a promising material for fracture therapy in patients with reduced bone density