Fatigue Behavior of an AM50 Die-Casting Alloy Anodized by Plasma Electrolytic Oxidation

While an anodizing process is essential for magnesium alloys to be used under corrosive environments, it sometimes stimulates a fatigue fracture that initiates at the interface between the coating layer and the substrate. In this study, a plasma electrolyte oxidation (PEO) technique was employed to provide excellent adhesion between the anodizing layer and the AM50 die-cast by applying an extremely high dielectric discharge in an alkaline phosphate electrolyte, and its effect on corrosion and fatigue behaviors was investigated. The stress intensity factor at the fatigue limit was estimated to be 0.28 MPam0.5. The specimen anodized using the PEO technique exhibits enhanced strength and corrosion resistance compared to the unanodized counterpart. Furthermore, it shows a relative fatigue life in spite of the thick anodizing layer because the crack initiates from the interface, not from the pore near the interface.

Expert-analytical approach to assessing activity of vitamin D based on determination of vitamin D associated links by indicators of water-electrolyte metabolism

The authors used the proposed method of mathematical and statistical processing of laboratory data (indicators of electrolyte metabolism and osteomarkers) of archived data of 82 patients with various bone diseases aged 9.90 ± 0.55 years compared the structural changes in the panel of ratios of individual electrolytes and the influence of individual indicators on them in personalized data, on the basis of which a conclusion was made about a single mechanism of coinciding influences in the exchange of bone tissue. At the same time, it was found that the complex of associated links detected by the vitamin influence on the panel of electrolyte ratios may differ signifcantly in some cases from each other. These differences consisted in highly pronounced differences in the activity of vitamin D in relation to various components of osteosynthesis and osteolysis, which are described in the modern literature. On this basis, the authors conclude that the used method (analytical system) allows to identify the functional connections of the dynamics of the indicator of vitamin D in individual cases with the dynamics of other indicators of bone, which signifcantly expands the informativeness of the results of laboratory examination of the patient in determining the leading systems the implementation of functional activity of the vitamin. The presented results justify the possibility of creating and describing different images of vitamin D-related changes in the plasma electrolyte composition, followed by their use in the identifcation of certain disorders of calcium metabolism and/or evaluating the effectiveness of the therapy used in each individual case.

Obtaining and plasma-electrolyte modification of fibers of ultralight magnesium alloy

The results of researches for the transformation to fiber state the Mg-8Li-1Al-0.6Ce-0.3Y ultralight magnesium alloy by the Pendant Drop Melt Extraction (PDME), and subsequent modifying obtained fibers by Plasma-Electrolytic Treatment (PET) are presented. The results demonstrate possibility of successful application of the above-mentioned methods in relation to chemically active materials. Purposeful modifying of ultralight magnesium alloys by PDME and PET methods is capable to significantly expand areas of using to these materials.

Photocatalytic activity of oxide systems based on doped d-elements of titanium alloys

CO-, W-, MO- and Zn-containing hetero-oxide nanostructured coatings on titanium and its alloys formed by plasma-electrolyte oxidation in galvanostatic mode from alkaline electrolytes were investigated. The morphology of the surface of the formed coatings was studied by scanning microscopy on the Zeiss Evo 40XVP microscope. The phase composition of the obtained coatings was determined on the X-ray diffractometer Drone-2. Photocatalytic activity of ZnO-WO3/TiO2 films, ZnO-MOO3/TIO2, ZnO-Co3O4/TiO2, CoO-WO3/TiO2 tested in a model reaction of decomposition of an aqueous solution of azobye with a concentration of 12,2·10-5 mol/L (MО) at UV irradiation. It is shown that with plasma-electrolyte oxidation of titanium and its alloys in alkaline diphosphate electrolytes in the mode of «drop-down power» forming heterostructural composites with micro-globular surface morphology. The possibility of controlling the phase and elemental composition of oxide layers, as well as the topography of the surface by changing the composition of the electrolyte and the content of individual components, as well as the modes of formation is confirmed. Heteroxide coatings formed in PEO modes differ in composition and surface morphology, but all exhibit photocatalytic properties of varying degrees of activity. The study of the photocatalytic activity of the obtained coatings in the azo dye decomposition reaction by means of UV testing allowed to rank the heteroxide systems according to the specified parameter. Thus, the degree of decomposition of MF on ZnO-WO3/TiO2 films in 50 minutes was 23 %. Metal oxide systems ZnO-Co3O4/TiO2 had similar characteristics of the degree of decomposition – 21 %. The incorporation of CoO and WO3 oxides into the coating composition reduced the catalytic activity of the system to 19 %. The unstable mode of formation of ZnO-MoO3/TiO2 oxides and the low speed of the process have affected the quality of the catalytic coating activity, reduced the degree of decomposition of MO to values of titanium monoxide Ti/TiO2 without dopants. Comparison of quantitative characteristics of the properties of the obtained coatings allowed to determine the effects of dopants, incorporated into metal oxide systems, on their photocatalytic activity.

Comparing the methods of copper substrate polishing for CVD graphene synthesis

This paper presents a comparison of chemical and plasma electrolyte polishing methods for preparing a copper substrate for graphene synthesis by chemical vapour deposition. It is shown that in order to achieve the most uniform morphology of the surface of the copper substrate, it is preferable to use the electrolyte-plasma polishing method. With its help, the proportion of multilayer regions in the graphene coating obtained as a result of CVD synthesis decreases. The obtained results may serve a recommendation for creating a graphene coating with specified parameters.

FUNCTIONAL ELECTROCHEMICAL COATINGS IN DUAL-USE TECHNOLOGIES

Technological approaches to the application of functional electrochemical coatings in civil and military technologies are analyzed. It is shown that the existing technical solutions are aimed at solving the problems of strengthening and protection of surfaces and detoxification of environments from pollutants of natural and man-made origin. Electrochemical coatings based on the iron triad, doped with refractory metals, increase corrosion resistance, microhardness and wear resistance of surfaces. Doped with transition metals heteroxide coatings, which are synthesized by the method of plasma electrolytic oxidation on aluminum and titanium alloys have catalytic properties to neutralize toxic substances in the gas and liquid phases. Peculiarities of electrochemical formation of functional coatings on construction materials of different types are investigated. It is shown that cathodic deposition by direct and pulsed current on low-carbon steel and gray cast iron forms uniform ternary coatings of Fe-Mo-W and composite systems of Fe-Co-Mo (Fe-Co-W), which have increased corrosion resistance and mechanical properties compared to base metal material. The obtained thin-layer coatings are recommended for the restoration and strengthening of worn surfaces, in particular in the technology of repair of weapons and military equipment. It was found that plasma-electrolyte treatment of piston silumin in alkaline solutions based on diphosphates synthesized heteroxide systems that are active in reducing the number of toxic emissions of internal star engines and reducing hourly fuel consumption. It is shown that nanocomposite coatings on titanium show photocatalytic activity on the destruction of model pollutants. The obtained materials have a set of enhanced functional properties and are promising for use in industrial and repair production, including the security and defense sector.

Risk factors for new-onset atrial fibrillation during critical illness: A Delphi study

Background New-onset atrial fibrillation (NOAF) is common during critical illness and is associated with poor outcomes. Many risk factors for NOAF during critical illness have been identified, overlapping with risk factors for atrial fibrillation in patients in community settings. To develop interventions to prevent NOAF during critical illness, modifiable risk factors must be identified. These have not been studied in detail and it is not clear which variables warrant further study. Methods We undertook an international three-round Delphi process using an expert panel to identify important predictors of NOAF risk during critical illness. Results Of 22 experts invited, 12 agreed to participate. Participants were located in Europe, North America and South America and shared 110 publications on the subject of atrial fibrillation. All 12 completed the three Delphi rounds. Potentially modifiable risk factors identified include 15 intervention-related variables. Conclusions We present the results of the first Delphi process to identify important predictors of NOAF risk during critical illness. These results support further research into modifiable risk factors including optimal plasma electrolyte concentrations, rates of change of these electrolytes, fluid balance, choice of vasoactive medications and the use of preventative medications in high-risk patients. We also hope our findings will aid the development of predictive models for NOAF.

Immediate and Delayed Response of Simulated Human Atrial Myocytes to Clinically-Relevant Hypokalemia

Although plasma electrolyte levels are quickly and precisely regulated in the mammalian cardiovascular system, even small transient changes in K+, Na+, Ca2+, and/or Mg2+ can significantly alter physiological responses in the heart, blood vessels, and intrinsic (intracardiac) autonomic nervous system. We have used mathematical models of the human atrial action potential (AP) to explore the electrophysiological mechanisms that underlie changes in resting potential (Vr) and the AP following decreases in plasma K+, [K+]o, that were selected to mimic clinical hypokalemia. Such changes may be associated with arrhythmias and are commonly encountered in patients (i) in therapy for hypertension and heart failure; (ii) undergoing renal dialysis; (iii) with any disease with acid-base imbalance; or (iv) post-operatively. Our study emphasizes clinically-relevant hypokalemic conditions, corresponding to [K+]o reductions of approximately 1.5 mM from the normal value of 4 to 4.5 mM. We show how the resulting electrophysiological responses in human atrial myocytes progress within two distinct time frames:(i) Immediately after [K+]o is reduced, the K+-sensing mechanism of the background inward rectifier current (IK1) responds. Specifically, its highly non-linear current-voltage relationship changes significantly as judged by the voltage dependence of its region of outward current. This rapidly alters, and sometimes even depolarizes, Vr and can also markedly prolong the final repolarization phase of the AP, thus modulating excitability and refractoriness.(ii) A second much slower electrophysiological response (developing 5–10 minutes after [K+]o is reduced) results from alterations in the intracellular electrolyte balance. A progressive shift in intracellular [Na+]i causes a change in the outward electrogenic current generated by the Na+/K+ pump, thereby modifying Vr and AP repolarization and changing the human atrial electrophysiological substrate.In this study, these two effects were investigated quantitatively, using seven published models of the human atrial AP. This highlighted the important role of IK1 rectification when analyzing both the mechanisms by which [K+]o regulates Vr and how the AP waveform may contribute to “trigger” mechanisms within the proarrhythmic substrate. Our simulations complement and extend previous studies aimed at understanding key factors by which decreases in [K+]o can produce effects that are known to promote atrial arrhythmias in human hearts.