Improvement of Protective Oxide Layers Formed by Highfrequency Plasma Electrolytic Oxidation on Mg-RE Alloy with LPSO-Phase

Received: 17.04.23. Revised: 17.05.23. Accepted: 23.05.23. Available online: 29.05.23.PEO of Mg-RE (LPSO) alloy allows improving its corrosion behaviour and surface mechanical properties.Increase of pulse frequency under PEO allows decreasing the porosity and heterogeneity of the oxide layers.The best corrosion resistance and adhesive strength demonstrate the oxide layer obtained in aluminate electrolyte under high-frequency PEO.Oxide layers on Mg97Y2Zn1 magnesium alloy with strengthening LPSO-phase were formed by plasma electrolytic oxidation (PEO) in bipolar mode with frequency variation of forming current pulses (50 and 500 Hz) and addition of sodium aluminate or sodium silicate to alkali phosphate fluoride electrolyte. Microstructure, chemical and phase composition, corrosion and mechanical properties of the oxide layers formed were investigated. With increasing current frequency for both electrolytes, an increase in homogeneity of the oxide layers structure and a decrease in their porosity and fracturing at constant thickness were recorded. The oxide layers formed at 500 Hz even with some decrease in hardness have better adhesive strength and 2 orders of magnitude higher short-term corrosion resistance values. PEO of Mg-alloy with LPSO-phase in the electrolyte with addition of sodium aluminate in combination with increased pulse frequency (500 Hz) allows forming the best-quality uniform oxide layer with high hardness, adhesive strength and corrosion resistance properties. The use of electrolyte with addition of sodium silicate reduced the adhesive strength by 1.5 times and brought down the long-term corrosion resistance of oxide layers by an order of magnitude, as compared with the electrolyte with sodium aluminate. The reason for a significant improvement in the complex of protective properties of the oxide layers with an increase in the current pulse frequency is supposed to be a decrease in the power and duration of individual microarc discharges with simultaneous increase in their number per unit oxidized area.Financial support is provided by the Russian Science Foundation (grant No. 20-79-10262), https://rscf.ru/project/20-79-10262/

Improvement of protective oxide layers formed by high-frequency plasma electrolytic oxidation on Mg-RE alloy with LPSO-phase

Oxide layers on Mg97Y2Zn1 magnesium alloy with strengthening LPSO-phase were formed by plasma electrolytic oxidation (PEO) in bipolar mode with frequency variation of forming current pulses (50 and 500 Hz) and addition of sodium aluminate or sodium silicate to alkali phosphate fluoride electrolyte. Microstructure, chemical and phase composition, corrosion and mechanical properties of the oxide layers formed were investigated. With increasing current frequency for both electrolytes, an increase in homogeneity of the oxide layers structure and a decrease in their porosity and fracturing at constant thickness were recorded. The oxide layers formed at 500 Hz even with some decrease in hardness have better adhesive strength and 2 orders of magnitude higher short-term corrosion resistance values. PEO of Mg-alloy with LPSO-phase in the electrolyte with addition of sodium aluminate in combination with increased pulse frequency (500 Hz) allows forming the best-quality uniform oxide layer with high hardness, adhesive strength and corrosion resistance properties. The use of electrolyte with addition of sodium silicate reduced the adhesive strength by 1.5 times and brought down the long-term corrosion resistance of oxide layers by an order of magnitude, as compared with the electrolyte with sodium aluminate. The reason for a significant improvement in the complex of protective properties of the oxide layers with an increase in the current pulse frequency is supposed to be a decrease in the power and duration of individual microarc discharges with simultaneous increase in their number per unit oxidized area

Characterization of the cork oak transcriptome dynamics during acorn development

Background: Cork oak (Quercus suber L.) has a natural distribution across western Mediterranean regions and is a keystone forest tree species in these ecosystems. The fruiting phase is especially critical for its regeneration but the molecular mechanisms underlying the biochemical and physiological changes during cork oak acorn development are poorly understood. In this study, the transcriptome of the cork oak acorn, including the seed, was characterized in five stages of development, from early development to acorn maturation, to identify the dominant processes in each stage and reveal transcripts with important functions in gene expression regulation and response to water. Results: A total of 80,357 expressed sequence tags (ESTs) were de novo assembled from RNA-Seq libraries representative of the several acorn developmental stages. Approximately 7.6 % of the total number of transcripts present in Q. suber transcriptome was identified as acorn specific. The analysis of expression profiles during development returned 2,285 differentially expressed (DE) transcripts, which were clustered into six groups. The stage of development corresponding to the mature acorn exhibited an expression profile markedly different from other stages. Approximately 22 % of the DE transcripts putatively code for transcription factors (TF) or transcriptional regulators, and were found almost equally distributed among the several expression profile clusters, highlighting their major roles in controlling the whole developmental process. On the other hand, carbohydrate metabolism, the biological pathway most represented during acorn development, was especially prevalent in mid to late stages as evidenced by enrichment analysis. We further show that genes related to response to water, water deprivation and transport were mostly represented during the early (S2) and the last stage (S8) of acorn development, when tolerance to water desiccation is possibly critical for acorn viability. Conclusions: To our knowledge this work represents the first report of acorn development transcriptomics in oaks. The obtained results provide novel insights into the developmental biology of cork oak acorns, highlighting transcripts putatively involved in the regulation of the gene expression program and in specific processes likely essential for adaptation. It is expected that this knowledge can be transferred to other oak species of great ecological value.Fundação para a Ciência e a Tecnologi

STRATEGIC MANAGEMENT OF AN ENTERPRISE STEADY DEVELOPMENT

The article views the issues of management of an enterprise steady development as a key factor ensuring its competitiveness. The author proposes the model of management of an enterprise steady development allowing to analyze and coordinate all elements of management system, and the technique of complex optimization ensuring the dynamic character of managerial decisions making