Search

The use of ceramics as matrices for immobilization of radionuclides for the purpose of their safe long-term disposal or useful application is studied with an emphasis placed on phase stability, structural integrity, hydrolytic stability, etc. This work implements a combined approach based on the sol–gel citrate synthesis of nanosized La2Ti2O7 powder and its subsequent spark plasma sintering to produce dense ceramics. The phase composition and structure of the nanosized La2Ti2O7 powder and the ceramic samples obtained in the temperature range of 900–1300°C were studied by powder X-ray diffraction and SEM. It was shown that the conditions of synthesis of the powder ensure the formation of nanosized crystalline La2Ti2O7 grains, consolidation of which under spark plasma heating is accompanied by a change in the phase composition of La2Ti2O7 from a single-phase monoclinic structure to orthorhombic structure with a LaTiO3 impurity at temperatures above 1200°C. It was found that a change in the ceramic structure is accompanied by the formation of non-porous and defect-free monolithic samples. This type of change was shown to lead to an increase in the relative density (81.3–95.7%) and compressive strength (78–566 MPa) of the ceramics. However, the hydrolytic stability decreases, as indicated by increasing La3+ leaching rate from 10–7 to 10–5 g/(cm2 day). The obtained results are useful for the systematic study of materials suitable for immobilization of radioactive waste in ceramics. [ABSTRACT FROM AUTHOR]

Composite sorbents based on Fe3O4 and Zn-Al-LDH with different weight ratios of magnetic and sorbing phases were obtained by the precipitation method. The optimal weight ratio of Zn/Fe was 16, which resulted in a 62% increase in hydromechanical strength. The maximum sorption exchange capacity towards U(VI) was 268.65 ± 22.22 mg/g. The efficiency of U(VI) adsorption was not affected by the presence of Cl−, SO42−, NO3− and Na+, Ca2+. The distribution coefficient in a groundwater model solution was Kd(U(VI) = 0.5–3 × 105 mL/g. The materials possess high exchange capacity and selectivity, which makes them suitable sorbents for U(VI) removal. [ABSTRACT FROM AUTHOR]

The manuscript points on the new challenges in higher education in terms of wartime in Ukraine after the world pandemic. The real country experience in English on-line teaching and learning is defined as it was important during the lockdown and it is suitable now in wartime in Ukraine. The aim of the research is to show helpful ideas, experience, to stress the advantages for English on-line teaching and learning. Some general theoretical methods as analysis and synthesis, and the empirical one as questionnaires discovered the advantages of the issue under study. The research has pointed out to the results: on-line teaching and learning prove the development of all the English language skills; off-line teaching and learning are basically useful for the students with high motivation. The Moodle platform (version 3.7), the University platform “Educational Electronic Information Complex” (EEIC), Zoom, Meet, Skype, Microsoft Teams are used for on-line teaching and learning. The most common advantages are the prospect to watch learning material on a laptop or mobile phone screen, to start any type the recordings as audio as video in the best quality. The conclusion is it is necessary to find a balance between on-line and off-line learning, communication, and interaction. [ABSTRACT FROM AUTHOR]