Search academic texts

Information × Registration Number 0224U031511, 0122U001972 , R & D reports Title Phase transitions and kinetic properties of molecular systems with spatial nanohomogeneities relevant to environmental safety and medicine popup.stage_title Head Lazarenko Maksym M., Доктор фізико-математичних наук Registration Date 03-05-2024 Organization Taras Shevchenko National University of Kyiv popup.description2  A new thermodynamic model for the melting of nanocrystals within a solid matrix and a comprehensive model for studying relaxation processes therein have been presented. For the first time, these models allow the determination of characteristics such as the density, magnitude of structural stress, surface energy, and entropy of nano-inclusions in nanocrystals. An advanced experimental photoacoustic technique for analyzing temperature changes and thermoelastic disturbances in gel-based structures has been developed, along with a new theory on the mechanism of photoacoustic response formation in such systems. This photoacoustic response is associated with the periodic thermoelastic deformation of the polymer membrane under the influence of temperature waves. It has been discovered that relaxation processes in solid cellulose-water systems and substituted cellulose-water systems with ionic impurities result from a superposition of several types of relaxations. These include two dielectric relaxations in pure ice caused by the motion of a) orientational L and D Bjerrum defects and b) ion pairs of defects H3O+ and OH-; c) dielectric relaxation in salt ice clusters associated with the hydrate shells of ions Na+ and Cl-, and d) dielectric relaxation in the external hydrate shells of nanocrystal cellulose and substituted cellulose molecules. The molecular mechanism of the last dielectric relaxation process is related to the conformational changes of methoxyl groups on the surface of cellulose nanocrystals and methoxypropoxy groups in substituted cellulose molecules, which are hydrogen-bonded to the hydrate shell. The addition of ions to the solution leads to partial blocking of the formation of hydrate shells, which results in changes to the position of the dielectric relaxation region, energy, and entropy of the activation processes. Product Description popup.authors Alieksieiev Oleksandr M. Aleksieiev Serhii O. Andrusenko Dmytro A. Vergun Liena Yu. Hnatyuk Kateryna I. Kovalchuk Valerii I. Ohorodnyk Kateryna О. Sosnovska Mariia О. popup.nrat_date 2024-05-03 Close