Study of Magnetite Nanoparticles by the Method of Mössbauer Spectroscopy

In this work, we studied the Mössbauer spectra of magnetite samples of various compositions. To protect magnetite from oxidation, the resulting particles are coated with protective shells, among which silanes are promising, which polymerize on the surface of magnetite nanoparticles, forming strong covalent bonds. The coating of nanoparticles protects them from aggressive environmental influences, evens out their size distribution, and also protects the environment from the possible toxic effects of the particles themselves. It was shown that the magnetite phase predominates in the sample of native particles, the coating of native particles with alkoxysilane does not lead to fundamental changes in the phase state of the sample particles, and oxidation with nitric acid leads to the complete transformation of magnetite into maghemite. It is obvious that the reason for the distortions of the relaxation nature in the Mössbauer spectra of the samples is the small sizes of the iron-containing domains, which allows us to consider the description of the spectra within the framework of the model of multilevel superparamagnetic relaxation.

Adiabated flowing streams in nozzles: influence of regular characteristics on relaxation steam formation

Two-phase nozzles, in which the phase transition process takes place, can work in jet superchargers for various purposes, including jet thermal pumps (steam-water injectors) and thermal compressors. In such schemes of thermal transformers, the ejector performs the function of a preliminary compression stage in order to reduce the load on the compression of the working substance in the main compressor. The use of fluxes of boiling liquid as energy-efficient working fluids is inhibited due to the lack of a reliable description of the mechanism of their flow. Finding the dependence of the steam content on the pressure and temperature at the nozzle exit will make it possible to determine the variant of the initial parameters at which the overproduction of steam will be greatest. It is also worth determining the change in the velocity factor, as well as the change in the thrust of the nozzle in the studied range of parameters, in order to find out whether the pressure at the nozzle outlet is a determining factor when choosing the design parameters of the nozzles. The article proposes to investigate the boiling streams in such nozzles by the method of mathematical modeling using a model that takes into account the relaxation nature of vaporization. The study used a compressible two-phase medium model, a kinetic model of evaporation / condensation. The model also takes into account the dynamic and mechanical equilibrium of the process of evaporation-condensation. The calculations were performed using an Ansys CFX commercial CFD product. The value of the mean square relative error of pressure measurement does not exceed 0,119%. The average discrepancy between the obtained data between the mathematical model and the field experiment does not exceed 3%.

Improved dielectric energy storage performance of Pb-free 0.5Na0.5Bi0.5TiO3-0.5SrTiO3 ceramics modified with CaO

CaO doped 0.5Na[Formula: see text]Bi[Formula: see text]TiO3 (NBT)-0.5SrTiO3 (ST) were prepared by a traditional solid-reaction method under various sintering temperatures. X-ray diffraction (XRD), electron scanning microscopy (SEM), and electrical measurements were employed to check the phases, microstructures, and energy storage properties. The doping of CaO can deeply affect the relaxation nature of NBT-ST ceramics. So the energy storage performance could be modified. Specially, sample with 1 at.% CaO exhibits a high energy storage density of 1.51[Formula: see text]J/cm3. Any further details can be found within this study.

Effect of Composition on the Physical Properties of (TlInSe2)1-х (TlGaTe2)х Solid Solutions

ABSTRACTWe carried out thermodynamic study of the TlInSe2-TlGaTe2 system based on the data of physicochemical analysis. Based on thermodynamic analysis and concentration dependence of physical properties, it was found that there is anion-cation substitution in TlInSe2-TlGaTe2 system. Continuous series of (TlInSe2)1-x (TlGaTe2)x solid solutions is forming throughout entire concentration range. We determined dielectric characteristics of samples, their frequency dispersion and nature of dielectric losses. The results demonstrate that the dielectric dispersion in the studied crystals TlInSe2 and (TlInSe2)0.5(TlGaTe2)0.5 has a relaxation nature. Hyperbolic decline of loss tangent with increasing frequency from 50 kHz to 35 MHz indicates the loss of pass-through conduction in (TlInSe2)1-x(TlGaTe2)x solid solutions.

Perceived Psychosocial Benefits Associated with Perceived Restorative Potential of Wilderness River-Rafting Trips

Analysis of the restorative experiences and psychosocial benefits of wilderness river rafting trips of varying difficulty with 186 Canadian participants of different ages supported the restorative potential of natural settings for all age groups as measured by the Perceived Restorativeness Scale. The two-factor structure (General Restorativeness and Coherence) was confirmed. Significant associations were found between scores on the General Restorative subscale and perceived psychosocial benefits (relaxation, nature appreciation or kinship, and physical fitness or achievement) and positive affect. However, the findings associated with the Coherence subscale were not conclusive.