Suchergebnisse

The results of processing experimental data on heat treatment in drying processes of thin thermal insulation materials are presented. As a result of processing the experimental data by generalized complex variables, formulas for determining the heat flux density, average integral temperatures, the intensity of moisture evaporation, and the duration of the heat treatment process of materials were obtained. Based on the elements of the thermal regular regime theory, formulas for determining the rate of heating of the wet body and the rate of loss of moisture content have been established by processing experimental data using the least squares method. The conditions of the drying process in the regular mode are considered. Processing experimental data with generalized complex variables allows you to move from one coordinate system to another, from one variable to another, without performing additional time-consuming experiments. Based on the equation of drying kinetics and the generalized drying curve, the relationship between the dimensionless heat flux and the relative drying rate is given. For the single-zone method of calculating the drying rate curve, an approximate relationship for determining the relative drying rate is given. The relationship between material surface temperature and the relative drying rate in the heat treatment processes of ceramic tiles, asbestos sheets, wool felts was established. All of the above formulas were used to check the reliability of the obtained dependencies, as well as to compare the calculated values of the main parameters of the drying kinetics with the experiment.

The effect of duration and annealing temperature in the range of 400–800 °C on the thermokinetic EMF value in titanium nickelide, the composition of which is close to the equi-atomic one, at a reverse phase transition was investigated. Thermokinetic EMF was measured directly using a digital millivoltmeter MNIPI V7-72. The phase and elemental composition of the alloy and the kinetics of thermoelastic phase transformations have been checked by X-ray diffraction and calorimetric studies, and X-ray microanalysis. Annealing at temperatures of 500 and 800 °C leads to an increase in the thermokinetic EMF value from 0.22 to 0.25 mV. Removal of the oxide layer from the sample surface annealed at 700 °C for 0.5 h leads to an increase in the thermokinetic EMF value from 0.22 to 0.26 mV for the 1-st thermal cycle. It was found that thermal cycling causes a decrease in the thermokinetic EMF values down to 0.98 mV for the 20th thermal cycle for the samples without an oxide layer and to 0.3 mV for the samples with an oxide layer, respectively. With the increase in annealing time up to 20 h at 700 °C, the decrease in the thermokinetic emf value to 0.16 mV was observed. The thermokinetic EMF value after heat treatment is associated with changes in the physical and mechanical properties of the alloy and characterized by a shift of the characteristic temperatures of the phase transition. The research results are important for understanding the physics of thermoelectric phenomena in shape memory alloys during nonstationary heating and can be used both to control the homogeneity of their physical and mechanical properties and to design smart actuators and sensors, mechanisms of control systems.

This work was supported by The Centre National de la Recherche Scientifique (CNRS) of France and the French Embassy Program. The authors are also grateful for partial support by COST Action CA15216, the Estonian Science Foundation (grants PUT1689 and PUT1372), the Estonian Centre of Excellence in Zero Energy and Resource Efficient Smart Buildings and Districts, ZEBE, grant 2014-2020.4.01.15.0016 and Latvian Science Council grant lzp-2018/2-0083. ; In the present paper, we investigate the effect of heat treatment on the geometry and mobility of Au nanoparticles (NPs) on a Si substrate. Chemically synthesized Au NPs of diameter ranging from 5 to 27 nm were annealed at 200, 400, 600 and 800 °C for 1 h. A change in the geometry from faceted to more rounded shapes were observed with increasing annealing temperature. Kinetic Monte Carlo simulations indicate that the NPs become rounded due to the minimization of the surface area and the transition to lower energy surface types (111) and (100). The NPs were manipulated on a silica substrate with an atomic force microscope (AFM) in tapping mode. Initially, the NPs were immovable by AFM energy dissipation. However, annealed NPs became movable, and less energy was required to displace the NPs annealed at higher temperature. However, after annealing at 800 °C, the particles became immovable again. This effect was attributed to the diffusion of Au into the Si substrate and to the growth of the SiO2 layer. ; Centre National de la Recherche Scientifique; Latvian Council of Science lzp-2018/2-0083; Eesti Teadusfondi PUT1372,PUT1689,2014-2020.4.01.15.0016; European Cooperation in Science and Technology CA15216; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART² ; https://www.beilstein-journals.org/bjnano/content/pdf/2190-4286-11-6.pdf

The coating on the 22MnB5 steel is intended to protect it against oxidation during the forming process. This steel is hot-pressed. A preheating before the pressing and subsequent hardening in the tool affects the properties of the AlSi coating. This study summarizes the results of investigating the effect of heat treatment parameters on the formation of intermetallics in the AlSi coating. The chemical analysis of the coating was performed by the EDX and EBSD method and the mechanical properties were determined by the Hysitron TI 950 TriboIndenter™ system. The result of this study is that, due to a diffusion during the heat treatment, the brittle coating was transformed into a tougher phase.