Papers by Keyword: Thermoelectric Power

Abstract: According to the well-known concept of multicomponent high-entropy alloys, high entropy of mixing can stabilize the formation of solid solutions (simple bcc or fcc crystal structure) during solidification. Stabilization of the solid solution and prevention of the formation of intermetallic phases during solidification is provided by the high entropy of mixing in the solid and liquid states. High-entropy alloys have increased strength, high hardness, thermal stability in combination with good resistance to oxidation and corrosion. These properties allow to significantly expand the scope of these alloys. In this work, the electrical resistivity, thermoelectric power and surface tension of binary Cu–Sn, Cu–Ga and Cu–Bi alloys, which are the sub-system components of model low-temperature high-entropy Bi–Cu–Ga–Pb–Sn alloys, have been studied in a wide temperature range including solid and liquid states. The lack of the surface tension data of the above-mentioned alloys is compensated by the model predicted values.

Abstract: The results of studies of magnetic and thermoelectric properties of pearlite, martensitic and austenitic steels, as well as cobalt and nickel based alloys are presented. The magnetization curves for materials from among the studied ones, as well as dependences of absolute thermoelectric power on the material temperature, are obtained. It was found that for ferromagnetic substances in weak magnetic fields the dependence of magnetic induction on the magnetic field strength is non-linear. This allows to conclude that magnetic permeability of such medium is not a constant, but can be described, for example, by a third-order polynomial.

Abstract: Ionic Seebeck effect has been investigated in Li (Na,K)₂O‐Nb₂O₅‐P₂O₅ glasses. Ionic Seebeck coefficients and heats of ion transfer have been measured. Soret coefficients have been calculated for glasses being studied. Temperature dependence and content of Nb₂O₅ dependence of Soret coefficients have been analyzed. Hypotheses of coefficients of self-diffusion and thermodiffusion ratio when temperature and content of Nb₂O₅ change have been proposed.

Abstract: The precipitation sequence of an Al-Mg-Si alloy with silicon excess was determined between 150°C and 300°C by combining ThermoElectric Power measurements and Transmission Electron Microscopy observations. From these studies, an experimental Isothermal Transformation Curve could be proposed in the investigated temperature range. After calibration of a model of KWN type allowing the simultaneous precipitation of two types of metastable rod-shaped precipitates to be taken into account, the same type of curve could be obtained and the yield strength evolution of the alloy during isothermal ageing treatments could be predicted.

Abstract: The paper presents an approach of non-destructive testing of plastic deformation of metals and alloys by measuring the differential thermoelectric power. Using the developed measuring device for this purpose, measurements of thermoelectric power were performed on several types of steels that are used in the manufacture of product pipelines. Incisions were made on the surface of the testes objects, for the purpose of experimental detection of the place of plastic deformation. In the process of stretching, thermoelectric power was measured at and near the place of the proposed plastic deformation. During the process of stretching the sample, the decrease in thermoelectric power measurement occurs almost linearly. The maximum change in the thermoelectric power measurement of the tested object was observe before the rapture discontinuity.

Abstract: This work presents experimental studying the effect of processing by severe plastic deformation (SPD) on the thermoelastic and thermoelectric properties of pure aluminum and copper under pulsed laser radiation. The studies were carried out on technical aluminum AD1 (99.3%) and pure copper M1 (99.9%). High pressure torsion (HPT) was used for processing by SPD. After the HPT processing, the materials samples in the form of a plane disk were subjected to pulsed laser radiation focused on the disk center. Pulsed lasers with a wavelength of 1.06 micron and operating in the free laser oscillation mode with pulse duration of 100 microseconds or in the mode of a single pulse with duration of about 10 nanoseconds were used. The thermoelastic and thermoelectric responses of the materials were determined by measuring acoustic waves and the thermoelectric power. The disks with the initial coarse-grained material state were considered as a reference sample, and the disks of the materials after SPD processing were considered as a controlled object. The results demonstrated a very high sensitivity of the parameters of thermoelastic and thermoelectric response to structural changes in the materials. For example, the used HPT mode led to a reduction in the maximum thermoelectric power value for aluminum by 40% and for copper by 35%.

Abstract: The aim of this study was to investigate the effect of the previously applied cold rolling and the latter heat treatment for the eutectoidal decomposition of δ-ferrite in 2507 type superduplex stainless steel (SDSS). The samples were cold rolled at seven different deformation rates which was followed by heat treatment at were 20, 700, 750, 800 and 850 °C temperatures. The rolled and heat treated samples were investigated by hardness tester, AC magnetometer and thermoelectric power measurement. The activation energy of the decomposition was determined by the Arrhenius equation through the results of the AC magnetometer measurement.

Abstract: Nanocomposite Fe_x(Al₂O₃)_100-x films with concentration gradient along the long axis of the samples (40 mm) have been obtained by sputter deposition technique and investigated. Based on the electric and magnetoresistive investigations the gradient Fe_x(Al₂O₃)_100-x samples in which concentration of one edge of the sample is smaller than concentration of a percolation threshold while concentration of opposite edge of this sample is upper the threshold have been determined. Influence of the heat flow direction on the thermoelectric power of the gradient samples has been investigated. Hysteresis of the thermoelectric power is observed when temperature gradient direction is changed.

Abstract: The measurement of thermoelectric power is a powerful method to investigate the metallurgical processes occurring in steels. In this study, four low carbon cold rolled steel sheets having different composition were investigated. The cold rolled sheets were heated up at heating rate 20 °C/hour up to different temperatures, whilst the change of thermoelectric power and hardness have been measured at room temperature after slow cooling. The thermoelectric power of steels increases with temperature until the recrystallization finishes. The raise of thermoelectric power during recrystallization is ranging between 50 and 160 nV/K, depends on the composition of the sheet. Specimens consist of boron exhibit lower thermoelectric power after recrystallization than the steel without any boron, probably due to metastable borocarbide dissolution. This fact could be a good starting point to investigate the effect of boron on thermoelectric power of steels.

Abstract: We report the structural and thermo-power measurement of the ruthenium doped YMnO₃ compounds. The room temperature XRD study shows the single phase formation of the reported compounds with the incremental unit cell volume and lattice parameters attributed to the larger ionic radius of the Ru³⁺ (0.68 Å) and Ru⁴⁺ (0.62 Å) as compared with that of the Mn³⁺ (0.65 Å) Mn⁴⁺ (0.52 Å). The observed variation of lattice parameters provides us valuable information into the better consideration of the valence state of ruthenium, in these compounds. The thermo-power measurement reveals hole-like conduction mechanism for the thermo-electric transport.