Features of the formation and development of scientific research in the laboratory of physics of interfacial phenomena in ChISU named after L. N. Tolstoy in the 1970-1980s of the last century are ...considered in this paper. Particular attention is paid to the development and improvement of various methods for measuring the density of liquid metals and alloys. We determined the contribution of ChSU scientists in the study of metals and alloys properties and gave a scientific assessment of the obtained results. The development of methods and techniques for measuring the density of liquid metals and alloys went in two directions. Primarily, we took significant steps towards improving the accuracy of density measurements. The instruments were designed in which the accuracy of measuring density and, in particular, the temperature coefficient of density was significantly increased. Foremost, this concerns advanced pycnometers and areometers designed in ChSU laboratories. The instruments received inventor's certificates, and they were awarded the bronze medal of the Exhibition of Achievements of National Economy in 1977. The second direction improving the measuring technique of the metal properties is characterized by instrument designing for the joint measurement of physico-chemical properties in the same thermal vacuum conditions. Both areometers and pycnometers were used to determine density in these instruments.
Abstract
A comparative analysis of the experimental data on the surface tension (ST) of low- melting metals, obtained by the method of maximum pressure in a drop and the method of a large drop, shows ...that the values of ST obtained by the large drop method for all studied metals are noticeably higher than those obtained by the method of maximum pressure in a drop. The reasons for such discrepancies, although in some cases they exceed the total errors of the ST measurement by the indicated methods, have not yet been clarified. In this regard, the paper gives a comparative analysis of the methodological specificity of measuring the surface tension by the methods of maximum pressure in a gas bubble or a drop and a lying or “large” drop. It is shown that these methods are theoretically substantiated, technically perfect, have a sufficiently high accuracy and are relatively simple. Based on the identification and critical analysis of the influence of the main factors on the measured value of the surface tension, the main reasons for the discrepancy between the experimental data on the surface tension of low-melting metals obtained by different methods are determined. It is shown that the underestimated ST values obtained by the method of maximum pressure in a droplet are due to the fact that all factors influencing the measured value of surface tension are directed towards a decrease in its value. Although the influence of each of these factors separately is insignificant, they together lead to a noticeable decrease in the value of surface tension. It is shown in the work that the method of maximum pressure in a drop, being the most accurate method for measuring ST, gives somewhat underestimated ST values for all low-melting metals.
—The surface tension (σ) and density (ρ) of indium–tin melts are measured by various methods. The surface tension is measured by the sessile drop method and the method of the maximum pressure in a ...drop, and the density is measured by an aerometer and the sessile drop method. High-purity metals, In-00 and OVCh tin, are used for this research. The maximum σ measurement error is 0.8% and that of ρ is 0.2%. The composition dependence of σ of In–Sn melts is characterized by an extreme (flat minimum) in the region of the equimolar composition. As the temperature increases, the depth of the minimum decreases and its position shifts toward pure indium. The molar volumes have small positive deviations from the additive values. The sessile drop method is used to measure the temperature dependences of σ and ρ of In–Sn solutions diluted with indium. Indium additives are shown to decrease the surface tension of tin. Since the surface tension of indium is higher than that of tin, this result indicates that the surface tension isotherms of the indium–tin system should pass through a minimum.
A study is performed of the advantages and disadvantages of different ways of determining adsorption that differ only in how the position of a dividing surface is fixed. Formulas are obtained and the ...concentration dependence of the distance between different positions of a Gibbs dividing surface (
V
and
M
in Gibbs’ version;
N
in those of Guggenheim–Adam variants) is calculated for indium–tin, gallium–bismuth, and thallium–bismuth binary systems. The results from calculations show that the concentration dependence of this distance is complex (there are extrema in the form of a maximum and minimum). Contrary to existing opinion, however, the considered positions of a Gibbs dividing surface do not move apart much upon a change in the composition of the solution. The maximum distance between different positions of a dividing surface in the studied systems thus does not exceed the size of atoms (i.e., it remains within the thickness of the monolayer). This distance in the studied systems therefore does not exceed the dimensions of the effective thickness of the surface layer.
The study proposes the self-consistent theory that combines an activation model, a free volume model and a cluster model. The theory makes it possible to explain why the flow of fluid in slip ...conditions requires extremely minimal tangential stresses and describes the real structure of the fluid in the boundary layer, as well as to explain why the fluid is almost not squeezed out of the capillary gap.
It was found that at the stage of fast spreading (τ≤ 0,02c) at constant driving force within the wetting perimeter, the following exerts the main impact on the spreading kinetics: inertial forces ...that prevent spreading and change their sign when the speed slows, viscous resistance forces, the influence of which increases in proportion to the growth of the thickness of the boundary layer and vertical forces, which begin to appear when the spreading velocity slows down.
The polytherms of density, surface tension of the Cu-Al system melts and wetting angles of Ni-Cr, Co-Cr substrates, 25X18H9C2 stainless steel and titanium were studied by the sessile drop method. The ...drop contour was processed by dint of current information technologies, in particular, using the ImageJ software package 1. The equations of density polytherms and surface tension of the Cu-Al system melts were established. It was shown that Cu-Al melts wet the substrates at 1000 K and more. We revealed the features of temperature dependences of the wetting angles.
Surface tension of indium-tin-gallium melts Dadashev, R. Kh; Kutuev, R. A.; Elimkhanov, D. Z. ...
Russian Journal of Physical Chemistry A,
11/2007, Letnik:
81, Številka:
11
Journal Article
PDF
