«Proceedings of Gubkin University»

ASPECTS OF CALCULATING FREE ENERGY OF DROP ON SOLID SURFACE

UDC: 547
DOI: 10.33285/2073-9028-2020-4(301)-141-148

Authors:

¹ Shukhov Belgorod State Technological University, Belgorod, Russian Federation

Keywords: Young’s equation, the boundary angles of wetting, the parametric model of wetting, isobaric-isothermal potentia

Annotation:

The analysis of the wetting model based on the measurement of the areas of the interface of the contacting phases: liquid-gas, solid-gas, solid-liquid is carried out. It is shown that the calculations of the Isobaric-isothermal potential Δ F during wetting must take into account all the main components of the surface energies (the free energy of the drop before the wetting process); this condition is rather important if the variational principle of the minimum energy is not realized in the process of wetting - the shape of the drop before the wetting process is not spherical, and the wetting process is not equilibrium, or it is necessary to take into account the forces of gravity at large drop sizes, and for a water drop with a small radius (less than 0.5 mm), all cases of wetting can be interpreted by representing the drop as a spherical segment with different section heights. To improve the accuracy of determining wetting parameters, one must enter a dimensionless parameter m, equal to the ratio of the section height of the spherical segment to its radius. Hysteresis phenomena when using the parameter m to a lesser extent affect the measurement accuracy, since the measurements determine the linear characteristics of the drop rather than the contact angles of wetting. Formulas for calculating the work of adhesion, Isobaric-isothermal potential depending on the wetting parameter m , as well as conditions under which the change in Isobaric-isothermal potential in the wetting process is zero are revealed. The use of a parametric wetting model can improve the accuracy of measurements and calculations of thermodynamic parameters of wetting. The model has advantages in the study of systems where the edge angle of wetting is difficult to measure.

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