Investigation and Estimation of Interface Energy Characteristics
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Journal of Engineering Physics and Thermophysics, Vol. 93, No. 6, November, 2020
INVESTIGATION AND ESTIMATION OF INTERFACE ENERGY CHARACTERISTICS V. M. Gasanov
UDC 66-911.38+66.069.82+532.526.5+536.521
A new equation has been obtained for calculating the equilibrium contact wetting angle on the basis of the capillary constant evaluated from the shape of a real droplet of liquid on a solid surface. The value of the surface tension of liquid is determined experimentally using the geometric parameters of the liquid droplet on a solid surface. The proposed equations make it possible to determine the equilibrium contact wetting angle of the solid body surface with thermodynamic parameters σliq–g, σs.b–liq and σs.b–g on the interface between three phases: solid body–liquid–gas. Keywords: equilibrium contact wetting angle, capillary constant, surface energy of a solid phase, interphase surface energy. Introduction. The processes of wetting and spreading have been studied for more than two hundred years. Theoretically, the processes of wetting and spreading studied by T. Young in 1804 were very important for development of the fundamental science [1]. T. Young showed that the shape of the liquid droplet on the interface between three phases (solid body–liquid–gas) is determined by the relationship between the forces of intermolecular attraction between the molecules of the liquid and solid body and by mutual attraction of the molecules of liquid. Moreover, as a result of his classical studies, T. Young introduced a fundamental concept for physicochemical surface phenomena — the concept of equilibrium angle of wetting the interface θeq as a quantitative characteristic of the process of wetting and spreading. The equilibrium contact angle of wetting the phase interface θeq depends only on the surface tensions on the phase interfaces participating in wetting. Therefore, for each system at the given external conditions the equilibrium contact angle of wetting has one definite value. Simultaneously with T. Young, in 1806 Laplace developed the general theory of capillary phenomena and obtained an equation [2] for calculating the liquid surface curvature in capillaries — the law of the Laplace capillary pressure. Nevertheless, unsolved problems exist up to now in this region. The Nobel prize winner Pier-Gilles de Gennes in 1991 in his review paper [3] remarked that despite the exclusive importance, the processes of wetting and spreading were understood insufficiently up to the present time. As to the theory, only 215 years after the pioneer works of Young and Laplace (1804– 1805) did some fundamental problems of capillarity begin to be solved. The surface and interface tensions are important thermodynamic characteristics because they determine the vectors of the progress of technological processes. The main concern in determination of the interface energy of the surface for obtaining maximally trustworthy results is the development of the calculation procedure. Note that the energy state of the interface of bodies plays the ba
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