期刊
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
卷 206, 期 1-3, 页码 47-67出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0927-7757(02)00072-9
关键词
equilibrium; contact angle; vibration; heterogeneity; roughness
The common measurement of the contact angle is performed in conditions not corresponding to true equilibrium states and gives non-equilibrium values, the advancing and receding contact angles. To solve this problem, a very simple experimental device, based on the Wilhelmy experiment, is proposed in the present paper. It is able to transfer mechanical energy to the three-phase system in a controlled way through a simple loudspeaker; the analysis of some common surfaces is made through this method showing as a new stable minimum of the surface free energy can be attained, independent on the initial conditions and corresponding to a value of the contact angle intermediate between the advancing and receding ones. A comparison is developed with literature results on heterogeneous and rough surfaces, some 'first-order'-approximation equations proposed in the literature are examined and compared with the new results. A simple but useful theoretical treatment is also compared with the experimental results to allow a more detailed, although qualitative-level, analysis. An important consequence with respect to the calculations of solid surface free energies is indicated. (C) 2002 Elsevier Science B.V. All rights reserved.
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