Study of wetting of surfaces with depressions


Аuthors

Kuzma-Kichta Y. A.1*, Alyautdinova М. М.2, Ivanov N. S.1**

1. National Research University “Moscow Power Engineering Institute”, 14, Krasnokazarmennaya str., Moscow, 111250 Russia
2. National Research University «Moscow Power Engineering Institute», Krasnokazarmennaya str., 17, bldg. 1G, Moscow, 111250, Russia

*e-mail: kuzma@itf.mpei.ac.ru
**e-mail: ivanovniks@mpei.ru

Abstract

The paper studies wetting of a surface with depressions formed in different ways. Distributions of the diameters of abrasive particles and depressions formed by forcing by these particles are obtained. It is established that forcing allows obtaining a surface with a normal distribution of depression diameters. The contact angle was determined using software (HiView) for a microscope, which allows determining the contact angle with an uncertainty of ±1°. Using a microscope, a photograph of the surface and a macrophotography of a drop were taken, then the photographs were processed in the software, the depression diameters were determined, the contact angles on the surface with depressions were measured, and the distribution of depression diameters was plotted. The surface with depressions was formed by forcing with a Nordberg N3612 hydraulic press. A sheet with an abrasive was fixed between an aluminum substrate and a press, after which forcing was carried out with a force of 5 tons. For comparison, reliefs formed by impact action on a plate with fixed abrasive paper were obtained. The same abrasive paper was used. The method consisted of applying mechanical blows with a hammer to the abrasive paper.The contact angles for the studied surfaces were measured, and it was found that the wetting process occurs with the displacement of air. At the initial stage, the surface with depressions has maximum hydrophobic properties, due to the presence of air in the depressions, however, over time, the liquid displaces it and the wetting angle decreases to stable values. When the drop stabilizes for 5 minutes, the angle decreases by 10 degrees. The contact angle for the studied cases decreases with an increase in the diameter of the depression, which is consistent with the known data. The method of forming depressions on the surface does not affect wetting.



Keywords:

wetting, contact angle, hydrophobic coatings, micro- and nanostructures, depressions on the surface

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