Sessile drop technique

About: Sessile drop technique is a research topic. Over the lifetime, 2827 publications have been published within this topic receiving 68943 citations.

Measurement of dynamic/advancing/receding contact angle by video‐enhanced sessile drop tensiometry

Abstract: A sessile drop tensiometer enhanced by video‐image digitization is designed for the experimental measurement of dynamic/advancing/receding contact angle. A collimated light beam passes through the sessile drop of liquid and a silhouette of the drop is created. The equipment video images the silhouette, digitizes the image, and locates the edge coordinates of the drop. A new technique, replacing the classical selected plane method, is developed to obtain the values of capillary constant and the radius of curvature at apex from the edge coordinates of digitized drop profile. Four parameters (location of apex, radius of curvature at apex, and the capillary constant) are calculated from the best fit between the edge coordinates and the theoretical curve obtained from the Laplace equation. The contact angle is then obtained from the location of the air/solid interface and the best‐fitted sessile drop profile. By controlling the humidity of air phase surrounding the drop, this technique can measure the advancing and receding contact angles and monitor the rate of advancing and receding of the three‐phase line simultaneously. This technique works well on contact angle measurement for sessile drops with or without an equator. Preliminary studies on the dynamic contact angle have been made for water drops on paraffin, polymethylmethecrylate, and glass. The technique is capable of giving contact angle of 0.2° precision.

Wetting of Ceramics by Liquid Metals

Abstract: A linear relation is established between the cosine of the contact angle and the temperature of a liquid metal sessile drop resting on a ceramic substrate. This relation is demonstrated for many liquid metal/ceramic systems. The work of adhesion and the effects of surface roughness, porosity, chemical reactions, and structural transformations in the substrate surface are also discussed.

Studies of the wetting characteristics of liquid iron on dense alumina by the X-ray sessile drop technique

Abstract: In the present work, the reaction between a molten iron drop and dense alumina was studied using the X-ray sessile-drop method under different oxygen partial pressures in the gas atmosphere. The changes in contact angles between the iron drop and the alumina substrate were followed as functions of temperature and varying partial pressures of oxygen in the temperature range 1823 to 1873 K both in static and dynamic modes. The results of the contact angle measurements with pure iron in contact with dense alumina in extremely well-purified argon as well as under different oxygen partial pressures in the gas atmosphere showed good agreement with earlier measurements reported in the literature. In the dynamic mode, when argon was replaced by a CO-CO2-Ar mixture with a well-defined PO, in the gas, the contact angle showed an initial decrease followed by a period of nearly constant contact angle. At the end of this period, the length of which was a function of the P-O2 imposed, a further steep decrease in the contact angle was noticed. An intermediate layer of FeAl2O4 was detected in the scanning electron microscope (SEM) analysis of the reacted substrates. An interesting observation in the present experiments is that the iron drop moved away from the site of the reaction once the product layer covered the interface. The results are analyzed on the basis of the various forces acting on the drop.

Wettability of Aluminum on Alumina

Abstract: The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10−8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 °C to 1400 °C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al2O3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700 °C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al2O3 system increases with temperature.