Showing papers on "Sessile drop technique published in 1985"

Interfacial phenomena between molten metals and sapphire substrate

Abstract: Interfacial energies and contact angles for liquid Cu-sapphire and liquid Ag-sapphire systems as a function of O2 partial pressure were experimentally determined using the sessile drop technique. For very low values of Po2the variation of γlg is small, but at Po2, values high enough to establish a monolayer on the liquid metal, γlg decreases linearly with increasing logP o2. The slope of this line is related to the surface concentration of oxygen through Gibb's absorption equation. For various metal-sapphire systems, γlg is found to be a cosine function of the contact angle (θ) whereas γsl seems to be a linear function of (θ). A theoretical model has been developed to predict this behavior. One empirical constant relating to the free energy of formation of an interfacial compound was employed. The validity of the model has been tested for the Cu, Ag, Fe, and Ni-sapphire systems. The model has also been used to predict the effect ofP o2on the interfacial energies and contact angle for the Co-sapphire system.

Interfacial tension of aluminum in cryolite melts

Abstract: The interfacial tension between aluminum and cryolite melts containing different salt additions has been measured based on a combination of the sessile drop and X-ray radiographie technique. A computer program was used to calculate the interfacial tension from approximately twenty randomly measured coordinate points of the drop profile. Aluminum and salt mixtures containing different amounts of Na3AlF6, A1F3, NaF, A12O3, CaF2, KF, LiF, and NaCl were melted in a graphite or alumina crucible in a graphite resistor furnace under an argon atmosphere. The interfacial tension was found to be strongly dependent on the NaF/AlF3 ratio. At the cryolite composition the interfacial tension was 481 mN/m at 1304 K, while it was 650 mN/m when the NaF/AlF3 ratio was equal to 1.5. The change in interfacial tension with composition is explained by sodium enrichment of the Al/melt interface. Additions of A12O3 increased the interfacial tension for a given NaF/AlF3 ratio. KF was found to be surface active, while CaF2, LiF, and NaCl slightly increased the interfacial tension by decreasing the sodium activity.

Contact Angle Equilibrium on Thin Elastic Solids

Abstract: A theoretical analysis has been carried out on the system consisting of an axisymmetric sessile drop resting on a thin elastic solid in the presence of gravity. The solid is treated in one case as a thin plate and in the other case as a membrane. The consequences of the variational treatment employed are equations relating to contact angle equilibrium, drop and solid profiles. It is shown that contact angles are not intrinsic surface properties of the phases involved but invoke equally such characteristics as bulk properties of the solid and physical dimensions when the solid in question is deformable.

A technique for measuring interfacial tension by quadrupole oscillation of drops

Abstract: A technique for measuring interfacial tension is presented. A drop of one liquid is acoustically levitated in another liquid (host) and is also acoustically driven into quadrupole shape oscillations. The interfacial tension is inferred from the resonance properties of the drop, provided that the size of the drop and the densities of the two liquids are known. The relevant results of theories are mentioned. The apparatus and procedure are described. Some special features of this technique are discussed; for example, the drop has an indefinite lifetime, the interface has no contact with any solid surface, and any changes of the interfacial tension can be tracked automatically. Data for the interfaces such as water-hexane, water-propane (superheated by 65°C), and water-hexane-surfactant are reported.

Wetting characteristics of copper on niobium

Abstract: Sessile drop experiments have been performed in a temperature range between 1090 and 1300° C, aiming to study the wetting of niobium by liquid copper and the influence of different atmospheres (argon, hydrogen, vacuum), crystallographic orientation, roughness, and oxygen doping of niobium on the wetting angle. At the peritectic temperature in the Cu-Nb system (1090° C) the contact angle is high,θ=67°, denoting poor wetting. With increasing temperature,θ decreases steadily for all samples. The wetting is at its lowest for the oxygen-doped samples and at its best for samples annealed under a hydrogen atmosphere. A new mechanism is suggested and discussed for oxygen degassing of niobium through liquid copper.

Surface energetics characterization and relationship to adhesion using a novel contact angle measuring technique

Abstract: A method has been developed for measuring contact angles with a drop of water on a solid surface in an octane medium and to determine the polar components of surface tension for the solid surface. This has been utilized to characterize the surfaces of a plasticized polyvinyl butyral interlayer (PVBI) and float glass which are laminated to form safety glass. The effect of changes in the surfaces of both materials is reflected in the contact angles measured by the above method and this is then related to the level of adhesion between glass and PVBI.

Measurement of Ultralow Interfacial Tension in the Vicinity of Critical Solution Temperature

Abstract: A new apparatus adopting the sessile drop technique has been designed to measure the ultralow interfacial tension between two liquids of a binary mixture. The equilibrium interfacial tension of the mixture of isobutyric acid and water has been determined near its upper critical solution temperature up to the value of 0.02 μN m−1.

A laser interferometric study of sessile drop shape and contact angle

Abstract: Small contact angles, such as water on glass, have been shown to be measurable interferometrically using fringes of equal thickness after the fashion of Newton's rings. The measured angle for the water on glass system was 0.049 ± 0.006 degrees of arc.