Abstract

Interfacial phenomena are the processes that occur at the interface between two phases of matter: solid-liquid, solid-gas, liquid-liquid, and liquid-gas. Wetting, spreading, adsorption, and capillarity are some features of interfacial phenomena. This research explores two areas of interfacial phenomena: the interfacial tension between a liquid and gas, and wetting transitions in microcavities. Surface tension has been a widely studied topic in surface chemistry. Many techniques have been employed to study the surface tension of liquids in various studies and research areas, but the interfacial tension between a liquid and gas has not been extensively researched. For this reason, part of my research investigates the interfacial tension between molten salt and inert gases. Molten salts are hygroscopic and are mostly used in glove boxes filled with either nitrogen or argon, both abundant gases in nature. Hence, we aim to discover if there is any interaction between inert gases and molten salts and how this interaction affects the salts. Additionally, I want to determine if different gases interact differently with molten salts based on the molecular weight and density of the gases. The interfacial tension between molten salts and inert gases was measured using the sessile drop and the pendant drop methods. The molten salts investigated are Solar Salt and LiF-NaF-KF (NaNO₃-KNO₃ and FLiNaK), and the inert gases used were argon, xenon, and SF₆, at different temperatures. The results with the pendant drop method for Solar Salt with argon, xenon, and SF₆ were similar, showing a general trend where an increase in temperature results in decreased interfacial tension. The results for FLiNaK with argon, xenon, and SF₆ also followed the same trend. The sessile drop method was used only with argon, and the results from both techniques were compared to the model generated by Janz et al. from which he used experimental data from the maximum bubble pressure method and the Wilhelmy method. My data from both techniques demonstrated good reproducibility, and the interfacial tension values were close to those of Janz et al. There was no significant difference in the interfacial tension values between molten salt and inert gases at low pressures, indicating that the interfacial tension between molten salt and each gas is similar. Furthermore, from our experiments, we found that the interfacial tension between molten FLiNaK salts and inert gases at high temperatures deviates from a linear relationship due to changes in the ionic structure of the salt. Measuring the interfacial tension between these salts and inert gases has provided valuable information for the scientific community. This research also examines factors affecting wetting transitions in initial hydrocarbon-filled microcavities displaced by water saturated with a specific hydrocarbon. While wetting transitions in solid-liquid-vapor (SLV) systems are well studied, solid-liquid-liquid (SL1L2) systems have received less emphasis. SL1L2 systems are significant in applications such as skin care products on human skin and enhanced oil recovery. To investigate this, a set of hydrocarbons was selected to study wetting transitions. These hydrocarbons were dyed Nile red and introduced onto a silicon wafer etched with microcavities. Water saturated with the same hydrocarbons was introduced to the substrate in a petri dish. The replacement time for saturated water to displace the hydrocarbon in the microcavities was recorded and analyzed. Differences in replacement times were observed and may be attributed to the properties of each hydrocarbon, such as adhesion energy, viscosity, density, solubility, and contact angle. Further investigation using modeling and regression analysis aims to confirm the relationship between individual hydrocarbon properties and replacement time.

Degree

College and Department

Ira A. Fulton College of Engineering; Chemical Engineering

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