Nucleation of Gas Hydrates by Nobuo Maeda

Author:Nobuo Maeda
Language: eng
Format: epub
ISBN: 9783030518745
Publisher: Springer International Publishing

4.2 Interfacial Gaseous Layers

4.2.1 Introduction

The availability of the guest gases and their physical states (i.e., whether the guests are in a dissolved state or form a separate gaseous phase) next to a solid substrate have direct impacts on the heterogeneous nucleation of clathrate hydrates. Therefore, the physical properties of interfacial gaseous states on a solid surface in water are of great interest to the nucleation of clathrate hydrates. It turned out that a variety of interfacial gaseous states may exist or coexist in water under suitable physicochemical conditions. Given that a distinct attribute of a gas phase is that all types of gases are miscible with each other at all proportions, it is surprising that multiple gaseous states can coexist in an aqueous media, which presents a surprisingly rich domain [20].

It has long been known that formation of a gaseous layer can be thermodynamically favorable for sufficiently rough surfaces as shown in Fig. 4.5, left panel. The interfacial free energy of the system can decrease by the formation of an interfacial gaseous layer when (1) the water–gas interfacial area is sufficiently smaller than the gas–solid interfacial area and (2) the gas–solid specific interfacial free energy is much lower than the water–solid specific interfacial free energy. Wetting on such rough and/or heterogeneous surfaces has a long history since the days of Wenzel [21] and Cassie and Baxter [22].

Fig. 4.5Schematic illustration of how the formation of a gaseous layer can lower the free energy of a system on a sufficiently rough surface (left), which cannot occur on a smooth surface (right)

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