Nucleation of Gas Hydrates

Abstract

Clathrate hydrate is, by definition, a multi-component system that has at least two components of a guest gas and water. Nucleation of clathrate hydrate is thus more complex than nucleation of a single-component crystal like ice. Given the similarities between ice and clathrate hydrates, it is therefore pertinent to cover some aspects of nucleation of ice first, which incidentally has been studied much more extensively and for a far longer period than nucleation of clathrate hydrates. Nucleation of ice is commonplace in winters of the temperature regions, in summers of the polar regions and in the upper atmosphere of the earth. Cloud seeding has a direct impact on weather patterns and climate change because clouds reflect incoming sunlight back to the outer space. Heterogeneous nucleation of ice is also directly relevant to building up of ice on aircraft wings, which has been a well-recognized hazard to flight safety. For these reasons, nucleation of ice has been studied for many decades. We make three general points about nucleation at this stage before we go into the main topic of nucleation of ice in this section and nucleation of clathrate hydrate in the following sections. First, even in a system that does not involve any foreign solid walls or solid impurity particles, nucleation of a crystalline phase preferentially occurs at a liquid-vapor interface than deep inside the bulk of a liquid medium, and in such cases the nucleation rate does not scale with the system volume but with the interfacial area [1, 2]. We therefore prefer to use the term heterogeneous nucleation for such nucleation at a liquid-vapor interface even no foreign solid particles or walls are involved, because the system symmetry breaks at a liquid-vapor interface, and such breaking of system symmetry is spatially inhomogeneous. As such, we refer to such nucleation as heterogeneous nucleation in this book and we reserve the term homogeneous nucleation to nucleation in a system that consists of a single metastable parent phase, like spontaneous emulsification we detailed in Chap. 1. Of © Springer Nature Switzerland AG 2020 N. Maeda, Nucleation of Gas Hydrates, https://doi.