Chapter 5
Nucleation of Gas Hydrates
5.1 Nucleation of Ice
5.1.1 Introduction
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 wellrecognized 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.org/10.1007/978-3-030-51874-5_5
111
Nucleation of Gas Hydrates
5.1 Nucleation of Ice
5.1.1 Introduction
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 wellrecognized 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.org/10.1007/978-3-030-51874-5_5
111