Chapter 3
Interaction of Molten Salts with Graphite
Abstract The evaluation of the corrosion behavior of graphite in molten salts is an
emerging important issue. It is because the molten salt corrosion of graphite can either
be technologically undesirable, for instance in molten salt nuclear reactors, or highly
desirable, for example, in the molten salt preparation of carbon nanostructures. This
chapter provides an overview of the chemical corrosion of graphite in molten salts
and particularly in molten lithium chloride. For this, thermokinetic characteristics of
graphite and LiCl are reviewed individually and in combination. The morphological
and structural changes occurred upon the exposure of graphite to molten lithium
chloride are also discussed.
Keywords Graphite · Molten salts · Thermal analysis · Corrosion · Carbon
nanostructures
The polycrystalline synthetic graphite (so-called graphite), which consists of
extended networks of graphene sheets, has a unique combination of properties,
including relatively high electrical and thermal conductivity, chemical inertness,
resistance to oxidation in air (which is negligible below 500 °C), excellent machinability and tribological properties as well as the low cross section for neutron
absorption [1–3]. These properties make graphite the prime candidate for a variety of applications in many technological fields such as electrochemistry, melting
and nuclear industry [4–6]. Among them, there are some promising technologies in
which graphite is exposed to molten salts. The first example is the fourth generation
molten salt breeder nuclear reactors where a mixture of molten fluoride salts, such
as NaF, LiF, ZrF 4 , ThF 4 and UF 4 are used both as fuel and coolant, flows between
the graphite reactor core and the heat exchanger [7, 8]. The second example is the
pyrochemical reprocessing of spent nuclear fuels using a LiCl-based molten salt,
where graphite is proposed as one of the candidate materials for various equipments
such as electrodes and crucibles [9].
In both applications, the inertness of graphite in the operating conditions is
required in order to ensure the reliability of the processes as neither corrosion nor
interaction phenomena are acceptable. Hence, it is important to evaluate the corrosion
behavior of graphite in molten salts. Despite its importance, however, there are few
published studies concerning the impact of molten salts on graphite. Accordingly,
© Springer Nature Singapore Pte Ltd. 2020
A. R. Kamali, Green Production of Carbon Nanomaterials in Molten Salts
and Applications, https://doi.org/10.1007/978-981-15-2373-1_3
19
Interaction of Molten Salts with Graphite
Abstract The evaluation of the corrosion behavior of graphite in molten salts is an
emerging important issue. It is because the molten salt corrosion of graphite can either
be technologically undesirable, for instance in molten salt nuclear reactors, or highly
desirable, for example, in the molten salt preparation of carbon nanostructures. This
chapter provides an overview of the chemical corrosion of graphite in molten salts
and particularly in molten lithium chloride. For this, thermokinetic characteristics of
graphite and LiCl are reviewed individually and in combination. The morphological
and structural changes occurred upon the exposure of graphite to molten lithium
chloride are also discussed.
Keywords Graphite · Molten salts · Thermal analysis · Corrosion · Carbon
nanostructures
The polycrystalline synthetic graphite (so-called graphite), which consists of
extended networks of graphene sheets, has a unique combination of properties,
including relatively high electrical and thermal conductivity, chemical inertness,
resistance to oxidation in air (which is negligible below 500 °C), excellent machinability and tribological properties as well as the low cross section for neutron
absorption [1–3]. These properties make graphite the prime candidate for a variety of applications in many technological fields such as electrochemistry, melting
and nuclear industry [4–6]. Among them, there are some promising technologies in
which graphite is exposed to molten salts. The first example is the fourth generation
molten salt breeder nuclear reactors where a mixture of molten fluoride salts, such
as NaF, LiF, ZrF 4 , ThF 4 and UF 4 are used both as fuel and coolant, flows between
the graphite reactor core and the heat exchanger [7, 8]. The second example is the
pyrochemical reprocessing of spent nuclear fuels using a LiCl-based molten salt,
where graphite is proposed as one of the candidate materials for various equipments
such as electrodes and crucibles [9].
In both applications, the inertness of graphite in the operating conditions is
required in order to ensure the reliability of the processes as neither corrosion nor
interaction phenomena are acceptable. Hence, it is important to evaluate the corrosion
behavior of graphite in molten salts. Despite its importance, however, there are few
published studies concerning the impact of molten salts on graphite. Accordingly,
© Springer Nature Singapore Pte Ltd. 2020
A. R. Kamali, Green Production of Carbon Nanomaterials in Molten Salts
and Applications, https://doi.org/10.1007/978-981-15-2373-1_3
19