Chapter 2
Production of Advanced Materials
in Molten Salts
Abstract Molten salt-based methods have been prime candidates for the commercial extraction of a variety of metals, such as aluminum and lithium, which are
impossible or very difficult to be produced by other techniques. In addition to these
well-developed technologies, molten salt methods have also created new strategies
for the preparation of advanced metallic, intermetallic and ceramic materials as well
as carbon nanostructures. This chapter focuses on the latter. In contact with carbonaceous materials, molten salts can either be relatively inert or reactive. Both behaviors
have been employed for the preparation of carbon nanomaterials. An inert molten
salt system can provide a uniform ionically conductive heating medium for the occurrence of reactions with an enhanced reactivity, leading to a significant promotion of
reaction kinetics. This promoting influence is mainly due to the enhanced values of
the diffusion coefficient of ions in molten salts. In contrast, there are some molten
salt methods in which the molten salt involved is reactive against solid or gaseous
carbonaceous species, leading to the preparation of a variety of different carbon
nanostructures. Molten salt reduction of graphene oxides and the electrochemical
exfoliation of graphite are also discussed.
Keywords Molten salts · Advanced materials · Reactivity · Carbon
nanostructures · Graphitization · CO 2 capture
Molten salts, which are ionic liquids with a melting point typically above 200 °C,
have historically provided the opportunity for large scale production of some of the
most useful metals. The best example of this kind is aluminum which is currently the
second most widely used metal in the world with an annual production of more than
60 Mt in 2018. The industrial primary production of aluminum is entirely based on
the Hall–Héroult smelting process, involving the electrolysis of alumina dissolved in
molten cryolite [1]. Another example is lithium; the lightest metal which is used in
various applications such as an alloying element to aluminum and magnesium alloys
and in the production of organolithium compounds. Lithium, which is also facing
an increasing demand due to the rising interest in lithium–ion batteries, is mainly
produced by the electrolysis of LiCl-based molten salts [2, 3]. The electrolytic molten
salt production of magnesium [4] and calcium [5] should also be added to this list.
© 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_2
5
Production of Advanced Materials
in Molten Salts
Abstract Molten salt-based methods have been prime candidates for the commercial extraction of a variety of metals, such as aluminum and lithium, which are
impossible or very difficult to be produced by other techniques. In addition to these
well-developed technologies, molten salt methods have also created new strategies
for the preparation of advanced metallic, intermetallic and ceramic materials as well
as carbon nanostructures. This chapter focuses on the latter. In contact with carbonaceous materials, molten salts can either be relatively inert or reactive. Both behaviors
have been employed for the preparation of carbon nanomaterials. An inert molten
salt system can provide a uniform ionically conductive heating medium for the occurrence of reactions with an enhanced reactivity, leading to a significant promotion of
reaction kinetics. This promoting influence is mainly due to the enhanced values of
the diffusion coefficient of ions in molten salts. In contrast, there are some molten
salt methods in which the molten salt involved is reactive against solid or gaseous
carbonaceous species, leading to the preparation of a variety of different carbon
nanostructures. Molten salt reduction of graphene oxides and the electrochemical
exfoliation of graphite are also discussed.
Keywords Molten salts · Advanced materials · Reactivity · Carbon
nanostructures · Graphitization · CO 2 capture
Molten salts, which are ionic liquids with a melting point typically above 200 °C,
have historically provided the opportunity for large scale production of some of the
most useful metals. The best example of this kind is aluminum which is currently the
second most widely used metal in the world with an annual production of more than
60 Mt in 2018. The industrial primary production of aluminum is entirely based on
the Hall–Héroult smelting process, involving the electrolysis of alumina dissolved in
molten cryolite [1]. Another example is lithium; the lightest metal which is used in
various applications such as an alloying element to aluminum and magnesium alloys
and in the production of organolithium compounds. Lithium, which is also facing
an increasing demand due to the rising interest in lithium–ion batteries, is mainly
produced by the electrolysis of LiCl-based molten salts [2, 3]. The electrolytic molten
salt production of magnesium [4] and calcium [5] should also be added to this list.
© 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_2
5