Chapter 1
Introduction
Abstract The 200 years documented history of molten salt science and technology has been full of surprises, some of which brought revolutionary changes to our
world. Here, a brief history of these discoveries is provided. Carbon materials, and
especially the crystalline graphite, have undoubtedly played an important role in
the development of molten salt-based technologies, particularly in the electrolytic
production of metals as well as the construction of molten salt nuclear reactors. In
these applications, carbon is a desirable material due to its moderate electrical conductivity and relatively chemical and physical stability in high-temperature molten
salts. More recently, interactions between molten salts with carbonaceous materials
become more interesting, since these phenomena may lead to the low cost and highly
efficient fabrication advanced carbon nanostructures, including carbon nanotubes,
graphene, and nanodiamonds.
Keywords Molten salts · History · Graphite · Carbon nanostructures
The history of molten salt technologies is almost the same as that of the extractive
metallurgy of reactive metals. In 1807, the British scientist Humphry Davy delivered
the Bakerian Lecture before the Royal Society and surprised the scientific community by describing the metal potassium that could be produced, for the first time,
by the electrolysis of potash (potassium carbonate) in “igneous fusion.” He, in fact,
had discovered that potassium carbonate becomes conductor upon melting in a platinum spoon. Potassium could then be isolated on a platinum wire negative electrode
immersed in the melt, while the spoon was connected to the positive pole [1]. This
discovery was the birthday of fused salt or molten salt technologies, and made a
foundation for the scalable production of other alkali and also alkaline earth metals
such as Mg. The latter was first produced in laboratory scale by the electrolysis of
molten MgCl 2 by Michael Faraday in 1833 and in larger scales by Robert Bunsen
in 1852 [2]. It was not long until aluminum was produced by Charles Martin Hall in
1886 by passing an electric current through a solution of aluminum oxide in molten
cryolite. In 1918, Debye and Scherrer described the ionization of symmetrically
arranged atoms in a salt upon heating. Today, the molten salt production of Al is the
world’s largest electrochemical industry, with an output of over 63 million tons in
2018. In a typical Al smelter, molten salt is accommodated within large carbon or
© 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_1
1
Introduction
Abstract The 200 years documented history of molten salt science and technology has been full of surprises, some of which brought revolutionary changes to our
world. Here, a brief history of these discoveries is provided. Carbon materials, and
especially the crystalline graphite, have undoubtedly played an important role in
the development of molten salt-based technologies, particularly in the electrolytic
production of metals as well as the construction of molten salt nuclear reactors. In
these applications, carbon is a desirable material due to its moderate electrical conductivity and relatively chemical and physical stability in high-temperature molten
salts. More recently, interactions between molten salts with carbonaceous materials
become more interesting, since these phenomena may lead to the low cost and highly
efficient fabrication advanced carbon nanostructures, including carbon nanotubes,
graphene, and nanodiamonds.
Keywords Molten salts · History · Graphite · Carbon nanostructures
The history of molten salt technologies is almost the same as that of the extractive
metallurgy of reactive metals. In 1807, the British scientist Humphry Davy delivered
the Bakerian Lecture before the Royal Society and surprised the scientific community by describing the metal potassium that could be produced, for the first time,
by the electrolysis of potash (potassium carbonate) in “igneous fusion.” He, in fact,
had discovered that potassium carbonate becomes conductor upon melting in a platinum spoon. Potassium could then be isolated on a platinum wire negative electrode
immersed in the melt, while the spoon was connected to the positive pole [1]. This
discovery was the birthday of fused salt or molten salt technologies, and made a
foundation for the scalable production of other alkali and also alkaline earth metals
such as Mg. The latter was first produced in laboratory scale by the electrolysis of
molten MgCl 2 by Michael Faraday in 1833 and in larger scales by Robert Bunsen
in 1852 [2]. It was not long until aluminum was produced by Charles Martin Hall in
1886 by passing an electric current through a solution of aluminum oxide in molten
cryolite. In 1918, Debye and Scherrer described the ionization of symmetrically
arranged atoms in a salt upon heating. Today, the molten salt production of Al is the
world’s largest electrochemical industry, with an output of over 63 million tons in
2018. In a typical Al smelter, molten salt is accommodated within large carbon or
© 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_1
1