Chapter 14
Nanostructures Obtained with Plasma
Discharge Processes
14.1 Carbon Nanostructures: Nanotubes and Nanoonions
The discovery of the carbon nanotubes (CNTs) was related to the arc discharge
process [1] formerly applied for the production of fullerenes (even though earlier
and nearly forgotten observations of similar structures have also been documented
[2, 3]). After an early expansion period of the field [4, 5], the arc discharge process
was finely tuned for the production of nanotubes, too. Beside laser ablation and
chemical vapour deposition, arc discharge remained one of the major production
modes of CNTs due to its advantageous features.
Due to the popularity of the CNT research and the variety of the expected application field of the resulting carbon nanostructures, reviews focusing on various aspects
of the field are available (general [6, 7], synthesis with any method [8, 9] or particularly with arc discharge [10–13], continuous production of nanotubes [14], growth
mechanism of carbon nanotubes [15], solar cell applications [16]).
The basic structural properties of CNTs can be understood on the basis of the
graphene sheet and the virtual roll-up of its segment cut with parallel edges to form
single-wall carbon nanotubes (SWCNTs). This is shown in Fig. 14.1. Depending
on the direction of the so-called chiral vector, one can obtain zig-zag, armchair and
chiral nanotubes by folding a slice of the graphene sheet so that the carbon atoms at
the initial and final points of the chiral vector overlap. While the structural character
of a CNT depends on the direction of the chiral vector, its length determines the CNT
diameter.
Multiwalled carbon nanotubes (MWCNTs, see Fig. 14.2) can be imagined as
SWCNTs embedded into each other. For MWCNTs, the diameter difference between
the neighbouring nanotubes is not arbitrary but it equals to that of the planar graphene
sheets in graphite (0.34 nm), hence defining a regular spacing between the neighbouring nanotubes. The interaction between the curved graphene sheets in MWCNTs
is an energetic stabilization factor of the resulting structure, even though the carbon
atoms of a particular CNT in the MWCNT structure are not as regularly positioned
© Springer Nature Switzerland AG 2021
L. Péter, Electrochemical Methods of Nanostructure Preparation,
Monographs in Electrochemistry, https://doi.org/10.1007/978-3-030-69117-2_14
511
Nanostructures Obtained with Plasma
Discharge Processes
14.1 Carbon Nanostructures: Nanotubes and Nanoonions
The discovery of the carbon nanotubes (CNTs) was related to the arc discharge
process [1] formerly applied for the production of fullerenes (even though earlier
and nearly forgotten observations of similar structures have also been documented
[2, 3]). After an early expansion period of the field [4, 5], the arc discharge process
was finely tuned for the production of nanotubes, too. Beside laser ablation and
chemical vapour deposition, arc discharge remained one of the major production
modes of CNTs due to its advantageous features.
Due to the popularity of the CNT research and the variety of the expected application field of the resulting carbon nanostructures, reviews focusing on various aspects
of the field are available (general [6, 7], synthesis with any method [8, 9] or particularly with arc discharge [10–13], continuous production of nanotubes [14], growth
mechanism of carbon nanotubes [15], solar cell applications [16]).
The basic structural properties of CNTs can be understood on the basis of the
graphene sheet and the virtual roll-up of its segment cut with parallel edges to form
single-wall carbon nanotubes (SWCNTs). This is shown in Fig. 14.1. Depending
on the direction of the so-called chiral vector, one can obtain zig-zag, armchair and
chiral nanotubes by folding a slice of the graphene sheet so that the carbon atoms at
the initial and final points of the chiral vector overlap. While the structural character
of a CNT depends on the direction of the chiral vector, its length determines the CNT
diameter.
Multiwalled carbon nanotubes (MWCNTs, see Fig. 14.2) can be imagined as
SWCNTs embedded into each other. For MWCNTs, the diameter difference between
the neighbouring nanotubes is not arbitrary but it equals to that of the planar graphene
sheets in graphite (0.34 nm), hence defining a regular spacing between the neighbouring nanotubes. The interaction between the curved graphene sheets in MWCNTs
is an energetic stabilization factor of the resulting structure, even though the carbon
atoms of a particular CNT in the MWCNT structure are not as regularly positioned
© Springer Nature Switzerland AG 2021
L. Péter, Electrochemical Methods of Nanostructure Preparation,
Monographs in Electrochemistry, https://doi.org/10.1007/978-3-030-69117-2_14
511