Chapter 9 - Encapsulation and crystallization behavior of materials inside carbon nanotubes

Abstract

This chapter focuses on methods of opening, filling, and purifying multiple and single-walled carbon nanotubes. The multiple-walled carbon nanotubes (MWTs) can be prepared in the bulk by a modified Krätschmer–Huffmann procedure. MWTs are prepared from 1-cm-diameter graphite rods under ∼0.17 atm of helium and from an arc generated by a dc voltage of 30 V and a current of ∼180 Å. The MWTs are formed in the carbon distilled on the cathode as a soft deposit covered by a hard cylindrical outer layer. The MWTs can then be removed from the soft inner core of the deposit and the outer shell is discarded. The nature of the products in the distillate obtained by this method can be radically altered by the introduction of additives to the source carbon electrode. Single-walled carbon nanotubes (SWTs) can be synthesized by coevaporating composite carbon rods mixed with certain metals, as in a modified Krätschmer–Huffmann-type experiment, and by laser vaporization of metal-doped graphite targets. Most techniques of SWT purification involve a method of isolating the undesired extraneous materials followed by some process of selective filtration.