Formation Mechanism of Carbon-Nanocapsules and -Nanoparticles Based on the In-Situ Observation

Abstract

A new way to form carbon nanotubes (CNTs), carbon nanocapsules (CNCs), and carbon nanoparticles (CNPs), where polyyne-containing carbons are heated and irradiated by an electron beam in a transmission electron microscope (TEM), has been developed. The technique was applied to carry out an in-situ observation of those formation processes. Though the CNPs have been reported to be formed accompanied by the CNTs, the CNPs and the CNCs were found to be formed independently from the CNTs. The CNTs are preferentially inside of the polyyne-containing carbon films, while the CNPs/CNCs are outside of the films. The difference of the inside and the outside are discussed to lead to understanding of the CNC and CNP formation process. From the in-situ observation, the existence of metal particles, the high surface energy, the high wettability, and the high viscosity of the polyyne-containing carbons are assumed to be relevant to the preferential formation of CNCs/CNPs to CNTs.