Metal Cluster Size-Dependent Activation Energies of Growth of Single-Chirality Single-Walled Carbon Nanotubes inside Metallocene-Filled Single-Walled Carbon Nanotubes

Abstract

By combining in situ annealing and Raman spectroscopy measurements, the growth dynamics of nine individual-chirality inner tubes (8,8), (12,3), (13,1), (9,6), (10,4), (11,2), (11,1), (9,3) and (9,2) with diameters from ~0.8 to 1.1 nm are monitored using a time resolution of several minutes. The growth mechanism of inner tubes implies two successive stages of the growth on the carburized and purely metallic catalytic particles, respectively, which are formed as a result of the thermally induced decomposition of metallocenes inside the outer SWCNTs. The activation energies of the growth on carburized Ni and Co catalytic particles amount to 1.85–2.57 eV and 1.80–2.71 eV, respectively. They decrease monotonically as the tube diameter decreases, independent of the metal type. The activation energies of the growth on purely metallic Ni and Co particles equal 1.49–1.91 eV and 0.77–1.79 eV, respectively. They increase as the tube diameter decreases. The activation energies of the growth of large-diameter tubes (dt = ~0.95–1.10 nm) on Ni catalyst are significantly larger than on Co catalyst, whereas the values of small-diameter tubes (dt = ~0.80–0.95 nm) are similar. For both metals, no dependence of the activation energies on the chirality of inner tubes is observed.

Temperature-Dependent Growth of 36 Inner Nanotubes inside Nickelocene, Cobaltocene and Ferrocene-Filled Single-Walled Carbon Nanotubes

“…The annealing of metallocene-filled SWCNTs leads to the decomposition of molecules with the formation of metal carbides and pure metals [7,21,29,30]. The encapsulated metal carbides and metals serve as catalysts for the inner tube growth.…”

“…Thus, the growth mechanism implies the stages of (i) decomposition of metallocene and (ii) growth of inner nanotubes on the metal carbide and metal particles. In [21,29,30], it was revealed that the growth mechanism of inner tubes includes two successive stages of the growth on carburized and purely metallic catalytic particles. Each stage is characterized with different growth rates and activation energies.…”

“…The morphology of the pristine SWCNTs was investigated by microscopic techniques. Figure 2 shows the scanning (SEM) [21] and transmission electron microscopy (TEM) data of the pristine SWCNTs [22]. The data show that the SWCNTs represent homogenous material and have a high purity.…”

Applications of Filled Single-Walled Carbon Nanotubes: Progress, Challenges, and Perspectives

“…Endohedral metallofullerene DySc 2 N@C 80 were filled inside well-purified SWC-NTs [188,189] with a narrow diameter distribution of 1.4 ± 0.1 nm [184]. This encapsulation achieves a controllable and uniform enhancement of SMM properties.…”

The Role of Temperature on the Degree of End-Closing and Filling of Single-Walled Carbon Nanotubes

“…There is a special interest in using SWCNTs as enclosures for the encapsulation of payloads [6][7][8][9]. The nanotubes offer protection to the hosted material from the external environment, thus allowing, for instance, the encapsulation of air sensitive materials [10], gases [11], and even radionuclides [12,13].…”