In-situ TEM observations of the structural stability in carbon nanotubes, nanodiamonds and carbon nano-onions under electron irradiation

The dynamic transformations and damage behavior of free-standing multi-wall carbon nanotubes (MWCNTs), carbon nano-onions (CNOs), as well as nanodiamonds (NDs) are systematically studied by carrying out in-situ transmission electron microscope (TEM) measurements. Three key factors, including sp²-sp³ hybrid, inherent defects and morphology, are employed in order to deeply explore the disordering or the graphitization process in this work. On top of that, by applying fluence calculations, interplanar spacing measurements and inverse fast-Fourier-transformations, the structural evolutions of the carbon nanomaterials are precisely described. Interestingly, under the enforcement of high dose (up to 26.98 × 10²⁴ e/cm²) and current density (1.66 × 10³ and 3.79 × 10³ A/cm²), we discovered that the NDs and CNOs with ∼10 nm average diameter presented better structural stability than the MWCNTs. The structural transition in NDs undergoes 4 stages, whereas NDs turn into the defective CNOs finally. By comparing the defective and the perfect CNOs and CNTs, the existence of inherent defects in the material leads to the degeneration of the stability under irradiation of 5.59 × 10²⁴ e/cm². In addition, the direction of the defect migration can be changed by the empty internal space, which is ultimately imposed by irradiation-induced pressure in the carbon nanostructures.