Title : Laser welded carbon nanotubes graphene hybrid structures: Modeling, formation, application
Abstract:
This report is devoted to the study of one of the topological varieties of graphene-nanotube hybrid structures. A technology has been developed and tested for the formation of hybrid structures from reduced graphene oxide RGO and single-wall carbon nanotubes (SWCNTs) of subnanometer and nanometer diameters, as well as their binding to a silicon substrate. This technology is based on the use of pulsed laser radiation of a certain wavelength. Using quantum calculations performed within the time-dependent density functional based tight binding method (TD-DFTB), the optimal laser wavelength of 266 nm was selected. At this wavelength, the laser-welded structure has the maximum hardness (54.4 GPa) and high electrical conductivity (~22.6 kS/m). Molecular dynamics modeling using the TD-DFTB method made it possible to establish that, under the action of laser radiation, covalent bonding of SWCNTs with graphene flakes occurs with the formation of non-hexagonal elements at the junction of graphene and SWCNTs. It has also been shown by quantum calculations that laser radiation induces a dipole moment in hybrid graphene-nanotube nanostructures due to the redistribution of the electron charge density. This dipole moment ensures the orientation of the hybrid carbon nanostructures along the lines of force of the radiation field. Theoretical and experimental studies of the emission characteristics of the formed graphene-nanotube nanostructures have been carried out. A cathode with an area of ~1 mm2 made on the basis of graphene–nanotube hybrids demonstrated a field emission current density of 562 mA/cm2 and stability of operation for 9 h at a current of 1 mA. Within the framework of the density functional theory, the effect of the functionalization of LaB6 nanoparticles on the work function of graphene-SWCNT hybrid structures was studied. It is shown that decorating the framework of graphene-SWCNT hybrid with LaB6 nanoparticles makes it possible to achieve a decrease in the work function by ~13% compared to a pure carbon framework. The proposed technology for laser welding of SWCNT and RGO hybrids has great potential for developing emission cathodes for electronic devices such as X-ray tubes, field emission displays, and vacuum microwave devices.
Audience Take Away:
- New possibilities of laser nanowelding technology in the field of carbon materials science
- Using quantum calculations, it is possible to select the optimal laser radiation wavelength for welding a superhard and highly conductive carbon framework
