Abstract
Aerosol-assisted catalytic chemical vapor deposition (AACCVD) is a powerful one-step process to produce vertically aligned carbon nanotubes (VACNTs), characterized by the continuous supply of the catalyst precursor (metallocene). The behavior of catalyst species all along the synthesis is essential for the continuous growth of VACNTs. It is there investigated through detailed observations and elemental analyses at scales of VACNT carpets and of individual CNTs. Our approach is based on two complementary experiments: quenching of the sample cooling, and sequential injection of two distinct metallocenes. Metal-based nanoparticles nucleated in the gas-phase during the whole synthesis duration are shown to diffuse in between the growing VACNTs from the top of the CNT carpet towards the substrate. They are much smaller than the catalyst particles formed on the substrate in the initial steps of the process and evidences are given that they continuously feed these catalyst particles at the VACNT roots. Particularly, the electron energy-loss spectroscopy (EELS) analyses of metal-based segments found into a single CNT show that the second injected metal is very gradually incorporated in the particle initially formed from the metal firstly injected. The feeding of the catalyst particles by the nanoparticles continuously nucleated in the gas-phase is therefore an essential feature of the base-growth of CNTs by AACCVD.
Highlights
Aerosol-assisted catalytic chemical vapor deposition (AACCVD) is a powerful one-step process to produce vertically aligned carbon nanotubes (VACNTs), characterized by the continuous supply of the catalyst precursor
Global as well as local characterizations have been combined in order to achieve a detailed analysis of the metal-based species in VACNT carpet grown by aerosol-assisted
The two synthesis approaches developed complementary answer to the dynamic steps followed by the catalyst species during the VACNTs growth
Summary
Aerosol-assisted catalytic chemical vapor deposition (AACCVD) is a powerful one-step process to produce vertically aligned carbon nanotubes (VACNTs), characterized by the continuous supply of the catalyst precursor (metallocene). Nanomaterials 2022, 12, 449 high enough to induce the thermal decomposition of the metallocene precursor, the partial vapor pressure of iron is high enough for a homogeneous nucleation of small metal-based nanoparticles (NPs) to occur in the gas phase These are deposited on the substrate along the reactor leading to the formation of the catalytic particles by coalescence [11]. The encapsulation is driven by their mobility at high temperature (800 ◦ C) and capillarity forces inside the growing CNT [17] This renewal is effective throughout the growth process, as demonstrated by specific syntheses using different metallocene precursors in a sequential manner, implying that the metal precursors are able to diffuse through the growing carpet to the substrate in the same way of the carbon precursors [19,20].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
