Aerosol CVD synthesis and applications of single-walled carbon nanotube thin films using spark-discharged produced catalyst

Saeed Ahmad

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Structural controlled synthesis of single-walled carbon nanotubes (SWCNTs) have attracted a great deal of attention due to their widespread potential applications in electronics and photonics. Floating catalyst chemical vapor deposition (FC-CVD) being a dry and continuous method, is a highly promising technique for the scalable synthesis of SWCNTs. However, due to in-situ catalyst formation in all the conventional FC-CVD approaches, it is hard to get full control of number concentration, composition and size of nanoparticles. Hence, it hinders to investigate the effects of catalyst composition on morphology, yield and structure of SWCNTs. In this thesis, firstly we designed a novel rod-to-tube type spark discharge generator (R-T SDG) to produce ex-situ catalyst nanoparticles for the FC-CVD growth of SWCNTs. We utilized highly time-stable and uniform number size distributions of monometallic (Fe, Ni, Co) and bimetallic (Co-Fe, Co-Ni) catalyst particles for the synthesis of SWCNTs using ethylene as carbon source and 1050 oC temperature. Optical characterizations revealed that as-grown SWCNTs have high-quality and their mean diameter is around 1 nm. The highest SWCNTs yield was obtained with Fe as a catalyst. From electron diffraction analysis, we observed that Co-Ni can produce comparatively narrower chirality and diameter distribution of SWCNTs. Secondly, we introduced sulfur in the FC-CVD reactor as a growth promoter for the fabrication of SWCNTs based transparent conducting films (TCFs). We systematically investigated the roles of sulfur on yield, morphology, and structure of SWCNTs. It was found that the yield of SWCNTs is largely dependent on amount of sulfur introduced into the FC-CVD reactor and catalyst composition. More importantly, the addition of an optimized amount of sulfur has enhanced approximately three times, the opto-electronic performance of SWCNT-TCFs, by increasing diameter and bundle length along with improving the quality of SWCNTs. The mean diameter of SWCNTs increased from 1 nm to 1.2 nm while the ratio of metallic nanotubes slightly increased from 39% to 41% with sulfur addition. Surprisingly, chirality determination of as-grown SWCNTs indicated that sulfur promotor has little influence on modulating the chirality of SWCNTs. Finally, we demonstrated that FC-CVD is a unique and versatile technique for the simultaneous growth of substrate-free 0D-fullerene, 1D-CNT and 2D-graphene. The formation of 0D-1D-2D carbon nanostructures were directly evidenced by lattice-resolved (scanning) transmission electron microscopy (STEM). We showed that the relative number density of graphene-nanoflakes can be tuned by optimizing the synthesis conditions. In addition, the as-synthesized hybrid films can be directly deposited on any surface at ambient temperature with an arbitrary thickness which offers a new route towards ultra-fast manufacturing and dry deposition of the hybrid structures.
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Kauppinen, Esko, Supervisor
  • Zhang, Qiang, Advisor
Publisher
Print ISBNs978-952-60-3795-0
Electronic ISBNs978-952-60-3796-7
Publication statusPublished - 2020
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • floating-catalyst CVD
  • single-walled carbon nanotubes
  • pre-made catalyst
  • ethylene
  • transparent conducting film
  • low dimensional carbon nanostructures

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