Defence of dissertation in the field of engineering physics, Saeed Ahmad, MPhil

Graphene Nano flakes can grow without any substrate

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Title of the dissertation is "Aerosol CVD synthesis and applications of single-walled carbon nanotube thin films using spark-discharged produced catalyst"

The catalyst particle that seeds the growth of single-walled carbon nanotubes (SWCNTs) is one of the most important parameters determining the morphology and chirality of as-synthesized SWCNT. The development of the spark discharged based floating catalyst chemical vapor deposition technique in the present thesis has enabled decoupling of the catalyst and SWCNT formation into two consecutive processes. We employed various spark discharge produced catalyst particles to investigate the roles of catalyst composition on various growth characteristics of SWCNTs. Moreover, we found that the addition of sulfur promoter in the growth process of SWCNTs enhances the performance of SWCNT-based transparent conductive films, which are an appealing material for the replacement of indium-doped tin oxide in emerging flexible, bendable and stretchable display devices.

In addition, we have developed a novel gas-phase, single step and substrate free method for the simultaneous growth of 0D-fullerene, 1D-SWCNTs and 2D-graphene. Fullerene and SWCNTs arise from graphene through selective removal of atoms that force the 2D-sheet into a 1D-tubular or 0D-spherical configuration. In this thesis, wedemonstrate that under a carefully chosen gas atmosphere along with SWCNTs and fullerenes that have been synthesized in similar processes graphene flakes emerge within the gas-suspension and grow to a size of up to several hundreds of nanometers without folding or crumpling. Our technique paves the way for the direct deposition of the hybrid material onto any surface at ambient temperature with an arbitrary thickness. This offers a new route towards ultra-fast manufacturing of the hybrid material at an industrial scale.

Opponent: Professor Thomas Wågberg, Umeå Universitet, Sweden.

Custos: Professor Esko I. Kauppinen, Aalto University School of Science, Department of Applied Physics.

Contact information: Saeed Ahmad, Department of Applied Physics, [email protected] and +358 50 4683244

Electronic dissertation

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