Graphene decorated substrates and their interfacial characteristics
Carbon nanotubes and graphene have been extensively studied for their excellent properties. As research on carbon expands, two major issues face the scientific community: (i) Expanding the scale of synthesis and (ii) Integration of different carbon structures for improved functionality. While significant advancements have been made in large-scale synthesis, room for improvement remains. As the scale of production increases, issues such as time, cost and energy that may otherwise not be very significant, begin to play greater roles. Thus, in order to effectively transition from laboratory prototypes to industrial products, a synthesis method that can address these issues is strongly needed. The work in this thesis is a step towards large-scale, rapid synthesis of a two-dimensional carbon nanostructure, namely graphene. Microwave plasma CVD (MPCVD) growth of graphene and graphene-based nanostructures has been developed. Very short growth times make MPCVD an attractive process. The same process has also been used to produce nitrogen-doped graphene and graphitic nanopetals. ^ Integrating carbon-based structures with each other is another area which is yet to be fully addressed. Interfaces play an important role in such integration. Seamlessly integrating different structures together with minimum interfacial resistance is one major challenge to almost all nanomaterials. The thesis demonstrates the growth of integrated graphene petals on carbon fibers and carbon nanotube arrays. Catalyst-free MPCVD synthesis of multi-layer graphene extensions from carbon fiber offers a unique possibility of minimizing interfacial losses in transport applications. Graphene petals grown on CNTs increase the mechanical stiffness and elastic recoverability of a vertically aligned CNT array. A 3ω method is used to study the effect of carbon deposition on thermal interface resistance between carbon fiber and epoxy in a carbon fiber composite. It is also shown that vertically oriented 2D graphene petals on flat substrates serve as facile, unique template for high-density nanoparticle deposition. Such nanoparticle-decorated graphene petals are demonstrated to serve as promising substrates for surface enhanced Raman spectroscopy (using Ag nanoparticles) and electrochemical sensing (using Pt nanoparticles). Finally, it is shown that few-layer graphene films on Cu serve as oxidation barrier under ambient, high temperature and under extreme conditions such as that of flow boiling^
Timothy S. Fisher, Purdue University.
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