Production of graphene based materials and their potential applications

Graphene is a promising material for many applications due to its unique properties. However, properties and yield of graphene-based materials show variations depending on which production route is used. Therefore, an appropriate production method has to be preferred according to the requirements of a specific application. In this thesis study, graphene-based materials have been successfully produced by liquid phase exfoliation (LPE) and chemical vapor deposition (CVD), which are promising graphene production methods in terms of quality, scalability, cost and applicability of the produced material to relevant applications, and a fundamental understanding on graphene production has been developed. LPE route allows one to produce graphene-based materials at a large-scale for applications such as nanocomposites. The challenge of this method is to increase graphene concentration as much as possible while maintaining the quality of the graphene flakes. Therefore, a comparative study, at which three different graphite-based powders were investigated as starting materials for an effective exfoliation process in isopropyl alcohol (IPA), was performed. High concentration (1.1 mg/ml), few-layer (smaller than 5 layers) graphene-based dispersions were prepared by sonication in IPA within 90 min by utilizing a high surface area graphite nano-powder. This graphene-based material was then incorporated into Al2O3 matrix nanocomposites as a reinforcing/filler phase. Ceramic matrix nanocomposites which exhibit anisotropic mechanical, thermal and electrical properties have been successfully prepared by spark plasma sintering. On the other hand, large-area graphene films, which are promising for electronic applications, were synthesized via low-pressure CVD method over Cu-foils. The influence of ramping atmosphere and Cu foil characteristics on the impurity level, quality of the synthesized graphene films and their thickness uniformity was investigated. High quality CVD-grown graphene films with a significantly reduced disorder level were used for device fabrication and characterized in terms of their electrical resistance at room temperature as a function of gate voltage and transport property measurements in Quantum Hall Effect (QHE) regime (at low temperature and high magnetic field) by pulsed magnetic field experiments. The preliminary results confirmed that single layer graphene with a relatively high electronic mobility reaching up to 46500 cm2/Vs at room temperature was successfully produced.