Graphene is a two dimensional material with extraordinary properties; it is transparent, only single atom thick, 50x stronger than steel, more electrically conductive than copper and more thermally conductive than diamond. We have developed a unique and revolutionary process of graphene synthesis, based on microwave plasma processing of large volume hydrocarbons.
Our process is unique in graphene synthesis rate, offering the possibility to synthesise kilograms of material in an hour in a continuous manner. The process is 95% efficient. There is no requirement for surfactants, solvents or catalysts. This makes it the only large scale synthesis method for freestanding, high quality graphene available. Reaction operates under normal pressure conditions, without the use of noble gases, catalysts, other expensive precursors, or external heating. We are currently tuning the process parameters to achieve the absolute control of the lateral graphene flake size.
At the present stage of the graphene development, there are a few proposed synthesis methods, like micromechanical cleavage, supramolecular assembly, solution-chemistry approach, graphitization of SiC wafer, molecular beam epitaxy, laser ablation and thermal delamination of oxidised graphite, chemical vapour deposition on a substrate and exfoliation of graphite in acidic or organic media. These methods suffer from many drawbacks, the main ones being little synthesis yield and rate making it often only suitable for laboratory demonstrations, ultra-high vacuum synthesis conditions, expensive substrates, complex and high energy input procedures, costly substrates and reagents, difficult to remove contaminants, impurities severely deteriorating material’s mechanical, electrical and thermal properties and lack of process continuity.
To overcome these limitations and exploit the large scale potential of graphene, we have developed a plasma approach as a synthesis technique. Our method employs a microwave plasma system run at atmospheric pressure conditions. Microwave plasma lacks thermodynamic equilibrium between electrons and other plasma species (radicals, ions, particles). Thus, processes occurring in plasma are determined mostly by electrons’ temperature, making them less sensitive to thermal processes and the temperature of the gas as in a thermal type of plasma. This allows for the potential of running processes under milder conditions, with reduction in the complexity and increased energy efficiency.
It also affords the possibility to exceed conventional processes in yield and selectivity, enabling the use of cheap reagents like methane, which in thermal processes would be poorly decomposed. After fragmentation, ionisation and excitation, species recombination occurs and graphene is formed rapidly, without requiring a substrate to grow from.
Single layer graphene flakes