Scale up of graphene production by liquid phase exfoliation

Graphene has been a significant topic of discussion in the scientific community since its isolation and characterisation by Geim and Novezelov in 2004, resulting in the awarding of the Nobel Prize in Physics in 2010. It boasts properties far superior to 'common' materials; with its strength, thermal and electrical conductivity, flexibility, surface area and transparency making it a viable choice in a wide range of applications. Graphene comes in many forms, whether dispersed in a solvent or on a film of plastic, or with functional groups attached such as graphene oxide. The form required is dependent on the type of application, and dictates the production method required. Herein lies the main motivation for the project, as a low-cost method of production to bulk produce graphene is yet to be realised.
Graphene can be produced via bottom-up (BU) or top-down (TD) methods. BU involves producing graphene by using hydrocarbon reagents, by techniques such as chemical vapour deposition. TD involves the exfoliation of graphite into graphene through techniques such as sonication. The most common way graphene is produced for commercial applications is BU, as it currently offers a high degree of accuracy not achieved through TD techniques; however it suffers from a lack of ability to scale up.
Tour compared TD versus BU fabrication of graphene based electronics, and noted that the significant advantage to BU fabrication is the control of resolution, but utilising the graphene produced is difficult. He proposed that in the future there is some potential for combining the two techniques, by mass producing using TD methods, then removing defects such as oxygen functionality on the edges using BU techniques. Since the focus of the project is on the scale up of production utilising liquid phase exfoliation (LPE), a TD technique, this is the method that will be focused on for the remainder. It should be further noted that novel techniques in all branches of science should be sustainable and not rely on a depleting resource. TD techniques utilise the abundant resource graphite to produce a material that can replace many expensive, limited materials in several applications, for example the use of platinum in catalysts.
This project will focus on the use of a spinning tube design, which is still currently being manufactured. The rotation of the cylinders will generate areas of high shear stress, and at high enough rotation speeds, Taylor vortices will form, enhancing the exfoliation. Experimental work, coupled with numerical simulation will be used to analyse the stress fields formed, and compared to the graphene produced. Several options exist for the analysis of the graphene itself, including UV-vis and Raman spectroscopy, TEM and AFM. Due to the wide range of possibilities and analysis available it is necessary to focus on particular elements, with the main focus of the project on how the fluid dynamics inside the device effect the graphene produced.