MOHAN Velram Balaji The University of Auckland

Characterisation and Functional Properties of Reduced Graphene Oxide and its Nanocomposites

Co-authors BHATTACHARYYA Debes, JAYARAMAN Krishnan

Graphene, a single layer consisting of hexagonally bonded carbon atoms is an attractive material because of its excellent electronic properties. Graphene and its derivatives can be used as functional reinforcements in polymers for applications, such as sensors, flexible devices, packaging, and functional nanocomposites. This article focuses on the modified synthesis method, reduction using five different reducing agents (Hydrobromic (HBr), Hydrazine hydrate (HH), Hydroiodic acid (HI), Sodium borahydride (SBH) and Dextrose (D)) and characterization using Raman spectroscopy and X-ray diffraction (XRD) of reduced graphene oxide in order to identify an electronic structure that possesses higher electrical conductivity. Conductivity measurements were made using four-probe method and thermo gravimetric analysis was conducted to identify difference in weight percentage caused by different reducing agents as well reduction hours. The reduction procedure removes functionalities such as ROH, R=O, ROOH and ROR. The reduction process also alters the d-spacing (space between layers of GO film). It was assumed that d-spacing would impact the electrical conductivity of GO film but the conductivity results show that the d-spacing variation between reduction hours performed does not have substantial impact. However, variation in amount of functional groups present in rGO changes the conductivity level. Results for reduced graphene oxide (rGO) that has been reduced with hydroiodic acid show an electrical conductivity of 103.3 S/cm with a highly oriented and uniform chemical structure. A nanocomposite prepared using this highly conductive rGO and LLDPE has been found to improve the conductivity of the system but it is not significant due to agglomeration of rGO particles. The issue of higher rGO loading in rGO based nanocomposites resulting in reduced conductivity is currently being re-examined from a compatibility perspective. New rGO/matrix systems are being synthesised with improved rGO/matrix miscibility. Improved miscibility is also likely to result in improved electrical properties and mechanical properties, as lower agglomeration reduces fracture points in the product.

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