• Aynalem, Andinet
• Kinloch, Ian A.
• Dryfe, Robert A. W.
• Wang, Fang
• Tenne, Reshef
• Young, Robert J.
• Wolverson, Daniel
• Bissett, Mark

Abstract

<p>The nature of the interface between a reinforcement and the matrix is crucial in determining the degree of dispersion and mechanical properties. Controlling the interface is particularly important when 2D materials are used as reinforcements, as their flat nature eliminates bonding mechanisms such as mechanical lock-in. For example, we have previously shown that unfunctionalised graphene in an epoxy matrix has just a tenth of the interfacial strength of a carbon fibre. Herein, we have developed chemical functionalization of two-dimensional (2D) materials as a route to control their interface with thermosets, thermoplastics and elastomers. One well-established method for functionalizing graphene is the use of aryl diazonium chemistry. This functional step is typically applied on as-made powder, however we have found that graphene can be simultaneously functionalized and exfoliated from graphite by electroreduction. This one-step process prevents aggregation, increases thin-flake yield and leads to high quality dispersions. However, similarly structured inorganic 2D materials such as transition metal dichalcogenides (TMDs) have generally been considered to be chemically inert, with few studies into the covalent modification and functionalization of them. Previously, it was believed that only the 1T phase of TMDs could be functionalised by aryl diazonium due to the difference in electronic structure. However, in this work we demonstrate that the more stable and naturally occurring 2H-phase can be successfully functionalised via aryl diazonium chemistry. We have measured the interfacial strength of these functionalized materials within different matrices using Raman mapping of in-situ mechanical tests of single flakes and applying a simple shear lag model. Bulk composites were then produced with flakes processing different aspect ratios to prove that these micromechanics approaches can be translated to the macroscale.</p>

Topics

• nanocomposite
• impedance spectroscopy
• dispersion
• Carbon
• phase
• liquid-assisted grinding
• strength
• two-dimensional
• interfacial
• thermoset
• thermoplastic
• functionalization
• elastomer