SiC nanoparticles encapsulated by graphene sheets: A Solvothermal approach
to impart superior tensile ductility to aluminium matrix nanocomposites
A. Fadavi Boostani 1, R. Taherzadeh Mousavian2, S. Tahamtan3, D. Wei4, J. Xu3, X. Zhang3, *Z. Y. Jiang1
1
School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522,
Australia
(*Corresponding author: jiang@uow.edu.au)
2
Faculty of Materials Engineering, Sahand University of Technology, Tabriz, Iran
3
4
State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang, Liaoning, 110004,
China
School of Electrical, Mechanical and Mechatronic Systems, University of Technology, Sydney, NSW 2007,
Australia
ABSTRACT
Metal matrix nanocomposites strengthened with ceramic nanoparticles outperform the disadvantages
associated with the conventional metal matrix composites because of the enhanced mechanical and
electrical properties. However, nanoparticles used in these methods still suffer from poor wetting
behaviour or weak interfacial bonding to matrix, agglomeration among themselves with Van-der-Waals
force, inhomogeneous distribution in the matrices and degraded thermal stability at high temperature
processing. The question, which arises here, is whether graphene, i.e. a single-atom-thick sheet of sp2
hybridised carbon atoms, has the ability to manipulate the interaction between the nanoparticles and the
interface to achieve better incorporation of these particles within the solidifying matrix. This study presents
an innovative fabrication route to diminish the agglomeration of SiC nanoparticles using graphene
encapsulating method stimulated by solvothermal process. The produced SiC nanoparticles were then
incorporated into A357 molten alloy using liquid processing route. Field-emission scanning electron
microscopy pictures have shown the agglomerated SiC nanoparticles (Fig. 1(a)) for composite
unreinforced with graphene sheets (NT-SiC) compared with uniform distribution of SiC nanoparticles (Fig.
1(b)) for composites reinforced with graphene sheets (AR-SiC). This is conferring 273% and 400%
enhancement in yield strength and tensile ductility, respectively, for the latter compared with former. This
is attributed to the manipulation of solidification mechanism of SiC nanoparticles from pushing to
engulfment, ensued from imparting higher thermal conductivity to these particles by onion-liked graphene
sheets. A devised analytical strengthening model has demonstrated the profound efficacy of thermal
activated dislocation mechanism in fortifying the matrix, capacitated by exceptional negative thermal
expansion coefficient of graphene sheets. Fractographic observations disclosed a dimple fracture surface
for aluminium matrix composite reinforced by the SiC nanoparticles encapsulated by graphene sheets
compared with the cleavage fracture surface of those fortified without the application of graphene.
Fig.1. FE-SEM micrograph of (a) NT-SiC and (b) AR-SiC samples
Keywords: Metal matrix composites; Graphene sheets; Strengthening mechanisms, Fracture; Ductility