Reinforcement of metal with liquid-exfoliated inorganic nano-platelets

Abstract

We have prepared metal matrix composites (MMCs) of a pewter alloy filled with liquid-exfoliated Molybdenum Telluride (MoTe 2 ) nano-platelets. The combination of MoTe 2 and pewter was chosen due to their near-identical densities, thus reducing the scope for buoyancy-induced separation during melt mixing. The addition of nanofiller results in a doubling of the Young's modulus, Y, for a volume fraction, V f , of <1 % MoTe 2 , corresponding to a reinforcement of dY/dV f =110 GPa. We find that this degree of reinforcement to be reasonably consistent with that predicted by a simplified version of Halpin-Tsai theory.Over the last decade, the study of 2-dimensional (2D) nano-materials has become one of the most active areas of nanoscience. Since the discovery of graphene 1 and more recently, the surge of interest in inorganic 2D materials, 2-4 such nanostructures have been used to demonstrate a host of applications in areas from composites to energy storage to optoelectronics. 2-5 Particularly important will be applications which harness the impressive mechanical properties of 2D nano-materials. It is well known that graphene is the strongest, stiffest material known to man with strength and elastic modulus values of 130 and 1000 GPa respectively. 6 Indeed graphene nanosheets have been used in a number of mechanical applications particularly as a reinforcing filler in composites. 7-9 Less well known is the fact that boron nitride (BN) nanosheets display very similar mechanical properties to graphene. 10 Indeed a host of 2D nano-materials have Young's moduli which surpass 100 GPa. 11 Perhaps more importantly these materials may have strengths 11 as high as 36 GPa (estimated for layered WO 2 assuming its strength,  B , and modulus, Y, scale in a manner similar to MoS 2 : Y=11.7 B ) 12 . However, to the author's knowledge only three papers describe using inorganic 2D materials to mechanically reinforce any matrices; in all cases reinforcement of polymer matrices with BN nanosheets. [13][14][15] In many ways this is surprising. It was recently shown that a range of layered compounds can be exfoliated by sonication in liquids to give large quantities of 2D nanosheets. [16][17][18][19] The advantage of such liquid processing is that the resultant suspensions can be used to make a range of materials and structures including composites. 3 Because of the exceptional mechanical properties of 2D materials, 11 we would expect such composites to display enhanced mechanical properties.The vast majority of reports on nano-composites describe using nano-materials to reinforce polymer matrices. 8 Yet, many other types of composites exist; including for

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On the Elastic Properties and Fracture Patterns of MoX2 (X = S, Se, Te) Membranes: A Reactive Molecular Dynamics Study

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Edge and confinement effects allow in situ measurement of size and thickness of liquid-exfoliated nanosheets

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