Graphene coating makes carbon nanotube aerogels superelastic and resistant to fatigue

Abstract

Lightweight materials that are both highly compressible and resilient under large cyclic strains can be used in a variety of applications. Carbon nanotubes offer a combination of elasticity, mechanical resilience and low density, and these properties have been exploited in nanotube-based foams and aerogels. However, all nanotube-based foams and aerogels developed so far undergo structural collapse or significant plastic deformation with a reduction in compressive strength when they are subjected to cyclic strain. Here, we show that an inelastic aerogel made of single-walled carbon nanotubes can be transformed into a superelastic material by coating it with between one and five layers of graphene nanoplates. The graphene-coated aerogel exhibits no change in mechanical properties after more than 1 × 10(6) compressive cycles, and its original shape can be recovered quickly after compression release. Moreover, the coating does not affect the structural integrity of the nanotubes or the compressibility and porosity of the nanotube network. The coating also increases Young's modulus and energy storage modulus by a factor of ∼6, and the loss modulus by a factor of ∼3. We attribute the superelasticity and complete fatigue resistance to the graphene coating strengthening the existing crosslinking points or 'nodes' in the aerogel.

Ultralight nanofibre-assembled cellular aerogels with superelasticity and multifunctionality

“…2a and Supplementary Movie 1. Figure 2a presents plots of the compressive s-e curves for the FIBER NFAs at set e maxima of 40, 60 and 80%, revealing two characteristic deformation regimes typically observed in open-cell foams 10,34 : a Hookean or linear elastic regime for eo60% with a stable tangent modulus (ds/de) of B30 kPa and a densification regime for e460% with s and the ds/de increasing steeply. The maximum s was 10.6 kPa for the first elastic regime and 36.1 kPa at 80% strain; these values were significantly higher than those of other fibrous aerogels with similar densities 11,35 .…”

Morphology and processing of aligned carbon nanotube carbon matrix nanocomposites

“…Another method that could yield very low porosity A-CMNCs is the use of successive infusions with a diluted phenolic resins, which could be designed to form approximately conformal coatings of polymer, and subsequently PyC (after pyrolysis). However, a drawback of such a synthesis method is the need for critical point drying (CPD) 52,53 to dry the samples before pyrolyzation, which is more difficult to use in an industrial scale. Future work should explore both methods, and determine which yields the CNT A-CMNCs with minimal porosities, and optimal combination of physical properties.…”

Biomimetic superelastic graphene-based cellular monoliths

“…A number of methods, such as self-gelation and chemical vapour deposition (CVD) over a porous catalyst have recently been developed to fabricate highly porous graphene cellular monoliths [5][6][7][8][9][10][11][12] . However, as with most of the existing porous carbon materials 13 , the resulting graphene monoliths are generally brittle and have small recoverable deformation before failure unless they are infiltrated with an elastomeric polymer 5 or grown on pre-formed carbon nanotube aerogels 14 . Superelasticity that has been observed in foams made of carbon-based tubular or fibrillar nanostructures [15][16][17][18][19][20][21] has not been achieved in foams solely based on graphene sheets.…”