Wrinkled Few-Layer Graphene as Highly Efficient Load Bearer

Androulidakis, Charalampos; Koukaras, Emmanuel Ν.; Rahova, Jaroslava; Sampathkumar, Krishna; Parthenios, John; Papagelis, Konstantinos; Frank, Otakar; Galiotis, Costas

doi:10.1021/acsami.7b07547

Cited by 52 publications

(53 citation statements)

References 48 publications

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“…Essentially, this means that up to that strain level the material system is in the regime of superlubricity and for further tension (>0.2%), sliding occurs which enhances this behaviour. In contrast such an effect is not observed in commensurable (Bernal stacked) bilayers up to quite high tensile strains 26 . It is worth remarking on the strain profiles for the top graphene layer shown in figure 4.…”

Section: Resultsmentioning

confidence: 87%

Tunable macroscale structural superlubricity in two-layer graphene via strain engineering

et al. 2020

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Achieving structural superlubricity in graphitic samples of macro-scale size is particularly challenging due to difficulties in sliding large contact areas of commensurate stacking domains.Here, we show the presence of macro-scale structural superlubricity between two randomly stacked graphene layers produced by both mechanical exfoliation and CVD. By measuring the shifts of Raman peaks under strain we estimate the values of frictional interlayer shear stress (ILSS) in the superlubricity regime (mm scale) under ambient conditions. The random incommensurate stacking, the presence of wrinkles and the mismatch in the lattice constant between two graphene layers induced by the tensile strain differential are considered responsible for the facile shearing at the macroscale. Furthermore, molecular dynamic simulations show that the stick-slip behaviour does not hold for achiral shearing directions for which the ILSS decreases substantially, supporting the experimental observations. Our results pave the way for overcoming several limitations in achieving macroscale superlubricity in graphene.

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Section: Resultsmentioning

confidence: 87%

Tunable macroscale structural superlubricity in two-layer graphene via strain engineering

et al. 2020

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“…At every strain level the whole graphene flake was scanned from edge to edge at steps of ~1 μm and Raman spectra were continuously taken. The magnitude of strain on the top surface of the PMMA bar where graphene was located was estimated by the beam deflection and also by means of electrical resistance strain gauges [15][16]20 .…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, in most cases the resulting graphene flakes are of small size (~3-5 μm) and of irregular shape. It is therefore clear that both size, thickness and shape of the flakes employed can play a critical role in the reinforcing capabilities of the filler [15][16] . Despite the extensive use of these few-layer graphenes in nano-composites there is very limited experimental work on the corresponding stress transfer mechanisms 17 and particularly the required characteristics for efficient reinforcing capabilities.…”

Section: Introductionmentioning

confidence: 99%

“…MPa for graphene-polymer systems by converting the Raman data to strain maps and by considering the balance of shear-to-axial forces at the interface 17,20,[22][23] . These values are relatively low and methods for increase them have been proposed by previous work of the group, such as the creation of a wrinkled interface which significantly enhances the stress transfer efficiency from the polymer to graphene 16 or the introduction of artificial 'defects' to the filler that enhances the anchoring of graphene to the host polymer 24 . Moreover, the chemical modification of the interface polymer-graphene has proven to be effective in increasing the ISS 25 .…”

Section: Introductionmentioning

confidence: 99%

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Stress-transfer from polymer substrates to monolayer and few-layer graphenes

et al. 2019

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In the present study the stress transfer mechanism in graphene-polymer systems under tension is examined experimentally using the technique of laser Raman microscopy. We discuss in detail the effect of graphene edge geometry, lateral size and thickness which need to be taken under consideration when using graphene as a protective layer. The systems examined comprised of graphene flakes with large length (over ~50 microns) and thickness of one to three layers simplydeposited onto PMMA substrates which were then loaded to tension up to ~1.60% strain. The stress transfer profiles were found to be linear while the results show that large lateral sizes of over twenty microns are needed in order to provide effective reinforcement at levels of strain higher than 1%. Moreover, the stress-built up has been found to be quite sensitive to both edge shape and geometry of the loaded flake. Finally, the transfer lengths were found to increase with the increase of graphene layers. The outcomes of the present study provide crucial insight on the issue of stress transfer from polymer to nano-inclusions as a function of edge geometry, lateral size and thickness in a number of applications.

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“…However, in this case the graphene sheets contain structural imperfections such as a network of wrinkles, cracks and folds [20][21][22][23][24][25], which can generally be defined as defects [26][27][28][29][30] and impair somewhat the properties of the finished products. According to Han et al [31], the onset of crack nucleation occurs near the presence of defects, determine graphene's performance under tensile loading.…”

Section: Introductionmentioning

confidence: 99%

Enhancing the adhesion of graphene to polymer substrates by controlled defect formation

et al. 2018

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The mechanical integrity of composite materials depends primarily on the interface strength and the defect density of the reinforcement which is the provider of enhanced strength and stiffness. In the case of graphene/ polymer nanocomposites which are characterized by an extremely large interface region, any defects in the inclusion (such as folds, cracks, holes etc.) will have a detrimental effect to the internal strain distribution and the resulting mechanical performance. This conventional wisdom, however, can be challenged if the defect size is reduced beyond the critical size for crack formation to the level of atomic vacancies. In that case, there should be no practical effect on crack propagation and depending on the nature of the vacancies the interface strength may be in fact increase.In this work we employed argon ion (Ar + ) bombardment and subsequent exposure to hydrogen (H2) to induce (as revealed by X-ray & Ultraviolet photoelectron spectroscopy (XPS/UPS) and Raman spectroscopy) passivated atomic single vacancies to CVD graphene. The modified graphene was subsequently transferred to PMMA bars and the morphology, wettability and the interface adhesion of the CVD graphene/PMMA system were investigated with Atomic Force Microscopy technique and Raman analysis. The results obtained showed clearly an overall improved mechanical behavior of graphene/polymer interface, since an increase as well a more uniform shift distribution with strain is observed. This paves the way for interface engineering in graphene/polymer systems which, in pristine condition, suffer from premature graphene slippage and subsequent failure.

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Wrinkled Few-Layer Graphene as Highly Efficient Load Bearer

Cited by 52 publications

References 48 publications

Tunable macroscale structural superlubricity in two-layer graphene via strain engineering

Tunable macroscale structural superlubricity in two-layer graphene via strain engineering

Stress-transfer from polymer substrates to monolayer and few-layer graphenes

Enhancing the adhesion of graphene to polymer substrates by controlled defect formation

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