Elastic properties of chemically derived single graphene sheets

Max-Planck-Institut fur Festkorperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
Nano Letters (Impact Factor: 13.59). 08/2008; 8(7):2045-9. DOI: 10.1021/nl801384y
Source: PubMed


The elastic modulus of freely suspended graphene monolayers, obtained via chemical reduction of graphene oxide, was determined through tip-induced deformation experiments. Despite their defect content, the single sheets exhibit an extraordinary stiffness ( E = 0.25 TPa) approaching that of pristine graphene, as well as a high flexibility which enables them to bend easily in their elastic regime. Built-in tensions are found to be significantly lower compared to mechanically exfoliated graphene. The high resilience of the sheets is demonstrated by their unaltered electrical conductivity after multiple deformations. The electrical conductivity of the sheets scales inversely with the elastic modulus, pointing toward a 2-fold role of the oxygen bridges, that is, to impart a bond reinforcement while at the same time impeding the charge transport.

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    • "This EMI shielding application of graphene paper is related to its low density, excellent flexibility and extraordinary electrical properties of graphene materials [20] [21] [22] [23]. Graphene paper [16] prepared by using graphene oxide (GO) as a template for synthesis and processing showed good mechanical properties with a breaking stress at 120 MPa. "
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    ABSTRACT: Syntheses of multifunctional structures, both in two-dimensional and three-dimensional space, are essential for advanced graphene applications. A variety of graphene-based materials has been reported in recent years, but combining their excellent mechanical and electrical properties in a bulk form has not been entirely achieved. Here, we report the creation of novel graphene structures such as graphene pellet and graphene paper. Graphene pellet is synthesized by chemical vapor deposition (CVD), using inexpensive nickel powder as a catalyst. Graphene pellet can be further processed into a graphene paper by pressing. The latter possesses high electrical conductivity of up to 1136 ± 32 S cm−1 and exhibits a breaking stress at 22 ± 1.4 MPa. Further, this paper-like material with thickness of 50 μm revealed 60 dB electromagnetic interference (EMI) shielding effectiveness
    Carbon 02/2015; 82:353–359. DOI:10.1016/j.carbon.2014.10.080 · 6.20 Impact Factor
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    • "In comparison to graphene, however, experimental investigations of the mechanical properties of monolayer GO are limited, despite widespread implementation of GO films as a stiffening and strengthening additive in composite applications [15] [16]. The 3D elastic modulus of monolayer GO membranes has been experimentally characterized and is reported to be approximately $25% of pristine graphene [17] [18]; however , the strength of monolayer GO has not been experimentally measured to date [19]. Computational studies have predicted that the strength of monolayer GO could be as high as approximately 50% of the intrinsic strength of pristine graphene [20] [21]. "
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    ABSTRACT: In this study, the strength of monolayer graphene oxide membranes was experimentally characterized. The monolayer GO membranes were found to have a high carbon-to-oxygen ratio (similar to 4:1) and an average strength of 17.3 N/m (24.7 GPa). This measured strength is orders of magnitude higher than previously reported values for graphene oxide paper and is approximately 50% of the 2D intrinsic strength of pristine graphene. In order to corroborate strength measurements, experimental values were compared to theoretical first-principles calculations. Using a supercell constructed from experimental measurements of monolayer graphene oxide chemistry and functional structure, density functional theory calculations predicted a theoretical strength of 21.9 N/m (31.3 GPa) under equibiaxial tension, in good agreement with the experimental data. Furthermore, computational simulations were used to understand the underlying fracture mechanism, in which bond cleavage occurred along a path connecting oxygenated carbon atoms in the basal plane. This work shows that monolayer graphene oxide possesses near-theoretical strength reaching tens of GPa.
    Carbon 01/2015; 81:497-504. DOI:10.1016/j.carbon.2014.09.082 · 6.20 Impact Factor
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    • "The parameter g L is a measure of reinforcement geometry that is dependent upon the loading conditions; it is basically controlled by the aspect ratio of the filler and depends only upon the loading conditions of the filler. The Young's modulus of the chemically reduced monolayer graphene oxide was previously reported to be $0.25 TPa [46], which we consider to be similar to that of the GO sheets in the GO/PU composite used in this study. The Young's modulus of pure PU is 0.012 GPa (from the experimental data). "
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    ABSTRACT: A masterbatch of graphene oxide (GO) in polyol was prepared and used for the preparation of polyurethane (PU)/GO nanocomposites by bulk in-situ polymerization. The prepared nanocomposites were characterized in terms of their thermal, mechanical, and morphological properties as a function of GO loading. Here, grafted PU chains on the surface of GO facilitated the beneficial stress transfer from the PU matrix to GO. This stress transfer occurs due to the reaction of the hydroxyl and carboxyl groups of GO with the isocyanate groups of 4,4'-methylene diphenyl diisocyanate (MDI) and the PU pre-polymer. The Young’s modulus of the PU was improved by 280.5% through the incorporation of 3 wt % GO. Additionally, an improvement of 40.5% in the tensile strength and 19% in the elasticity was achieved at 1 wt % GO. Strain hardening of PU was improved with GO loadings up to 1 wt% due to the synergetic orientation of the soft segment and the PU-grafted GO in the strain direction. However, the large increase in cross-link density that occurred at 2 wt % GO prevented strain hardening, and the ultimate tensile strength decreased. The Halpin–Tsai model was used to predict the orientation of GO in PU nanocomposites. The randomly oriented 3D arrangement of GO in PU showed better agreement between the theoretically calculated and experimentally determined moduli compared to the 2D alignment. These results demonstrate that the preparation of PU nanocomposites using masterbatch dilution is an excellent method to attain well dispersed GO. This technique can also be used to overcome the environmental problems associated with volatile organic compound (VOC) emission, as well as addressing some of the difficulties found in the plastics processing industry.
    The Chemical Engineering Journal 10/2014; 253:356–365. DOI:10.1016/j.cej.2014.05.046 · 4.32 Impact Factor
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