Biological materials, such as bones, teeth and mollusc shells, are well known for their excellent strength, modulus and toughness1,2,3. Such properties are attributed to the elaborate layered microstructure of inorganic reinforcing nanofillers, especially two-dimensional nanosheets or nanoplatelets, within a ductile organic matrix4,5,6. Inspired by these biological structures, several assembly strategies—including layer-by-layer4,7,8, casting9,10, vacuum filtration11,12,13 and use of magnetic fields14,15—have been used to develop layered nanocomposites. However, how to produce ultrastrong layered nanocomposites in a universal, viable and scalable manner remains an open issue. Here we present a strategy to produce nanocomposites with highly ordered layered structures using shear-flow-induced alignment of two-dimensional nanosheets at an immiscible hydrogel/oil interface. For example, nanocomposites based on nanosheets of graphene oxide and clay exhibit a tensile strength of up to 1,215 ± 80 megapascals and a Young’s modulus of 198.8 ± 6.5 gigapascals, which are 9.0 and 2.8 times higher, respectively, than those of natural nacre (mother of pearl). When nanosheets of clay are used, the toughness of the resulting nanocomposite can reach 36.7 ± 3.0 megajoules per cubic metre, which is 20.4 times higher than that of natural nacre; meanwhile, the tensile strength is 1,195 ± 60 megapascals. Quantitative analysis indicates that the well aligned nanosheets form a critical interphase, and this results in the observed mechanical properties. We consider that our strategy, which could be readily extended to align a variety of two-dimensional nanofillers, could be applied to a wide range of structural composites and lead to the development of high-performance composites.
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The data that support the findings of this study are available from the corresponding author on reasonable request.
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This research was supported by the National Key R&D Program of China (2017YFA0207800), the National Natural Science Funds for Distinguished Young Scholars (21725401), the National Natural Science Foundation (21988102, 21774004), the 111 project (B14009) and the Fundamental Research Funds for the Central Universities. The small-angle X-ray scattering measurements were performed at BL45XU in SPring-8 with the approval of the RIKEN SPring-8 Center (proposal 20180067).
The authors declare no competing interests.
Peer review information Nature thanks André Studart, Hongbin Lu and Karl W. Putz for their contribution to the peer review of this work.
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Extended data figures and tables
a, Coordinate system of the spreading process for a single droplet. b, Spreading on a solid wetting surface. c, Spreading on a soft gel surface. See Methods for nomenclature.
Extended Data Fig. 2 The spreading radius of reaction solutions with different concentrations as a function of time.
a, The spreading radius (R) of a single droplet as a function of time (t) for various spreading solutions with different concentrations. The time evolution of the radius shows a transition from t1 (red line) to t1/4 (blue line) scaling. b, The spreading radius R of various spreading solutions with different concentrations on a moving substrate as a function of time. The time evolution of the radius shows a transition from t1 (red line) to t1/3 (blue line) scaling. For a and b the compositions of the four kinds of reaction solutions are listed in Supplementary Table 5 (the reaction solutions for the resulting clay/CNT-based nanocomposite films).
a, The spreading diameter d as a function of the moving speed of the hydrogel substrate V for a given reaction solution with a viscosity of 6 mPa s. The flow rate Q was 70 ml h−1. The composition of the reaction solution is 0.03 wt% GO and 0.15 wt% NaAlg. b, The spreading diameter d as a function of the viscosity of the reaction solutions η. The moving speed of the hydrogel substrate V was 5 mm s−1 and the flow rate Q was 70 ml h−1. The viscosity of the aqueous solution was changed by altering the concentration of NaAlg and GO nanosheets. Red lines, fitting curves; error bars, ±1 s.d.
Extended Data Fig. 4 The influence of the concentration of the reaction solution on the orientation degree and on the mechanical properties of the GO/clay/CNT-based nanocomposite films.
a–c, Plots of azimuthal angle (φ; a), orientation order parameter (f) versus concentration (b), and stress–strain curves (c) of the prepared GO/clay/CNT-based nanocomposite films, using reaction solutions with different concentrations of nanofillers (in wt%, see key). The constitution of the four kinds of reaction solutions, the detailed orientation order parameter (f), and the detailed mechanical properties data are listed in Supplementary Tables 5 and 6.
Extended Data Fig. 5 Structural characterization of the layered nanocomposite films with various weight percentages of nanofillers (GO, clay and CNTs).
a, b, Plots of azimuthal angle φ (a) and the orientation order parameter (f) of the layered nanocomposite films with different weight percentages of nanofillers prepared by the superspreading strategy (see key). These results confirm that nanosheets were assembled into highly ordered structures in all these films. The constitution of the reaction solutions and the detailed orientation order parameter (f) are listed in Extended Data Table 1.
a, A failure crack propagates almost in a straight line and perpendicular to the tensile stress direction. b, The morphology of the cross-section view of the fracture surface. CNTs were rarely pulled out from the relatively neat fracture surface, indicating the strong interactions between nanofillers and polymers. c, The energy dispersive X-ray spectroscopy (EDS) image of Si originating from clay in the SS-GO/clay/CNT nanocomposite films, revealing the even distribution of clay nanosheets. The scale bar in SEM image b applies also to SEM image a and EDS image c.
a, The morphology of the cross-section view of the fracture surface. b, The crack path shows a wavy line parallel to the crack propagation path and a damaged zone around the propagating crack tip (indicated by yellow arrows), indicating the efficient dissipation of fracture energy. c, At a higher magnification, the pull-out of CNTs further contributes to fracture energy dissipation. a–c are SEM images.
This file contains Materials, Supplementary Figures 1-22, Supplementary Tables 1-9 and References.
The super spreading process of different reaction solutions on an immersed hydrogel surface. The detailed composition and viscosities of the reaction solution are listed in Supplementary Tables 1-2.
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Zhao, C., Zhang, P., Zhou, J. et al. Layered nanocomposites by shear-flow-induced alignment of nanosheets. Nature 580, 210–215 (2020). https://doi.org/10.1038/s41586-020-2161-8
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