Research ArticleMATERIALS SCIENCE

Extraordinary tensile strength and ductility of scalable nanoporous graphene

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Science Advances  15 Feb 2019:
Vol. 5, no. 2, eaat6951
DOI: 10.1126/sciadv.aat6951
  • Fig. 1 Fabrication and microstructure characterization of nanoporous graphene.

    (A) Schematic illustration of CVD-grown bicontinuous nanoporous graphene and a tubular structure with atomically thick walls. (B) Scanning electron microscopy (SEM) image of nanoporous graphene@Ni. Inset: A centimeter-sized sample. (C) SEM image of freestanding nanoporous graphene after etching away Ni. Inset: A centimeter-sized sample. (D) High-resolution transmission electron microscopy (TEM) images showing a few-atomic-layer graphene wall in low-density nanoporous graphene grown at 1000°C for 1 min and a multilayer graphene wall in high-density nanoporous graphene grown at 1000°C for 10 min. The wall thickness of graphene tubes is tunable from monolayer, bilayer, to multilayer by changing graphene growth time from 1 to 10 min. (E) Raman spectra of nanoporous graphene with different np-Ni annealing times before graphene growth and CVD growth periods at 1000°C. We annealed all np-Ni substrates at 1000°C for 3 min before CVD growth of graphene at various times from 1 to 10 min to change the thickness of graphene or fixed the CVD growth time and tuned the np-Ni annealing periods from 3 min to 10 hours to change the tube/pore sizes as marked on each Raman spectrum. a.u., arbitrary units. Scale bars, 2 μm (B and C).

  • Fig. 2 Tensile stress-strain curves of nanoporous graphene.

    (A) Effect of graphene growth temperature on the tensile properties of nanoporous graphene. Inset: The dog bone–shaped tensile sample with a total length of 15 mm and a gauge length of 6 mm. (B) Tensile stress-strain curves of high-quality nanoporous graphene with different densities between 3 and 70 mg cm−3. Inset: Tensile stress-strain curves of low-density nanoporous graphene. (C) Multistep loading-unloading of nanoporous graphene with a density of 49 mg cm−3. Curves show obvious self-stiffening where the modulus is increased from the original value of 60 MPa to 95 MPa (50%) in the last loading before fracture. (D) Multistep loading-unloading of nanoporous graphene with a density of 8 mg cm−3. Self-stiffening and work hardening are remarkable as the modulus is increased from 1.59 to 4.97 MPa (~300%).

  • Fig. 3 Mechanical properties versus density of high-strength ultralight carbon materials.

    (A) Tensile and indentation yield strength versus density of nanoporous graphene. For comparison, the graphene and CNT-based porous materials from the literature are also plotted. The black open circles represent the tensile strength of graphene foam, which has a coarse pore size of about 100 μm, and the high aspect ratio of struts fabricated using CVD of Ni foam (37). (B) Tensile and indentation elastic modulus versus density of nanoporous graphene and other ultralight graphene and carbon materials.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/2/eaat6951/DC1

    Fig. S1. Raman characterization of nanoporous graphene.

    Fig. S2. SEM images of nanoporous graphene with different feature sizes and densities.

    Fig. S3. Compression properties of nanoporous graphene.

    Fig. S4. Mechanical properties versus density of various high-performance ultralight materials.

    Fig. S5. SEM images taken from in situ tensile measurements of nanoporous graphene with a density of 49 mg cm−3.

    Fig. S6. SEM images taken from in situ tensile measurements of nanoporous graphene with a density of 11 mg cm−3.

    Fig. S7. In situ SEM observations of tensile deformation and failure of nanoporous graphene with a low density of 11 mg cm−3.

    Fig. S8. Specific tensile strength versus tensile strain to fracture of nanoporous graphene.

    Fig. S9. SEM image and digital photo of nanoporous graphene with a growth temperature of 1000°C and a thickness of 10 μm.

    Fig. S10. Tube/pore size distribution of nanoporous graphene under different CVD conditions.

    Table S1. Relationship between CVD condition, density, tube size, and tension testing results of nanoporous graphene.

    Table S2. Indentation testing results of nanoporous graphene with different densities.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Raman characterization of nanoporous graphene.
    • Fig. S2. SEM images of nanoporous graphene with different feature sizes and densities.
    • Fig. S3. Compression properties of nanoporous graphene.
    • Fig. S4. Mechanical properties versus density of various high-performance ultralight materials.
    • Fig. S5. SEM images taken from in situ tensile measurements of nanoporous graphene with a density of 49 mg cm−3.
    • Fig. S6. SEM images taken from in situ tensile measurements of nanoporous graphene with a density of 11 mg cm−3.
    • Fig. S7. In situ SEM observations of tensile deformation and failure of nanoporous graphene with a low density of 11 mg cm−3.
    • Fig. S8. Specific tensile strength versus tensile strain to fracture of nanoporous graphene.
    • Fig. S9. SEM image and digital photo of nanoporous graphene with a growth temperature of 1000°C and a thickness of 10 μm.
    • Fig. S10. Tube/pore size distribution of nanoporous graphene under different CVD conditions.
    • Table S1. Relationship between CVD condition, density, tube size, and tension testing results of nanoporous graphene.
    • Table S2. Indentation testing results of nanoporous graphene with different densities.

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