SUPPLEMENTARY INFORMATION Three-dimensional … · SUPPLEMENTARY INFORMATION Graphene Foam with A Three-Dimensional Interconnected Network and Its High-Conducting Composites S1

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SUPPLEMENTARY INFORMATION

Graphene Foam with A Three-Dimensional Interconnected Network and Its High-

Conducting Composites

S1. Characterization of the graphene foam (GF) and GF/PDMS composites

a b c

f e d

Figure S1. Photographs of the samples obtained in each step. (a) Ni foam; (b) Ni-G;

(c) Ni-G-PMMA; (d) GF-PMMA; (e) GF; and (f) GF/PDMS.

Three-dimensional flexible and conductiveinterconnected graphene networks grownby chemical vapour deposition

SUPPLEMENTARY INFORMATIONdoi: 10.1038/nmaT3001

naTure maTerials | www.nature.com/naturematerials 1

© 2011 Macmillan Publishers Limited. All rights reserved.

http://www.nature.com/doifinder/10.1038/nmat3001

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Figure S2. SEM images of the as-grown graphene films adhering to the surface of a

nickel foam. Ripples and wrinkles of the graphene films are observed.

2 naTure maTerials | www.nature.com/naturematerials

SUPPLEMENTARY INFORMATION doi: 10.1038/nmaT3001



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Figure S3. (a, b): Low- and high-magnification SEM images of one side of a GF. (c,

d): Low- and high-magnification SEM images of the cross section of a GF. The cross

section was obtained by cutting the GF with scissors.

Figure S4. SEM images of a GF without a PMMA protection layer, showing that the

GF collapses with severe distortion of graphene sheets.





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3 4 5 6 7 8 9 102

3

4

5

6

Spec

ific

surf

ace

area

(m2 /g

)

Den

sity

(mg/

cm3 )

Average number of layers

200

400

600

800

3 4 5 6 7 8 9 100

100

200

300

400

500

600

Mas

s (m

g)

Thin

knes

s ( μ

m)


0.2

0.4

0.6

0.8

1.0

1.2

1.4

ba

Figure S5. (a) Thickness and mass of GFs as a function of the average number of

graphene layers. (b) The density and specific surface area of GFs as a function of the

average number of graphene layers.

Figure S6. SEM images of (a, c) graphene films on nickel foams and (b, d) the

resultant GFs. The nickel foams used in a and c have 95 and 115 pores per inch,

respectively. All the scale bars are 250 μm.





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0.2 0.4 0.6 0.8 1.0 1.2 1.423456789

10

Ave

rage

num

ber o

f lay

ers

CH4 concentration (vol%)

Figure S7. Average number of graphene layers in GFs as a function of CH4

concentration used in CVD growth.

Figure S8. SEM images of (a, b) graphene films grown on copper foams and (c, d) the

resultant collapsed GFs.





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a b

c d

Figure S9. Photographs of a GF/PDMS composite under (a, b) bending, (c) stretching,

and (d) twisting, showing its good flexibility.

3 4 5 6 7 8 9 10

100

200

300

400

500

600

Res

ista

nce

(Ω)

Thin

knes

s ( μ

m)


0

2

4

6

8

10

12

14





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Figure S10. Thickness and resistance of GFs and GF/PDMS composites as a function

of the average number of graphene layers.

From our Raman measurements, multi-layer graphene can show a single narrow 2D

peak with a Lorentzian lineshape. This indicates that the graphene layers are

randomly stacked, unlike in graphite with an ordered stacking (i.e., ABAB stacking).

This result is consistent with those reported by other groups for CVD-grown graphene

by using Ni as a substrate1,2. The random stacking decouples the adjacent graphene

layers so that their electronic properties are nearly identical to isolated graphene3-5. As

a result, the overall electrical conductivity of multi-layer graphene is proportional to

the number of graphene layers3,5. However, because of the lower shrinkage of the GF

due to the increased stiffness of thicker graphene sheets, the resistance of the GFs and

GF/PDMS is not inversely proportional to the average number of layers with a linear

relation, as shown in Figure S10.

0.0

0.5

1.0

1.5

2.0

Tens

ile m

odul

us(M

Pa)

Stre

ss(M

Pa)

PDMS GF/PDMS PDMS GF/PDMS0.0

0.5

1.0

1.5

2.0

Figure S11. Average tensile strength and tensile modulus of PDMS and GF/PDMS

composites, which were calculated from the stress–strain curves of five specimens for

each sample, with error bars representing the standard deviation.





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Figure S12. Photographs of GF/PDMS (a−c and a´−c´) and Ni foam/PDMS (d−f and

d´−f´) composites before, under and after mechanical deformation. It can be found

that the GF/PDMS composites have good elasticity and can recover to their initial

form after releasing strain, while the Ni foam/PDMS composites cannot recover but

remain in bent or stretched forms.

a b

fed

c

Bending Initial Release





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Figure S13. Typical stress–strain curve of Ni foam/PDMS composites, showing its

plastic deformation under strain. The inset shows the breaking of a Ni foam/PDMS

composite after ~50% stretching.

The Ni foam/PDMS composites were synthesized by infiltrating free-standing Ni

foams with PDMS prepolymer, a viscous mixture of base/curing agent (Sylgard 184,

Dow Corning), followed by degassing in a vacuum oven for 30 min and thermally

curing at 80 °C for 4 h, the same as those for preparing GF/PDMS composites. The

electrical conductivity and stretch measurements are the same as those for GF/PDMS

composites.

0 10 20 30 40 500.0

0.5

1.0

1.5

Stre

ss (M

Pa)

Strain (%)





10

1 2 3 4 5 6 7 8 9 10 11 120

10

20

30

√

√

10%

30%

max strain zero strain

ΔR/R

0(%)

Stretching cycles

50%

√

Figure S14. Electrical resistance change of GF/PDMS composites after 10, 30, and

50% stretching and then releasing for each cycle. It can be seen that an irreversible

resistance change of the composites occurs in the first few cycles. Moreover, the

irreversible resistance increase is larger for a larger maximum tensile strain, indicating

that it can be intrinsically attributed to the partial breaking or cracking of the GF

network. The cycle when the resistance change becomes stable has been marked. The

number of cycles needed for GF/PDMS conductors becoming stable also depends on

the degree of mechanical deformation. Under larger maximum deformation, more

cycles are needed for the GF/PDMS conductors to become stable.





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S2. Comparison of the electrical conductivity of GF/PDMS with CNT based

composites.

Table S1. Typical CNT composites and their electrical conductivity

Conducting

fillers/polymer

Conducting

filler content

Electrical

conductivity Reference

SWNT/polyimide 0.5 vol% 3×10-7 S/cm Ounaies, Z., et al.6

SWNT/polystyrene 7 wt% 6.89×10-2 S/cm Ramasubramaniam,

R., et al.7

SWNT/polyimide 0.2 vol% ~1×10-6 S/cm McLachlan, D. S. et

al.8

SWNT/polystyrene 0.5 wt% ~1×10-3 S/cm Grossiord, N et al.9

SWNT/polystyrene 8.5 wt% 1.34×10-7S/cm Barraza, H.J et al.10

MWNT/PVA 0.54 wt% 1.14×10-8 S/cm Kilbride, B.E. et al.11

SWNT/polyimide 0.2 vol% 1×10-7S/cm Park, C. et al.12

SWNT/PMMA 1.3 wt% 1.18×10-3S/cm Haggenmueller, R et

al.13

GF/PDMS 0.5 wt%

(0.22 vol%) 10 S/cm Our work

S3. Evaluation of the specific surface area of GFs and their average number of

graphene layers.

Considering that a nickel foam is fully covered by graphene after CVD growth, the

surface area of the GF (SGF) is twice that of the nickel foam template used, which can

be measured by nitrogen gas cryosorption (Micromeritics, ASAP2010M). Therefore,

the specific surface area of GF and its average number of layers (N) of graphene

sheets can be calculated as follows:





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SGF=2×(SNi×WNi) (1)

S’GF= SGF/WGF (2)

N= SG/S’GF (3)

where SNi and WNi are the specific surface area and weight of the nickel foam template,

respectively; S’GF and WGF are the specific surface area and weight of the GF,

respectively; SG≈2600 m2/g14, corresponds to the theoretical value of the specific

surface area of a monolayer graphene.

References

1. Reina, A. et al. Large area, few-layer graphene films on arbitrary substrates by chemical vapor deposition. Nano Lett. 9, 30-35 (2009).

2. Alfonso Reina, S.T., Xiaoting Jia, Sreekar Bhaviripudi, Mildred S. Dresselhaus, Juergen A. Growth of large-area single- and bi-layer graphene by controlled carbon precipitation on polycrystalline Ni surfaces Nano Res. 2, 509-516 (2009).

3. Bae, S. et al. Roll-to-roll production of 30-inch graphene films for transparent electrodes. Nature Nanotechnol. 5, 574-578 (2010).

4. Hass, J. et al. Why multilayer graphene on 4H-SiC(0001) behaves like a single sheet of graphene. Phys. Rev. Lett. 100, 125504 (2008).

5. Li, X.S. et al. Transfer of large-area graphene films for high-performance transparent conductive electrodes. Nano Lett. 9, 4359-4363 (2009).

6. Ounaies, Z., Park, C., Wise, K.E., Siochi, E.J. & Harrison, J.S. Electrical properties of single wall carbon nanotube reinforced polyimide composites. Compos. Sci. Technol. 63, 1637-1646 (2003).

7. Ramasubramaniam, R., Chen, J. & Liu, H.Y. Homogeneous carbon nanotube/polymer composites for electrical applications. Appl. Phys. Lett. 83, 2928-2930 (2003).

8. McLachlan, D.S. et al. Ac and dc percolative conductivity of single wall carbon nanotube polymer composites. J. Polym. Sci., Part B: Polym. Phys. 43, 3273-3287 (2005).

9. Grossiord, N., Loos, J. & Koning, C.E. Strategies for dispersing carbon nanotubes in highly viscous polymers. J. Mater. Chem. 15, 2349-2352 (2005).

10. Barraza, H.J., Pompeo, F., O'Rear, E.A. & Resasco, D.E. SWNT-filled thermoplastic and elastomeric composites prepared by miniemulsion polymerization. Nano Lett. 2, 797-802 (2002).

11. Kilbride, B.E. et al. Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films. J. Appl. Phys. 92, 4024-4030 (2002).





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12. Park, C. et al. Dispersion of single wall carbon nanotubes by in situ polymerization under sonication. Chem. Phys. Lett. 364, 303-308 (2002).

13. Haggenmueller, R., Gommans, H.H., Rinzler, A.G., Fischer, J.E. & Winey, K.I. Aligned single-wall carbon nanotubes in composites by melt processing methods. Chem. Phys. Lett. 330, 219-225 (2000).

14. Stankovich, S. et al. Graphene-based composite materials. Nature 442, 282-286 (2006).





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SUPPLEMENTARY INFORMATION Three-dimensional … · SUPPLEMENTARY INFORMATION Graphene Foam with A Three-Dimensional Interconnected Network and Its High-Conducting Composites S1