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Understanding Mechanical Response of Elastomeric Graphene Networks.

Ni N, Barg S, Garcia-Tunon E, Macul Perez F, Miranda M, Lu C, Mattevi C, Saiz E - Sci Rep (2015)

Bottom Line: In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features.A better restoration of the graphitic nature also has a considerable effect.These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls.

View Article: PubMed Central - PubMed

Affiliation: Centre for Advanced Structural Ceramics, Department of Materials, Imperial College London, London SW7 2AZ, UK.

ABSTRACT
Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (<2 μm). A better restoration of the graphitic nature also has a considerable effect. In comparison, microstructural differences, such as the foam architecture or the cell size have smaller or negligible effect on the mechanical response. The recoverability and energy adsorption depend on density with the latter exhibiting a minimum due to the interplay between wall fracture and friction during deformation. These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls.

No MeSH data available.


Related in: MedlinePlus

(a) Side (parallel to freezing direction) and (b) top view (perpendicular to freezing direction) of a GO-PN fabricated by freeze casting of GO-sus. The material exhibits a lamellar structure with a honeycomb-like cross sectional morphology. (c) Foam-like porous networks fabricated by using high concentrated oil-in-water emulsions (75 vol. %) and (d) hybrid foam-lamellar structure fabricated through the freeze casting of oil in water emulsions with low oil content (25 vol. %). (e) A lamellar GO-PN produced from GO-sus of same density (5 mg/ml) as those used for samples shown in (a,b), but using smaller GO flakes (<2 μm) than (a,b) (20–60 μm). (f) A rGO-PN network after the heat treatment at 1223K.
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f2: (a) Side (parallel to freezing direction) and (b) top view (perpendicular to freezing direction) of a GO-PN fabricated by freeze casting of GO-sus. The material exhibits a lamellar structure with a honeycomb-like cross sectional morphology. (c) Foam-like porous networks fabricated by using high concentrated oil-in-water emulsions (75 vol. %) and (d) hybrid foam-lamellar structure fabricated through the freeze casting of oil in water emulsions with low oil content (25 vol. %). (e) A lamellar GO-PN produced from GO-sus of same density (5 mg/ml) as those used for samples shown in (a,b), but using smaller GO flakes (<2 μm) than (a,b) (20–60 μm). (f) A rGO-PN network after the heat treatment at 1223K.

Mentions: During freeze casting, ice crystals nucleate and grow in the aqueous phase while graphene oxide (GO) flakes are ejected from the moving ice front and align between the ice crystals, forming a continuous network. At the subsequent freeze drying step, the ice is sublimated, leaving behind a stable free-standing 3D GO-PN. The typical microstructures of GO-PNs are shown in Fig. 2. A lamellar structure with a honeycomb-like cross sectional morphology is observed for the samples fabricated without the emulsification step (Fig. 2a,b), similar to what have been reported for carbon based porous networks fabricated by freeze drying32425.


Understanding Mechanical Response of Elastomeric Graphene Networks.

Ni N, Barg S, Garcia-Tunon E, Macul Perez F, Miranda M, Lu C, Mattevi C, Saiz E - Sci Rep (2015)

(a) Side (parallel to freezing direction) and (b) top view (perpendicular to freezing direction) of a GO-PN fabricated by freeze casting of GO-sus. The material exhibits a lamellar structure with a honeycomb-like cross sectional morphology. (c) Foam-like porous networks fabricated by using high concentrated oil-in-water emulsions (75 vol. %) and (d) hybrid foam-lamellar structure fabricated through the freeze casting of oil in water emulsions with low oil content (25 vol. %). (e) A lamellar GO-PN produced from GO-sus of same density (5 mg/ml) as those used for samples shown in (a,b), but using smaller GO flakes (<2 μm) than (a,b) (20–60 μm). (f) A rGO-PN network after the heat treatment at 1223K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562249&req=5

f2: (a) Side (parallel to freezing direction) and (b) top view (perpendicular to freezing direction) of a GO-PN fabricated by freeze casting of GO-sus. The material exhibits a lamellar structure with a honeycomb-like cross sectional morphology. (c) Foam-like porous networks fabricated by using high concentrated oil-in-water emulsions (75 vol. %) and (d) hybrid foam-lamellar structure fabricated through the freeze casting of oil in water emulsions with low oil content (25 vol. %). (e) A lamellar GO-PN produced from GO-sus of same density (5 mg/ml) as those used for samples shown in (a,b), but using smaller GO flakes (<2 μm) than (a,b) (20–60 μm). (f) A rGO-PN network after the heat treatment at 1223K.
Mentions: During freeze casting, ice crystals nucleate and grow in the aqueous phase while graphene oxide (GO) flakes are ejected from the moving ice front and align between the ice crystals, forming a continuous network. At the subsequent freeze drying step, the ice is sublimated, leaving behind a stable free-standing 3D GO-PN. The typical microstructures of GO-PNs are shown in Fig. 2. A lamellar structure with a honeycomb-like cross sectional morphology is observed for the samples fabricated without the emulsification step (Fig. 2a,b), similar to what have been reported for carbon based porous networks fabricated by freeze drying32425.

Bottom Line: In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features.A better restoration of the graphitic nature also has a considerable effect.These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls.

View Article: PubMed Central - PubMed

Affiliation: Centre for Advanced Structural Ceramics, Department of Materials, Imperial College London, London SW7 2AZ, UK.

ABSTRACT
Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (<2 μm). A better restoration of the graphitic nature also has a considerable effect. In comparison, microstructural differences, such as the foam architecture or the cell size have smaller or negligible effect on the mechanical response. The recoverability and energy adsorption depend on density with the latter exhibiting a minimum due to the interplay between wall fracture and friction during deformation. These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls.

No MeSH data available.


Related in: MedlinePlus