Graphene has high mechanical and electrical properties with perfect sp2, but bulk-scale graphene is significantly inferior to graphene in terms of properties. This is because bulk-scale graphene shows less arrangement of graphenes, defects in the graphene in-plane, and the generation of grain bounda...
Graphene has high mechanical and electrical properties with perfect sp2, but bulk-scale graphene is significantly inferior to graphene in terms of properties. This is because bulk-scale graphene shows less arrangement of graphenes, defects in the graphene in-plane, and the generation of grain boundaries. In this research, we highly oriented the graphene and reduced in-plane defects of graphene and grain boundaries through fabrication of large-sized graphene (L-GO) and L-GO/poly(catecholamine) composite.
We reduced the edge area of graphene by synthesizing L-GO (150 ± 29 μm) and GO (using hummers‘ method: 28 ± 24 μm) using expanded graphite. The alignment of the graphene film was improved by the graphene oxide liquid crystals. In addition, the graphene oxide liquid crystal film was further aligned using a doctor blade. The L-GO film exhibited 1.32 times higher modulus (L-GO: 3.7 GPa, GO: 2.8 GPa), 1.98 times higher ultimate tensile strength (L-GO: 20.4 MPa, GO: 10.3 MPa), and 1.28 times higher elongation at break (L-GO: 0.55%, GO: 0.43%) than GO. The L-rGO (L-GO film reduced by HI) showed the modulus of 8.3 GPa (rGO: 5.7 GPa), ultimate tensile strength of 130.8 MPa (rGO: 47.0 MPa), and elongation at break of 3.09% (rGO: 1.53%). In addition, the L-rGO film (8.2 Ω/sq, 340 S/cm) showed only 37% of the sheet resistance of the rGO film (21.9 Ω/sq, 120 S/cm), indicating 2.8 times higher electrical conductivity.
Furthermore, the grain boundaries of bulk-scale graphene film and in-plane defects of the graphene were reduced by the incorporation of poly(catecholamine) into L-GO film and then thermal treatment (graphitization). As a result, a hybrid-structured L-rGO/PNE composite with AB stacking structure and turbostratic structure was synthesized. Due to the unique hybrid structures, the heat-treated L-rGO/PNE composite exhibited excellent mechanical properties: UTS (1012 ± 146 MPa) was about 2 times higher than that of L-rGO film with AB stacking only, strain-to-failure (8.91 ± 0.50%) and modulus (21.9 ± 2.2 GPa) were about 1.5 times higher with the hybrid-structure of AB stacking structure and turbostratic structure. These mechanical properties of hybrid carbon films can generate a variety of structural applications. In addition, the excellent in-plane electrical conductivity of this film (about 1,320 ± 159 S/cm) can be used in potential multi-functional applications such as high-strength flexible electrodes and wearable sensors.
Graphene has high mechanical and electrical properties with perfect sp2, but bulk-scale graphene is significantly inferior to graphene in terms of properties. This is because bulk-scale graphene shows less arrangement of graphenes, defects in the graphene in-plane, and the generation of grain boundaries. In this research, we highly oriented the graphene and reduced in-plane defects of graphene and grain boundaries through fabrication of large-sized graphene (L-GO) and L-GO/poly(catecholamine) composite.
We reduced the edge area of graphene by synthesizing L-GO (150 ± 29 μm) and GO (using hummers‘ method: 28 ± 24 μm) using expanded graphite. The alignment of the graphene film was improved by the graphene oxide liquid crystals. In addition, the graphene oxide liquid crystal film was further aligned using a doctor blade. The L-GO film exhibited 1.32 times higher modulus (L-GO: 3.7 GPa, GO: 2.8 GPa), 1.98 times higher ultimate tensile strength (L-GO: 20.4 MPa, GO: 10.3 MPa), and 1.28 times higher elongation at break (L-GO: 0.55%, GO: 0.43%) than GO. The L-rGO (L-GO film reduced by HI) showed the modulus of 8.3 GPa (rGO: 5.7 GPa), ultimate tensile strength of 130.8 MPa (rGO: 47.0 MPa), and elongation at break of 3.09% (rGO: 1.53%). In addition, the L-rGO film (8.2 Ω/sq, 340 S/cm) showed only 37% of the sheet resistance of the rGO film (21.9 Ω/sq, 120 S/cm), indicating 2.8 times higher electrical conductivity.
Furthermore, the grain boundaries of bulk-scale graphene film and in-plane defects of the graphene were reduced by the incorporation of poly(catecholamine) into L-GO film and then thermal treatment (graphitization). As a result, a hybrid-structured L-rGO/PNE composite with AB stacking structure and turbostratic structure was synthesized. Due to the unique hybrid structures, the heat-treated L-rGO/PNE composite exhibited excellent mechanical properties: UTS (1012 ± 146 MPa) was about 2 times higher than that of L-rGO film with AB stacking only, strain-to-failure (8.91 ± 0.50%) and modulus (21.9 ± 2.2 GPa) were about 1.5 times higher with the hybrid-structure of AB stacking structure and turbostratic structure. These mechanical properties of hybrid carbon films can generate a variety of structural applications. In addition, the excellent in-plane electrical conductivity of this film (about 1,320 ± 159 S/cm) can be used in potential multi-functional applications such as high-strength flexible electrodes and wearable sensors.
Keyword
#graphene graphene oxide expanded graphite liquid crystal catecholamine composite AB stacking structure turbostratic structure
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