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Improve the toughness of graphene film

source:beike new material Views:273time:2020-4-10 QQ Academic Group: 1092348845

As a lightweight structural material, graphene film with high toughness, strength, and conductivity has many promising applications in various applications such as airplanes, car bodies, windmill blades, and sports equipment. As an increasingly popular flexible conductive material for wearable electronic devices; as an electromagnetic interference shielding material, it can eliminate electromagnetic pollution of various electronic devices.
In the previous Nanowerk spotlight we “stitched” super graphene films together ), we reported that only a small amount of cross-linking agent can be used to “stitch” reduced graphene oxide (rGO) nanosheets to Strong and highly conductive graphene film strategy.
Based on their previous work, a research team led by Professor Zheng Qunfeng of Beijing University of Aeronautics and Astronautics has now developed a graphene thin film functionalized with black phosphorus (BP), which has achieved record toughness.
Cheng told Nanowerk: "The formation of a covalent bond POC between BP and graphene oxide (GO) nanosheets not only reduces the voids of the GO film, but also improves the alignment of the GO nanosheets, thereby achieving a high density of GO films sex. " "  after further chemical reduction and conjugated π-π stacking interactions after AD molecules, reducing the degree of orientation of graphene oxide (RGO) nanosheet is further improved, the layered graphene thin film voids further reduced. The toughness of this graphene film reaches up to ~ 51.8 MJ m  -3  – the highest record to date. "
The research team pointed out that the resulting ultra-tough black phosphorus functionalized graphene film with high tensile strength and excellent conductivity also has high environmental stability and electromagnetic shielding performance.
Cheng pointed out: "Our novel strategy can provide inspiration for the conversion of low-cost graphite powder into high-performance graphene-based films for various commercial uses in the future."  "These films can find many applications, such as various applications in aerospace. A kind of structural material for commercial applications, or other functional materials for electromagnetic interference shielding, flexible energy storage, and portable electronic products. "
The group published their findings in ACS Applied Materials & Interfaces "Strong Biologically Inspired Graphene Thin Films Cross-Linked by π-π" ).
Manufacturing process of rGO-BP-AD film
Illustration of the manufacturing process of rGO-BP-AD membrane cross-linked with long-chain AD molecules through stirring, vacuum filtration, chemical reduction, and π-π stacking interaction. (Reprinted with permission from the National Academy of Sciences) (click on the image to enlarge)
Researchers have realized that graphene films always contain voids, which greatly reduces the load transfer efficiency and leads to lower mechanical properties.
To solve this problem, the team‘s strategy-functionalization of BP nanosheets through GO nanosheets through POC covalent bonds-successfully reduced the voids in the layered graphene film and made the graphene film denser, while improving graphite The degree of orientation of the ene goes to the nanosheet.
"Our strategy opens the way for the assembly of graphene nanosheets into ultra-tough, strong and conductive graphene-based films," Cheng said. "In addition, our strengthening and toughening mechanism can also provide a way to assemble graphene nanosheets and other small nanosheets into high-toughness graphene-based films using covalent bonding to reduce voids and improve orientation."
The team‘s work is based on the first two papers. One person found that black phosphorus is easily oxidized in air, but it can be improved by coating with a polymer ( Journal of Materials Chemistry A "A New Strategy for Air Stabilized Black Phosphorus Reinforced PVA Nanocomposites" ) . Another proves that long-chain conjugated molecules easily form π-π stacking with graphene, resulting in a high-toughness graphene film ( ACS application materials and interfaces "a strong bio-inspired graphene film cross-linked by π-π" ) .
"In fact, we don‘t know what will happen before mixing black phosphorus and graphene oxide nanosheets." Cheng said. "I asked my two PhD students, Zhou Tianzhu and Ni Hong, to try some experiments. For example, what happens when GO and BP nanosheets are mixed together by continuous stirring overnight?"
One of these experiments produced hybrid GO-BP nanosheets, which is the basis of this work. Atomic force microscopy (AFM) shows that there are many single-layer BP nanosheets on the surface of GO nanosheets. The BP and GO monolayer nanosheets in the mixed solution reacted completely at ambient temperature, which was verified by the zeta potential. The researchers assembled the GO-BP membrane by vacuum-assisted filtration, and then chemically reduced it to rGO-BP membrane by hydroiodic acid.
The measurement of the mechanical properties of these new films confirms the researchers‘ hypothesis: the toughness of rGO-BP film (15.6 MJ m  -3 ) is 6 times the toughness of rGO film (2.5 MJ m  -3 ) and π-π with AD molecule added After stacking, the rGO-BP-AD film (51.8 MJ m  -3 ) is 21 times higher than the rGO film.
"The performance of the graphene-black phosphorus film we show is still lower than that of single-layer graphene nanosheets, so we need to develop new strategies to further improve the toughness, tensile strength and conductivity of large-size graphene films in many fields Practical applications. "  " In addition, although our graphene films show high toughness at room temperature, many practical applications will still be carried out in extreme environments, such as external spaces with strong radiation and frequent changes in high and low temperatures. "
Source: Nanowerk

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