Aerographene

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Aerographene or graphene aerogel is the least dense solid known to exist, at 160 g/m3 (0.0100 lb/cu ft; 0.16 mg/cm3; 4.3 oz/cu yd). [1] The material reportedly can be produced at the scale of cubic meters. [2] [3]

Contents

Discovery

Aerographene was discovered at Zhejiang University by a team of scientists led by Gao Chao. [1] He and his team had already successfully created macroscopic materials made out of graphene. These materials were one-dimensional and two-dimensional. However, when synthesizing aerographene, the scientists instead created a three-dimensional structure. The synthesis was accomplished by the freeze-drying of carbon nanotube solutions [4] and large amounts of graphene oxide. Residual oxygen was then removed chemically.[ citation needed ]

Fabrication

Graphene aerogels are synthetic materials that exhibit high porosity and low density. Typical syntheses of graphene aerogels involve reducing a precursor graphene oxide solution to form graphene hydrogel. The solvent can be subsequently removed from the pores by freeze-drying and replacing with air. [5] The resulting structure consists of a network of covalently bonded graphene sheets surrounding large pockets of air, resulting in densities on the order of 3 mg cm−3. [6]

Graphene aerogel morphologies have also been demonstrated to be controllable through 3D printing methods. Graphene oxide ink composed of graphene oxide gelled in a viscous solution with the addition of silica to lower viscosity and enable printability of the graphene oxide ink. The ink is then extruded from a nozzle into isooctane, which prevents the ink from drying too quickly. Subsequently, the solvent can be removed by freeze drying, while the silica can be removed with a hydrofluoric acid solution. The resulting 3D lattice can be highly ordered while maintaining the high surface areas and low densities characteristic of graphene aerogels. [6]

Mechanical properties

Graphene aerogels exhibit enhanced mechanical properties as a result of their structure and morphology. Graphene aerogels have a Young's modulus on the order of 50 MPa. [7] They can be compressed elastically to strain values >50%. [6] The stiffness and compressibility of graphene aerogels can be attributed in part to the strong sp2 bonding of graphene and the π-π interaction between carbon sheets. In graphene aerogels, the π-π interaction can greatly enhance stiffness due to the highly curved and folded regions of graphene as observed through transmission electron microscopy images. [5]

The mechanical properties of graphene aerogel have been shown to depend on the microstructure and thus varies across studies. The role that microstructure plays in the mechanical properties depends on several factors. Computational simulations show that graphene walls bend when a tensile or compressive stress is applied. [8] [9] The resulting stress distribution from the bending of the graphene walls is isotropic and can contribute to the high yield stress observed. The density of the aerogel can also significantly affect the properties observed. The normalized Young’s modulus is shown computationally to follow a power-law distribution governed by the equation E/Es = (ρ/ρs)m, where E is the Young's modulus.

Similarly, the compressive strength that describes the yield stress before plastic deformation under compression in graphene aerogels follows a power-law distribution: σy/Es = (ρ/ρs)n, where σy is the compressive strength, ρ is the density of the graphene aerogel, Es is the modulus of graphene, ρs is the density of graphene, and n is the power-law scaling factor that describes the system different from the exponent observed in the modulus. The power-law dependence observed agrees with trends between density and modulus and compressive strength observed in experimental studies on graphene aerogels. [8]

The macroscopic geometric structure of the aerogel has been shown both computationally and experimentally to affect mechanical properties observed. 3D-printed periodic hexagonal graphene aerogel structures exhibited an order-of-magnitude larger modulus compared to bulk graphene aerogels of the same density when the force is applied along the vertical axis. The dependence of stiffness on structure is commonly observed in other cellular structures. [7]

Applications

Due to the high porosity and low density, graphene aerogel has been explored as a potential replacement in flight balloons. [8] The large degree of recoverable compressibility and overall stiffness of the structure has been used in studies in graphene sponges capable of holding 1000× its weight in liquid while recovering all of the absorbed liquid without structural damage to the sponge due to the elasticity of the graphene structure. This has environmental implications, potentially contributing to cleanup of offshore oil spills. [10] [11] It can also be used to gather dust from the tails of comets. [1]

See also

Related Research Articles

<span class="mw-page-title-main">Carbon nanotube</span> Allotropes of carbon with a cylindrical nanostructure

A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range (nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized:

An elastic modulus is the unit of measurement of an object's or substance's resistance to being deformed elastically when a stress is applied to it.

<span class="mw-page-title-main">Graphene</span> Hexagonal lattice made of carbon atoms

Graphene is a carbon allotrope consisting of a single layer of atoms arranged in a honeycomb planar nanostructure. The name "graphene" is derived from "graphite" and the suffix -ene, indicating the presence of double bonds within the carbon structure.

Specific modulus is a materials property consisting of the elastic modulus per mass density of a material. It is also known as the stiffness to weight ratio or specific stiffness. High specific modulus materials find wide application in aerospace applications where minimum structural weight is required. The dimensional analysis yields units of distance squared per time squared. The equation can be written as:

<span class="mw-page-title-main">Nanocomposite</span> Solid material with nano-scale structure

Nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material.

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<span class="mw-page-title-main">Nanocellulose</span> Material composed of nanosized cellulose fibrils

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Ultralight materials are solids with a density of less than 10 mg/cm3, including silica aerogels, carbon nanotube aerogels, aerographite, metallic foams, polymeric foams, and metallic microlattices. The density of air is about 1.275 mg/cm3, which means that the air in the pores contributes significantly to the density of these materials in atmospheric conditions. They can be classified by production method as aerogels, stochastic foams, and structured cellular materials.

<span class="mw-page-title-main">Metallic microlattice</span> Ultra-light metallic material

A metallic microlattice is a synthetic porous metallic material consisting of an ultra-light metal foam. With a density as low as 0.99 mg/cm3 (0.00561 lb/ft3), it is one of the lightest structural materials known to science. It was developed by a team of scientists from California-based HRL Laboratories, in collaboration with researchers at University of California, Irvine and Caltech, and was first announced in November 2011. The prototype samples were made from a nickel-phosphorus alloy. In 2012, the microlattice prototype was declared one of 10 World-Changing Innovations by Popular Mechanics. Metallic microlattice technology has numerous potential applications in automotive and aeronautical engineering. A detailed comparative review study among other types of metallic lattice structures showed them to be beneficial for light-weighting purposes but expensive to manufacture.

<span class="mw-page-title-main">Aerographite</span> Extremely light synthetic foam of tubular carbon molecules

Aerographite is a synthetic foam consisting of a porous interconnected network of tubular carbon. With a density of 180 g/m3 it is one of the lightest structural materials ever created. It was developed jointly by a team of researchers at the University of Kiel and the Technical University of Hamburg in Germany, and was first reported in a scientific journal in June 2012.

<span class="mw-page-title-main">Freeze-casting</span>

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<span class="mw-page-title-main">Aerogel</span> Synthetic ultralight solid material

Aerogels are a class of synthetic porous ultralight material derived from a gel, in which the liquid component for the gel has been replaced with a gas, without significant collapse of the gel structure. The result is a solid with extremely low density and extremely low thermal conductivity. Aerogels can be made from a variety of chemical compounds. Silica aerogels feel like fragile styrofoam to the touch, while some polymer-based aerogels feel like rigid foams.

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References

  1. 1 2 3 Guinness World Records 2018. Jim Pattison Group. 7 September 2017. p. 188. ISBN   9781910561713.
  2. ↑ "Ultra-light Aerogel Produced at a Zhejiang University Lab-Press Releases-Zhejiang University". Zju.edu.cn. 2013-03-19. Archived from the original on 2013-05-23. Retrieved 2013-06-12.
  3. ↑ Mecklenburg, M.; Schuchardt, A.; Mishra, Y. K.; Kaps, S. R.; Adelung, R.; Lotnyk, A.; Kienle, L.; Schulte, K. (2012). "Aerographite: Ultra Lightweight, Flexible Nanowall, Carbon Microtube Material with Outstanding Mechanical Performance". Advanced Materials. 24 (26): 3486–3490. Bibcode:2012AdM....24.3486M. doi:10.1002/adma.201200491. PMID   22688858. S2CID   2787227.
  4. ↑ Starr, Michelle (2013-03-25). "Graphene aerogel is the new world's lightest substance". Archived from the original on 2013-06-30. Retrieved 2013-09-06.
  5. 1 2 Hu, Han; Zhao, Zongbin; Wan, Wubo; Gogotsi, Yury; Qiu, Jieshan (2013). "Ultralight and Highly Compressible Graphene Aerogels". Advanced Materials. 25 (15): 2219–2223. Bibcode:2013AdM....25.2219H. doi:10.1002/adma.201204530. ISSN   1521-4095. PMID   23418081. S2CID   38156706.
  6. 1 2 3 Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; Golobic, Alexandra M.; Kuntz, Joshua D.; Spadaccini, Christopher M.; Worsley, Marcus A. (2015-04-22). "Highly compressible 3D periodic graphene aerogel microlattices". Nature Communications. 6 (1): 6962. Bibcode:2015NatCo...6.6962Z. doi: 10.1038/ncomms7962 . ISSN   2041-1723. PMC   4421818 . PMID   25902277.
  7. 1 2 Worsley, Marcus A.; Kucheyev, Sergei O.; Mason, Harris E.; Merrill, Matthew D.; Mayer, Brian P.; Lewicki, James; Valdez, Carlos A.; Suss, Matthew E.; Stadermann, Michael; Pauzauskie, Peter J.; Satcher, Joe H. (2012-07-25). "Mechanically robust 3D graphene macroassembly with high surface area". Chemical Communications. 48 (67): 8428–8430. doi:10.1039/C2CC33979J. ISSN   1364-548X. PMID   22797515.
  8. 1 2 3 Qin, Zhao; Jung, Gang Seob; Kang, Min Jeong; Buehler, Markus J. (2017-01-01). "The mechanics and design of a lightweight three-dimensional graphene assembly". Science Advances. 3 (1): e1601536. Bibcode:2017SciA....3E1536Q. doi: 10.1126/sciadv.1601536 . ISSN   2375-2548. PMC   5218516 . PMID   28070559.
  9. ↑ Lei, Jincheng; Liu, Zishun (2018-04-01). "The structural and mechanical properties of graphene aerogels based on Schwarz-surface-like graphene models". Carbon. 130: 741–748. doi:10.1016/j.carbon.2018.01.061. ISSN   0008-6223.
  10. ↑ Wu, Yingpeng; Yi, Ningbo; Huang, Lu; Zhang, Tengfei; Fang, Shaoli; Chang, Huicong; Li, Na; Oh, Jiyoung; Lee, Jae Ah; Kozlov, Mikhail; Chipara, Alin C. (2015-01-20). "Three-dimensionally bonded spongy graphene material with super compressive elasticity and near-zero Poisson's ratio". Nature Communications. 6 (1): 6141. Bibcode:2015NatCo...6.6141W. doi: 10.1038/ncomms7141 . ISSN   2041-1723. PMID   25601131.
  11. ↑ Chen, Bo; Ma, Qinglang; Tan, Chaoliang; Lim, Teik-Thye; Huang, Ling; Zhang, Hua (2015-03-23). "Carbon-Based Sorbents with Three-Dimensional Architectures for Water Remediation". Small . 11 (27). Wiley-VCH: 3319–3336. doi:10.1002/smll.201403729. eISSN   1613-6829. ISSN   1613-6810. PMID   25808922.
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