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.
- Ultra-lightweight structural materials.
- Supercapacitor and battery electrodes.
- Hydrogen storage.
- Water treatment membranes.
Why & Solution
“Graphene aerogel is something of a wonder material,” says Debbie Senesky, assistant professor of aeronautics and astronautics at Stanford and director of a team of engineers and scientists who are researching this particular type of aerogel. Over the next year or so, Senesky and her colleagues will prepare a set of experiments that will take graphene aerogel somewhere it has never gone before – to the International Space Station.
- “With something so light, the effect of gravity can have a huge influence on its structure and maybe even the properties of the material,” says Jessica Frick, a postdoctoral researcher in Senesky’s lab. “We want to see what happens when we remove gravity.”
- The first thing to know about graphene aerogel is that the basic building block of the material, graphene, is itself is a wonder material in its own right. Only discovered in 2004, graphene is made up of a single layer of carbon atoms bonded together in a hexagonal pattern. If you could peer into its nanoscale structure, you would see something that looks like chicken-wire fence. Graphene is incredibly light, strong and electrically conductive, among other properties.
- Now, imagine billions of sheets of graphene bundled together in a disordered array, held together by nothing more than attractive atomic forces. What remains is an incredibly light, strong, electrically conductive and absorbent three-dimensional scaffolding of graphene.
- One use for it is in the production of supercapacitors – devices that store large amounts of energy that can be rapidly released, says Thomas Heuser, a graduate student in materials science and engineering, who is on the research team. This might lead to cellphones that forgo batteries for capacitors that could be quickly charged multiple times a day, rather than for one longer period. “It’s an interesting alternative to batteries. Graphene aerogel’s high surface area and electrical conductivity make it ideal for this type of storage,” he adds.
- Others suggest its porous structure and absorbency might lend itself to advanced water purification filters or super-mops that sop up oil spills in the ocean. It is believed graphene aerogel can soak up 900 times its own weight in oil, get wrung out and be used again, like a space-age sponge.
- By synthesizing graphene aerogel in the microgravity of low-Earth orbit, Senesky and team hope to learn how to make this wonder material using the limited resources available on the International Space Station. But that’s just the start. “Eventually, such research could point to useful products, makeable only in space, that are valuable enough to justify transporting the solvents, raw materials and machinery necessary to manufacture graphene aerogels in orbit,” says Barrett Weiss, a graduate student on the team. Senesky believes the possibilities are wide open. “That’s why there’s so much interest in studying the manufacturing of new materials in space,” she says.
Graphene aerogels, a class of materials made of 2D graphene sheets covalently crosslinked into a three-dimensional (3D) structure, largely retain many of the extraordinary properties of their graphene building blocks but are limited in size only by the container used during synthesis.
- In this work, graphene-based hydrogel synthesis in gravity (on Earth) and microgravity (on the International Space Station, ISS) conditions will be examined. Through experimentation in microgravity on the ISS, gravity-driven processes such as sedimentation and buoyancy-driven convection will be hindered, and underlying phenomena contributing to graphene aerogel assembly (e.g., random Brownian motion) will be isolated and investigated for the first time.
- To extend the knowledge of space-produced aerogel, we will compare the properties of microgravity-synthesized graphene aerogels to Earth-synthesized aerogels. The objectives are two-fold: (1) to study the growth behavior (cross-linking, agglomeration, drying) of graphene aerogels (GA) synthesis outside the presence of gravity; and (2) to examine and explain the influence of microgravity-based synthesis on the 3-dimensional (3D) mesostructure and multi-physical properties (thermal transport, mechanical behavior, and electrical characteristics) of GAs.
- Ultimately, this work will provide the foundation for engineering of graphene aerogels (and other aerogels) with highly homogenous microstructures and correspondingly superior electrical, mechanical, and thermal properties to enable a wide variety of Earth and space applications, such as, ultra-lightweight structural materials, supercapacitor and battery electrodes, hydrogen storage, and water treatment membranes. In addition, in-space production of aerogels on the ISS may enable direct use of materials and devices by ISS researchers and for future space missions.