By Liam Critchley (chemistry and nanotechnology writer)
Electric vehicles (EVs) have become an increasingly important topic in recent years as manufacturers and consumers try to offset vehicle carbon emissions by switching to an eco-friendlier alternative. While a lot of focus has been on ground vehicles, such as cars and trucks, there has been growing interest in electric aircraft—with pioneering research coming out of key organizations, such as NASA, as well as a plethora of private companies.
There are number of key material property cornerstones that apply to aerospace. The requirements of the aircraft to lift into the air, transport cargo or people and reach their destination safely, means that materials need to be very strong but also lightweight. Outside of the medical industry, the aerospace industry is one of the most regulated industries because lives are at stake—and mission critical materials that can perform under harsh conditions and with a high degree of performance are needed across all aspects of aerospace.
High quality graphene is one of the lightest, strongest and most conductive materials ever discovered. Because it can impart structural strength and integrity into other materials, high quality graphene is ideal for many aspects of an electric aircraft. Not surprisingly, this “super material” has garnered interest because of the applications work done by key graphene institutions and organizations such as the National Graphene Institute (NGI) in the UK and the EU’s Graphene Flagship.
Because safety and reliability are paramount, only the highest quality graphene is going to meet the needs of commercial aviation. So, this is going to be graphene materials that can not only be produced at scale to meet demand but also contain little to no defects, have excellent properties and are highly compatible with being integrated into existing materials used in aircraft. Large, thin and nearly defect free (LTDF) graphene flakes fit the requirements perfectly.
While commercial aviation generally can benefit in numerous ways from graphene because of its ability to de-weight while strengthening, electric aircraft in particular can be transformed by graphene because lighter weight translates into increased time-in-air.
Here are a few key examples:
More Efficient and Lighter Batteries for Electric Aircraft
Many graphene-based batteries have already made it to market thanks to Skeleton Technologies, Polyjoule, GAC Group, Lyten and Strategic Elements. Some of these batteries have been designed for use in EVs, others are for different applications (including small satellites). Among the benefits of graphene are that it makes batteries more efficient and lighter.
While graphene batteries on the market today have not focused on electric aircraft, NASA is already producing some exciting research in this area, so it shouldn’t be long before we see graphene batteries to power electric aircraft. NASA has been researching heavily into electric aircraft batteries through their Solid-state Architecture Batteries for Enhanced Rechargeability and Safety (SABERS) initiative, and they reached the headlines in 2023 after announcing a new solid-state battery using selenium and sulphur (something not seen before) for electric aircraft that reportedly has double the energy density of Li-ion EV batteries.
However, while everyone has been focusing on their use of sulphur and selenium materials, one of the aspects that was not widely publicized is that the battery functions efficiently due to a graphene mesh that arranges the sulphur and selenium particles in the cathode. NASA is also looking into creating graphene-based battery-supercapacitor hybrid systems that can store and release charge for electric aircraft applications.
Batteries in electric aircraft need to have different properties than other battery technologies—including other EV batteries. In short, they need to hold a high amount of charge, be able to rapidly discharge any stored charge, be lightweight, and be highly stable because the battery will be used in harsher conditions compared to land vehicles.
Graphene has already been used in batteries because of its ability to store higher degrees of charge, and it has also been used in commercial supercapacitors because of its ability to discharge that stored charge quickly. A combination of its lightweight nature, thermal conductivity (for heat dissipation) of up to 5000 W m-1 K-1, and high thermal stability, makes graphene an ideal choice for electric aircraft batteries.
But safety and quality are paramount in the aerospace sector, which is why LTDF graphene flakes are uniquely well suited. Larger area graphene provides a better conductive pathway when graphene is used in electrodes. LTDF graphene is typically used as an additive. In electrodes, providing uniform conductive coverage is key, and LTDF graphene provides a more uniform dispersion due to its larger surface area while not aggregating in the electrode. The lack of defects in LTDF graphene also means that the structure of any hybrid material containing the graphene is going to have more efficient conduction pathways (due to a lower degree of electron scattering) and will inherently be more stable.
Strong and Lightweight Composites
All aircraft rely on strong and lightweight (relatively speaking) composites. In addition to bringing a higher degree of strength and durability for aircraft, graphene composites help to reduce the overall weight of the aircraft. For traditional aircraft, this typically improves the fuel usage and reduces the CO2 emissions, but for electric aircraft, it will put less strain on the batteries and will ensure that they last longer—meaning that the aircraft can go farther between charges and/or carry larger payloads.
There are other benefits of using graphene. The high aspect ratio of graphene (the length to width ratio), its flexibility and mechanical strength enable LTDF graphene to strengthen weak points in aircraft composites. Studies so far have shown that graphene aircraft wings which use a graphene composite skin have an impact resistance of up to an additional 60% compared to normal carbon fibre wings. There are also benefits of using graphene inside the cabin because graphene-based composites can dampen vibration and reduce noise.
Composites in the aerospace sector are stringently regulated and need the highest quality materials and parts. Using large particle size graphene prevents agglomeration (reducing the potential for weak zones), has fewer transferable defects that could affect mechanical performance and offers a way to create more robust and durable composites that can meet the extreme demands of electric aircraft and the quality demands of the wider aerospace industry.
Protective Coatings for Harsh Environments
Graphene can also be integrated into a range of coating formulations—from water-based solutions to ink formulations—and can be used in the aerospace industry (as well as in the marine and automotive sectors) as a barrier coating.
One of the main functions of barrier coatings is corrosion resistance, and graphene is impermeable to both gases and water, and is largely unaffected by heat or harsh chemicals/environments. Moreover, LTDF graphene absorbs light and has a natural hydrophobicity that repels water which can be utilized to prevent corrosion. So, graphene can be applied in very thin coatings (or thin nanocomposites) to act as a corrosion and protection barrier for electric aircraft, and without adding virtually any weight.
There are a number of areas where graphene offers new functionalities for aerospace coatings. Aside from enhancing the strength of structural parts of the aircraft, graphene’s thermal stability and conductive properties can be used to create fire retardant coatings for the internal parts of the aircraft, while its corrosion resistance, electrical conductivity and low density can be used to create coatings that have electromagnetic interference (EMI) shielding properties.
Because thin coatings can be nanocomposites, a lot of the benefits of LTDF graphene flakes—including its large particle size and lack of defects—make it ideal for nanocomposite coatings. The same can also be said for more liquid or ink-based coatings, because the larger particle size can cover a wide area of the internal coating matrix without agglomerating and causing localized weaknesses, and the properties of LTDF graphene can be spread uniformly throughout the coating.
Aluminum enabled commercial aviation to become a reality. Light and abundant, it laid the foundation for aircraft, which have migrated to lighter carbon fibre composites. LTDF graphene flakes are the next generation of additive materials for commercial aviation, generally, and for the widespread adoption of electric aircraft.
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