Researchers at the University of Bath have developed a graphene oxide (GO)/polyvinyl alcohol (PVA) aerogel (GPA) weighing just 2.1 kg m^-3—making it the lightest sound insulation ever manufactured.

Over the 400–2500 Hz range, the reported average sound absorption coefficients are as high as 0.79, while the average sound transmission losses can reach 15.8 dB. The aerogel could be used as insulation within aircraft engines to reduce the 105-decibel roar of a jet engine taking off to a sound closer to that of a hair-dryer.

The aerogel’s meringue-like structure makes it extremely light, meaning it could act as an insulator within aircraft engine nacelles, with almost no increase in overall weight. The material is currently being further optimized by the research team to offer improved heat dissipation, offering benefits to fuel efficiency and safety.

Schematic illustration of the ultralight GPAs.

The researchers, from Bath’s Materials and Structures Centre (MAST), have published a method for manufacturing the materials in an open-access paper in the journal Nature Scientific Reports.

This is clearly a very exciting material that could be applied in a number of ways - initially in aerospace but potentially in many other fields such as automotive and marine transport, as well as in building and construction.

We managed to produce such an extremely low density by using a liquid combination of graphene oxide and a polymer, which are formed with whipped air bubbles and freeze-casted. On a very basic level, the technique can be compared with whipping egg whites to create meringues—it’s solid but contains a lot of air, so there is no weight or efficiency penalty to achieve big improvements in comfort and noise.

—Professor Michele Meo, who led the research

Although the team’s initial focus is in working with partners in aerospace to test the material as a sound insulator in aeroplane engines, they say it could also be used to create panels in helicopters, or car engines. They estimate that the aerogel could be in use within 18 months.

Resources

• Rapisarda, M., Malfense Fierro, GP. & Meo, M. (2021) “Ultralight graphene oxide/polyvinyl alcohol aerogel for broadband and tuneable acoustic properties.” Sci Rep 11, 10572 doi: 10.1038/s41598-021-90101-0