Nanoscale-thick graphite films are used to make heaters that work very well

Graphical abstract. Credit: ACS Applied Materials & Interfaces (2022). DOI: 10.1021/acsami.1c23803

When you mix multiple carbon nanomaterials into one substance, the results can be surprising. Researchers at KAUST have made thin graphite films that could be used as high-performance, flexible heater panels. When a small voltage is applied, the films heat up to several hundred degrees in seconds. They also showed that the graphene domains in the graphite film are what make the material so good at heating.

Graphitic carbon nanomaterials are used more and more for heat management. For example, they are used to get rid of heat from microchips. Electric heaters could also be made from the same things.

“Low-power, flexible heater panels are needed, and nanocarbons are strong candidates,” says G. Deokar, who led the research as a postdoc in Pedro Costa’s lab. “Their electrothermal performance has been limited, though, so far,” she says. Most nanocarbon-based heaters need 20–60 volts to reach a target temperature of 250 degrees Celsius. They can also break down quickly in hot air.

Costa, Deokar, and their colleagues recently came up with a way to make graphite films (NGFs) that are only one nanometer thick on a wafer-scale. They were also easy to move to different substrates and did not leave behind any residues like most graphene panels do. “These features of the NGF led us to look into how they could be used in thermal management technologies,” says Deokar.

When the team put NGFs on flexible Kapton sheets and put gold electrodes on them, the heaters worked much better than nanocarbon heaters that had been reported before. With less than 8 volts, the material quickly reached the desired temperature of 300 degrees Celsius. Just as quickly, it got cold. “We also saw that the NGF was very stable and that it could be used as an external, reusable patch to boil water,” says Deokar.

“We ran them at twice the maximum temperature of other nanocarbons while using about half the power,” Pedro says. “This made the panel much more efficient.”

The material could be used for everything from small heaters for sensors or microfluidic devices to large heaters for industry, like defoggers for aeroplanes or heat regulators for space.

The team thinks that the good performance of the NGF is because of graphene domains and wrinkles in the material, which act as hotspots. “These structural features are found all over the surface of the NGF, which explains why it is so hot and why the heat is spread out evenly,” says Deokar.

Even though other nanoscale-thick graphite films have wrinkles, the graphene domains in our NGFs are unique, says Pedro. “We want to learn more about the presence and function of the graphene domains,” he says.

Further information: Geetanjali Deokar et al, Flexible, Air-Stable, High-Performance Heaters Based on Nanoscale-Thick Graphite Films, ACS Applied Materials & Interfaces (2022). DOI: 10.1021/acsami.1c23803

Geetanjali Deokar et al, Fast, wafer-scale growth of a nanometer-thick graphite film on Ni foil and its structural analysis, Nanotechnology (2020). DOI: 10.1088/1361-6528/aba712

Geetanjali Deokar et al, Semi-transparent graphite films growth on Ni and their double-sided polymer-free transfer, Scientific Reports (2020). DOI: 10.1038/s41598-020-71435-7

Journal information: Nanotechnology , Scientific Reports , ACS Applied Materials and Interfaces

Source: King Abdullah University of Science and Technology