Graphite films show potential in large and small heating applications

The team at KAUST (King Abdullah University of Science and Technology) in Saudi Arabia also showed that graphene domains within the graphite film are key to the material’s excellent heating performance.

According to KAUST, graphitic carbon nanomaterials can be used for heat management, such as dissipating heat from microchips. The same materials could also be used as electric heaters.

“There’s a need to develop low-power, flexible heater panels, and nanocarbons are key contenders,” said G. Deokar, a postdoc in the lab of Pedro Costa, principal investigator at KAUST’s Laboratory for Carbon Nanostructures. “So far, however, their electrothermal performance has been limited.”

Nanocarbon-based heaters commonly require an input of 20-60V to reach a 250^oC target temperature. They can also degrade rapidly when heated in air.

Costa, Deokar and their colleagues recently developed a method to manufacture nanoscale-thick graphite films (NGFs) at wafer-scale. They also were able to easily transfer them to arbitrary substrates, without the residues often present in graphene panels.

“These characteristics of the NGF prompted us to investigate their application in thermal management technologies,” Deokar said.

When the team placed NGFs on flexible Kapton sheets and applied gold electrodes, their heater performance was found to be far superior to previously reported nanocarbon heaters. Applying under 8V, the material hit a target temperature of 300^oC within seconds, and cooling was said to be equally rapid.

“We also observed outstanding stability and showed the NGF could be used as an external reusable patch to boil water,” Deokar said.

“We operated them at double the maximum temperature of other nanocarbons - with roughly half the power input - and the useful heating area was also augmented, meaning the efficiency of the panel was considerably better,” said Pedro.

Potential applications for the material range from miniature heaters for sensors or microfluidic devices to industrial-scale heaters, such as aviation defoggers or space heat regulators.

The team’s working understanding is that the NGF’s excellent performance is due to the presence of graphene domains and wrinkles in the material, which act as hotspots.

“These structural features are distributed all over the NGF surface, explaining the high temperatures and uniform heat spread,” Deokar said.

Although wrinkles are common features in other nanoscale-thick graphite films, the graphene domains in KAUST’s NGFs are unique, Pedro added.

“The presence and function of the graphene domains is something that we want to better understand,” he said.

The team’s latest findings are detailed in ACS Applied Materials and Interfaces. Previous research is published in Nanotechnology and Scientific Reports.