Transparent material conducts and insulates heat at the same time
Different kinds of materials can play different roles when it comes to controlling heat. If we want to keep our home warm in the depths of winter, insulating layers in our walls can help to lock it in. If we want to keep things cool, thermally conductive materials like those used in computer processors can help carry it away. But could one material have it both ways? A new breakthrough suggests that it could, made by a team of scientists who believe heat needn’t just be a one way street.
The research was carried out by scientists at the University of Bayreuth and the Max Planck Institute for Polymer Research, who sought to combine the thermally insulating properties of materials like polystyrene, with the thermally conductive properties of heavy metals often used to dissipate heat.
Their breakthrough boils down to a way of manipulating the way heat travels, which is through the oscillation of individual molecules that pass on their movement to neighboring molecules.
The team addressed this by creating a material made up of nanometer-thick glass plates, interspersed with polymer chains to make up a wafer-thin stack that also happens to be transparent. The many layers within this material work in a similar way to a double-glazed window, only multiplied to give it some truly unique properties.
"In principle, our material produced in this way corresponds to the principle of double glazing," says Markus Retsch, Professor at the University of Bayreuth. "It only shows the difference that we not only have two layers, but hundreds.”
With so many layers making up the material, the scientists were able to greatly reduce the transfer of heat traveling in the perpendicular direction. Meanwhile, there are no interfaces within each layer that work to block the heat, so it is conducted in a parallel direction along individual layers very effectively.
Following their testing of the material, the scientists report that thermal conductivity along each layer is comparable to the performance of a thermal paste used to apply heat sinks to computer processors, and around 40 times higher than the perpendicular direction. Meanwhile, the heat insulating properties were also found to be very high, exceeding the performance of plastics currently used commercially by a factor of six.
The scientists say this unique material could offer some lessons when it comes to sound propagation as well, which behaves in a similar fashion to heat as it moves through a material.
"This structured yet transparent material is excellent for understanding how sound propagates in different directions," says co-author Professor Georg Fytas.
From here, the researchers will work to better understand these processes by tweaking the design of the material. As for where it could be used, one area the team imagines it finding a role is in high-performance LEDs, where there is a need to balance heat insulation and dissipation at the same time.
The research was published in the journal Angewandte Chemie - International Edition.
Source: University of Bayreuth