Researchers determined "white graphene" is likely the best material to keep small electronics from overheating.
A team of scientists released the first theoretical analysis of how 3-D boron nitride could be used as a tunable material to control heat flow in everyday electronic devices, Rice University reported.
Hexagonal boron nitride (h-BN), or "white graphene," looks similar to conventional graphene; the difference is boron nitride can act as an insulator while graphene does not provide a barrier to electricity. Like graphene, h-BN is a good conductor of heat, suggesting it would be the ideal material for controlling the behavior of heat within electronics.
"Typically in all electronics, it is highly desired to get heat out of the system as quickly and efficiently as possible," said Rice researcher Rouzbeh Shahsavari. "One of the drawbacks in electronics, especially when you have layered materials on a substrate, is that heat moves very quickly in one direction, along a conductive plane, but not so good from layer to layer. Multiple stacked graphene layers is a good example of this."
Computer simulations demonstrated that 3-D structures of h-BN planes connected by boron nitride nanotubes could move phonons in all directions. The team then calculated how the phonons would move across four different structures with nanotubes of various lengths and densities. They determined junctions of pillars and planes acted as "yellow traffic lights," and significantly slowed the phonon flow from layer to layer.
"Given the insulating properties of boron nitride, they can enable and complement the creation of 3-D, graphene-based nanoelectronics. This type of 3-D thermal-management system can open up opportunities for thermal switches, or thermal rectifiers, where the heat flowing in one direction can be different than the reverse direction," Shahsavari said. "This can be done by changing the shape of the material, or changing its mass - say one side is heavier than the other - to create a switch. The heat would always prefer to go one way, but in the reverse direction it would be slower."
The findings were published in a recent edition of the American Chemical Society journal Applied Materials and Interfaces.
