According to researchers from Rice University, boron nitride has the potential to take cooling gadgets and devices to the next level by controlling how heat flows from within.

In the journal Applied Materials and Interfaces, Rouzbeh Shahsavari and Navid Sakhavand detailed their first theoretical analysis on how a 3D structure of boron nitride can be tuned to direct heat flow, optimizing cooling in devices. Hexagonal boron nitride (also known as white graphene) appears similar to graphene (carbon in atom-thick form) in 2D. However, white graphene is a natural insulator while graphene is an excellent conductor.

White graphene also conducts heat well, an ability that can be quantified in terms of phonons, quasiparticles or one part of a collective excitation of atoms, and this is what prompted the researchers to take a closer look at the former as a means of controlling heat flow.

Getting rid of heat in the fastest, most efficient way is always the goal in electronics, explained Shahsavari. However, heat only moves quickly in one direction along a plane and not across layers. It behaves the same way on boron nitride but the researchers were able to show that white graphene in 3D form has the ability to let phonons move in all directions, whether across a plane or through layers.

"This type of 3D thermal-management system can open up opportunities for thermal switches or thermal rectifiers,"said Shahsavari, adding that heat flowing from one direction can differ from what is flowing from the other direction.

He noted that this can be achieved by changing the shape or mass of white graphene to produce a switch. Heat will always have a preference for flowing in a certain direction but flow in the other direction will be slower.

The study received support from the Rice Department of Civil and Environmental Engineering and the National Science Foundation. The researchers also utilized the DAVinCI supercomputer at the Ken Kennedy Institute for Information Technology, as well as resources from Adaptive Computing, Qlogic, CISCO, IBM and the National Institutes of Health.

Shahsavari is an environmental and civil engineering, nanoengineering and materials science professor at Rice, while Sakhavand was a former graduate student from the university.