AFRL Researchers Discover Atomistic Scale Design Methods for Tailoring 3D Thermal Properties of Materials

  • Published
  • By Dr. Ajit Roy
  • Materials and Manufacturing
WRIGHT-PATTERSON AIR FORCE BASE, Ohio --  Researchers from the Air Force Research Laboratory stand ready to advise materials processing professionals on heat management, a critical issue that plagues the electronics and aerospace industries. AFRL's groundbreaking research has discovered methods for designing materials at the atomistic scale, allowing the fine tuning of material properties.

Modeling materials to create three-dimensional truss-like nanostructures will allow AFRL researchers to develop directional thermal materials for a variety of electronic and aerospace applications. The new materials will enable systems engineers to solve problems with managing heat and to develop new materials for electrodes and energy storage. These activities represent a new frontier in materials design and are expected to result in a new class of cost-effective and innovative materials.

As aerospace system developers search for ways to create systems that are faster, more efficient and cost effective, they've given significant attention to thermal management challenges that hinder getting rid of or managing waste heat generated by electronics or other aerospace applications. With the development of micro and nanoscale electronic devices, the need to quickly dissipate thermal energy is absolutely critical for device performance. This concern has provided motivation for understanding, improving and guiding the development of materials with tailored, multi-dimensional thermal transport characteristics.

Carbon nanotubes and graphene are candidates for many nano/microscale integrated devices because of their thermal properties. However, neither system is isotropic in its thermal conduction, which limits performance as a three-dimensional thermal transport material. When carbon nanotubes and graphene are introduced as fillers or additives in polymer composites, researchers observe only a minor enhancement in the effective value of thermal conductivity.

One way to tailor this is to design alternative, carbon-based, three-dimensional (3D) nano architectures. In order to overcome thermal barriers, AFRL scientists are designing robust connectivity of the 3D architectures with low thermal interface resistance at the joints (connections) of the nano elements. Researchers are investigating thermal transport in one such novel architecture - a pillared-graphene (PG) network nanostructure that combines graphene sheets and carbon nanotubes to create a three- dimensional network.

AFRL scientists discovered that pillar length and minimum interpillar distance were the two parameters that governed thermal transport properties. Using atomic-area thermal conductivity predictions, researchers concluded that phonon scattering at the carbon nanotube pillar graphene junctions is the governing mechanism that limits thermal transport in this system. They also discovered that geometric aspects play a significant role in thermal conductivity from a material design perspective, and are keeping this in mind while designing template architectures.

These discoveries have resolved a major barrier in materials nanostructure design, enabling 3D property tailoring that is not achievable with the current state-of-the-art materials. Their design methodology and materials fabrication scale up was published in the American Chemical Society's magazine, ACS Nano, in 2010. AFRL researchers have also been invited to speak at several universities about their discoveries.