DOE funds research to advance adaptive & self-healing materials

The use of nuclear fusion as an energy-producing alternative may become more feasible with NPRE Associate Professor J.P. Allain’s work in advancing adaptive and self-healing materials.

“One of the challenges for fusion is materials,” said Allain, who recently was awarded a $1.1 million Fusion Energy Sciences grant from the U.S. Department of Energy to support his team’s research. “In fusion, radiation and plasma damages the materials used to build the machines. We’re looking for materials that can withstand the damage and tolerate the irradiation; they need to be adaptive to extreme environments.”

In this new grant, Allain focuses primarily on plasma-material interactions that involve the first few microns of the material surface.

Allain’s group has been working with materials that have either adaptive and/or self-healing properties. The performance of adaptive materials exposed to a defined extreme environment is either maintained or improved as the materials adapt to that particular environment – in this case, fusion plasma. Self-healing materials can freely repair themselves after damage without any external influence.

Allain’s group has been pioneering this work discovering adaptive materials capable of sustaining the far-from-equilibrium conditions found in nuclear thermonuclear reactors. These materials include: nanoporous and mesoporous tungsten composites, extreme-refined doped refractory alloys, and self-healing nanocomposite W-Li pseudo-alloys.

Allain’s group also is processing self-healing materials by combining porous solids with liquid metals. He gave an invited talk on the subject this past fall at the 17th International Conference on Fusion Reactor Materials held in Germany.

“We deal strictly with the surfaces and interfaces of the material, tailoring the surface in a way that it becomes radiation resistant,” he said.

Some of the work is motivated by porous materials Allain is designing in bioengineering applications. Porous materials such as magnesium and titanium can become bioactive when irradiated. The biomimetic self-healing and adaptive properties he studies are adopted in fusion materials applications across the nano and meso scales.

This is the first time this type of work has been done with porous materials such as metal sponges and foams. In addition to processing the materials, Allain’s group examines results through high-heat flux testing and in-situ characterization to decipher the dynamic material properties as they evolve during plasma exposure. The researchers also construct multi-scale computational modeling of the plasma-material interfaces.

“The development and testing of new materials for fusion energy is a very complex process,” Allain contends. “It takes more than a single institution to make this happen and this is why we have established very strong collaborations worldwide.”

The group’s international collaborations have included work with Prof. Eduardo Saiz from the Department of Materials at Imperial College London, and self-healing systems consisting of advanced metallic alloy (i.e. Fe-Au systems) nanocomposites synthesized by Sybrand van der Zwaag’s group at the Delft University of Technology.

For high-heat flux testing, collaborations with the FOM Dutch Institute for Fundamental Fusion Energy Research (DIFFER) in Eindhoven will use the Magnum-PSI linear plasma device. Unique throughout the world, this device simulates conditions expected in future energy-producing fusion reactors. Allain has a long history with FOM-DIFFER, including exchange visits of his students over the past few years.

Due to the nature of self-healing and adaptive materials being strongly coupled to their environment, in-situ characterization is critical. Allain has developed a state-of-the art facility in the Micro and Nanotechnology Lab (MNTL) known as IGNIS (Ion-gas-neutral Interaction with Surfaces). IGNIS is capable of observing the surface composition and morphology in-situ during particle irradiation under conditions mimicking the nuclear fusion plasma edge.

In addition to using the in-situ IGNIS facility Allain’s group has developed at Illinois, the group has collaborated significantly with Stephen Donnelly’s group at the University of Huddersfield in using their MIAMI device, an in-situ irradiation TEM. Work on additional in-situ facilities has been planned with Sandia’s new ion-beam facilities in collaboration with Dr. Khalid Hattar, an alumnus of Materials Science and Engineering at Illinois.

Allain also will be working closely with NPRE Prof. James Stubbins, a co-principal investigator on the project, to understand thermo-mechanical properties of these complex materials.

To enhance the understanding of both the processing and performance of the proposed adaptive and self-healing materials systems, experimental research will be closely coupled to on-going efforts in multi-scale computational modeling with Prof. Brian Wirth at the University of Tennessee Knoxville (UTK).