TPU researchers: new 'self-healing' coatings for thermonuclear reactors maintain structural integrity under irradiation

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TPU researchers: new "self-healing" coatings for thermonuclear reactors maintain structural integrity under irradiation

TPU researchers together with their colleagues studied how new multilayer (nanolaminate) coatings behave when irradiated with protons and helium ions. Such materials have the ability to "self-heal" when operating in extreme conditions and may be promising for the elements of thermonuclear reactors. It has been established that a functional gradient material (FGM) based on niobium and zirconium preserves the integrity of the structure during irradiation, and also effectively limits the accumulation of defects.

The results have been published in the journal Journal of Materials Research (Q2, IF: 2.9). The project was supported by the grant from the Ministry of Science and Higher Education of the Russian Federation (no. FSWW-2026-0044).

Multilayer or nanolaminate coatings are widely studied for the use in the nuclear industry, since they have high strength, corrosion resistance and resistance to radiation exposure. Such structural materials are particularly promising for creating thermonuclear energy systems. However, the operational characteristics of existing nanolaminate coatings remain insufficient.

Earlier, TPU researchers proposed a new multilayer coating architecture - a functional gradient material (FGM) based on niobium and zirconium. This material consists of alternating layers with spatially varying composition and thickness, forming a gradual transition between chemically and structurally different components.

"Previous in situ studies demonstrated that the new material, when heated to 900 °C, proved to be resistant to thermal effects due to effective recombination of defects, and also, due to reversible phase transformations, it is able to withstand extreme heating and cooling cycles without significant degradation. In the new study, it has been found that FGM samples retain their layered structure when irradiated with helium ions and protons without the signs of amorphization (transformation of a solid substance from the ordered to the disordered state - editor's note) or phase transformations. Mechanisms controlling defect evolution, atomic displacements, and interface reactions in gradient systems exposed to radiation have been established. A physical understanding of how gradient structures respond to extreme conditions, including the generation and redistribution of defects caused by radiation, is critically important for the transition of FMG from conceptual architectures to engineering materials with controlled and predictable behavior," says Roman Laptev, one of the authors of the article, professor of the Department of Experimental Physics at TPU.

In this work, the researchers have studied these issues through a combined experimental and theoretical study of radiation effects in functionally gradient nanolaminates based on niobium and zirconium. Using the magnetron sputtering method, the researchers obtained FGM samples that consist of four functional layers: an outer layer of niobium with a thickness of 3 ± 1 microns, a nanoscale multilayer coating consisting of alternating layers of zirconium and niobium with an individual thickness of 60 ± 15 nm and a total thickness of approximately 1.0 ± 0.3 microns, and an adhesive intermediate layer of zirconium with a thickness of 8 ± 3 microns and a zirconium-niobium alloy substrate with a thickness of about 0.7 mm. The samples were then irradiated with helium ions and protons on electrostatic accelerators. The energy of the proton beam is 800 keV, and that of the helium beam is 2 MeV (stabilization accuracy is ± 0.02%). The irradiation took place at room temperature.

Further, using various methods, including transmission electron microscopy, X-ray diffraction, positron annihilation spectrometry, and calculations based on density functional theory, the researchers analyzed the microstructural response and defective behavior of FGM.

It has been established that nanolaminate coatings based on niobium and zirconium effectively limit the accumulation of defects and preserve structural integrity under ion irradiation. The accumulation of defects and mechanical modification in the samples are limited by a thin outer region. Its radiation sensitivity is determined by internal lattice distortions caused by interphase interaction and the effective placement of defects at the boundaries of heterophases. The results obtained provide a physically sound basis for designing gradient nanolaminates intended for extreme radiation conditions relevant for thermonuclear energy systems,

- notes Anton Lomygin, assistant at the TPU Department of Experimental Physics.

The study involved employees of the Department of Experimental Physics and Research Nuclear Reactor of the Engineering School of Nuclear Technologies of TPU, the Department of Materials Science of the Engineering School of New Production Technologies of TPU and the Joint Institute for Nuclear Research.