| Summary: | As the world faces an energy and resource crisis, there is a growing need to develop more efficient energy production, conversion, and storage technologies for sustainability. However, these technologies often require materials that can cyclically absorb, convert, and release a significant amount of free energy during service, which can result in dynamic behaviors similar to metabolism in biological systems. Such “active” materials encompass a wide range of materials, including nuclear fusion reactor walls and battery electrodes, and can be prone to structural instabilities and abrupt failure. This thesis aims to enhance the damage tolerance of active materials by designing multi-phase composites incorporating secondary phases that can “proactively” divert damage into more benign forms.
The specific focus is on fusion structural metals subject to 14.1 MeV fast neutron radiation, which produces transmutation helium (He) that embrittles grain boundaries. The strategy pro-posed is to incorporate nano-phases that can absorb and store helium in their bulk lattice, forming a “helide” compound. To identify potential helide formers, this thesis first defines and validates a metric for evaluating helium-absorbing capability and performs a large-scale computational screening. Second, the thesis develops a machine-learning model that can predict the wettability of nano-phases by metals to assess the manufacturability of such multi-phase composites and con-duct matrix-dependent down-selection. Third, the thesis experimentally verifies that the designed nano-phases can absorb and store > 10 at% He within their lattice interior, thereby reducing both the size and number density of helium bubbles at grain boundaries. Lastly, the thesis examines the collateral effect of nano-phases on the phase evolution of metal matrices and provides a guideline for redesigning composites considering this effect.
Together, the results suggest that incorporating the identified helide formers at a concentration of 1–2 vol% can delay the development of critical helium damage in fusion structural materials. This study demonstrates that the atomic energy landscape associated with critical damage carriers can be adjusted even up to a few electron-volts by simply incorporating secondary phases, enabling damage-tolerant active materials.
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