Development of High Entropy, Irradiation Resistant MAX Phases – HEIRMAX

MAX phases are compounds with Mn+1AXn stoichiometry, where M is an early transition metal, A is an element of groups 12 to 16 and X is carbon or nitrogen. They have attracted a particular attention due to their combination of both metallic and ceramic properties. Several MAX phases also exhibit a good resistance to irradiation, a low neutron activation and in some cases, a good resistance to corrosion. This combination of properties makes the MAX phases good candidates for several nuclear applications such as core structures of Gen IV reactors and also as zircaloy coating for enhanced accident tolerant fuel in pressurized water reactors.
However, their microstructure tends to evolve under irradiation. It results in a degradation of their mechanical properties. By tuning the composition of MAX phases and tending toward more complex composition, one can expect High Entropy (HE)-MAX phases (3 to 5 elements are used for M or A constituents) combining expected properties for nuclear applications (mechanical damage and corrosion resistances) and improved stability under irradiation.
The main objective of this proposal is to design a HE-MAX phase and evaluate its irradiation resistance in comparison to conventional MAX phases. Both conventional and HE-MAX phases will be synthetized by Hot Isostatic Pressure and will be ion irradiated. The radiation tolerance will be assessed in terms of stability of the microstructure and mechanical properties. The microstructures will be investigated with complementary techniques to get chemical and crystalline information from nano- to meso-scales. Micro-mechanical tests will be performed to evaluate hardness and toughness evolution. In addition, the irradiation primary damage will be modelized by molecular dynamic.
A better understanding of radiation damage mechanisms and of microstructure-mechanical properties relationships; and the elaboration a dense and high purity bulk HE-MAX phase with improved properties are expected.