Extreme Materials by Atomic Layer Deposition: High Entropy Intermetallic Coatings for Nuclear Claddings

New more capable materials are a key component of any strategy to ease the energy crisis and energy generation effects on the planet's weather. Nowhere is the need for improved material properties more evident than in nuclear electricity generation. Of the limited available base load options, nuclear is attractive as a proven, carbon-free, dispatchable option. While in the US, the nuclear power industry has a remarkable record for safe, reliable operation events such as the recent failure of a power plant in Fukishima, Japan demonstrate the need for material improvements that can make reactors passively safe.

We have been working on intermetallic coatings as a viable option, which could be applied to present reactors and to advanced reactors as they are built around the world. Intermetallic materials are alloys whose bond strengths are so large that the material takes on an ordered structure rather than a the normal alloy randomly distributed structure. Of the many phases that have been discovered, a few are remarkably refractory and corrosion resistant. In a sense these materials exhibit properties which are midway between metals and ceramics. Their use in current devices has been limited to for instance coatings on turbine blades for both jet engines and power generation because of difficulty in synthesizing phase pure materials and in subsequent fabrication. Using Atomic Layer Deposition we have been able to demonstrate synthetic methods that allow generation of only high enthalpy phases such as Zr2Al3 or Pt3Zr. The films form at remarkably low temperatures (given their refractory nature) and inherit excellent conformality as is typical for ALD coatings. We will describe some of our progress towards coating and testing large cladding tubes.