No abstract

We use neutron reflectometry to find the critical helium (He) fluence required to form He bubbles at interfaces between fcc and bcc metals. Our findings are in agreement with previous experimental as well as modeling results and provide evidence for the presence of stable He platelets at fcc-bcc interfaces prior to bubble formation. The stable storage of He in interfacial platelets may provide the basis for the design of materials with increased resistance to He-induced degradation.

First principles calculations show that two-body forces are sufficient to describe interactions of He with fcc Cu and bcc Nb. This property is explained directly from calculated charge density distributions and used to construct a Cu–Nb–He interatomic potential that predicts accurate He impurity energies despite not being fitted to them.

The structure of metal/oxide interfaces is important to the radiation resistance of oxide dispersion-strengthened steels. We find evidence of gradual variations in stoichiometry and magnetization across a Fe/Y2O3 metal/oxide heterophase interface using neutron and x-ray reflectometry. These findings suggest that the Fe/Y2O3 interface is a transitional zone approximately ∼64 Å-thick containing mixtures or compounds of Fe, Y, and O. Our results illustrate the complex chemical and magnetic nature of Fe/oxide interfaces and demonstrate the utility of combined neutron and x-ray techniques as tools for characterizing them.