The effect of beryllium oxide on retention in JET ITER-like wall tiles

Surface, Structural, and Mechanical Properties Enhancement of Cr2O3 and SiO2 Co-Deposited Coatings with W or Be

Direct current (DC) and radio frequency (RF) magnetron sputtering methods were selected for conducting the deposition of structural materials, namely ceramic and metallic co-depositions. A total of six configurations were deposited: single thin layers of oxides (Cr₂O₃, SiO₂) and co-deposition configurations (50:50 wt.%) as structural materials (W, Be)-(Cr₂O₃, SiO₂), all deposited on 304L stainless steel (SS). A comprehensive evaluation such as surface topology, thermal desorption outgassing, and structural/chemical state was performed. Moreover, mechanical characterization evaluating properties such as adherence, nano indentation hardness, indentation modulus, and deformation relative to yielding, was performed. Experimental results show that, contrary to SiO₂ matrix, the composite layers of Cr₂O₃ with Be and W exhibit surface smoothing with mitigation of artifacts, thus presenting a uniform and compact state with the best microstructure. These results are relevant in order to develop future dense coatings to be used in the fusion domain.

Molecular dynamics study of hydrogen isotopes at the Be/BeO interface

Molecular dynamics simulations are used to investigate the behaviour of D atoms at two interfaces between beryllium (Be) and beryllium oxide (BeO). After relaxation of the simulation cell, there are (a) localised defects at the interface and (b) a hexagonal misfit dislocation network creating a succession of compressed and expanded area from each side of the interface. The simulations between 750 K and 1500 K for tens to hundreds of nanoseconds show that both interfaces act as trapping sites for D atoms. The simulations also show that D atoms tend to migrate in the material where the hydrogen isotope solubility is the highest as predicted by thermodynamics. However, the simulations also shows that there are additional kinetic barriers (D trapping sites, D₂formation/dissociation in BeO) that slow down the path to equilibrium. These additional kinetic barriers may influence the fuel retention and permeation in Be materials.