Deuterium erosion and retention properties of WAlB as integrated plasma-facing and shielding materials for compact tokamaks

Abstract

Tungsten aluminum boride (WAlB) has been proposed as a promising candidate for integrated plasma-facing and shielding materials in compact tokamaks due to its excellent neutron and gamma-ray shielding properties, as well as its resistance to radiation-induced damage. However, the hydrogen isotope erosion and retention properties remain unclear. This study assesses and compares the erosion and retention properties of WAlB, molybdenum aluminum boride (MoAlB), and tungsten (W) using a combination of experiments and first-principle calculations. The WAlB sample, which contained impurity phases of W-Al and W-B, was annealed at 600 °C for 2 h prior to irradiation. This treatment increased the WAlB phase to over 80 %, making it the primary focus of this investigation. Both WAlB and W were subjected to deuterium (D) ion irradiation with fluences of 7.20 × 10²³ – 1.71 × 10²⁴ D/m² at temperatures of 452–598 K. Results show that WAlB undergoes preferential sputtering under D ions irradiation with a sputtering yield slightly higher than that of W but lower than MoAlB. D retention in the near-surface region of WAlB is only half of that in pure W but greater than that in MoAlB. Notably, no significant blistering or plastic deformation appeared on the WAlB surface, whereas a substantial amount of D-induced blisters formed on the W surface. These findings imply that while WAlB may not match W in D retention resistance, it demonstrates superior resistance to surface blister formation. Optimistically, this work suggests that future advancements in composition and structural design could enhance WAlB's resistance to D retention and sputtering, boosting its potential for application in compact tokamak reactors.