Wetting of liquid lithium on fusion-relevant materials microtextured by femtosecond laser exposure

As the use of liquid metals in plasma facing components becomes more widespread, it is important to investigate how these liquid metals interact with the surfaces onto which they are deposited. An important example of these interactions is the ability to control liquid metal wettability on fusion relevant substrates. In this work, we explore the influence of femtosecond laser induced nanostructured surfaces on the wetting degree of liquid lithium versus temperature. Three material candidates as a lithium wall in magnetic fusion devices have been investigated: molybdenum, tungsten and 304 L stainless steel. Laser parameters were tuned to induce periodical self-organized nanostructures (ripples or LIPSS) formation on each material. Wettability of laser treated materials was changed from lithium-philic to lithium-phobic for temperatures beyond 320 °C - 360 °C compared to untreated material. The effect of both laser induced topography and chemistry are quantified to explain the observed liquid lithium contact angles on each material. Finally, it was shown that topography in the form of self-organized periodical nanostructures as well as the surface chemistry in the form of oxides enrichment, both induced by a single step laser process, strongly influence the wetting degree of liquid lithium and enhance lithium-phobicity at high temperatures.