Contact angle measurements of liquid lithium on surface-modified stainless steel, insulating materials, and other metals and coatings

Liquid lithium plasma facing components (PFCs) may provide an attractive alternative to more conventional solid PFCs due to improved plasma performance and the reduction of erosion and wall damage issues. Conceptual designs for liquid lithium divertors have been proposed, but a complete understanding of the interaction between liquid lithium and structural materials will be required for their successful implementation. One aspect of the interaction is the wetting of different materials by liquid lithium at temperatures relevant to fusion applications. Contact angle measurements were used to study the wetting of liquid lithium on 304 stainless steel with varying surface roughnesses, metallic coatings, advanced alloys, and insulating materials in the temperature range from 200 °C to 350 °C. A mirror finish on 304 stainless steel was found to decrease the contact angle and lower the critical wetting temperature while all rougher 304 stainless steel treatments behaved similarly. For thin film coatings and other alloys, the surface roughness was found to impact the wettability more than the change in chemical composition. Compatibility issues with all three insulating materials tested are discussed and limited contact angle data was collected for these samples.