Wettability of lithium by liquid sodium, potassium and rubidium

The wettability of the lithium surface by liquid alkali metals $\mathrm{Na}$, $\mathrm{K}$ and $\mathrm{Rb}$ is investigated for the first time by the sessile drop method in an all-soldered instrument under conditions of a high vacuum. The presence of the temperature threshold of wetting is found in $\mathrm{Li}$–$\mathrm{Na}$ and $\mathrm{Li}$–$\mathrm{K}$ systems at temperatures of $325^\circ$C and $160^\circ$C, respectively. A conclusion is drawn that an abrupt decrease in wetting angles in the investigated systems is associated with a marked decrease in the interfacial tension at lithium-lithium, lithium-potassium, and lithium–rubidium interfaces owing to the beginning of a noticeable mutual solubility of the components at relatively high temperatures.