The wettability of sapphire, polycrystalline alumina, and quartz by molten metal halide salts

The sessile drop technique has been used to measure the wetting angle of molten metal halide salts on polycrystalline alumina, sapphire (crystalline alumina), and quartz substrates. The metal halide salts studied are pure NaI, and a typical metal halide lamp chemistry containing NaI, TlI, DyI3, HoI3, and TmI3. Measurements were made in argon filled quartz ampoules at temperatures varying from the melting point of the salts to a maximum of 1050 °C. In all the cases, the measured wetting angles were less than 90° indicating strong wettability of the substrates by the molten salts.