Dewetting kinetics of calcium dufluoride with copper—tin—titanium melts

Анотація

It was previously established that when alkaline earth metal fluorides are wetted with alloys containing chemically aggressive metals, primarily titanium, zirconium, niobium, dewetting occurs. This phenomenon, when with increasing temperature the value of the contact angle first decreases, as for other ionic compounds (oxides), and then increases sharply at temperatures above 1000°C, was studied in the calcium dufluoride — (Cu— 11,9% (at.) Sn)—Ti system. The process of rapid growth of the contact angle was studied by the sessile drop method in vacuum using high-speed film recording (up to 5000 frames/s). Contact angles were recorded at temperatures of 900, 1100 and 1250 °C. The angle value varied from 60 to about 130 and 150°, respectively. The explanation for this phenomenon is related to the formation of at the contact interface fluoride substrate / titanium-containing melt of gaseous titanium fluorides. At a temperature of 900 °C, at the contact interface of calcium fluoride/melt containing titanium, a chemical interaction of titanium with fluorine of the ionic compound occurs with the formation of a new fluoride phase. The new phase is a solid compound that provides wetting in the system under study. Further, with increasing temperature, the new solid fluoride phase passes into a gaseous state, evaporates from the contact interface. This leads to an increase in the value of the contact angle — non-wetting, the process of dewetting occurs.

Keywords: contact angle, calcium dufluoride, chemically aggressive metals, dewetting kinetics, high-speed film recording.