N. Froumin

The Nature of TiB2 Wetting by Cu and Au

TiB2 among other borides like ZrB2 and HfB2 represents a unique class of ceramics, which displays good wetting by liquid metals, such as Cu and Au, without chemical interaction that may be detected by conventional characterization techniques. The nature of the wetting in these systems is commonly attributed to the “metallic-like” character of borides. In this study, improved wetting of TiB2 by Cu and Au (50° and 15°, respectively) was confirmed and evidence of a limited chemical interface interaction was observed using TEM analysis. Moreover, it was shown that the addition of B to Au and Cu improves wetting. It was suggested that not only “metallic-like” character of TiB2 but also the chemical interaction stands behind good wetting in these systems.

Wetting/Dewetting Phenomena in the CaF2/Ga and CaF2/Ge Systems

The wettability of calcium fluoride by liquid Ga and Ge was studied. The initial contact angles indicate that pure liquid Ge and Ga do not wet CaF2. Different spreading kinetics during the experiments was observed. The contact angle in CaF2/Ge system increases with time, while the contact angle in CaF2/Ga system decreases. The same differences were also observed for temperature dependences of the contact angle. It was suggested that these wetting/dewetting tendencies are related to the ratio of the vapor pressure values for the melt and for the substrate. The experimental observations were confirmed by a thermodynamic analysis.