Wetting of h-BN by molten Cu-8.8Zr-xTi ternary alloys at 1373 K

The wetting of hexagonal boron nitride (h-BN) by molten Cu-Zr eutectic alloy with different Ti concentration (0-10 at.%) was studies by a modified sessile drop method at 1373 K under high vacuum. h-BN cannot be wetted by Cu-Zr eutectic alloy (equilibrium contact angle is similar to 128 degrees), but a small addition of Ti (2.5 at.%) can decrease contact angle significantly. Interfacial reaction products Ti-nitride, Ti-diboride, Zr-nitride and Zr-diboride were observed and identified using SEM and XRD. The reason of contact angle decreasing with Ti concentration in wetting case of Cu-8.8Zr-xTi (x = 2.5, 7.5, 10) system is the reducing of stoichiometry of TiNy, which makes TiNy has a better metallic property. In addition, the adsorption of Ti at liquid/solid interface is not a negligible factor. In non-wetting cases of Cu-8.8Zr and Cu-10Ti, the negative molar exchange energy values between Cu-Zr and Cu-Ti indicate Zr and Ti would be attracted by the bulk of liquid. Thereby, the improvement in the wettability of h-BN by Cu-Zr and Cu-Ti binary alloys is very limited.