WETTABILITY AND SPREADING KINETICS OF LIQUID ALUMINUM ON BORON-NITRIDE

The wettability and spreading kinetics of liquid Al on CVD-BN were investigated by the sessile drop method in a vacuum of about 1.1 x 10(-3) Pa at 1070 to 1430 K. The wettability on the Al-BN system was different from that of the Al-SiC system reported in the literature. The wetting angle of Al-BN linearly decreased with an increase of temperature in high temperature range, and tended towards 15-degrees at 1430 K. Complete wetting could be obtained at about 1470 K. The interface energy between liquid Al and the reaction layer and the surface energy of CVD-BN were calculated by means of Warren thermodynamics analysis. The surface of CVD-BN was examined by XRD. The results show that the surface of CVD-BN was chiefly composed of those low energy planes parallel to (001). According to the relationship of the spreading kinetics from the experiments, the apparent activation energy of the liquid Al spreading on the surface of CVD-BN was calculated. The result shows that the activation energy of interfacial reaction accounts for about 54% of the spread activation energy. The spread of liquid Al on CVD-BN was affected by the interfacial reaction, diffusion and liquid movement on the surface.