The wettability of molten aluminum on sintered aluminum nitride substrate

The contact angle of molten aluminum on sintered aluminum nitride (AlN) is measured by means of the fresh droplet method over the substrate temperature range of 670–850°C. The angle remains at 110° below 800°C but drops to 75° at 850°C. It is suggested that an oxide on the AlN surface exerts a strong influence on wettability. The contact angle is much lower than that reported previously. A theoretical estimation of partial pressures of decomposition products of oxide on the droplet surface is presented. The calculation suggests that the suboxide Al2O is the major decomposition product. A similar conclusion was drawn previously by Eustathopoulos and coworkers.