Reactive wetting of rutile by liquid aluminium

Sessile drop wetting experiments of liquid Al on polycrystalline rutile (TiO2) were conducted in the 973.1273 K temperature range under a low total pressure (similar to 9.3 - 10(-3) Pa, Ar) and a low oxygen partial pressure (<1.33 10(-7) Pa), as a function of temperature and time. A non-wetting (similar to 150 degrees, 973 K, t > 120 min.) to partial wetting (similar to 85 degrees, 1273 K, 50-60 min.) transition reflects reactive wetting characteristics. Microstructural investigations of the metal-ceramic interface shows that TiO2 is reduced by liquid Al, resulting in the formation of Al2O3. The steady-state contact angle at 1273 K of Al on alpha-Al2O3 and Al on rutile are very similar, and the role of Ti segregation is minimal. It appears that spreading of the Al drop on TiO2 is governed by the reduction reaction at the solid-liquid interface. The measured activation energy corresponds well to the activation energy for volume diffusion of Al, Ti and O in rutile and the volume diffusion of Al in polycrystalline alpha-Al2O3. (C) 2005 Springer Science + Business Media, Inc.