Material transport mechanisms during the diffusion bonding of niobium to Al 2O 3

Abstract

Many different material transport phenomena may occur during the diffusion-bonding process of a metal to a ceramic at high temperatures. The operating transport mechanisms depend on the selected combination of materials as well as on the bonding conditions. Systematic studies at the Nb/Al 2O 3 interface allow an identification of the dominating mechanisms. Experiments were performed in which different structures in the niobium surface were bonded to a polished alumina surface. The niobium sample had either a very flat polished surface, or well-defined defects of different dimensions and shapes that were introduced into the surface. It is shown that chemical reactions dominate the material transport under the conditions selected for these experiments.