The role of high resolution electron microscopy in the characterization of ceramic/metal joined interfaces is assessed taking, as examples, alumina/niobium solid state joining. Both atomic and electronic structures are considered taking into account both the pre and post joining stages as well where both physical and chemical reactions take place leaving various types of micro to nano structures at or near the joined interface. The major consideration was the mechanism to relax the thermal stress which is generally inevitable when the selection of both ceramic and metal is made a priori to meet the engineering need. Conservative or nonconservative motion of interface structures such as misfit dislocations and atomic ledges at ambient and elevated temperatures respectively and ductility of metal near the interface were considered to be operative to relax the thermal stress. A design of the joined interface must be made to realize the above mechanism. It is stressed that future high resolution electron microscopy should be able to or at least cooperate with other thechniques to reveal the nature of bonding at the metal/ceramic interface to characterize the joining fundamentally.
(Received May 12, 1990)
Keywords: ceramics-metal joining, Nb/Al2O3, high resolution electron microscopy, interface structure, thermal stress, ledge structure
* Institute of Industrial Science, University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan.