Chapter 93. Interfacial Characteristics in Ceramic Joining with Glass Interlayers

Summary

A joining technique for oxide ceramics is presented. It is based on the use of a glass powder as bonding interlayer between two ceramic pieces. At the bonding temperature, the glass melts, wets the ceramic and flows through the interface driven by the capillary pressure that builds up between the two contacting ceramic surfaces promoting their adhesion. Examples are presented for the systems formed by ZrO₂ (3 mol %Y₂O₃) and the composite 80 Al₂O₃ - 20 ZrO₂ (wt %) as the ceramic component and a silicate glass (CaO-Al₂O₃-SiO₂). The microstructure at the interface of the bonded samples is function of the relative mobility of the ceramic grains when the glass wets them. The glass interlayer penetrates in the grain boundaries of ZrO₂ as a consequence of the mutual mobility between the glass and the ceramic grains. Conversely, in case of the composite Al₂O₃-ZrO₂, the Al₂O₃, grains have a limited mobility; therefore a glass layer forms at the interface with a thickness that is function of the starting glass amount. High flexural strength values are obtained (up to 313 MPa), but associated with large standard deviations due to presence of large pores (about 200 m̈m) at the interface.