Joining by Liquid Wetting and Capillarity of silicon nitride and silicon carbide

The joining technique based on the use of a glass powder as bonding
interlayer between two ceramic pieces is applied to systems formed by
liquid phase sintered Si3N4 or SiC as the ceramic part and Y-Al-Silicate
as the glassy interlayer. The features influencing the adhesion and
reaction between the ceramics and the glass are studied. The
microstructure of the interfacial region is function of the relative
mobility of the ceramic grains when the glass wets them. The glass tends
to penetrate in Si3N4 joints through grain boundaries, because the van der
Waals attractive forces between the Si3N4 grains are weak. In case of SiC,
the glass forms an interlayer characterized by well defined interfaces
with the ceramic, because the strong attractive forces among the SiC
grains inhibits the glass penetration. Mechanical properties of selected
bonded samples are presented.