Joining by Liquid Wetting and Capillarity of Silicon Nitride and Silicon Carbide

摘要

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 Si_3N_4 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 Si_3N_4 joints through grain boundaries, because the van der Waals attractive forces between the Si_3N_4 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.