Diffusion bonding of zirconia to silicon nitride using nickel interlayers

The possibilities of diffusion bonding of zirconia to silicon nitride using a nickel interlayer were studied by carrying out bonding experiments under various processing conditions. The process parameters considered were temperature, bonding pressure and interlayer thickness. The optimal process conditions were determined by evaluating the mechanical strength using shear strength testing. It was found that the bonding is optimal in the temperature range 1000-1100 degrees C. The bond strength appears to be independent of the bonding pressure and interlayer thickness if threshold values are exceeded (bonding pressure > 14 MPa, interlayer thickness > 0.2 mm). At the Si3N4-Ni interface, Si3N4 decomposes, forming a solid solution of silicon in nickel. At the ZrO2-Ni interface, no reaction was observed. (C) 1998 Kluwer Academic Publishers.