Ceramic joining III bonding of alumina via Cu/Nb/Cu interlayers

A method of ceramic-ceramic joining that exploits a multilayer interlayer designed to form a thin, potentially transient layer of liquid phase has been used to join alumina to alumina. Microdesigned multilayer Cu/Nb interlayers were used to achieve bonding at 1150 °C. Flexure strengths of as-bonded samples ranged from 119 to 255 MPa, with an average of 181 MPa. The ability to form strong ceramic/metal interfaces is also indicated by instances of ceramic failure. Microstructural and chemical characteristics of fracture surfaces were evaluated using SEM, EDS and microprobe. The impact of post-bonding anneals of 10 h duration at 1000 °C in gettered argon on room-temperature joint strength was assessed. High strengths (198 to 238 MPa) were obtained. The retention of strength following annealing in low oxygen partial pressure argon differs from the behaviour previously observed in Cu/Pt bonded alumina. Effects of the anneal on interfacial microstructure were determined, and an explanation for this difference in behaviour is proposed.