Joining oxide ceramic matrix composites by ionotropic gelation

Abstract The production of complex‐shaped all‐oxide ceramic matrix composites (Ox‐CMC) is somewhat restricted by their current processing methods, as well as by the lack of applicable joining techniques. Thus, we present a new method for joining Ox‐CMCs based on the gelation of slurries with the polysaccharide polymer alginate. For this investigation, Nextel 610/alumina‐zirconia composites were produced using alginate as binder and aluminum acetate as gelling agent. The joining capabilities of this technique were investigated with microstructural analyses and single‐lap compression shear tests. For that, a slurry‐containing alginate was used to join two composite plates at different stages of the processing: gel state, dried green body and after sintering. Joining composites plates in their gel or green state was successful as the joints showed shear strength values similar to the interlaminar shear strength of the composites plates. The quality of the joints was attributed to the interactions between the alginate chains of the composite plates and the joint. We also show that even the joining of already sintered Ox‐CMCs is feasible. However, densification cracks and lower shear strength are observed for such cases.