Joining of alumina ceramics using nanocrystalline tape cast interlayer

Nanocrystalline transition alumina tape casts were used as interlayers to j oin conventional alumina ceramic pellets. The joining experiments were perf ormed by hot pressing at 1200-1300 degrees C under uniaxial pressures of 55 and 80 MPa for 1- and 5-h durations, with and without a nanocrystalline in terlayer. Successful joints were enabled only above 1250 degrees C in the p resence of the interlayer. Generally, the joint 4-point bending strength in creased with the increase in joining temperature, pressure, and duration. T he average bending strength of the interface joined at 1250 degrees C was 2 45 +/- 65 MPa compared to the pellet strength of 268 MPa. Postjoining heat treatments at 1400 degrees C for 3 h caused reduction in the joint strength . The interlayer at the joint exhibited homogeneous and crack-free microstr ucture. The changes in the joint strength were discussed with respect to th e densification and grain growth behavior of the nanocrystalline interlayer .