Surface synthesis of aluminum borate whiskers on the ZTA ceramics and its application to joining

In this study, aluminum borate whiskers were prepared on the zirconia-toughened alumina (ZTA) substrates for the first time. This result was achieved by calcining a mixture of B2O3 powders with and without adding the MnO2 flux in air. The morphologies of as-prepared whiskers were carefully characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The length-diameter ratio of whiskers prepared by adding MnO2 flux is larger than those prepared by using only B2O3 powders, and the growth mechanisms of whiskers follow solid–liquid–solid theory. In addition, aluminum borate whiskers were successfully used to join ZTA ceramics. By adding the MnO2 flux in the interlayer, the strength of the joints can be significantly improved. The highest flexural strength for the ZTA/whiskers/ZTA joints bonded using B2O3 + 5 wt% MnO2 powders reached 162 ± 11 MPa at 1100 °C after holding for 4 h.