Joining of Al 2 O 3 by epitaxial growth of aluminum borate whiskers for high-temperature applications

Abstract Alumina ceramics were directly bonded for high-temperature applications by epitaxial growth of aluminum borate whiskers in air. The Al 2 O 3 /whisker/Al 2 O 3 joints were characterized via scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The microstructural observations showed that the Al 18 B 4 O 33 whiskers along the [001] crystallographic direction grew across the seam and thereby achieving the joining of alumina substrates. Both of whiskers diameter and density of joints increased with the increase of bonding temperatures. Three-point bending results showed that the maximum strength of the joints tested at 800 °C was 27 MPa. The possible mechanism of the bonding process was discussed as well.