Joining of Al2O3 by epitaxial growth of aluminum borate whiskers for high-temperature applications

•Al2O3 was directly bonded by epitaxial growth of Al18B4O33 whiskers in air.•The Al2O3/whisker/Al2O3 joints were characterized in detail.•The maximum flexural strength of the joints tested at 800 °C reached 27 MPa.•The possible mechanism of the bonding process was discussed.

Alumina ceramics were directly bonded for high-temperature applications by epitaxial growth of aluminum borate whiskers in air. The Al2O3/whisker/Al2O3 joints were characterized via scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The microstructural observations showed that the Al18B4O33 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.

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