Ceramic joining through reactive wetting of alumina with calcium aluminaterefractory cements

Compositions in CaO-Al2O3 system have been prepared by gel-to-crystallite c onversion method. Reactive powders of 1 : 2, 1 : 1, 2: 1 and 3 : 1 of CaO a nd Al2O3 compositions were obtained by calcining the product at 800-1200 de grees C. Fine grained powders were used as refractory cement for joining al umina ceramics. An optimum temperature of 1450 degrees C for 4 h produced j oints of satisfactory strength. The microstructure and X-ray phase analysis of the fractured joint surface clearly indicate reactive wetting of the al umina ceramics. This wetting enhances the joining of alumina substrates and can be attributed to the formation of Ca12Al14O33 liquid phase. The result s are explained by using CaO-Al2O3 phase diagram.