Theoretical analysis and synthesis of Al4O4C and Al2CO phase in the resin bonded Al-Al2O3 refractory in N2-flowing

In flowing nitrogen, Al4O4C and Al2CO bonded Al2O3-based composite was successfully prepared by a gaseous phase mass transfer pathway at 1600 degrees C for 3 h after an Al-AlN core-shell structure was formed in the resin bonded Al-Al2O3 refractory at 580 degrees C for 8 h. The formation mechanism of Al4O4C and Al2CO phase is as follows. An Al-AIN core-shell structure is built at 580 degrees C for 8 h and broken at higher temperatures, and then, Al(g) reacts with C from the resin and N-2 to form Al4C3 and AlN, respectively. Owing to the exothermic reaction of the Al4C3 and AlN formation, the reaction temperature in the resin bonded Al-Al2O3 refractory is above the practical environmental temperature; for instance, the reaction temperature is above 1715 C at 1600 C in this work. Therefore, Al4C3 reacts with Al2O3 to generate Al4O4C and then Al4O4C is transformed into Al2OC by the reaction Al4O4C(s)+Al4C3(s) -> 4Al(2)OC(s) at elevated temperatures. Al2OC solid solution is finally formed through the dissolution of AlN into Al2OC.