Study on the synthesis and formation mechanism of Al2OC-AlN solid solution in Al–Al2O3 composite material in air at 1500 °C

Abstract

The Al2OC-AlN solid solution reinforced Al–Al2O3 composite material was successfully synthesized by sintering Al–Al2O3 composites with the phenolic resin as binding reagent in air at 1500 °C. The reaction mechanism was investigated by XRD, SEM and thermodynamic analysis. Results showed that the surface layer of the sintered sample was fully oxidized. But Al2OC-AlN solid solution whiskers and particles were observed in the interior layer. In the surface layer, Al and C from resin were oxidized to Al2O3(s) and CO2(g). With the consumption of oxygen, p (O2) gradually decreased from the surface layer to the interior layer. And the oxidation product of Al and C transformed into Al2O(g) and CO(g). When the p (O2) further decreased, the metastable phase AlN was generated in the interior layer. Under the induction of the highly active AlN nucleus, the isostructural Al2OC-AlN solid solution whisker was generated from the gas phase reaction among Al2O(g), CO(g), Al(g) and N2(g). In the region with even lower oxygen partial pressure, particle-like Al2OC-AlN solid solution was generated from the reaction among Al(l), Al2O3(s), C(s) and N2(g).