27Al MAS NMR spectroscopic identification of reaction intermediates in the carbothermal reduction and nitridation of alumina

The reaction intermediates in the carbothermal reduction and nitridation (CRN) reaction of γ-Al2O3 were identified by 27Al magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. This identification ruled out the possibility of a reaction mechanism involving the gaseous reaction intermediates. In the CRN reaction of γ-Al2O3, AlO4 units were converted to AlN stepwise via AlNxO4−x (x = 1, 2, 3) intermediates, while AlO6 units were more slowly converted to AlN than AlO4 units and the NMR peaks of partially nitridated AlO6 units were not detected. The NMR peak intensities of partially nitridated AlO4 units became weaker with increasing reaction temperature.