Direct nitriding of large grains of aluminum with 2 mm size

Aluminum grains with 2 mm size have been completely nitrided in one batch process. Aluminum grains with added promoter (13.8 wt.% of Y(NO3)3·6H2O) were almost completely nitrided by heating at 1300°C for 2 h in N2 atmosphere. It was deduced that aluminum was vaporized by heat of initial nitriding to react with nitrogen in vapor phase in a short period of time. Nitriding of large-sized aluminum was also attempted without additive. Electrolytically etched aluminum wires were also used as starting material. The aluminum wires without additive were also completely nitrided at 1300°C by preheating at 600°C for 2 h. It seemed that the oxide layer produced by a trace amount of oxygen in N2 gas during preheating activated the initial nitriding. Finally, the complete nitriding of aluminum grains was achieved by preheating at 600°C, without the additive. The oxygen content in the product was only 0.3%, in spite of the oxidation of the aluminum surface. This is because the surface area of the aluminum grains with 2 mm size is relatively small.