Carbothermal reduction - Nitridation study of aluminum containing raw materials

Synthesis of AIN powder from two different Al containing raw materials (Al(OH)₃ and Al₂O₃) was investigated. Starting alumina and aluminum hydroxide powders were wet mixed with carbon black separately in different stoichiometric ratios (C:Al₂O₃ = 2.83, C:Al(OH)₃ = 2.83 and 3.5) in a ball mill for 360 min. Initially, Al(OH)₃ with carbon black was calcined to Al ₂O₃ in an argon atmosphere at 600°C for 30 min. The carbothermal reduction and nitridation process was carried out in a horizontal tube furnace under flow of nitrogen gas. The effects of reaction temperature (1400-1600°C) and time (0-240 min) on the AlN conversion and powder morphologies were investigated using XRD and SEM methods. When Al ₂O₃ was used as starting material, full conversion to submicron spherical AlN powder was obtained at 1600°C for 60 min and at 1500°C for 240 min with 2.83 times of stoichiometric C:Al₂O ₃ ratio. However, for Al(OH)₃ as starting material, a full AlN conversion was obtained only when the stoichiometric ratio of C:Al(OH) ₃ was 3.5 at 1600°C for 60 min.