Seed-assisted hydrothermally synthesized AACH as the alumina precursors

Ammonium Aluminum Carbonate Hydroxide (AACH) is one of the nanostructure materials with a high surface area, which is mostly produced by the hydrothermal method. In this study, kinetics of the hydrothermal reaction has been accelerated with the addition of seed. Nucleation and growth steps have been studied by characterizing the obtained precipitate at different reaction times by FTIR, XRD, FE-SEM, and BET. Different amounts of seeds were added, and the optimum amount in reducing AACH crystallization time has been determined. By seed addition the time required for AACH formation has been reduced from 24h to around 10h, also the specific surface area of the AACH whiskers have been increased about 2.8 times. Mechanism of the reaction and the effect of seed addition have been discussed. Synthesized AACH was calcined at different temperatures to obtain different phases of alumina fibers. The surface area of the obtained Aluminas was investigated by BET; results showed that the highest surface area is achieved when the alumina is in the form of gamma structure.