Effect of peptiser species on crystallisation of alumina gel produced by sol-gel process

The present work reports a study on the effect that a peptiser species has on the crystallisation of alumina gel produced by a sol-gel process to help develop a method for producing alpha-Al2O3 at low temperature. The white precipitate of aluminium hydroxide, which was prepared with a homogeneous precipitation method using aluminium nitrate and urea in an aqueous solution, was peptised using various peptisers at room temperature to form a transparent alumina sol. The alumina gel obtained from the alumina sol, which was produced using formic acid as the peptiser, was most dominantly crystallised into alpha-Al2O3 by annealing at 900 degrees C. The optimal [peptiser]/[Al3+] (P/A) molar ratio for the crystallisation into alpha-Al2O3 was 0.2. The alumina gel began to crystallise into alpha-Al2O3 with annealing at as low as 500 degrees C when formic acid and a P/A ratio of 0.2 were used.