Vapor-phase synthesis of a solid precursor for α-alumina through a catalytic decomposition of aluminum triisopropoxide

A new solid precursor, hydrous aluminum oxide, for α-alumina nanoparticles was prepared by thermal decomposition of aluminum triisopropoxide (ATI) vapor in a 500 mL batch reactor at 170–250 °C with HCl as catalyst. The conversion of ATI increased with increasing temperature and catalyst content; it was nearly complete at 250 °C with the catalyst at 10 mol% of the ATI. The obtained precursor particles were amorphous, spherical and loosely agglomerated. The primary particle size is in the range 50–150 nm. The ignition loss of the precursor was 24%, considerably lower than 35% of Al(OH)3, the popular precursor for alumina particles. Upon calcination of the precursor at 1200 °C in the air with a heating rate of 10 °C/min and a holding time of 2 h, the phase was completely transformed into α. The spherical particles composing the precursor turned worm-like by the calcination probably due to sintering between neighboring particles. The surface area equivalent diameter of the resulting α-alumina was 75 nm.