Transformation of the seeded aluminum hydroxide into sinter-active α-alumina

Abstract Mechanical treatment of aluminum hydroxide containing 0.5-5wt.% α-Al2O3 nanoparticles has been carried out in a planetary ball mill at various milling intensities. It was shown that, when the ball acceleration developing in the mill is equal to or exceeds 10 g, the subsequent calcination at 800°C is sufficient for the complete transformation of the hydroxide into α-alumina with a crystallite size of less than 100 nm. After calcination of the ball-milled powder in the flow of humid air, the alumina particles were somewhat larger, had a spherical shape and did not form strong agglomerates. A body obtained by dry compaction of the powder calcined in the flow of humid air sinters up to 98% of the theoretical density at 1350°C. Nearly the same results were obtained when a simple tumbling mill was used, although a much longer duration of mechanical treatment was needed..