Disperse alumina nanoparticles prepared by ball milling and acid corrosion

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High-yield production of high-purity, disperse, ultrafine, and equiaxed gamma-alumina (γ-Al2O3) nanoparticles with narrow size distributions are essential for their applications. However, the synthesis of γ-Al2O3 nanoparticles by calcination of alumina precursors usually results in severe aggregates. In our present work, commercial γ-Al2O3 particles with an irregular shape, large size, and severe aggregates were directly ball-milled. The milled powders were subsequently corroded with hydrochloric acid to obtain γ-Al2O3 nanoparticles. The γ-Al2O3 nanoparticles obtained are dispersed without aggregates, equiaxed in shape, and ultrafine with a mean particle size of 6.2 nm. The disperse γ-Al2O3 nanoparticles are with high purity (99.994 %, mass per cent) and yield. Then γ-Al2O3 nanoparticles were separated by fractionated coagulation to narrow their size distribution. After coagulation separations, γ-Al2O3 nanoparticles with mean particle sizes of 4.8, 6.6, and 7.7 nm and respective size distributions of 2–9, 2–12, and 2–15 nm were acquired. This high-yield preparation process for γ-Al2O3 nanoparticles is simple and scaled up. Furthermore, using commercial γ-Al2O3 powders as starting material, disperse, and equiaxed α-Al2O3 nanoparticles with a mean particle size of 7.6 nm and purity of 95.98 % (mass per cent) were also prepared by ball milling at a higher ball-to-powder weight ratio of 60:1 and acid corrosion.