Disperse alumina nanoparticles prepared by ball milling and acid corrosion

Abstract

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.