Preparation Method of Submicrometer‐Sized α‐Alumina by Surface Modification of γ‐Alumina with Alumina Sol

Abstract

A method is introduced to prepare almost‐spherical submicrometer‐sized α‐alumina via surface modification of γ‐alumina with an alumina sol. Milled γ‐alumina, in the presence of 3 wt% of α‐alumina with a median particle size ( d 50 ) of 0.32 μm (AKP‐30), produced irregularly shaped α‐alumina with d 50 ∼0.3 μm after heat treatment at 1100°C for 1 h. γ‐alumina that had been surface‐modified by milling in the presence of 3 wt% of the alumina sol resulted in almost‐monosized, spherical α‐alumina ∼0.3 μm in size after heat treatment at 1100°C for 1 h. Furthermore, almost‐spherical α‐alumina 0.1—0.2 μm in size was obtained by milling γ‐alumina with 3 wt% of AKP‐30 alumina in the presence of 3 wt% of the alumina sol, followed by heat treatment at 1100°C for 1 h. The alumina sol that has been introduced in this work seems to act as a dispersant, in addition to helping to form a spherical shape.