Synthesis of monodisperse α‐Al 2 O 3 nanoparticles by a salt microemulsion method

Alpha alumina nanocrystals that are highly dispersible and have a high specific surface area play an important role in the field of catalytic supports and others. As the phase‐transformation temperature of α ‐Al 2 O 3 is 1000°C, it is extremely difficult to fabricate monodisperse nanoparticles. Here, the study reports a new method, referred as the salt microemulsion method, for the fabrication of monodisperse α ‐Al 2 O 3 nanoparticles, and the particle size could be tuned between 3 and 8 nm. The particles precipitated by demulsifying the microemulsion were analysed by transmission electron microscopy. The precipitated particles are found to be inclusions, with the Al 2 O 3 precursor nanoparticles are dispersed and isolated by the K 2 SO 4 nanoparticles. As the melting point of K 2 SO 4 is 1065°C, the Al 2 O 3 precursor nanoparticles are separated by the solid K 2 SO 4 over the entire high‐temperature phase‐transition process. As a result, agglomeration and sintering of the α ‐Al 2 O 3 nanoparticles are prevented, leading to monodisperse α ‐Al 2 O 3 nanoparticles.