Role of organic solvents and surface-active agents in the sol-emulsion-gel synthesis of spherical alumina powders

Spherical alumina particles were prepared following the sol-emulsion-gel method by systematic variation of (i) the concentration of the surfactant Span 80 above or below the critical micelle concentration (CMC) in different organic solvents and (ii) hydrophilic–lipophilic balance (HLB) of different surfactants in cyclohexane. The experimentally determined CMC of Span 80 was found to increase with increasing dielectric constant of the organic solvent, influencing the sol droplet and alumina particle size. With an increase in the HLB value of the surfactants, the tendency of monodispersed sphere formation among the particles increased with a decrease in the size distribution and average particle size (d₅₀).