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

Spherical alumina particles were prepared following the sol-emulsion-gel me thod by systematic variation of (i) the concentration of the surfactant Spa n 80 above or below the critical micelle concentration (CMC) in different o rganic solvents and (ii) hydrophilic-lipophilic balance (HLB) of different surfactants in cyclohexane. The experimentally determined CMC of Span 80 wa s found to increase with increasing dielectric constant of the organic solv ent, influencing the sol droplet and alumina particle size. With an increas e in the HLB value of the surfactants, the tendency of monodispersed sphere formation among the particles increased with a decrease in the size distri bution and average particle size (d(50)).