Effects of nitric acid concentration on the stability of alumina sols

Alumina sols with a molar ratio of 1:50 between aluminum sec-butoxide (ASB) and H₂O were fabricated by adding various amounts of nitric acid. The particle shape, zeta potential, polydispersity and effective particle size of alumina sol were examined by a TEM, a zeta PALS granularity analyzer and a zetaPALS zeta potential analyzer, respectively. By analyzing the change of zeta potential and double- layer thickness with nitric acid concentration, the potential energy curves of colloidal particles were mapped on the basis of DLVO theory, and the effects of nitric acid concentration on the stability of alumina sols were intensively studied. The results show that for the alumina sols with a mol ratio of 1:50 between ASB and H₂O, the total interaction energy of the colloidal particle is at a maximum when the nitric acid concentration is 0.22 mol/L. Therefore, the stability of the colloid reaches optimum at the nitric acid concentration of 0.22 mol/L.