Peptization mechanism of aluminum phosphate sol

Abstract

Aluminum phosphate sol attracts more and more attention due to its excellent particle size and bonding properties. The structure, morphology and Zeta potential of aluminum phosphate sol during the peptizing process were investigated with NMR, FTIR, Raman, TEM and DLS. The results show that the pseudo boehmite particles were fragmentated, dissolved, and then peptized under the electrostatic repulsion of H+. The peptization process presents three stages: the fragmentation-polymerization stage, the reaction stage, and the stabilization stage. The particle diameter of the stable aluminum phosphate sol ranged from 30 to 50 nm, and the particles with varying sizes were interconnected to form a “hand-in-hand” cyclic system. Meanwhile, the dehydration condensation reaction between H3PO4 and pseudo boehmite was occurring continuously. When 2.1 ≤ n(P)/n(Al) < 3, the proportion of QP01, QP10 and QP11 polymers in the system increased to 25–27 %, the degree of polymerization was deepened, and some cyclic oligomers and polymers appeared. Additionally, the crystal water concentration was increased and the peptization solubility was enhanced.