Effect of milling time on the viscosity of hydroxyapatite suspension

Wet processing of hydroxyapatite is useful in the preparation of a green body with a complex structure such as a porous body. For successful wet processing, a suspension with low viscosity and high solid loading is essential. The optimization of the suspension is typically achieved through the careful control of the parameters such as the amount of dispersant and the pH. The milling time was also presented as a significant parameter for the preparation of the suspension in this work. Excessive milling brought about an increase in viscosity, which subsequently resulted in a green body with reduced density. Due to the loose network of primary particles in the green body, the densification was not successfully achieved. The loose packing in the green body was attributed to the reduction of the absolute zeta potential with the increase in milling time.

► The importance of milling time was found in the optimization of HAp suspension.
► Excessive milling led to the green body with a loose network of primary particles.
► The reduction of absolute zeta potential was responsible for the reduced density.