Effect of Dispersant Agent and Suspension pH in Colloidal Processing of Nano Zirconia Powder

Nano-sized ceramic powder tends to agglomerate during powder processing because of the existence of van der Waals forces between the fine particles, which promote particle aggregation. Colloidal processing can help prevent the agglomeration of fine particles and allow particle dispersion to be controlled during powder processing. The influence of a dispersant agent and suspension pH in the colloidal processing of nano-zirconia powder (3Y-ZP) is studied in this paper. Dispersant agents Polyethyleneimine (PEI) and Polydiallyldimethyl Ammonium Chloride (PDADMAC) were used in the experiment, with the quantity of each dispersant agent at 0.0%, 0.3%, 0.4%, 0.5%, 0.6%, and 0.7 % of the zirconia weight. The type and optimum quantity of the dispersant agent that can maximize zirconia dispersion in the suspension is determined by using a viscometer. The effect of suspension pH was investigated in suspensions with and without a dispersant agent. A green body is then produced by slip casting and is presintered at 600 °C for 45 minutes, then further sintered at 1100 °C for 2 hours. This study shows that the dispersant agent PEI is suitable for use in an acidic condition. The density and hardness of the samples are high at pH 4 with the addition of 0.5 wt% PEI. The density is 98% of the theoretical density, and hardness is 4.35 GPa. It was found that mechanical properties of zirconia may be enhanced with the use of dispersion agent at the correct quantity as well as optimum suspension pH.