COLLOIDAL PROCESSING AND SINTERING OF NANO-ZrO2 POWDERS USING POLYETHYLENIMINE (PEl)

Abstract

A stable colloidal suspension is important for fabricating dense samples with uniform microstructure using colloidal processing methods. Aqueous nano-ZrO<inf>2</inf> suspensions were prepared using polyethylenimine (PEl) as a dispersant. PEl adsorption on nano-ZrO<inf>2</inf> surfaces was influenced by PEl content and suspension pH. The isoelectric point (IEP) shifts from pH 7 at o wt% PEl to pH 10.3 at 3 wt% PEL Stable suspensions had mean particle sizes in the range of 100 to 150 nm and sedimentation rates less than 0.4 mmIh, as compared to 2-5.5 Ilm and 10-50 mmIh for unstable suspensions. Electrostatic interactions, hydrogen bonding and PEl conformation were found to be controlling mechanisms on the colloidal stability of the suspensions. The amount of PEl adsorbed on nano-ZrO<inf>2</inf> surfaces was characterized using Thermogravimetric analysis (TG) and Fourier transform infrared spectrometer (FT-IR). The densification behavior of samples containing 3 wt% PEl at pH 7.1 sintered for 4 h at 1000 to 1300 °C was characterized. Relative density was found to increase rapidly from 54 % at 1100 °C to 92 % at 1200 °C and finally to 98 % at 1300 °C. Therefore, pellets were sintered at 1300 °C for 4 h to quantitatively correlate the processing conditions such as effect of pH and PEl content with densification. © 2025 Elsevier B.V., All rights reserved.