The effects of carboxylic acids on the aqueous dispersion and electrophoretic deposition of ZrO2

TL;DR

This study investigates how carboxylic acids influence the stability and electrophoretic deposition of ZrO2 suspensions, demonstrating improved deposition and stabilization compared to traditional pH adjustment methods.

Contribution

It reveals the specific adsorption behavior of citric acid, EDTA, and oxalic acid on ZrO2 surfaces and their effect on suspension stability and electrophoretic deposition.

Findings

Citric acid imparts negative zeta-potential and electrosteric stabilization.

Carboxylic acids cause a sharp zeta-potential drop at surface saturation.

Carboxylic acids improve electrophoretic deposition over pH adjustment.

Abstract

The agglomeration, electrokinetic properties and electrophoretic deposition behaviour of aqueous suspensions of ZrO2 with carboxylic acid additives were studied in comparison with conventional pH adjustment. It was found that citric acid imparted negative zeta-potential values and electrosteric stabilisation to particles in suspensions at all pH levels. The examination of additions of carboxylic acids to ZrO2 suspensions revealed that these reagents cause a sharp drop in zeta-potential at distinct addition levels, which correspond to surface saturation of the particles with negatively charged carboxylate groups. Adsorption cross sections of citric acid, EDTA and oxalic acid were evaluated from these results, showing that both citric acid and EDTA coordinate to ZrO2 surfaces by two carboxylate groups while oxalic acid is coordinated by one group. The use of carboxylic acids was shown to facilitate superior electrophoretic deposition in comparison with zeta-potential modification by conventional pH adjustment through improved suspension stability.