Rheology of colloidal nanosized BaTiO3 suspension with ammonium salt of polyacrylic acid as a dispersant

In this work, we have investigated the dispersion and rheological behavior of BaTiO3 nanoparticles aqueous suspension using ammonium polyacrylate (PAA-NH4) as a dispersant agent over a wide range of solids concentration (Φ = 0.03–0.5) and of shear rate 1–1000 s−1. The results showed that the addition of PAA-NH4 decreased the suspension viscosity pronouncedly. The suspensions all appeared pseudoplastic over the shear-rate range investigated, revealing that the mixtures were flocculated in structure. The relative viscosity (ηr) of the suspension, defined as the suspension viscosity over the viscosity of the suspension medium, was found increasing substantially when Φ exceeds 0.4. A derivative of ηr, i.e., 1−ηr−1/2, appeared linearly proportional to Φ, from which maximum solids fraction (Φm) was determined as Φm = 0.574 for the given suspension system. Casson model was used to fit the experimental data and a useful parameter yield stress (τy) obtained. Shear rate dependence on viscosity was accurately described by the Casson equation and the yield stress of the suspensions presented a power-law dependence with the solid fraction.