Abstract
This study reports useful application of the electrokinetic sonic amplitude (ESA) technique in combination with rheometry and electron microscopy techniques for direct probing the stability of low and high-concentrated zirconia (ZrO2) nanosuspensions in the presence of an alkali-free anionic polyelectrolyte dispersant Dolapix CE64. A comparative study of the electrokinetic characteristics and the rheological behavior of concentrated ZrO2 nanosuspensions has been done. Good agreement was obtained from relationship between the electrokinetic characteristics (zeta potential, ESA signal), viscosity, and its pH dependence for each concentrated ZrO2 nanosuspension with different dispersant concentration in the range of 0.9–1.5 mass%. A nanoscale colloidal hypothesis is proposed to illustrate that the addition of different amounts of dispersant influences on both the stability and the electrokinetic and rheological properties of concentrated ZrO2 nanosuspensions. It is found that an optimum amount of 1.4 mass% dispersant at the inherent pH (>9.2) can be attached fully onto the nanoparticles with sufficient electrosteric dispersion effects, suitable for casting applications. Supplementary scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses followed by colorization effect were taken to verify the visible interaction between dispersant and nanoparticles surfaces. SEM and HR-TEM images proved the existence of visible coverage of dispersant on the surface of individual nanoparticles and showed that thin polyelectrolyte layers were physically bound onto the particles’ surfaces. This study will be of interest to materials scientists and engineers who are dealing with dispersion technology, nanoparticle surface treatments, functionalization, characterization, and application of bio/nanoparticle suspensions at various concentrations using different types of polymers.
Highlights
Dispersion of nanoparticles in liquids and characterization of their dispersion stabilities at different colloidal concentrations are on the center stage in ceramic processing methods, such as tape casting [1], slip casting [2,3,4], and direct ink writing [5], and in nano/biotechnology development [6,7,8]
All suspensions exhibit shear-thinning behavior with a reduction in viscosity at increasing shear rate, see Effects of Dispersant Concentration on Electrokinetic Properties To determine the effect of dispersant concentration on electrokinetic properties (ESA signal, ζ-potential and pH)
Characterization of Low (2 vol.%)-Concentrated Suspensions The electrokinetic properties of low-solids loading 2 vol.% ZrO2 nanosuspensions without and with addition of insufficient 1.0 mass% and optimum 1.4 mass% amounts of Dolapix CE64 were characterized
Summary
Dispersion of nanoparticles in liquids and characterization of their dispersion stabilities at different colloidal concentrations are on the center stage in ceramic processing methods, such as tape casting [1], slip casting [2,3,4], and direct ink writing [5], and in nano/biotechnology development [6,7,8]. Ceramic colloidal processing methods require stable, well-dispersed suspensions with extremely high levels of solids loading to achieve optimal casting condition and green body properties and to minimize drying induced shrinkage [9,10,11]. Several techniques are available to characterize the dispersion quality of micron and sub-micron-sized powder suspensions at low solids loading. These include rheological, sedimentation, adsorption, electrophoresis, charge quantity, and zeta (ζ)-potential measurements or optical light scattering techniques [4, 12, 13]. There are no many standard techniques available for dispersion characterization of nanoparticles suspensions at high (>2 vol.%) solids loading. One of the available techniques that can be used for characterization of the electrokinetic properties of dispersed nanoparticle suspensions is laser light scattering technique. The majority of standard laser light scattering techniques are indirect
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