Preparation of High Solids Content Nanozirconia Suspensions

Abstract

A new colloidal route leading to the production of ~99% dense 3 mol% yttria stabilized zirconia nanostructured ceramics, whilst retaining a final average grain size of ~75 nm, has been developed. The process was based on the production of stable, homogeneous nanosuspensions with solids contents of up to 28 vol% (70 wt%) but viscosities less than 0.05 Pa s at any shear rate in the range of study were obtained. The suspensions were formed by the concentration and optimization of precursor, dilute (5.0 vol%) commercial nanosuspensions, the approach requiring a change of pH, from the 2.4 of the as-received suspension to 11.5, and the use of an appropriate anionic dispersant. Exposure of the nanosuspensions to ultrasound also helped to reduce the viscosity further, though it only worked when the dispersant was optimized. The nanosuspension was slip cast to form homogenous green bodies with densities of ~55% of theoretical without agglomeration in the nanostructure; these were subsequently densified using a two-step sintering technique.

Role of suspension preparation in the spray drying process to obtain nano/submicrostructured YSZ powders for atmospheric plasma spraying

“…Some works have reported the effect of different types of dispersants [14,15] or the effect of solid loadings [16][17][18]. In fact, some authors have obtained YSZ granules by spraydrying and freeze-drying but the starting suspensions were quite diluted and the granules obtained were then highly porous (apparent specific mass of 230-1200 kg/m 3 ) [19][20][21].…”

Characterization of silica–water nanofluids dispersed with an ultrasound probe: A study of their physical properties and stability

“…Both the processing time and the energy influence the dispersion effect. It has been demonstrated that the ultrasonic probe is the most effective dispersion system due to its higher energy density that breaks the agglomerates more easily than the other mechanisms [11,14,15]. Only 2-4 minutes (depending on the conditions of the nanofluid) are needed to obtain well-dispersed suspensions.…”

“…To make stable dispersions it is necessary to disperse the large agglomerates that form the initial dry powder into primary particles. The equipment used to disperse nanoparticles includes ultrasonic bath [5][6][7][8][9], ultrasonic probe [10][11][12], magnetic stirrer, high-shear mixer [13], homogenizer and ball mill. Both the processing time and the energy influence the dispersion effect.…”

Dispersion of mixtures of submicrometer and nanometre sized titanias to obtain porous bodies

“…Handling of nanoparticulate systems is difficult and hazardous due to their volatility and the subsequent inhalation risks. One of the most extended routes to allow handling of nanoparticulate systems is the production of free-flowing agglomerates from colloidal suspensions subjected to a controlled drying process, such as spray and freeze drying [18][19][20][21][22][23].…”