Granulating Titania Powder by Colloidal Route Using Polyelectrolytes

Abstract

A new, convenient, and inexpensive approach to process and granulate titania powders by a chemical route is proposed. It is based on the use of a formulation that includes a polyanion such as poly(sodium 4-styrenesulfonate) (PSS). Such a polyelectrolyte is most often considered to achieve dispersion of oxide powders in water. Basically, it adsorbs onto the surface of particles and induces electrical and/or steric interactions between particles in the suspension, which prevents agglomeration and rapid sedimentation. The advantages of polyelectrolytes in ceramic processing is well documented in the literature to produce low viscosity suspensions that are further used to form ceramic parts. In the case of TiO2 powders, such aqueous dispersions were obtained by adding small quantities of PSS. However, when exploring the behavior of mixtures containing lower contents of dispersant, we have discovered that, well below the optimum concentration required to get stable dispersions, the polyelectrolyte can act as a binder for titania particles. This can confer cohesion to the agglomerates, which can be processed to form large size (e.g., millimeter size) spheres. This phenomenon takes place when the oxide surface carries both positive and negative electrical charges and can be explained on a simple basis involving surface chemistry. For the optimum concentration of PSS that disperses titania, a polycation such as chitosan should be added to get spheres. This simple technique is expected to receive increasing attention due its potentialities and strong advantages with respect to other granulation techniques, such as spray-drying, which are energy consuming.

Synthesis and Characterization of Anatase‐Structured Titania Hollow Spheres Doped with Erbium (III)

“…9 The band gap of titania depends on its particle size and on its crystallographic phase being 3.2 and 3.0 eV for the anatase and rutile phases, respectively. 10 Many different shapes for TiO 2 have been developed such as wires, 11 rods, 12 tubes, 13 and solid 14 or hollow spheres [15][16][17][18][19] using different methods in each case. Hollow spheres have attracted the interest of researchers during the last few years due to the potential applications of materials having low density, higher specific surface area (SSA) or better separation of electrons and holes under ultraviolet light due to the light scattering produced inside.…”

Recent Progress in the Synthesis of Spherical Titania Nanostructures and Their Applications

“…[ 149 ] Through a facile and inexpensive colloidal route, Pagnoux and co-workers fabricated millimeter sized titania beads by granulating commercial anatase powders dispersed in aqueous solution in the presence of polyelectrolytes such as poly(sodium 4-styrenesulfonate) and chitosan (a polycation). [150][151][152] temperature range. After solvothermal treatment and calcination, the pore diameters of the resulting mesoporous titania beads can be increased from 5 to 13 nm by doubling the carbon chain length of the n-alkylamine from 8 to 16, along with an increase in the corresponding pore volumes from 0.12 to 0.41 cm 3 g − 1 .…”

Steel binder cermets processed by combination of colloidal processing and powder metallurgy

“…The colloidal processing has been used for long in ceramics to achieve complex shapes and microstructures [4,5] being less common its use in metals. Recently this technique has being used in the processing of metallic materials as Ni and Ni-ceramic composites for structural or energetic applications [6,7].…”