Aluminum hydroxide microstructural units in gelled media aged, or nonaged, with alcohol and water

Aluminum hydroxide gelled media dispersed and then aged in alcohol (ES) or in water (WS) were prepared with a solid phase concentration equal to 0.45% v/v. The media were characterized through rheological measurements and detailed analysis. Xerogels were obtained through a designed drying process at 8 °C under vacuum for 24 h, followed by a heating treatment at 105 °C and a pressure of 10−3 Pa for 2 h. The xerogel microstructure was carefully investigated using N2 adsorption–desorption methods at 78 K. Rheology data on ES and WS colloidal dispersions were compared with data computed from adsorption isotherms of corresponding xerogels, in order to infer information about particles organization in the dispersions. On this ground, a model for microstructural units dispersed in the liquid phase has been derived. The beneficial action of alcohol in giving xerogel powders with higher specific surface area and higher porosity has been explained on the basis that alcohol produces changes in the corresponding dispersed microstructural units. The effect of the aging time in alcohol and in water was evaluated, and the evolution of all microstructural parameters was described.

The sizes of liquid dispersed crystallites and clusters of Al(OH)3 have been derived from the corresponding xerogel microstructure. The observed effects of alcohol, which is shown to increase surface area and porosity of the xerogels, have been explained.Figure optionsDownload as PowerPoint slide