Aqueous Colloidal Processing Of Fluorapatite Bodies

ALBANO, M. P.; GARRIDO, L. B.

Congreso; 55º Congresso Brasileiro de Cerâmica; 2011

In order to produce stable aqueous fluorapatite (FA) suspensions, its surface reactivity in an aqueous solution having two initial pH values with a concentration of ammonium polyacrylate (NH4PA) was investigated as a function of time. The influence of the slip viscosity on the casting rate and the microstructure of the resultant green slip cast compacts was determined. Upon the FA introduction in the aqueous solutions, an initial release of F anions located at the surface was found, which was not dependent of the pH and the presence of dispersant. The increase in the initial pH of the solution above 7 and/or the addition of NH4PA markedly reduced the Ca++/ H+ exchange reaction rate. As a result, well-stabilized concentrated aqueous suspensions could be obtained at pH close to 9. The greater permeability of cakes produced from slips with high viscosity values (0.5 wt% PVA) increased the casting rate.