Organic gels in the preparation of silico-aluminate powders. II. Cordierite

The elaboration of cordierite powders from aqueous or alcoholic solutions, gelled by organic polymers, has been studied. The aqueous solution, made from Al and Mg nitrates or citrates and Si alkoxide, tetraethylorthosilicate (TEOS) or 3-(triethoxysilyl)propylamine (TESPA), is gelled by polyacrylamide and the aqueous gel is calcined at 750°C. The behaviour of the powder depends strongly on the precursor solution. A powder produced from citrates and TESPA expands upon sintering to a porous cordierite, while that elaborated from nitrates and TEOS densifies completely before crystallizing into μ- and then -cordierite.

In the same way, an ethanolic solution of nitrates and TEOS, gelled by poly(2-hydroxyethyl methacrylate) (pHEMA) produces a very homogeneous powder that densifies completely; -cordierite is obtained at a particularly low temperature (1000°C).