Processable aluminosilicate alkoxide precursors from metal oxides and hydroxides. The oxide one-pot synthesis process

Abstract

An inexpensive and facile way to make processable aluminosilicate precursors has been developed. In this process, the ‘oxide one-pot synthesis process’, mixtures of SiO₂, Al(OH)₃ and a group I/II hydroxide/oxide, in any stoichiometric ratio, are reacted with one mole of triethanolamine (TEAH₃) per mol of metal, by heating in ethylene glycol (EGH₂) such that the byproduct H₂O distills off. Solvent removal provides relatively moisture- and air-stable, viscous, polymer-like precursors that probably consist of silatrane (TEASi-EGH) and alumatrane [(TEAAl)₄] complexes. Spinel, mullite and cordierite precursor syntheses are described. The mullite and cordierite precursors most probably are homogeneous mixtures of single-metal alkoxides rather than atomically mixed, bi- and tri-metallic alkoxides. The precursors are soluble in common solvents, and offer viscoelastic properties suitable for powder, coating and fibre spinning applications. Pyrolysis (in air) to 700 °C provides glass or ceramic materials with exactly the stoichiometry of the starting oxide mixture.