David R. Treadwell

Ultrafine titania by flame spray pyrolysis of a titanatrane complex

Ultrafine titania particles can be produced by flame spray pyrolysis of a chelated metal alkoxide. The precursor can be made by reacting a titanium hydrosol with triethanolamine in ethylene glycol. The chelate, dissolved in ethanol, is misted as an aerosol into an oxidizing flame where it undergoes combustion. The combustion process generates particles, probably by a gas phase condensation process, that are discrete single crystals that exhibit some faceting. The powder is a mixture of anatase and rutile (<10%), with a 45±5 m2 g−1 BET surface area. The calculated equivalent spherical diameter (34+4 nm) is consistent with typical particle sizes found in TEM micrographs. The particles are briefly compared with commercial ultrafine particles produced by flame hydrolysis of TiCl4 and by Ti vapor condensation.

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

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.