Spinel fibers from carboxylate precursor

Abstract

A spinel precursor was synthesized from a 1:2 stoichiometric mixture of Al(O 2CH) 3·3H 2O and Mg(O 2CCH 3) 2·4H 2O dissolved in H 2O with stabilizing additives. The precursor, as well as individual compounds were characterized using TGA, DTA, DRIFTS and XRD techniques to establish decomposition profiles. During pyrolysis, Mg(O 2CCH 3) 2·4H 2O decomposes first to an amorphous oxide contaminated with minor amounts of carbonate. At 300°C, rock salt (MgO) crystallizes. The spinel precursor behaves like a separate compound and decomposes directly to crystalline spinel at ≈600°C without any evidence of phase separation. The spinel precursor is easily extruded or hand drawn to form well-defined green fibers. Extruded green fibers (20 μm dia.) were pyrolyzed at 300°C/2 h/air to remove carboxylate ligands, and then heated at 15°C/min to 1500°C/2 h/air to sinter. The mechanical strength of these fibers was evaluated using a bending test method. The final fibers are ≈10 μm in dia., with 1·2±0·4 μm grain size and offer an average bend strength of 1·0±0·4 GPa. ©