Spinel fibers from carboxylate precursor

A spinel precursor was synthesized from a 1:2 stoichiometric mixture of Al(O2CH)(3). 3H(2)O and Mg (O2CCH3)(2). 4H20 dissolved in H2O 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(O2CCH3)(2). 4H(2)O decomposes first to an amorphous oxide contaminated with minor amounts of carbonate. At 300 degrees C, rock salt (MgO) crystallizes. The spinel precursor behaves like a separate compound and decomposes directly to crystalline spinel at approximate to 600 degrees 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 mu m dia.) were pyrolyzed at 300 degrees C/2h/air to remove carboxylate ligands, and then heated at 15 degrees C/min to 1500 degrees C/2h/air to sinter. The mechanical strength of these fibers was evaluated using a bending test method. The final fibers are approximate to 10 mu m in dia., with 1.2+/-0.4 mu m grain size and offer an average bend strength of 1.0+/-0.4 GPa. (C) 1999 Elsevier Science Limited. All rights reserved.