GLYCINE NITRATE COMBUSTION SYNTHESIS OF OXIDE CERAMIC POWDERS

A new combustion synthesis method, the glycine-nitrate process, has been used to prepare oxide ceramic powders, including substituted chromite and manganite powders of high quality. A precursor was prepared by combining glycine with metal nitrates in their appropriate stoichiometric ratios in an aqueous solution. The precursor was heated to evaporate excess water, yielding a viscous liquid. Further heating to about 180°C caused the precursor liquid to autoignite. Combustion was rapid and self-sustaining, with flame temperatures ranging from 1100 to 1450°C. The chromite product was compositionally homogeneous with a specific surface area of 32 m2/g, while the manganite product was composed of two distinct phases with a 23 m2/g surface area after calcination. When compared to similar compositions made using the amorphous citrate process, glycine-nitrate-produced powders had greater compositional uniformity, lower residual carbon levels and smaller particle sizes. © 1990.