A wet-chemical process yielding reactive magnesium aluminate spinel (MgAl2O4) powder

Ammonium carbonate was used as the precipitant to synthesize Mg-Al spinel p recursors from a mixed solution of magnesium and aluminum nitrates. The pre cursor, composed of crystalline ammonium dawsonite hydrate [NH4Al(OH)(2)CO3 .H2O] and hydrotalcite [Mg6Al2(CO3)(OH)(16).4H(2)O] phases, transformed to pure spinel at similar to 900 degreesC via the decomposition of hydrotalcit e at similar to 400-800 degreesC and a solid-state reaction between MgO (de composed from hydrotalcite) and gamma -Al2O3 (derived from NH4Al(OH)(2)CO3. H2O) at similar to 800-900 degreesC. Sinterability of the resultant spinel powders was evaluated by the constant-rate-of-heating sintering method. The effect of calcination temperature on particle morphology and sinterability of the resultant spinel powders was investigated. Spinel ceramics of simil ar to 99% dense were produced by vacuum sintering at 1550 degreesC for 2 h from the powder calcined at 1100 degreesC for 2 h. (C) 2001 Elsevier Scienc e Ltd and Techna S.r.l. All rights reserved.