IN-SITU MICROSTRUCTURAL CONTROL OF NI AL2O3 AND NI/NIAL2O4 COMPOSITESFROM LAYERED DOUBLE HYDROXIDES/

The transformation of Ni/Al layered double hydroxides to Ni/Al2O3 and Ni/NiAl2O4 composites was studied via X-ray diffraction and electron m icroscopy. The Ni/Al layered double hydroxide powders, with Ni2+:Al3cation ratios varying from 0.5 to 3.3, were first synthesized by a cop recipitation route. The powders were then reduced ia a tube furnace un der hydrogen to yield Ni/Al2O3 or under a CO/CO2 mixture to yield Ni/N iAl2O4. The reduced powders were uniaxially hot-pressed to form sinter ed pellets. In the case of the Ni/NiAl2O4 hot-pressed composites, the platelike morphology of the precursor was preserved in the final sinte red microstructure. in contrast, due to the nucleation and growth mech anism that takes place in alpha-Al2O3, the Ni/Al2O3 hot-pressed compos ites exhibited no microstructural memory.