Synthesis and characterization of Co - Hydrotalcite - Like compounds

Co-Hydrotalcite-like compounds (Co-HTlcs), as precursors of mixed oxides, were synthesized by coprecipitation technique from Mg(NO₃) ₂·6H₂O, Al(NO₃) ₃·9H₂O and Co(NO₃) ₂·6H₂O, with a constant molar ratio Mg/Al of 1.6 and a variable molar ratio Co/Mg from 0.01 to 0.1. The pH was controlled around 10. It is shown by XRD results, processed with the Winplotr software, that the "c" lattice parameter increases with an increasing of Co/Mg ratio and there is no change on the "a" lattice parameter. This behaviour is discussed and it was attributed to the substitution between the Mg and Co atoms in the hydrotalcite structure. Moreover, the microstructural parameters (crystallite size and strain) were analyzed by XRD, using the Williamson-Hall plot and the Two Stages Approach. It was observed that the crystal perfection is increased as the Co content increases. The morphology and layers size were studied by SEM and it was observed that the particles are stacked and formed by several layers, which causes porosity into the particles.