Thermal, solution and reductive decomposition of Cu-Al layered double hydroxides into oxide products |
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Authors: | Sylvia Britto |
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Affiliation: | Department of Chemistry, Central College, Bangalore University, Bangalore 560 001, India |
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Abstract: | Cu-Al layered double hydroxides (LDHs) with [Cu]/[Al] ratio 2 adopt a structure with monoclinic symmetry while that with the ratio 0.25 adopt a structure with orthorhombic symmetry. The poor thermodynamic stability of the Cu-Al LDHs is due in part to the low enthalpies of formation of Cu(OH)2 and CuCO3 and in part to the higher solubility of the LDH. Consequently, the Cu-Al LDH can be decomposed thermally (150 °C), hydrothermally (150 °C) and reductively (ascorbic acid, ambient temperature) to yield a variety of oxide products. Thermal decomposition at low (400 °C) temperature yields an X-ray amorphous residue, which reconstructs back to the LDH on soaking in water or standing in the ambient. Solution decomposition under hydrothermal conditions yields tenorite at 150 °C itself. Reductive decomposition yields a composite of Cu2O and Al(OH)3, which on alkali-leaching of the latter, leads to the formation of fine particles of Cu2O (<1 μm). |
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Keywords: | Layered double hydroxide Solution decomposition |
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