Thermal behaviour of synthetic pyroaurite-like anionic clay |
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| Authors: | Kovanda F Balek V Dorničák V Martinec P Mašláň M Bílková L Koloušek D Bountseva I M |
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| Institution: | (1) Department of Solid State Chemistry, Institute of Chemical Technology, Technická, 5 166 28 cPrague, Czech Republic;(2) Řež Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 250 68 Řež, Czech Republic;(3) Institute of Geonics CAS, Studentská, 1768 708 00 Ostrava - Poruba, Czech Republic;(4) Department of Physics, Palacky University, Kéíűkovského 8, 772 00 Olomouc, Czech Republic |
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| Abstract: | Thermal behaviour of synthetic pyroaurite-like anionic clay with molar ratio Mg/Fe=2 was studied in the range of 60-1100°C during heating in air. TG/DTA coupled with evolved gas analysis, emanation thermal analysis (ETA), surface area measurements, XRD, IR and Mössbauer spectroscopy were used. Microstructure changes characterized by ETA were in a good agreement with the results of surface area measurements and other methods. After the thermal decomposition of the pyroaurite-like anionic clay, which took place mainly up to 400°C, a predominantly amorphous mixture of oxides is formed. A gradual crystallization of MgO (periclase) and Fe2O3 (maghemite) was observed at 400-700°C by XRD. The MgFe2O4 spinel and periclase were detected at 800-1100°C. The spinel formation was also confirmed by Mössbauer spectroscopy. |
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| Keywords: | layered double hydroxide Mg-Fe hydrotalcite thermal decomposition pyroaurite-like anionic clay ETA |
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