The composite materials prepared from clay and iron oxides in different weight ratios and temperatures denoted as A85 and E20 were heated at 300 °C in reductive atmosphere and up to 650 °C in inert atmosphere. The changes in the structure, surface and pore properties were examined by XRD, N2 adsorption method and TG, DTA method. The morphology was studied using scanning electron microscope. The heating of composites up to temperature 300 °C in the reductive atmosphere caused the transformation of the present oxide phases. The distribution curve of the heated composites is narrower and is shifted to the lower pores. The composites heated up to 650 °C in the N2 atmosphere showed to the transformation of iron oxide phases to hematite; the composites contained less pores, became denser and due to sintering of iron oxides particles a decrease in specific surface area was observed.
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