Characterization of coprecipitated Fe2O3–Al2O3powders
| Autor: | José Manuel Gallardo Amores, Maria del Carmen Prieto, Vicente Sanchez Escribano, Guido Busca |
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| Rok vydání: | 1994 |
| Předmět: | |
| Zdroj: | J. Mater. Chem.. 4:1123-1130 |
| ISSN: | 1364-5501 0959-9428 |
| DOI: | 10.1039/jm9940401123 |
| Popis: | Powders belonging to the Fe2O3–Al2O3 system prepared by a coprecipitation method have been characterized from the point of view of their solid-state and surface structure by X-ray diffraction (XRD), Fourier-transform (far) infrared (FTIR/FT-FIR), diffuse reflectance ultraviolet–visible (DR-UV–VIS) Spectroscopy, BET surface area and porosity and adsorption of probe molecules. In samples calcined at 673 K a disordered defective spinel-type phase, γ-FeAlO3, has been found, containing Fe3+ in octahedral sites and Al3+ in both octahedral and tetrahedral sites, both in the bulk and on the surface. Samples calcined at 1173 K are composed of mixtures of two saturated solid solutions with corundum–haematite-type structures. The surface of these biphasic materials is dominated by the higher reactivity of α-Fe2O3 with respect to α-Al2O3, although tetrahedral Al3+ is also found at the surface of the saturated solid solution of Fe2O3 in α-Al2O3. Al3+ added to Fe2O3 tends to stabilize the spinel-type phase and to hinder sintering, while Fe3+ added to Al2O3 accelerates the γ→α phase transition and sintering. |
| Databáze: | OpenAIRE |
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