Dependence of the oxide-support interaction on the size and nature of iron oxide particles on SiO 2

• Published in: The Journal of physics and chemistry of solids Vol. 58; no. 12; pp. 2119 - 2125
• Main Authors: Marchetti, S.G., Cagnoli, M.V., Alvarez, A.M., Gallegos, N.G., Bengoa, J.F., Yeramian, A.A., Mercader, R.C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1997
• Subjects: A. microporous materials; A. oxides; C. Mössbauer Spectroscopy; D. surface properties; D. surface properties; A. microporous materials; A. oxides; C. Mössbauer Spectroscopy
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/S0022-3697(97)00161-3

The thermal dependence of the hyperfine fields and of the relative Mössbauer factors have been used to investigate the oxide-support interaction in the Fe-SiO 2 system. The calcination temperature (698, 898 and 1098 K in N 2) has an influence on the nature and particle size of the iron species, while the atmosphere (air and N 2 at 698 K) affects the oxide particle size only. α-Fe 2O 3 particle diameters of ≅ 45 and ≅ 150 A ̊ were found for samples calcinated at 698 K in air and nitrogen, respectively. γ-Fe 2O 3 particles of ≅ 90 A ̊ were obtained after calcination in air at 898 K and migration of iron ions into the SiO 2 matrix was verified after the 1098 K heat treatment. It is found that for α-Fe 2O 3, the smaller particles have a stronger oxide-support interaction and γ-Fe 2O 3 particles have an even higher strength than α-Fe 2O 3.