Iron oxohydroxide-polyacrylic acid magnetic composite materials

• Published in: Journal of magnetism and magnetic materials Vol. 161; pp. L6 - L10
• Main Authors: Mata-Zamora, M.E., Arriola, H., Nava, N., Saniger, J.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1996
• Subjects: Iron oxohydroxide; Maghemite; Magnetite; Mössbauer spectroscopy; Nanometer-sized particles; Polyacrylates; 75.60.Jp; Magnetite; Polyacrylates; Mössbauer spectroscopy; 75.50.Gg; Iron oxohydroxide; Nanometer-sized particles; Maghemite
• ISSN: 0304-8853
• DOI: 10.1016/S0304-8853(96)00459-3

Powdered nanometer-sized precipitates of Fe(II)Fe(III) 2O x (OH) y were obtained by reacting solutions of ferrous-ferric salts with a Fe(III)/Fe(II) ratio < 2, with an excess of ammonium hydroxide. These precipitates were then mixed at room temperature with a solution of polyacrylic acid (PAA) in order to obtain a composite material. The XRD analysis showed that the iron oxohydroxide precipitates, with an average size around 10 nm, were crystalline and had a spinel structure resembling to either magnetite or maghemite. The Mössbauer spectra of the iron oxohydroxide particles presented a major magnetic phase with the double Zeeman splitting characteristic of magnetite and a minor paramagnetic phase probably originated by the nanometer size of the particles. Its structure was found to correspond to a disordered spinel, as result of the analysis of the intrinsic magnetic field and its splitting parameters. The composite material PAA-Fe(II)Fe(III) 2O x (OH) y presented a diffractogram close to the original oxohydroxide, but its Mössbauer spectrum showed a major paramagnetic phase. This change was explained as a consequence of the chemical coordination of the nanometer sized iron oxohydroxides particles with the PAA carboxylate groups.