Insight into microstructural and magnetic properties of flame-made γ-Fe2O3 nanoparticles

Dan Li; Wey Yang Teoh; Cordelia Selomulya; Robert C. Woodward; Paul Munroe; Rose Amal

doi:10.1039/B711705A

Insight into microstructural and magnetic properties of flame-made γ-Fe₂O₃ nanoparticles†

Dan Li,^a Wey Yang Teoh,^a Cordelia Selomulya,^b Robert C. Woodward,^c Paul Munroe^d and Rose Amal*^a

* Corresponding authors

^a ARC Centre of Excellence for Functional Nanomaterials, School of Chemical Sciences and Engineering, The University of New South Wales, Sydney, Australia
E-mail: r.amal@unsw.edu.au
Fax: +61 2 9385 5966
Tel: +61 2 9385 4361

^b Department of Chemical Engineering, Clayton Campus, Monash University, Melbourne, Australia

^c Centre for Strategic Nano-fabrication, School of Physics, M013, The University of Western Australia, Crawley, Australia

^d Electron Microscope Unit, The University of New South Wales, Sydney, Australia

Abstract

Superparamagnetic and ferromagnetic γ-Fe₂O₃ nanoparticles of different sizes (d_XRD = 6–53 nm) were synthesized via a rapid, one-step flame spray pyrolysis (FSP) technique. Insightful information on the structural characteristics of γ-Fe₂O₃ nanoparticles were obtained by combining extensively various characterisation techniques such as XRD, TEM, EDS, AFM, FTIR, and SQuID magnetometry. The morphology of γ-Fe₂O₃ crystals transformed gradually from near-spherical shapes to 2-D hexagonal/octagonal platelet structures, as a function of increasing particle size. Along with the morphological transformtaion, the synthesized particles evolved from disordered cubic phase to fully ordered tetragonal γ-Fe₂O₃. Saturation magnetisation (M_s) of the nanoparticles increased from 21–74 emu g⁻¹ as a function of particle size up to 13 nm, above which the M_s approached the values reported for bulk γ-Fe₂O₃. The magnetic properties (M_s, exchange bias and coercivity) correlated strongly with the microstructure and the degree of cation vacancy ordering of the nanoparticles. The study provided an insightful view on the use of the flame aerosol technique to design magnetic nanoparticles with closely controlled physicochemical and magnetic properties.

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Article information

DOI: https://doi.org/10.1039/B711705A
Article type: Paper
Submitted: 31 Jul 2007
Accepted: 01 Oct 2007
First published: 10 Oct 2007

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J. Mater. Chem., 2007,17, 4876-4884

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Insight into microstructural and magnetic properties of flame-made γ-Fe₂O₃ nanoparticles

D. Li, W. Y. Teoh, C. Selomulya, R. C. Woodward, P. Munroe and R. Amal, J. Mater. Chem., 2007, 17, 4876 DOI: 10.1039/B711705A

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Journal of Materials Chemistry