Structure, Cation Distribution, and Properties of Nanocrystalline Titanomagnetites Obtained by Mechanosynthesis: Comparison with Soft Chemistry

• Published in: Journal of solid state chemistry Vol. 139; no. 1; pp. 66 - 78
• Main Authors: Millot, N., Begin-Colin, S., Perriat, P., Le Caër, G.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01-08-1998; Elsevier
• Subjects: Clusters, nanoparticles, and nanocrystalline materials; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; mechanosynthesis; Mössbauer spectrometry; nanometric particles; Nanoscale materials and structures: fabrication and characterization; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals; Physics; soft chemistry; spinels; Structure of solids and liquids; crystallography; Titanium ferrite; X-ray diffraction; nanometric particles; mechanosynthesis; soft chemistry; X-ray diffraction; spinels; Titanium ferrite; Mössbauer spectrometry; Inorganic compounds; Crushing; Moessbauer spectroscopy; XRD; Ion distribution; Aqueous solutions; Chemical preparation; Thermal annealing; Structure; Soft chemistry; Nanocrystal; Powders; Ball mill; Chemical precipitation; Ternary compounds; Transition element compounds; Experimental study; Mechanical activation; Titanium oxides; Ferrites spinels; High energy; SEM; Surface area; Iron oxides; TEM
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1998.7808

Nanocrystalline Fe-based spinels with composition Fe2.5Ti0.5O4were synthesized using two different routes: soft chemistry and high-energy ball milling. In the first case, two steps were involved: precipitation in an aqueous solution followed by thermal annealing under a reducing mixture of N2/H2/H2O gases. In the second case, the spinel phase was directly formed in the mill at room temperature and under argon atmosphere from Fe, Fe2O3, and TiO2in stoichiometric proportions. The as-prepared powders are characterized by X-ray diffraction, scanning and transmission electron microscopy, surface area measurement, and Mössbauer spectrometry. In both cases, the crystallite's size is about 15 nm, but whereas in the case of mechanosynthesis, the ball-milled powders consist of aggregates, those obtained by soft chemistry are very well dispersed. In contrast to the soft chemistry route, both lattice defects and cation site inversion are induced by high energy ball milling, as evidenced by X-ray diffraction and thermogravimetric analysis. Finally, the particle coercivity is studied and discussed according to particle size and the degree of oxidation of Fe cations inferred from thermogravimetry.