Nanocrystalline Maghemite (γ-Fe2O3) in Silica by Mechanical Activation of Precursors

• Published in: Journal of the American Ceramic Society Vol. 85; no. 4; pp. 807 - 811
• Main Authors: Xue, Junmin, Zhou, Zhaohui, Wang, John
• Format: Journal Article
• Language: English
• Published: Westerville, Ohio American Ceramics Society 01.04.2002; Blackwell; Wiley Subscription Services, Inc
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; ferrites; magnetic materials/properties; Materials science; nanoparticulates; Nanoscale materials and structures: fabrication and characterization; Physics; Raman spectra; Inorganic compounds; Phase transformations; Transition element compounds; Crystallization; Moessbauer spectroscopy; Oxides; XRD; Amorphous state; Experimental study; Mechanical activation; Transmission electron microscopy; Alpha phase; Valence; DSC; Gamma phase; Silicon oxides; Matrices; Iron oxides; Nanocrystal
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1151-2916.2002.tb00176.x

γ‐Fe2O3 nanocrystallites dispersed in an amorphous silica matrix have been successfully prepared for the first time by mechanical activation of a chemistry‐derived precursor at room temperature. The initial 10 h of mechanical activation triggered the formation of nanocrystallites of Fe3O4 in a highly activated matrix. Increasing the mechanical‐activation time led to a phase transformation from Fe3O4 to γ‐Fe2O3. The γ‐Fe2O3 phase was well established after mechanical activation of the precursor for 30 h. Further increasing the mechanical‐activation time to 40 h induced the formation of α‐Fe2O3. The mechanical‐activation‐grown γ‐Fe2O3 nanocrystallites were ∼10–12 nm in size and well dispersed in the silica matrix, as observed using TEM. They demonstrated superparamagnetic behavior at room temperature when measured using a Mössbauer spectrometer and a vibrating sample magnetometer (VSM). In addition, the γ‐Fe2O3 derived from 30 h of mechanical activation exhibited a value of saturation magnetization as high as 62.6 emu/g.