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Nanocrystalline Maghemite (γ‐Fe 2 O 3 ) in Silica by Mechanical Activation of Precursors
Author(s) -
Xue Junmin,
Zhou Zhaohui,
Wang John
Publication year - 2002
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2002.tb00176.x
Subject(s) - nanocrystalline material , superparamagnetism , activation energy , materials science , maghemite , mössbauer spectroscopy , phase (matter) , chemical engineering , nanocrystal , matrix (chemical analysis) , analytical chemistry (journal) , magnetization , nanoparticle , chemistry , crystallography , nanotechnology , composite material , physics , organic chemistry , quantum mechanics , magnetic field , engineering , chromatography
γ‐Fe 2 O 3 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 Fe 3 O 4 in a highly activated matrix. Increasing the mechanical‐activation time led to a phase transformation from Fe 3 O 4 to γ‐Fe 2 O 3 . The γ‐Fe 2 O 3 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‐Fe 2 O 3 . The mechanical‐activation‐grown γ‐Fe 2 O 3 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‐Fe 2 O 3 derived from 30 h of mechanical activation exhibited a value of saturation magnetization as high as 62.6 emu/g.