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    Hard magnetism in structurally engineered silica nanocomposite

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    Type
    Article
    Authors
    Song, Hyon-Min
    Zink, Jeffrey I.
    Date
    2016-08-02
    Permanent link to this record
    http://hdl.handle.net/10754/678425
    
    Metadata
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    Abstract
    Creation of structural complexity by simple experimental control will be an attractive approach for the preparation of nanomaterials, as a classical bottom-up method is supplemented by a more efficient and more direct artificial engineering method. In this study, structural manipulation of MCM-41 type mesoporous silica is investigated by generating and imbedding hard magnetic CoFe2O4 nanoparticles into mesoporous silica. Depending on the heating rate and target temperature, mesoporous silica undergoes a transformation in shape to form hollow silica, framed silica with interior voids, or melted silica with intact mesostructures. Magnetism is governed by the major CoFe2O4 phase, and it is affected by antiferromagnetic hematite (α-Fe2O3) and olivine-type cobalt silicate (Co2SiO4), as seen in its paramagnetic behavior at the annealing temperature of 430 °C. The early formation of Co2SiO4 than what is usually observed implies the effect of the partial substitution of Fe in the sites of Co. Under slow heating (2.5 °C min−1) mesostructures are preserved, but with significantly smaller mesopores (d100 = 1.5 nm). In addition, nonstoichiometric CoxFe1−xO with metal vacancies at 600 °C, and spinel Co3O4 at 700 °C accompany major CoFe2O4. The amorphous nature of silica matrix is thought to contribute significantly to these structurally diverse and rich phases, enabled by off-stoichiometry between Si and O, and accelerated by the diffusion of metal cations into SiO4 polyhedra at an elevated temperature.
    Citation
    Song, H.-M., & Zink, J. I. (2016). Hard magnetism in structurally engineered silica nanocomposite. Physical Chemistry Chemical Physics, 18(35), 24460–24470. doi:10.1039/c6cp04843a
    Sponsors
    The authors gratefully acknowledge the support from Dong-A University and NSF Grant DBI-1266377. This work also leveraged the support provided by the National Science Foundation and the Environmental Protection Agency under Cooperative Agreement Number, DBI 0830117. We also acknowledge Dr Khashab at King Abdullah University of Science and Technology (KAUST) for her partial help in the magnetization measurement.
    Publisher
    Royal Society of Chemistry (RSC)
    Journal
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS
    DOI
    10.1039/c6cp04843a
    Additional Links
    http://xlink.rsc.org/?DOI=C6CP04843A
    ae974a485f413a2113503eed53cd6c53
    10.1039/c6cp04843a
    Scopus Count
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