Microstructure of iron particles reduced from silica-coated hematite in hydrogen

Yuichi Yonemochi, Motoyuki Iijima, Mayumi Tsukada, Hua Jiang, Esko I. Kauppinen, Mitsumasa Kimata, Masahiro Hasegawa, Hidehiro Kamiya (Corresponding Author)

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Abstract

Poly- and nearly monocrystalline hematite particles having diameters of around 2 and 0.1 μm, respectively, were prepared by the gel-sol method and coated with a uniform silica layer by the sol-gel method. The core in the silica shell was reduced to iron without agglomerate formation between the particles by using a hydrogen stream. The microstructure and morphology of these cores and the silica layers were examined by high-resolution transmission electron microscopy, and electron and X-ray diffraction analysis. In hematite particles, around 2 μm in diameter, the reduced products were mostly α-Fe, but partially magnetite. In hematite particles, around 0.1 μm in diameter, only α-Fe was observed. Most of the raw hematite and iron particles produced were monocrystalline, and part of core grew hexagonal prism-shaped monocrystalline particles. In the case of the growth of a crystal to a hexagonal prism, a nanometer-scaled space at the interface between the iron crystal core and the silica layer was discovered.
Original languageEnglish
Pages (from-to)621-637
JournalAdvanced Powder Technology
Volume16
Issue number6
DOIs
Publication statusPublished - 2005
MoE publication typeA1 Journal article-refereed

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Yonemochi, Y., Iijima, M., Tsukada, M., Jiang, H., Kauppinen, E. I., Kimata, M., Hasegawa, M., & Kamiya, H. (2005). Microstructure of iron particles reduced from silica-coated hematite in hydrogen. Advanced Powder Technology, 16(6), 621-637. https://doi.org/10.1163/156855205774483325