FORMATION MECHANISM OF MONODISPERSE PEANUT-TYPE ALPHA-FE2O3 PARTICLES FROM CONDENSED FERRIC HYDROXIDE GEL

被引:85
作者
SUGIMOTO, T
KHAN, MM
MURAMATSU, A
ITOH, H
机构
[1] Institute for Advanced Materials Processing, Tohoku University, Aobaku, Sendai, 980
关键词
FERRIC HYDROXIDE; HEMATITE; MONODISPERSE PARTICLES; PRECIPITATION; SHAPE CONTROL;
D O I
10.1016/0927-7757(93)80178-H
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The formation mechanism of monodisperse peanut-type hematite particles obtained in large quantities from highly condensed ferric hydroxide gel in the presence of sulfate ion, has been studied. It is disclosed that sulfate ions restrain the growth in all directions normal to the c axis. The anisotropy was elucidated in terms of the specific adsorption of sulfate ions onto the subcrystals of each hematite particle, retarding the surface reaction of ferric complexes such as Fe(OH)2+ on the planes parallel to their c axes. From close observation of the surface structure of a growing anisometric particle With a transmission electron microscope and from X-ray diffraction (XRD) analysis of an oriented particulate monolayer of the anisometric particles, the formation mechanism of the peanut-like shape was explained by a characteristic growth mode of the subcrystals on both ends of an ellipsoidal particle. The fundamental growth process is otherwise the same as that of monodisperse pseudocubic hematite particles grown in the absence of sulfate ions through a two-step phase transformation from Fe(OH)3 to beta-FeOOH and from beta-FeOOH to alpha-Fe2O3 via the solution phase.
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页码:233 / 247
页数:15
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