Hydrothermal synthesis of monodisperse α-Fe2O3 hexagonal platelets

Peng, Dengfeng; Beysen, Sadeh; Li, Qiang; Sun, Yi; Yang, Linyu

doi:10.1016/j.partic.2010.05.003

Cited by 60 publications

(20 citation statements)

References 29 publications

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“…Finally, the phase transition was completed at the reaction time of 9 h. The Fe 3 O 4 polyhedral particles show strong ferromagnetic behaviors with the highest saturation magnetization of 80 emu/g and the lowest coercive force of 5 Oe, as shown in Figure 7d. The magnetic properties of α-Fe 2 O 3 hexagonal plates and Fe 3 O 4 polyhedral particles are similar to the previous reports [27,43]. …”

Section: Resultssupporting

confidence: 90%

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Hydrothermal phase transformation of hematite to magnetite

Tsai

2014

Nanoscale Res Lett

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Different phases of iron oxide were obtained by hydrothermal treatment of ferric solution at 200°C with the addition of either KOH, ethylenediamine (EDA), or KOH and EDA into the reaction system. As usually observed, the α-Fe2O3 hexagonal plates and hexagonal bipyramids were obtained for reaction with KOH and EDA, respectively. When both KOH and EDA were added into the reaction system, we observed an interesting phase transformation from α-Fe2O3 to Fe3O4 at low-temperature hydrothermal conditions. The phase transformation involves the formation of α-Fe2O3 hexagonal plates, the dissolution of the α-Fe2O3 hexagonal plates, the reduction of Fe3+ to Fe2+, and the nucleation and growth of new Fe3O4 polyhedral particles.

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Section: Resultssupporting

confidence: 90%

“…Morphologies like wires [19], rods [20], tubes [21], rings [22], disks [23], cubes [24], spheres [25], hexagonal plates of α-Fe 2 O 3 [26,27], and polyhedral particles of Fe 3 O 4 [28,29] have been synthesized successfully.…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal phase transformation of hematite to magnetite

Tsai

2014

Nanoscale Res Lett

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“…It is concluded, from nearly all of these studies, that the nucleation and growth of nano-sized hematite involves a combination of aggregation, dehydration, and condensation reactions among the particles of ferrihydrite (Cornell et al 1989). Note that transformation of ferrihydrite into hematite in Cl-containing solution occurs through an intermediate phase, akaganeite [FeO(OH, Cl)], which was also investigated using TEM (Shindo et al 1993;Park et al 1996;Sugimoto et al 1998;Peng et al 2010). While it might be postulated that evidence of these formation mechanisms would be present within nanohematite, the internal structure has not previously been directly characterized, due to the small particle size.…”

Section: Introductionmentioning

confidence: 99%

Nanopores in hematite ( -Fe2O3) nanocrystals observed by electron tomography

Echigo

Monsegue

Aruguete

et al. 2012

American Mineralogist

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We report the first characterization of the internal structural features within rhombohedral nanocrystals of hematite (α-Fe 2 O 3 ), specifically nanoscale pores (nanopores) within these crystals observed by high-angle annular dark-field scanning transmission electron microscopy tomography. Threedimensional observations of the internal structure of hematite nanocrystals suggest that the nanopores are formed due to a large reduction in solid volume during the transformation of a poorly crystalline precursor [aggregates of ferrihydrite: Fe 8.2 O 8.5 (OH) 7.4 ⋅3H 2 O], which results in the formation of pores between grain boundaries. This formation mechanism is different from those previously reported, such as hollow cores originating from screw dislocations. We also discuss dissolution experiments of the hematite nanocrystals in ascorbic acid solution, in which we demonstrated that the nanopores are reactive sites for dissolution and enlarged by preferential etching. Our findings are of fundamental importance to understanding how certain crystal morphologies, internal structures, defects, and reactive sites occur in nanocrystals formed from a poorly crystalline precursor.

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“…Uniformly sized hematite fine hexagonal platelets are observed when the OH − /Fe III ratio is near to 8-10. As illustrated in Figure 10.1, 2D hexagonal platelets are formed with (001) basal plane and (012) side planes according to hematite hexagonal close-packed (hcp) structure. For low OH − quantity, the growth rates of the (001) and (012) planes are not effectively controlled, and some irregular particles are formed instead of well-defined platelets [11]. The thickness of the platelets also seems to be related to OH − quantity.…”

Section: Versatility Of Hematite Morphologymentioning

confidence: 98%