Morphological and magnetic changes during mechano-chemical transformation of lepidocrocite to hematite

Mendelovici, E.; Nadiv, S.; Lin, I. J.

doi:10.1007/bf00563053

Cited by 16 publications

(5 citation statements)

References 12 publications

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“…Later, as a consequence of the interaction of active broken edges following grinding， the particles become agglomerated and, therefore, the specific surface area (nitrogen adsorption) begins to decrease to 7 m2.g-1. These active surface groups are very important in the processes of mechanochemical agglomeration (Mendelovici et al, 1984). Henmi & Yoshinaga (1981) reported a rapid decrease in specific surface area when grinding time increased for imogolite, and at the same time, the particle morphology changed from fibres to coarse aggregates.…”

Section: Si Almentioning

confidence: 99%

Effects of dry grinding on pyrophyllite

1988

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Dry grinding of pyrophyllite (Hillsboro, USA) has been studied by X-ray diffraction (XRD), specific surface area measurements (BET) and scanning electron microscopy (SEM). At the beginning of the grinding process, some effects such as delamination, gliding and folding of the layers, and decrease in particle size were detected by SEM and XRD, resulting in a large increase in specific surface area, up to a maximum of ~ 60 m 2 . g-1. Marked changes in the structure take place between 30 and 32 mins grinding. Longer grinding times increase the degree of disorder and SEM and specific surface area data suggest that aggregation occurs. XRD results indicate that some residual order persists in the degraded structure.

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Section: Si Almentioning

confidence: 99%

Effects of dry grinding on pyrophyllite

1988

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“…[17][18][19][20][21][22][23][24] The formation of hematite by mechanical treatment of iron oxide hydroxides, namely, ␣-FeOOH, ␥-FeOOH, and ␦-FeOOH, has been described. [25][26][27][28][29][30][31][32] The products obtained by grinding have been characterized in terms of their composition under different experimental conditions. However, there is a lack of information about the morphology and texture of the intermediate and final products.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Nanosized Hematite Particles by Mechanical Activation of Goethite Samples

Šubrt

Pérez‐Maqueda

Criado

et al. 2000

Journal of the American Ceramic Society

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Nanosized single crystals of hematite with a very narrow particle size distribution were prepared by mechanical activation of two different goethite samples. Both goethite samples transformed completely into hematite after 70 h grinding time. Transmission electron microscopy showed that the final particles were spherical in shape and of ϳ17 nm average particle size. This particle size was coincident with that estimated from specific surface measurements, indicating that the hematite samples consisted of nonporous and nonaggregated particles. The crystallite size, calculated from the broadening of the XRD peaks, in the hematite samples indicated that particles consisted of single crystals. No influence of the precursor was observed in the products, so both goethite samples yielded identical rounded single crystals with a narrow particle size distribution.

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“…Topotactic transformations and syntheses have relatively higher RTD, otherwise microcrystallinity (XRD-detected "amorphization") is observed. Another factor favouring higher RTD is a low shear rigidity in certain crystallographic planes [23]. Topotaxy is more frequently observed in the thermochemical conversions of clays which are pseudomorphic in character, than in counterpart mechanochemical transformations.…”

Section: Discussionmentioning

confidence: 99%

Comparative study of the effects of thermal and mechanical treatments on the structures of clay minerals

Mendelovici

1997

Journal of Thermal Analysis

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Controlled heating (in air) of clay minerals leads to transformations into disordered structures and recrystallization into new phases at high temperatures. These phase transformations are of topotactic nature. On the other hand, prolonged dry-grinding treatments of the same silicates causes structural amorphization with no recrystallization into new phases. The mechanical energy relaxation mechanism, invoked to explain these differences, accounts for the particle size changes and the large growth of dislocations. The latters affect sensibly the reactivity of the materials submitted to such solid-state treatments.These processes are monitored mostly by XRD, DTA and IR spectroscopy. The latter method allows to study in some silicates submitted to progressive grinding the location and nature of OH groups and water molecules.

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Morphological and magnetic changes during mechano-chemical transformation of lepidocrocite to hematite

Cited by 16 publications

References 12 publications

Effects of dry grinding on pyrophyllite

Effects of dry grinding on pyrophyllite

Preparation of Nanosized Hematite Particles by Mechanical Activation of Goethite Samples

Comparative study of the effects of thermal and mechanical treatments on the structures of clay minerals

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