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US4382822A Synthetic rhombohedral magnetite pigment

The process wherein said magnetite is calcined at a temperature of from 650°-925° C. in the presence of oxygen to produce alpha ferric oxide is claimed and a synthetic rhombohedral magnetite having a BET surface area of greater than about 13 m 2 /g and an average particle size of less than about 0.08 microns as measures along the long axis is

Mechanism and kinetics of magnetite oxidation under

bipyramidal or rhombohedral morphology. The oxidation kinetics was consistent with a diffusion controlled process. The reaction probably proceeded via the outward diffusion of ferrous ions from the magnetite, forming a magnetite/maghemite core/shell structure in conjunction with the dissolution of maghemite and reprecipitation of hematite.

Highly Ordered Nanostructured Magnetite and Maghemite of

Highly Ordered Nanostructured Magnetite and Maghemite of Micrometric Sized and Rhombohedral Habit Both iron oxyde crystals exhibit magnetic hysteresis, with saturation magnetization of 92.1

High-pressure study of rhombohedral iron oxide, FeO, at

Jan 05, 2007 A possible explanation for these features is that a pressure-induced magnetic spin transition in iron occurs in rhombohedral FeO. It is known that the HS to LS transition of iron occurs in some iron-bearing materials [2, 17, 18]. When the HS to LS transition occurs, the effective ionic radius of iron

As-Prepared Single-Crystalline Hematite Rhombohedra and

Monodisperse nanocrystalline rhombohedral composites of Fe and Fe3O4 magnetic materials have been obtained employing a reduction reaction, in a flowing gas mixture of H2 and N2, of single-crystalline, submicron-sized α-Fe2O3 rhombohedral precursors. This synthesis is significant in that we were able to create a nanocomposite with hard and soft magnetic phases juxtaposed within one discrete

Synthesis, Characterization, and Magnetic Studies of

XRD studies show that iron oxide was formed as α -Fe 2 O 3 instead of the commonly formed magnetite nanoparticles (Fe 3 O 4 ) or a mixture of magnetite (Fe 3 O 4 ) and maghemite ( γ -Fe 2 O 3,cubic), and it has rhombohedral structure. Magnetic measurements showed that iron oxide has five unpaired electrons and is ferromagnetic in nature, Ms

Maghemite an overview ScienceDirect Topics

Maghemitization is an iron-leaching process, usually occurring in the presence of water, that leaves the spinel lattice intact but one-sixth of the octahedral sites vacant. M s of maghemite is therefore somewhat lower than that of magnetite although T C is higher, intermediate between those of magnetite and rhombohedral hematite (αFe 2 O 3).

(PDF) Highly crystalline porous magnetite and vacancy

Porous crystals of magnetite and vacancy-ordered maghemite, rhombohedron-shaped, reaching 150 μm in size, and having remarkably large specific surface area (88.55 m2/g for magnetite, 40.14 m2/g

Titanomagnetite an overview ScienceDirect Topics

Maghemitization is an iron-leaching process, usually occurring in the presence of water, that leaves the spinel lattice intact but one-sixth of the octahedral sites vacant. M s of maghemite is therefore somewhat lower than that of magnetite although T C is higher, intermediate between those of magnetite and rhombohedral hematite (αFe 2 O 3).

Mechanism and kinetics of magnetite oxidation under

bipyramidal or rhombohedral morphology. The oxidation kinetics was consistent with a diffusion controlled process. The reaction probably proceeded via the outward diffusion of ferrous ions from the magnetite, forming a magnetite/maghemite core/shell structure in conjunction with the dissolution of maghemite and reprecipitation of hematite.

High-pressure study of rhombohedral iron oxide, FeO, at

Jan 05, 2007 A possible explanation for these features is that a pressure-induced magnetic spin transition in iron occurs in rhombohedral FeO. It is known that the HS to LS transition of iron occurs in some iron-bearing materials [2, 17, 18]. When the HS to LS transition occurs, the effective ionic radius of iron

Structural Study on Iron Oxide Nanoparticles Prepared by

Magnetite is also known as black iron oxide, magnetic ironore, loadstone, ferrous ferrite, or Hercules stone. It exhibits the strongest magnetism of any transition metal oxide. Maghemite occurs in soils as a crystallographic system is rhombohedral or hexagonal. By

Highly crystalline porous magnetite and vacancy-ordered

Oct 01, 2013 Porous crystals of magnetite and vacancy-ordered maghemite, rhombohedron-shaped, reaching 150 μm in size, and having remarkably large specific surface area (88.55 m 2 /g for magnetite, 40.14 m 2 /g for maghemite) were obtained via topotactical conversion, starting from hydrothermally grown siderite single crystals. The increase in density (from 3.9 g/cm 3 for siderite to 5.24 g/cm 3 for

Ab initio study of the half-metal to metal transition in

Jan 17, 2007 As an example for a metallic state induced by rhombohedral deformation, we show the band structures of magnetite with lattice parameters Δa hex /a hex 0 = −5.5% and Δc hex /c hex 0 = −3.5% in figures 6(c) and (d). The Fe oct –O interatomic distance is 1.97 Å in this case.

Rhombohedron and plate-like hematite (α-Fe2O3

Jan 01, 2021 Hematite (α-Fe 2 O 3) is a very important material extensively used in catalysis, pigments, battery cathodes, photo electrodes, gas sensors, electrochromic films, environmental protection, biomedicine and magnetic devices [,,,,,,,,,,, ]. α-Fe 2 O 3 crystallizes in the rhombohedral system with space group R-3c and lattice parameters

Titanomagnetite an overview ScienceDirect Topics

Maghemitization is an iron-leaching process, usually occurring in the presence of water, that leaves the spinel lattice intact but one-sixth of the octahedral sites vacant. M s of maghemite is therefore somewhat lower than that of magnetite although T C is higher, intermediate between those of magnetite and rhombohedral hematite (αFe 2 O 3).

How do you explain the martitization of magnetite?

Hematite crystallizes in the rhombohedral lattice system while magnetite is cubic. So, magnetite oxidizes and become a hematite but the cubic system of magnetite remains. That's why it is said to

Synthesis, properties, and applications of magnetic iron

Mar 01, 2009 Magnetite is also known as black iron oxide, magnetic iron ore, loadstone, ferrous ferrite, or Hercules stone. It exhibits the strongest magnetism of any transition metal oxide [1],[2] . Maghemite occurs in soils as a weathering product of magnetite, or as a product of heating of other iron

Ferromagnetism Wikipedia

Ferromagnetism is the basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets.In physics, several different types of magnetism are distinguished. Ferromagnetism (along with the similar effect ferrimagnetism) is the strongest type and is responsible for the common phenomenon of magnetism in magnets encountered in everyday life.

Please, How can I differentiate between the different

α-Fe2O3 has the rhombohedral, corundum (α-Al2O3) structure and is the most common form. It occurs naturally as the mineralhematite which is mined as the main ore of iron. It is antiferromagnetic

Hematite Wikipedia

Hematite, also spelled as haematite, is a common iron oxide compound with the formula, Fe 2 O 3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe 2 O 3.It has the same crystal structure as corundum (Al 2 O 3) and ilmenite (FeTiO 3).With this it forms a complete solid solution at temperatures above

A Deposit Model for Magmatic Iron-Titanium-Oxide Deposits

Quebec, Canada, displaying a contour line of equal magnetic-field intensity.. 15 10. The subsystem FeO-Fe. 2. O. 3-TiO. 2. showing major solid solution joins for the cubic (ulvøspinel-magnetite), rhombohedral (ilmenite-hematite), and orthorhombic

Ilmenite Physical Optical Properties, Varieties, Uses

Ilmenite an outstanding tabular group of large parallel-growth crystals; Ilmenite-magnetite by James St. John (Flickr) Ilmenite, otherwise called manaccanite, is a titanium-iron oxide mineral with formula: FeTiO3.It is a noteworthy wellspring of titanium.

Mechanism and kinetics of magnetite oxidation under

bipyramidal or rhombohedral morphology. The oxidation kinetics was consistent with a diffusion controlled process. The reaction probably proceeded via the outward diffusion of ferrous ions from the magnetite, forming a magnetite/maghemite core/shell structure in conjunction with the dissolution of maghemite and reprecipitation of hematite.

Remanent magnetization, magnetic coupling and interface

Another example of a rhombohedral host is Ti-free hematite with very fine lamellae of magnetite or magnetite-maghemite solid solution. Its origin is uncertain, perhaps produced by high-grade metamorphism of an older hematite ore, itself derived by well known desilication of banded iron formation (Schmidt et al. 2007).

Highly crystalline porous magnetite and vacancy-ordered

Oct 01, 2013 Porous crystals of magnetite and vacancy-ordered maghemite, rhombohedron-shaped, reaching 150 μm in size, and having remarkably large specific surface area (88.55 m 2 /g for magnetite, 40.14 m 2 /g for maghemite) were obtained via topotactical conversion, starting from hydrothermally grown siderite single crystals. The increase in density (from 3.9 g/cm 3 for siderite to 5.24 g/cm 3 for

A Deposit Model for Magmatic Iron-Titanium-Oxide Deposits

Quebec, Canada, displaying a contour line of equal magnetic-field intensity.. 15 10. The subsystem FeO-Fe. 2. O. 3-TiO. 2. showing major solid solution joins for the cubic (ulvøspinel-magnetite), rhombohedral (ilmenite-hematite), and orthorhombic

How do you explain the martitization of magnetite?

Hematite crystallizes in the rhombohedral lattice system while magnetite is cubic. So, magnetite oxidizes and become a hematite but the cubic system of magnetite remains. That's why it is said to

Rhombohedral Shape of Hematite Nanocrystals Synthesized

The morphology and structure of hematite nanoparticles synthesized from the widespread technique developed by Matijevic 30 years ago is revisited. The thermolysis of acidic ferric chloride is shown to lead to monodispersed hematite nanocrystallites of rhombohedral shape with facets belonging to the {104} family, as derived from a joint atomic force microscopy (AFM) and transmission electron

Ilmenite Physical Optical Properties, Varieties, Uses

Ilmenite an outstanding tabular group of large parallel-growth crystals; Ilmenite-magnetite by James St. John (Flickr) Ilmenite, otherwise called manaccanite, is a titanium-iron oxide mineral with formula: FeTiO3.It is a noteworthy wellspring of titanium.

Titanomagnetite an overview ScienceDirect Topics

Maghemitization is an iron-leaching process, usually occurring in the presence of water, that leaves the spinel lattice intact but one-sixth of the octahedral sites vacant. M s of maghemite is therefore somewhat lower than that of magnetite although T C is higher, intermediate between those of magnetite and rhombohedral hematite (αFe 2 O 3).

Chapter 4: Minerals Identification Flashcards Quizlet

- Rhombohedral Colorless/ white gray, yellow, green Vitreous luster White streak Highly magnetic. Hematite Iron Oxide Trigonal Red, metallic grey Metallic luster Red streak No cleavages Hardness of 6 Most common Iron Oxide.

Ferromagnetism Wikipedia

Ferromagnetism is the basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets.In physics, several different types of magnetism are distinguished. Ferromagnetism (along with the similar effect ferrimagnetism) is the strongest type and is responsible for the common phenomenon of magnetism in magnets encountered in everyday life.

Research Article Synthesis, Characterization, and Magnetic

instead of the commonly formed magnetite nanoparticles (Fe 3 O 4) or a mixture of magnetite (Fe 3 O 4)andmaghemite( -Fe 2 O 3, cubic), and it has rhombohedral structure. Magnetic measurements showed that iron oxide has

MINERALS Flashcards Quizlet

magnetic iron. Talc (Mg2Si4O10(OH)2) 1 nonmetallic foliated/fine-grained masses white or green or grey greasy metamorphic rocks. Gypsum (CaSO4*2H2O) 2 nonmetallic perfect rhombohedral cleavage colourless weakly soluble in HCl. Plagioclase Feldspar (Na,Ca)(Al,Si)AlSi2O8. 6 nonmetallic massive, cleavable, granular

Mineral Reference

Comments: The iron and titanium oxide mineral ilmenite is present in small amounts in many igneous rocks and placer sands and is the principal titanium ore. Ilmenite forms iron black, thick tabular or acute rhombohedral crystals (hexagonal system), as well as thin plates, compact masses and embedded grains. Luster metallic to dull.

Solved: 38. Which Of The Following Minerals Has Rhombohedr

38. Which of the following minerals has rhombohedral cleavage? a. graphite b. magnetite c. hornblende d. calcite 39. Which of the following statements about the formation of banded iron ore deposits is not correct? a. Formed in early Proterozoic Time when the atmosphere was poor in oxygern b. Composed of hematite and magnetite minerals c.