Iron (III) oxide or ferric oxide is an inorganic compound with the formula Fe 2 O 3 . This is one of the three main iron oxides, the other two being iron (II) oxide (FeO), which are rare, and iron (II, III) oxide (Fe 3 O 4 ), which also occurs naturally as mineral magnetite. As a mineral known as hematite, Fe 2 O 3 is the main source of iron for the steel industry. Fe 2 O 3 is ferromagnetic, dark red, and easily attacked by acid. Iron (III) oxide is often called rust, and is acidic and to some extent the label is useful, because the rust has several properties and has the same composition. For a chemist, rust is considered an obscure material, described as a hydrated iron oxide.
Video Iron(III) oxide
Structure
Fe 2 O 3 can be obtained in various polymorphs. The main,? and ?, iron adopts octahedral coordination geometry. That is, each Fe center is tied with six oxygen ligands.
Alpha Phase
? -Fe 2 O 3 has a rhombohedral structure, corundum (? -Al 2 O 3 ) and the most common form. It occurs naturally as a mineral hematite that is mined as the main iron ore. It is antiferomagnetic under ~ 260 K (Morin transition temperature), and shows weak ferromagnetism between 260 K and NÃ © temperature, 950 K. It is easy to prepare using thermal decomposition and precipitation in liquid phase. Its magnetic properties depend on many factors, eg. pressure, particle size, and magnetic field intensity.
Gamma phase
? -Fe 2 O 3 has a cubic structure. It is metastable and converted from the alpha phase at high temperatures. It happens naturally as a maghemite mineral. It is ferromagnetic and finds applications in cassette recordings, although ultrafine particles smaller than 10 nanometers are superparamagnetic. This can be prepared by thermal dehydration of gamma iron (III) oxides-hydroxides. Another method involves the careful oxidation of iron (II, III) oxide (Fe 3 O 4 ). The ultrafine particles can be prepared by thermal decomposition of iron (III) oxalate.
Other phases
Several other phases have been identified or claimed. The -phase is the center-centered cubic (Ia3 space group), metastable, and at temperatures above 500 ° C (930 ° F) converts to the alpha phase. This can be prepared by reducing hematite by carbon, pyrolysis of iron (III) chloride solution, or thermal decomposition of iron (III) sulfate. The epsilon phase is rhombic, and shows the nature between alpha and gamma, and may have useful magnetic properties. Preparation of pure epsilon phase has proved very challenging due to contamination with the alpha and gamma phases. Material with a high proportion of epsilon phase can be prepared by gamma phase thermal transformation. This phase is also metastable, changing into an alpha phase between 500 and 750 ° C (930 and 1,380 ° F). It can also be prepared by iron oxidation in an electric arc or with sol-gel precipitation of iron (III) nitrate. Moreover at high pressure amorphous form is claimed. Recent research has revealed the epsilon iron (III) oxide in an ancient Chinese Jian ceramic glaze, which can provide insight into ways to produce that form in the laboratory.
Maps Iron(III) oxide
Hydrated iron (III) oxide
Some Iron hydrate (III) oxide exists. When the alkali is added to the dissolved Fe (III) salt solution, the gelatin form is red-brown. This is not Fe (OH) 3 , but Fe 2 O 3 Ã, Â · H 2 O (also written as Fe (O) OH). Some forms of hydrated oxide of Fe (III) are also present. The Red lepidocrocite ? -Fe (O) OH, occurs on the outside of the rusticles, and the orange goethite , which occurs internally in the rusticles. When Fe 2 O 3 Ã, Â · H 2 O is heated, the water loses hydration. Further heating at 1670 K converts Fe 2 O 3 to black Fe 3 O 4 (Fe II III 2 O 4 ), known as mineral magnetite . Fe (O) OH is soluble in acid, giving [Fe (OH 2 ) 6 ] 3 . In aqueous aqueous alkalies, Fe 2 O 3 gives [Fe (OH) 6 ] 3 - .
Reaction
The most important reaction is the reduction of carbothermal, which gives the iron used in steel making:
Another redox reaction is a very exothermic thermic reaction with aluminum.
- 2 Al Fe 2 O 3 -> 2 Fe Al 2 O 3
This process is used to weld thick metals such as railways using ceramic containers to drain the melting iron between the two rail sections. Thermite is also used in weapons and making sculptures and small-scale cast iron tools.
Partial reduction with hydrogen at about 400 Â ° C results in magnetite, black magnetic materials containing Fe (III) and Fe (II): 2 O 3 H 2 -> 2 Fe 3 O 4 H 2 O
Iron (III) oxide is insoluble in water but easily soluble in strong acids, such as hydrochloric acid and sulfate. It also dissolves in chelating agent solutions such as EDTA and oxalic acid.
Iron heater (III) oxide with other metal oxides or carbonates produces a material known as ferrite: Zn (FeO 2 ) 2
Preparation
Iron (III) oxide is a product of iron oxidation. These can be prepared in the laboratory by electrolysis sodium bicarbonate solution, inert electrolyte, with anode iron:
- 4 Fe 3 O 2 2 H 2 O -> 4 FeO (OH)
The resulting hydrated iron (III) oxide, written herein as Fe (O) OH, is dehydrated about 200 ° C.
- 2 FeO (OH) -> Fe 2 O 3 H 2 O
Usage
Iron industry
The exceptional application of iron (III) oxide is as a raw material for steel and iron industries, such as the production of iron, steel, and many alloys.
Polishing
The very fine powder of iron oxide is known as "rouge jewelry", "red rouge", or just rouge. Used for final polishing on jewelery and metallic lenses, and historically as cosmetic. Rouge cuts slower than some modern polishes, such as cerium (IV) oxide, but is still used in optical fabrication and by jewelry for the end result that can be produced. When polishing gold, the rouge slightly stains the gold, which contributes to the appearance of the finished piece. Rouge is sold as a powder, paste, attached to a polish cloth, or a solid rod (with a wax or fat binder). Other polishing compounds are also often called "rouge", even when they do not contain iron oxide. Jewelers remove the remaining rouge on jewelry by using ultrasonic cleaning. Products sold as "stropping compounds" are often applied to the skin of the skin to assist in obtaining a razor on a knife, straight razor, or other cutting tool.
Pigment
Iron (III) oxide is also used as a pigment, with the names "Brown Pigment 6", "Chocolate Pigment 7", and "Red Pigment 101". Some of them, e.g. Pigment Red 101 and Pigment Brown 6, approved by the US Food and Drug Administration (FDA) for use in cosmetics. Iron oxide is used as a pigment in a joint composite of titanium oxide.
Hematite is a characteristic component of Swedish red paint Falu color.
Magnetic recording
Iron (III) oxide is the most commonly used magnetic particle in all types of magnetic storage and recording media, including magnetic disk (for data storage) and magnetic tape (used in audio and video recording and data storage). Its use in computer disks is replaced by cobalt alloys, allowing thinner magnetic films with higher storage densities.
Photocatalysis
Because of its acidic nature (1.9-2.2 eV) lies in the intense region of the solar spectrum ,? -Fe 2 O 3 has been studied as a photoanode for solar water oxidation. However, its efficacy is limited by the short diffusion length (2-4Ã, m) of the photo-excited load and subsequent rapid recombination, requiring a large overpotential to induce reactions. Research has focused on improving the water oxidation performance of Fe 2 O 3 using nanostructuring, surface functionalization, or by using alternative crystal phases such as? -Fe 2 O 3 .
Medicine
The zinc oxide mixture with about 0.5% iron (III) oxide is called calamine, which is the active ingredient of calamine lotion.
See also
- Chalcanthum
- https://www.instagram.com/oleighsa_osanakpo/
References
External links
- The NIOSH Pocket Guide for Chemical Hazards
Source of the article : Wikipedia
0 Comments