Template:Short description

File:Almindeligt rust - jernoxid.jpg
Electrochemically oxidized iron (rust)

An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust.<ref name="cor">Template:Cite book</ref>

Iron oxides and oxyhydroxides are widespread in nature and play an important role in many geological and biological processes. They are used as iron ores, pigments, catalysts, and in thermite, and occur in hemoglobin. Iron oxides are inexpensive and durable pigments in paints, coatings and colored concretes. Colors commonly available are in the "earthy" end of the yellow/orange/red/brown/black range. When used as a food coloring, it has E number E172.

StoichiometriesEdit

File:IronOxidePigmentUSGOV.jpg
Iron oxide pigment. The brown color indicates that iron is at the oxidation state +3.
File:Red and green iron oxides.jpg
Green and reddish brown stains on a limestone core sample, respectively corresponding to oxides/hydroxides of Fe2+ and Fe3+.

Iron oxides feature as ferrous (Fe(II)) or ferric (Fe(III)) or both. They adopt octahedral or tetrahedral coordination geometry. Only a few oxides are significant at the earth's surface, particularly wüstite, magnetite, and hematite.

Thermal expansionEdit

Iron oxide CTE (× 10−6 °C−1)
Fe2O3 14.9<ref name=":0">Template:Cite journal</ref>
Fe3O4 >9.2<ref name=":0" />
FeO 12.1<ref name=":0" />

Oxide-hydroxidesEdit

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}}

ReactionsEdit

In blast furnaces and related factories, iron oxides are converted to the metal. Typical reducing agents are various forms of carbon. A representative reaction starts with ferric oxide:<ref>Template:Greenwood&Earnshaw2nd</ref>

Template:Chem2

In natureEdit

Iron is stored in many organisms in the form of ferritin, which is a ferrous oxide encased in a solubilizing protein sheath.<ref>Template:Cite journal</ref>

Species of bacteria, including Shewanella oneidensis, Geobacter sulfurreducens and Geobacter metallireducens, use iron oxides as terminal electron acceptors.<ref>Template:Cite journal</ref>

UsesEdit

Almost all iron ores are oxides, so in that sense these materials are important precursors to iron metal and its many alloys.

Iron oxides are important pigments, coming in a variety of colors (black, red, yellow). Among their many advantages, they are inexpensive, strongly colored, and nontoxic.<ref>Template:Ullmann</ref>

Magnetite is a component of magnetic recording tapes.

See alsoEdit

ReferencesEdit

Template:Reflist

External linksEdit

Template:Sister project

Template:Iron compounds Template:Oxides

Template:Authority control