Iron oxides and oxyhydroxides are widespread in nature and play an important role in many geological and biological processes. They are used asiron ores,pigments,catalysts, and inthermite, and occur inhemoglobin. 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 hasE number E172.
Iron oxide pigment. The brown color indicates that iron is at the oxidation state +3.Green and reddish brown stains on a limestone core sample, respectively corresponding to oxides/hydroxides of Fe2+ and Fe3+.
Inblast furnaces and related factories, iron oxides are converted to the metal. Typicalreducing agents are various forms of carbon. A representative reaction starts with ferric oxide:[9]
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 importantpigments, coming in a variety of colors (black, red, yellow). Among their many advantages, they are inexpensive, strongly colored, and nontoxic.[12]
Magnetite is a component of magnetic recording tapes.
^Merlini, Marco; Hanfland, Michael; Salamat, Ashkan; Petitgirard, Sylvain; Müller, Harald (2015). "The crystal structures of Mg2Fe2C4O13, with tetrahedrally coordinated carbon, and Fe13O19, synthesized at deep mantle conditions".American Mineralogist.100 (8–9):2001–2004.Bibcode:2015AmMin.100.2001M.doi:10.2138/am-2015-5369.S2CID54496448.
^abcFakouri Hasanabadi, M.; Kokabi, A.H.; Nemati, A.; Zinatlou Ajabshir, S. (February 2017). "Interactions near the triple-phase boundaries metal/glass/air in planar solid oxide fuel cells".International Journal of Hydrogen Energy.42 (8):5306–5314.doi:10.1016/j.ijhydene.2017.01.065.ISSN0360-3199.
