Iron oxides maghemite

In the case of roasting, the pretreatment process destroys the sulfide matrix by driving off sulfur from the structure. This results in the formation of iron oxide particles that are made of concentrically zoned and porous hematite and maghemite (Paktunc et al. 2006). Arsenic is volatilized as As203 and oxidised to... 

D. Miser, E. J. Shin, M. R. Hajaligol, and F. Rasouli, HRTEM characterization of phase changes and the occurrence of maghemite during catalysis by an iron oxide, Appl. Catal. A Gen. 258(1), 7-16 (2004). 

Leland and Bard (1987) found that the different iron oxides induced photooxidation of oxalate and sulphite at rates that varied by up to two orders of magnitude. For oxalate, the rate was greater for maghemite than for hematite, but this order was reversed for sulphite. Lepidocrocite (layer structure) induced faster oxidation of both compounds that did the other polymorphs of FeOOH (tunnel structures) the authors considered that the rate differences were probably associated with structural differences between the adsorbents. 

Burnishing is the formation of black-brown oxide films on iron and its alloys by controlled oxidation of cleaned metal surfaces. These films are extremely complex and contain, in addition to maghemite and magnetite (or a substituted magnetite for Ni, Mo or Co alloys), various nitride phases - Fe4N, FeaN and FeN. The nitride phases are adjacent to the metal and the iron oxides are in the outer layers of the film (Gebhardt, 1973). 

Litter, M.I. Baumgartner, E.C. Urmtia, G.A. Blesa, M.A. (1991) Photodissolution of iron oxides. 3. Interplay of photochemical and thermal processes in maghemite/carboxylic acid systems. Environ. Sci. Technol. 25 1907-1913... 

Schwertmann, U. Eechter, H. (1984) The influence of aluminum on iron oxides. XI. Aluminum-substituted maghemite in soils and its formation. Soil Sci. Soc. Am. J. 48 1462-1463... 

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