Spinels, iron

Copper (Cu) and zinc (Zn), when mixed, form the alloy brass. Magnesia (MgO) and alumina (AljOj) when mixed in equal proportions form spinel. Iron (Fe) and carbon (C) mix to give carbon steel. 

Aust. J. Soil Res. 16 215-227 Joint Committee on Powder Diffraction Standards Mineral powder diffraction fde. Data book. Published by the JCPDS International Centre for Diffraction Data, Swarfhmore, Pennsylvania, U SA, pp. 942 Jolivet, J.P. Tronc, E. (1988) Interfadal electron transfer in colloidal spinel iron oxide. Conversion of Fe304 to y- Fe203 in aqueous medium. J. Colloid Interface Sci. 125 688—... 

Flexibility of the bulk/surface structure and reaction media effect. For such systems as manganese oxides, copper oxides, spinel iron oxides Fe304-y-Fe203 [4, 5, 24, 25 ], reaction media effect at enhanced temperatures (up to 400 °C ) and at prolonged (up to 10 h) exposures in reaction mixtures was found to remove all initial differences in the phase composition and defect structure. All extended defects were washed out due to interaction with a flux of point defects created by reaction media. As a result, a constant level of the catalytic activity was achieved for these oxide systems demonstrating apparent structural insensitivity of the reaction of CO oxidation. Hence, in this case, great flexibility of the oxide bulk structure allows to reach the same true steady state of the catalyst. 

Ortiz, C., Lim, G., Chen, M. M. Castillo, G. (1988). Physical properties of spinel iron oxide thin films. Journal of Materials Research, 3, 344-50. 

P.A. Castro, E.R. Vago, E.J. Calvo, Surface electrochemical transformations on spinel iron oxide electrodes in aqueous solutions, J. Chem. Soc. Faraday Trans. 92 (1996) 3371—3379. 

Jolivet, J.P. Belleville, P. Tronc, E. Livage, J. (1992), Influence of Fe(II) on the formation of the spinel iron oxide in alkaline medium. Clays Clay Miner., 40(5) 531-539. 

Kojima, K Miyazaki, M. Mizukami, F. Maeda, K. (1997), Selective formation of spinel iron oxide in thin films by complexing agent-assisted sol-gel processing.. Sol-Gel Sci. TechnoL, 8 77-81. 

V. FLOW PROCESS FOR THE PRODUCTION OF SPINEL IRON OXIDE... 

Spinel ferrites, isostmctural with the mineral spinel [1302-67-6] MgAl204, combine interesting soft magnetic properties with a relatively high electrical resistivity. The latter permits low eddy current losses in a-c appHcations, and based on this feature spinel ferrites have largely replaced the iron-based core materials in the r-f range. The main representatives are MnZn-ferrites (frequencies up to about 1 MH2) and NiZn-ferrites (frequencies 1 MHz). 

Reaction 3 also occurs on cooling since the concentration of SO is very low at roaster temperatures of 950°C and approaches zero at 1000°C. Another important reaction that occurs during roasting is the formation of zinc ferrite, Zn0-Fe2 03 above 650°C (see Ferrites). Zinc ores contain 5—12% iron. Zinc ferrite forms soHd solutions with other spinels, such as Fe0-Fe203, and therefore the zinc—iron compositions formed are of indefinite stoichiometry. Ferritic zinc is difficult to solubilize in hydrometaHurgical leaching but several recovery processes are discussed below. 

Garnets have played an important role in the development of highly sophisticated microwave devices since the development of yttrium—iron garnet, yttrium iron oxide [12063-56-8]. The iron is strongly constrained to be trivalent in order to maintain electrical neutraUty in the crystal, which is essential for low microwave losses. Garnets have lower values of saturation magneti2ation than spinels, but provide superior performance in microwave devices because they have a narrower resonance line width. 

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