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Synthesis of magnetic nanometer pigment Fe3O4 by co-precipitation and gaseous reduction

M.M.Hessien, Q.Mohsen, A.El-Maghraby

Nanocrystalline magnetite (Fe3O4) powders have been successfully synthesized using both co-precipitation and isothermal gaseous reduction of hematite (Fe2O3). In the co-precipitation route, the ferrite precursors were obtained fromaqueousmixtures of ferrous chloride and ferric chloride with Fe3+/Fe2+ mole ratio equals 2. The precipitation of ferrous ions and ferric ions was carried by using 5 M sodium hydroxide solution. In the isothermal gaseous reduction route, gas composition 20%CO-80%CO2 and reduction temperature 1000oC for 2 hours were used in this study. The effects of synthesis conditions on the formation, crystal phase analysis, morphology analysis, Color characteristics of pigment were investigated.Moreover, the effects of CoOdoping (0, 1, 2, 4 and 7%) on the physicochemical properties ofmagnetite produced via isothermal reduction were also investigated. The powders formed were investigated usingX-ray diffraction (XRD), and scanning electronmicroscope (SEM) while colour propertiesweremeasurement according to the ASTM-C 609-71 by using a colorimeter instrument type Hunter Lab. The results obtained showed that the single-phase Fe3O4 powders were achieved at Fe3+/Fe2+mole ratio value 2 via co-precipitation route with nanocrystalline size for themost intense peak (311) of Fe3O4 phase was in the range of 13.7 nm. In the gaseous reduction route, the single-phase Fe3O4 powders were achieved at 20%CO-80%CO2 gas composition and reduction temperature 1000oC. The crystallite size of the most intense peak of Fe3O4 phase was in the range between 133.9 and 180 nm. The addition of CoOoxide up to 2%to the hematite before reduction enhancing the colouring properties of the magnetite and beyond which a decreasing in the colouring properties were observed. The synthesized pigments were tested in typical ceramic glazes and ceramic bodies. The colouring properties ofCIE- L*a*b* and X,Y, Z color-measurementswere near a commercial black pigment. The results demonstrate the viability of using these powders at 2% CoO in Fe3O4 spinel as black ceramic pigments.