Modification of magnetic properties of siderite by thermal treatment

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2007
Alkaç, Dilek
Obtaining high magnetic susceptibility phases from HekimhanDeveci siderite orevia preliminary thermal treatment has been the basic target of the thesis study.Thermal decomposition characteristics of samples, determined bythermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC), were referenced in advancement of thestudy. Heat treatment experiments, particularly roasting, were carried out byconventional heating and microwave heating. Results showed that roasting of HekimhanDeveci siderite samples could not be achieved by microwave energywhilst conventional heating experiments recorded success. Subsequentlowintensity magnetic separation of roasted samples gave recovery above 90%, where lowintensity magnetic separation of runofmine sample had failed. Formation of high magnetic susceptibility phases was verified by magneticsusceptibility balance and xray diffraction analysis (XRD), on roasted samples. Statistical modeling was applied to determine the optimum conditions of roastingin conventional heating system; based on heating temperature, time of heating, particle size as factors.It was concluded that roasting at T= 560 ºC, for t= 45 minutes was adequate toobtain desired results. Particle size was noted to be not much effective on the process as other factors at the studied size range. Kinetics (E, n) and reaction mechanism for the thermal decomposition in conventional heating system were evaluated with different solidstate reaction models by interpretation of the model graphs.Threedimensional diffusion reaction models reported to characterize the thermal decomposition well, with values of activation energy (E), E= 85.53 kJ/mol (Jander); E= 85.49 kJ/mol, (GinstlingBrounshtein).

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Citation Formats
D. Alkaç, “Modification of magnetic properties of siderite by thermal treatment,” M.S. - Master of Science, Middle East Technical University, 2007.