Date

2013-06-19

Author

Kaya, Seray
Aydoğan Güngör, Eda
Dericioğlu, Arcan Fehmi

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Micron size barium hexaferrite (BaHF, BaFe12O19) platelets were prepared by molten-salt synthesis method in various weight proportions of NaCl-KCl salt mixtures as the liquid medium. The effects of calcination temperature and molten salt composition –x wt% NaCl and (100-x) wt% KCl-on the formation kinetics and amount of BaHF phase formation as well as on the morphology and magnetic properties of the final products have been discussed. Inductively coupled plasma-mass spectroscopy (ICP-MS) was used to determine the solubility of the starting materials in the salts to understand the formation mechanism of BaHF. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were used to identify the characteristics of the synthesized BaHF platelets. ICP-MS analysis showed that Fe2O3 solubility is negligible, while BaCO3 has very high solubility in both molten KCl and NaCl. Quantitative XRD results showed that the usage of the molten salt containing 100 wt% NaCl results in the highest amount of conversion to BaHF at 900°C in 2 hours. On the other hand SEM results showed that KCl rich molten salt concentrations led to the formation of proper platelet morphology with sharp corners, while NaCl rich ones resulted in smoother platelet shapes. Flux compositions containing 70 to 90 wt% NaCl have led to the largest average platelet size. According to the magnetic measurements, as the content of NaCl in the molten salt increases, hysteresis loss of the ceramics become pronounced pointing out to the achievement of a more hard magnetic behavior in the synthesized BaHF ceramics. The magnetic saturation values of the synthesized ceramics change around 55 emu/g for all the flux compositions, where the highest saturation value is obtained with 44 wt% NaCl, which is 56.5 emu/g. The highest magnetic coercivity values were obtained with 90 wt% NaCl-10 wt% KCl and 100 wt% NaCl flux compositions. In conclusion, the results obtained from the experiments have shown that the composition of the NaCl-KCl molten salts plays an important role on the extent of BaHF formation, along with resulting platelet morphology and magnetic properties.

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https://hdl.handle.net/11511/72381

Collections

Department of Metallurgical and Materials Engineering, Conference / Seminar