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Mullite whiskers were prepared from Si powders in molten Al2(SO4)3-Na2SO4 mixture salts with different Al/Si molar ratio (R) of raw materials. The resulting mullite whiskers, had been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and infrared spectroscopy analysis (FT-IR). Mullite phase was obtained in molten salts when the temperature reached at 850 ℃. SEM and EDS results revealed that two kinds of microstructures were formed in the final product, Al-rich mullite pellets and clusters of tiny mullite crystals, and the content of Al-rich mullite pellets increased with the higher Al/Si molar ratio (R) adopted in raw materials. A new oxidation-dissolution mechanism was proposed to explain mullite whiskers growth. According to thermodynamic analysis, mullite phase might be spontaneously formed as the temperature reached the decomposition temperature of aluminum sulfate (1023 K).


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Mullite whiskers prepared by molten salt method using Si powders

Show Author's information Wei WANGa,*( )Hongwei LIbYajie GUObQiang SUNaChen CHENa
Department of Chemical Engineering, College of Environment Science and Engineering, Chang'an University, Xi'an 710054, China
College of Materials Science and Engineering, Chang'an University, Xi'an 710061, China

Abstract

Mullite whiskers were prepared from Si powders in molten Al2(SO4)3-Na2SO4 mixture salts with different Al/Si molar ratio (R) of raw materials. The resulting mullite whiskers, had been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and infrared spectroscopy analysis (FT-IR). Mullite phase was obtained in molten salts when the temperature reached at 850 ℃. SEM and EDS results revealed that two kinds of microstructures were formed in the final product, Al-rich mullite pellets and clusters of tiny mullite crystals, and the content of Al-rich mullite pellets increased with the higher Al/Si molar ratio (R) adopted in raw materials. A new oxidation-dissolution mechanism was proposed to explain mullite whiskers growth. According to thermodynamic analysis, mullite phase might be spontaneously formed as the temperature reached the decomposition temperature of aluminum sulfate (1023 K).

Keywords:

chemical preparation, whiskers, mullite, infrared spectroscopy
Received: 14 September 2012 Revised: 04 November 2012 Accepted: 12 November 2012 Published: 09 January 2013 Issue date: December 2012
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Publication history

Received: 14 September 2012
Revised: 04 November 2012
Accepted: 12 November 2012
Published: 09 January 2013
Issue date: December 2012

Copyright

© The author(s) 2012

Acknowledgements

This work was supported by the Fundamental Research Funds for the Central Universities (CHD2009JC143) and the Open Fund of State Key Laboratory for Mechanical Behavior of Materials (201011004).

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