Preparation and characterization of mullite whiskers from silica fume by using a low temperature molten salt method |
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| Authors: | Wei Wang HongWei LiKunRong Lai KeHui Du |
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| Affiliation: | a Department of Chemical Engineering, College of Environment Science and Engineering, Chang’an University, Xi′an 710054, People's Republic of China
b College of Materials Science and Engineering, Chang’an University, Xi′an 710061, People's Republic of China |
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| Abstract: | Mullite whiskers were prepared from silica fume in molten Al2(SO4)3-Na2SO4 mixture salts at low temperatures. The resulting mullite whiskers, as well as the nucleation and growth mechanism in the molten environment, have been investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TG-DTA) techniques. XRD studies showed that the materials obtained were orthorhombic mullite. SEM, TEM and HRTEM results revealed that the mullite whiskers were single crystal fibers with diameters ranging from 30 to 150 nm and lengths of over several microns. According to thermodynamic analysis, mullite phase might be spontaneously formed in molten salts as the temperature reached the decomposition temperature of aluminum sulfate (1023 K). Moreover, the mullite crystals grew along [1 1 1] crystal plane firstly and developed into fibrous microstructure finally. |
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| Keywords: | Ceramics Thermal analysis Crystal growth Scanning electron microscopy X-ray diffraction |
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