کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
72299 | 49016 | 2016 | 6 صفحه PDF | دانلود رایگان |
• Transformation of AlPO4-5 into AlPO4-tridymite was realized by heating with water.
• In situ multinuclear MAS NMR was used to study the phase transformation.
• Water first activates residue amorphous phase to transform into AlPO4-tridymite.
• Water participates the transformation by hydrolysis and condensation reaction.
• Water establishes the mass transportation between AlPO4-5 and AlPO4-tridymite.
Water assisted phase transformation process from crystalized AlPO4-5 to AlPO4-tridymite was studied by the combination of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and in situ multinuclear MAS NMR. It is found that water first activates the residue amorphous aluminophosphate in crystalized AlPO4-5 sample through hydrolysis and condensation reactions. Then the activated aluminophosphate species reassemble into AlPO4-tridymite crystalline. Meanwhile, AlPO4-5 transforms into orthorhombic phase during heating process. With further crystallization of AlPO4-tridymite, the amorphous phase is gradually consumed, and mass transportation between AlPO4-5 and AlPO4-tridymite is established through gradually amorphization of AlPO4-5. Finally, most of the AlPO4-5 transforms into the thermodynamically stable dense phase AlPO4-tridymite.
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Journal: Microporous and Mesoporous Materials - Volume 223, 15 March 2016, Pages 241–246