Multinuclear solid-state NMR studies on phase transition of mesostructured aluminophosphate
Multinuclear solid-state NMR studies on phase transition of mesostructured aluminophosphate
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DOI：
10.1016/j.micromeso.2009.06.031
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发表时间：
2010
影响因子：
5.2
通讯作者：
W. Shen;Jun Yang;Shenhui Li;Huazhang Wei;Jun Xu;Hailu Zhang;Qin Zou;Lei Chen;F. Deng
中科院分区：
文献类型：
--
作者：
W. Shen;Jun Yang;Shenhui Li;Huazhang Wei;Jun Xu;Hailu Zhang;Qin Zou;Lei Chen;F. Deng
采用多核固体核磁共振技术，结合低角x射线衍射和元素分析测量，研究了六方结构到层状介观结构磷酸铝的相变过程。XRD结果表明，水热处理9h后，初始的六方相开始转变为片层相。核磁共振还发现，在水热处理的最初2h内，一些初始形成的磷酸铝被水解，无机磷酸铝骨架在相变过程中越来越凝聚。有机表面活性剂在六方相中以间扭式构象为主，而在层状相中以反式构象为主，排列更加紧密。发现Br−阴离子参与了相变，并可能进入界面以补偿因磷酸铝凝聚而产生的负电荷的损失。最后，提出了相变的机理。
The phase transition process from a hexagonal to a lamellar mesostructured aluminophosphate was studied by multinuclear solid-state NMR techniques in combination with low-angle XRD and elemental analysis measurements. The XRD result showed that after hydrothermal treatment for 9h, the initial hexagonal phase began to transform to a lamellar phase. It was also found by NMR that some initially formed aluminophosphate was hydrolyzed during the earliest 2h of the hydrothermal treatment, and the inorganic aluminophosphate framework became more and more condensed during the phase transition. The organic surfactant mainly has a gauche conformation in the hexagonal phase, whereas it mainly has a trans conformation in the lamellar phase and is packed more compactly. The Br−anion is found to be involved in the phase transition and likely enters into the interface to compensate the lost of negative charges that generated by the condensation of the aluminophosphate. Finally, a mechanism for the phase transition is proposed.