Time-resolved in situ X-ray diffraction study of the liquid-phase reconstruction of Mg-Al-carbonate hydrotalcite-like compounds
Time-resolved in situ X-ray diffraction study of the liquid-phase reconstruction of Mg-Al-carbonate hydrotalcite-like compounds
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DOI：
10.1039/b002827o
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发表时间：
2000-01-01
影响因子：
--
通讯作者：
O'Hare, D
中科院分区：
文献类型：
--
作者：
Millange, F;Walton, RI;O'Hare, D
采用共沉淀法合成了类水镁石型Mg 2 +/Al 3+层状双氢氧化物（LDH）。通过X射线衍射、红外光谱和热重分析对起始LDH和煅烧产物（二元氧化物和尖晶石的混合物）进行了表征。这些技术使我们能够确认双氢氧化物具有水镁石样结构，其中阳离子是八面体排列。在中等温度下，煅烧产物具有类MgO结构，其中Al离子溶解在晶格中以形成固溶体。在高温（高达1000摄氏度）下煅烧产生对应于MgO和MgAl 2 O 4（尖晶石）的良好结晶相的混合物。采用时间分辨能量色散X射线衍射（EDXRD）原位研究了400 ℃焙烧后层状双金属氢氧化物的重构过程。反应的动力学数据已经确定，并使用Avrami-Erofe'ev成核-生长模型建模，与起始材料溶解和LDH从溶液中结晶的过程一致。
The brucite-like Mg2+/Al3+ layered double hydroxide (LDH) was synthesized by using the coprecipitation method and calcined at a variety of temperatures. The starting LDH and the calcination products (mixtures of binary oxides and spinels) were characterized by X-ray diffraction, IR spectroscopies and thermogravimetric analysis. These techniques allowed us to confirm that the double hydroxide possesses a brucite-like structure in which cations are octahedrally arranged. At moderate temperatures, the calcination products have a MgO-like structure where Al ions are dissolved in the lattice to form a solid solution. Calcination at high temperatures (up to 1000 degrees C) yields a mixture of well-crystallized phases corresponding to MgO and MgAl2O4 (spinel). The reconstruction of layered double hydroxides from material calcined at 400 degrees C has been studied in situ by time resolved energy dispersive X-ray diffraction (EDXRD). Kinetic data for the reaction have been determined and modelled using the Avrami-Erofe'ev nucleation-growth model, consistent with the process taking place by dissolution of the starting material and crystallisation of the LDH from the solution.