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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Aluminosilicates with varying alumina-silica ratios: Synthesis via a hybrid sol-gel route and structural characterisation
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Aluminosilicates with varying alumina-silica ratios: Synthesis via a hybrid sol-gel route and structural characterisation

机译：氧化铝/二氧化硅比例不同的铝硅酸盐：通过混合溶胶-凝胶法合成和结构表征

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摘要

Aluminosilicates with varying Al_2O_3:SiO_2 molar ratios (3:1, 3:2, 3:3 and 3:4) have been synthesized using a hybrid sol-gel route using boehmite sol as the precursor for alumina and tetraethyl orthosilicate (TEOS) as the precursor for silica. The synthesis of boehmite sol from aluminium nitrate, and its use as the alumina precursor, is cost effective compared to alkoxide precursors. Structural aspects, including bonding and coordination, are studied in detail for samples calcined in the temperature range 400-1400 °C using both NMR and FTIR spectroscopy: the results are correlated with phase formation data (spinel and high temperature phases) obtained from XRD and thermal analysis. FTIR results show a broadening of peaks at 800 °C indicating a disordered distribution of octahedral sites caused by crosslinking between AlO_6 octahedral and SiO_4 tetrahedral units prior to the formation of mullite. ~(27)Al MAS NMR spectra are consistent with a progressive decrease in the number of AlO_6 polyhedra with increasing temperature corresponding to Al in these units being forced to adopt a tetrahedral coordination due to the increasing presence of similarly coordinated Si species. XRD results confirm the formation of pure mullite at 1250 °C for a 3Al_2O_3:2SiO_2 system. At 1400 °C, phase pure mullite is observed for all compositions except 3Al_2O_3:SiO_2 where α-Al _2O_3 is the major phase with traces of mullite. The synthesis of aluminosilicates through a hybrid sol-gel route and the detailed insight into structural features gained from spectroscopic and diffraction techniques contributes further to the development of these materials in applications ranging from nanocatalysts to high-temperature ceramics.
机译：使用勃姆石溶胶作为氧化铝和四乙基原硅酸酯（TEOS）的前体，使用杂化溶胶-凝胶途径合成了具有不同Al_2O_3：SiO_2摩尔比（3：1、3：2、3：3和3：4）的硅铝酸盐二氧化硅的前体。与硝酸盐前体相比，由硝酸铝合成勃姆石溶胶及其作为氧化铝前体的用途具有成本效益。使用NMR和FTIR光谱对在400-1400°C温度范围内煅烧的样品的结构方面（包括键合和配位）进行了详细研究：结果与从XRD和XRD获得的相形成数据（尖晶石相和高温相）相关。热分析。 FTIR结果显示在800°C时峰变宽，表明由莫来石形成之前AlO_6八面体和SiO_4四面体单元之间的交联导致八面体位点的无序分布。 〜（27）Al MAS NMR光谱与随着对应于Al的温度升高，AlO_6多面体数目的逐渐减少而一致，这些单元由于相似配位的Si种类的增加而被迫采用四面体配位。 XRD结果证实了3Al_2O_3：2SiO_2系统在1250°C形成纯莫来石。在1400°C时，除3Al_2O_3：SiO_2以外，所有成分均观察到纯莫来石相，其中α-Al_2O_3是含莫来石的主要相。通过混合溶胶-凝胶路线合成铝硅酸盐以及对通过光谱和衍射技术获得的结构特征的详细了解，进一步促进了这些材料在从纳米催化剂到高温陶瓷的应用中的发展。

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