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• 作者：Petr Br谩zda ; Jaroslav Kohout ; Petr Bezdi膷ka ; Tom谩拧 Kmje膷
• 刊名：Crystal Growth & Design
• 出版年：2014
• 出版时间：March 5, 2014
• 年：2014
• 卷：14
• 期：3
• 页码：1039-1046
• 全文大小：396K
• 年卷期：v.14,no.3(March 5, 2014)
• ISSN：1528-7505

文摘

The influence of added sucrose on the phase composition of iron oxide nanoparticles was studied in the Fe₂O₃/SiO₂ nanocomposites. The nanocomposites were prepared by impregnation of mesoporous silica SBA-15 with iron nitrate containing various amounts of sucrose and their subsequent annealing at 1100 and 1200 掳C. The phase composition of the iron oxide nanoparticles in the prepared nanocomposites was analyzed by X-ray diffraction and ⁵⁷Fe M枚ssbauer spectroscopy on polycrystalline samples. Profile analysis of the X-ray diffraction maxima was used to determine the apparent crystallite size of the different polymorphs. The content of 尾-Fe₂O₃ in the samples increased with an increasing amount of sucrose, and no 尾-Fe₂O₃ was observed in the samples without sucrose. These samples contained only 蔚-Fe₂O₃ and hematite. The apparent crystallite size was found to be similar for both hematite and 尾-Fe₂O₃. Therefore, sucrose was identified as the primary variable, which directs the 蔚-Fe₂O₃ transformation to either hematite or 尾-Fe₂O₃. Our findings shift the way we understand the 尾-Fe₂O₃ formation from 蔚-Fe₂O₃ in the Fe₂O₃/SiO₂ system from the size-directed to the starting material-directed transformation.