Structural Evolution in a Hydrothermal Reaction between Nb2O5 and NaOH Solution: From Nb2O5 Grains to Microporous Na2Nb2O6&
详细信息 查看全文
- 作者：Huaiyong Zhu ; Zhanfeng Zheng ; Xueping Gao ; Yining Huang ; Zhimin Yan ; Jin Zou ; Hongming Yin ; Qingdi Zou ; Scott H. Kable ; Jincai Zhao ; Yunfei Xi ; Wayde N. Martens ; and Ray L. Frost
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：February 22, 2006
- 年：2006
- 卷：128
- 期：7
- 页码：2373 - 2384
- 全文大小：747K
- 年卷期：v.128,no.7(February 22, 2006)
- ISSN：1520-5126
文摘
Niobium pentoxide reacts actively with concentrate NaOH solution under hydrothermal conditionsat as low as 120 
C. The reaction ruptures the corner-sharing of NbO7 decahedra and NbO6 octahedra inthe reactant Nb2O5, yielding various niobates, and the structure and composition of the niobates dependon the reaction temperature and time. The morphological evolution of the solid products in the reaction at180 C is monitored via SEM: the fine Nb2O5 powder aggregates first to irregular bars, and then niobatefibers with an aspect ratio of hundreds form. The fibers are microporous molecular sieve with a monocliniclattice, Na2Nb2O6·2/3H2O. The fibers are a metastable intermediate of this reaction, and they completelyconvert to the final product NaNbO3 cubes in the prolonged reaction of 1 h. This study demonstrates thatby carefully optimizing the reaction condition, we can selectively fabricate niobate structures of high purity,including the delicate microporous fibers, through a direct reaction between concentrated NaOH solutionand Nb2O5. This synthesis route is simple and suitable for the large-scale production of the fibers. Thereaction first yields poorly crystallized niobates consisting of edge-sharing NbO6 octahedra, and then themicroporous fibers crystallize and grow by assembling NbO6 octahedra or clusters of NbO6 octahedra andNaO6 units. Thus, the selection of the fibril or cubic product is achieved by control of reaction kinetics.Finally, niobates with different structures exhibit remarkable differences in light absorption and photoluminescence properties. Therefore, this study is of importance for developing new functional materials bythe wet-chemistry process.
C. The reaction ruptures the corner-sharing of NbO7 decahedra and NbO6 octahedra inthe reactant Nb2O5, yielding various niobates, and the structure and composition of the niobates dependon the reaction temperature and time. The morphological evolution of the solid products in the reaction at180 C is monitored via SEM: the fine Nb2O5 powder aggregates first to irregular bars, and then niobatefibers with an aspect ratio of hundreds form. The fibers are microporous molecular sieve with a monocliniclattice, Na2Nb2O6·2/3H2O. The fibers are a metastable intermediate of this reaction, and they completelyconvert to the final product NaNbO3 cubes in the prolonged reaction of 1 h. This study demonstrates thatby carefully optimizing the reaction condition, we can selectively fabricate niobate structures of high purity,including the delicate microporous fibers, through a direct reaction between concentrated NaOH solutionand Nb2O5. This synthesis route is simple and suitable for the large-scale production of the fibers. Thereaction first yields poorly crystallized niobates consisting of edge-sharing NbO6 octahedra, and then themicroporous fibers crystallize and grow by assembling NbO6 octahedra or clusters of NbO6 octahedra andNaO6 units. Thus, the selection of the fibril or cubic product is achieved by control of reaction kinetics.Finally, niobates with different structures exhibit remarkable differences in light absorption and photoluminescence properties. Therefore, this study is of importance for developing new functional materials bythe wet-chemistry process.© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |