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纳米晶Mg-Al水滑石的水热合成及合成机理

王永在
  

  1. (山东理工大学 分析测试中心, 淄博 255049)
  • 收稿日期:2006-12-26 修回日期:2007-02-11 出版日期:2008-01-20 网络出版日期:2008-01-20

Hydrothermal Synthesis Nano Mg-Al LDHs and its Formation Mechanism

WANG Yong-Zai

  

  1. (Center of Analysis and Testing, Shan Dong University of Technology, Zibo 255049, China)
  • Received:2006-12-26 Revised:2007-02-11 Published:2008-01-20 Online:2008-01-20

摘要: 讨论了不同的Mg、Al源为起始反应物、反应温度、时间和碱度对水热合成Mg-Al水滑石物相组成和晶粒度的影响. 用XRD、SEM对合成产物进行了表征, 用X射线全谱拟合法计算了Mg-Al水滑石晶粒度. 以MgO和Al(OH)3为起始反应物, Mg/Al=2,在140℃反应4~10h, 可以制备出高结晶度的单相纳米晶Mg-Al水滑石. Mg-Al水滑石的形成机理可概括为: 水解反应-沉淀成核-晶粒长大. 反应物类型及合成条件会影响前驱物的水解速率和水解程度, 进而影响晶体成核和生长速率,控制物相的组成和晶粒度大小.

关键词: 纳米晶, Mg-Al水滑石, 水热合成, 全谱拟合法, 合成机理

Abstract: Nano Mg-Al LDHs were prepared by a hydrothermal method in one step. Effects of precursors, alkalinity of the starting solution, temperature and time on phase purity and crystallite sizes of Mg-Al LDHs were systematically investigated. Reaction products were characterized by powder XRD and SEM. Crystallite sizes of Mg-Al LDHs were determined by the X-ray whole powder pattern fitting method. The optimal parameters for preparing Mg-Al LDHs are keeping the ratio of MgO:Al(OH)3:Na2CO3=2:1:1
at 140℃ for 4h to 10h. The formation mechanism proposed for Mg-Al LDHs is dissociationprecipitiationcrystal growth. The reactant type and hydrothermal conditions may influence the dissociation rate of the precursors, nucleation and growth rates of Mg-Al LDHs, as well as phase combination and crystallite sizes of the reaction products.

Key words: nano crystallites, Mg-Al LDHs, hydrothermal synthesis, whole powder pattern fitting, formation mechanism

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