Acta Phys. -Chim. Sin. ›› 2004, Vol. 20 ›› Issue (03): 318-322.doi: 10.3866/PKU.WHXB20040321

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Preparation and Thermal Decomposition Mechanism of Nanocrystalline Mg, Al-hydrotalcite

Ren Qing-Li;Zhang Zan-Feng;Luo Qiang   

  1. State Key Laboratory of Electrical Insulation for Power Equipment, Xi’an Jiaotong University, Xi’an 710049; School of Technical Physics, Xidian University, Xi’an 710071; School of the Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049; The Second Artillery Institute of Engineering, Xi’an 710025
  • Received:2003-08-13 Revised:2003-10-28 Published:2004-03-15
  • Contact: Ren Qing-Li

Abstract: The preparation and the thermal decomposition mechanism of nanocrystalline Mg, Al-hydrotalcite were studied. The phase composition and the microstructures of the samples were tested by XRD and TEM. The highly pure acicular nanocrystalline Mg, Al-hydrotalcite was synthesized by the one-step liquid reaction method at atmospheric pressure. Based on the DSC, DTA and TG test results, the thermal properties of the nanocrystalline Mg, Al-hydrotalcite were investigated, and two thermal decomposition process stages were recognized. In its first decomposition stage, the crystal water is released. In its second decomposition stage, the hydroxyl(OH-) octahedral structure is destroyed, with the hydroxyl(OH-) released as the gas of H2O and CO32- anion released as the gas of CO2, and MgO and Al2O3 are formed. Moreover, it is also found that the longer the reaction time, the higher the beginning decomposition temperature and the more the amount of the residual oxides (MgO and Al2O3). Besides, the non-isothermal chemical reaction kinetic theory was employed here, and the Šatava-Šesták integral method, Achar differential method and Ozawa integral method were used. After the calculation and comparison, the thermal decomposition mechanical function of the acicular nanocrystalline Mg, Al-hydrotalcite in its second thermal decomposition is confirmed as the functional form of (1-α)-1-1.

Key words: Mg, Al-hydrotalcite, Acicular nanocrystalline, Thermal analysis,  Mechanical function