反应时间对镁铝水滑石结构的影响

Effect of Reaction Time on the Structure of Mg-Al Hydrotalcite

以NaAlO_2和MgCl_2·6H_2O为主要原料,Na_2CO_3和NaOH为沉淀剂和pH值调节剂,采用共沉淀法,在不同反应时间和反应温度下制备了镁铝水滑石,并利用X射线衍射(XRD)、热重分析(TG)、傅里叶红外光谱(FT-IR)和扫描电子显微镜(SEM)对镁铝水滑石进行表征。结果表明,制备的水滑石的衍射峰强且尖锐,对称性较高,具有良好的结晶度,反应时间增加使水滑石晶面的层间距增加,而且有利于水滑石的结晶与生长;反应时间增加,能延缓水滑石向金属氧化物转化的过程,提高水滑石的热稳定性,水滑石由片状结晶逐步向小尺寸晶型转变,且水滑石晶粒越来越规整;随着温度的升高,水滑石的晶粒结晶性更好但尺寸有增大趋势。

The Mg-Al hydrotalcite was prepared by precipitation method using MgCl 2 ·6H 2 O and NaAlO 2 as the raw material with Na 2 CO 3 and NaOH as precipitator and pH regulator at different reaction time and reaction temperature. The Mg-Al hydrotalcite was characterized by using Fourier transform infrared spectra (FTIR), X-Ray powder diffraction (XRD), thermogravimetric analysis (TG) and scanning electron microscopy (SEM). The results showed that the Mg-Al hydrotalcite had strong diffraction peaks and high symmetry with good crystallinity. The interlayer spacing of hydrotalcite crystal surface was increased with reaction time increasing and is beneficial to the crystallization and growth of Mg-Al hydrotalcite. With the increase of reaction time, the transformation of the Mg-Al hydrotalcite to metal oxide could be delayed, and the thermal stability of the Mg-Al hydrotalcite was improved. The micromorphology of Mg-Al hydrotalcite was gradually transformed from the sheet crystal to the small size crystal, and the grain of the Mg-Al hydrotalcite was more and more regular. With the increase of temperature, the crystallinity of Mg-Al hydrotalcite was better and the size of Mg-Al hydrotalcite increased.