规整、均一纳米水滑石晶体的水热合成与表征

Hydrothermal Synthesis and Characterization of Regular and Homogeneous Nanocrystalline Hydrotalcite

采用一种简便的新方法,以Mg2+/Al3+/CO23?摩尔比为6∶2∶1的比例在水热条件下合成了[Mg-Al-CO3]水滑石.获得的水滑石样品用XRD,FE-SEM,TEM,HRTEM,TG-DSC进行了物相、晶体形貌结构和热分析.用动态光散射原理分析了粒度分布,考察了水热合成的主要条件水热温度和时间对水滑石晶体尺寸及粒度分布的影响.结果表明,本法合成的水滑石具有均一、规整的六边形片状晶体形貌,片状晶体直径在350nm左右,片的厚度约20nm,纯水滑石相,粒度分布在80～420nm.水热温度和时间主要影响片状晶体的直径,而对晶体形貌影响不大;延长反应时间,升高水热温度可使六边形晶片长大.

A simple and novel method was developed to synthesize Mg-Al-CO3 hydrotalcite. With this method, Mg^2＋/Al^3＋/CO3^2- hydrotalcite with molar ratio of 6 ： 2 ： 1 was hydrothermally synthesized. The synthesized Mg-Al-CO3 hydrotalcite samples were characterized by X-ray diffraction （XRD）, field emission scanning electron microscope （FE-SEM）, transmission electron microscope （TEM）, high resolution transmission electron microscopy （HRTEM） and thermal analysis （TG-DSC）. The FE-SEM, TEM and HRTEM images show that the hydrotalcite has morphology of a homogeneous and regular hexagonal sheet with thickness of about 20 nm. The XRD results indicated that the synthesized Mg-Al-CO3 hydrotalcite was well crystallized. Furthermore, the distribution of particle size was analyzed with dynamic light scattering technique. The results are consistent with the SEM images and the measured diameter of each hexagon in hydrotalcite is about 350 nm. The effects of preparation condition on the micro-structure were also investigated. It is found that the diameter of the sheet crystal, rather than the morphology, is influenced by hydrothermal treatment temperature and time, indicating that increasing treatment temperature and time only resuits in larger hexagonal crystal.