水热体系合成锂皂石结构的演化和影响规律研究

以氟化锂、氯化镁、水玻璃、氨水为主要原料，采用水热体系合成了锂皂石（Hectorite）。通过化学成分分析、粉末X-射线衍射（XRD）、场发射扫描电镜（SEM）、 傅立叶变换红外光谱（FTIR）、 热重和差示扫描量热（TG-DSC）、激光纳米粒度分析等技术，考察了晶化时间、原料比、晶化温度对锂皂石产物结构演化的影响规律。实验结果表明，采用水热晶化体系合成锂皂石，6 h后体系中即能生成锂皂石。在实验的6～49 h晶化时间范围内，体系为锂皂石、硅酸锂、氟化锂、氢氧化镁等组成的多相共存体系。经72 h晶化后生成结晶好的锂皂石。在水热晶化体系增加锂盐的量，有利于提高锂皂石结晶性，并能促进Li取代片层上六配位Mg，导致产生更高的层电荷和更多的层间可交换离子。提高水热晶化温度，对提高锂皂石产物结晶性有利。晶化时间短，锂皂石产物粒径小，结晶性差，但颗粒分布窄。晶化时间长，锂皂石产物粒径增大，结晶性好，热稳定性提高。

Structure Development of Hectorite in Hydrothermal Crystallization Synthesis Process

Hectorite was synthesized in hydrothermal system by using lithium fluoride, magnesium chloride, water glass, and ammonium hydroxide as starting materials. The structure development in synthesis processes was in- vestigated by chemical composition analysis, powder X-ray diffraction(XRD), field emission scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), thermogravimetry and differential scanning calorimetry(TG-DSC)and laser nano particle size analyzer. The influences of synthesis parameters such as crystal- lization time, hydrothermal temperature and reactant ratio on the structure development of hectorite were explored and discussed. Some hectorite could be formed in 6 h, and the crystallization was completed in 72 h. Between 6 and 49 h the hydrothermal systems comprised hectorite, lithium silicate, lithium fluoride, and magnesium hydrox- ide. The crystallinity of hectorite could be enhanced with more Li substitution for octahedral Mg when the amount of lithium fluoride increased, leading to somewhat higher layer charge, thus more exchangeable cations in the interlayers. With the increasing of the temperature of hydrothermal crystallization the crystallinity of hectorite in- creased accordingly. Under less crystallization time, the obtained hectorite had smaller particle sizes and narrow size distribution with poor crystallinity, on the contrary, the products was in better crystallinity with larger grain sizes and higher thermal stability when the crystallization time was long enough.