Buhl J C, Hoffmann W, Buckermann W A, Müller-Warmuth W
Institut für Mineralogie, Universität Münster, Germany.
Solid State Nucl Magn Reson. 1997 Dec;9(2-4):121-8. doi: 10.1016/s0926-2040(97)00052-0.
The hydrothermal transformation of kaolinite to basic sodalite Na8[AlSiO4]6 (OH.H2O)2 and hydroxoborate sodalite Na8[AlSiO4]6 [B(OH)4]2 has been investigated at different temperatures (353 and 473 K). In the early stage of the reactions, the crystallization kinetics was studied by X-ray powder diffraction, thermogravimetry, IR spectroscopy and 29Si MAS NMR spectroscopy. Besides the crystallization of the sodalites, no further intermediate phases were formed. MAS NMR of the 29Si nucleus has been found to be a versatile tool to follow the progress of reactions from the signal ratio of the initial material and the crystallization product because the differences in chemical shifts result in well-separated signals. From these measurements, the growth rates of the sodalites could be determined quantitatively even for the very early stages of crystallization. It was found that sodium carbonate impurities in the NaOH solution used for the synthesis has an important influence on the reaction kinetics.
在不同温度（353K和473K）下研究了高岭土向碱方钠石Na8[AlSiO4]6 (OH.H2O)2和羟基硼方钠石Na8[AlSiO4]6 [B(OH)4]2的水热转变。在反应初期，通过X射线粉末衍射、热重分析、红外光谱和29Si MAS NMR光谱研究了结晶动力学。除了方钠石的结晶外，没有形成进一步的中间相。由于化学位移的差异导致信号分离良好，因此发现29Si核的MAS NMR是一种通过初始材料和结晶产物的信号比来跟踪反应进程的通用工具。通过这些测量，即使在结晶的非常早期阶段也可以定量确定方钠石的生长速率。发现用于合成的NaOH溶液中的碳酸钠杂质对反应动力学有重要影响。
