高岭石/甲酰胺插层的Raman和DRIFT光谱

用Raman和漫反射红外光谱研究高岭石/甲酰胺插层反应机理及插层作用对高岭石微结构的影响.

Raman and DRIFT Spectra of Kaolinite/Formamide Intercalation Compound

Raman spectroscopy and diffuse reflectance infrared spectroscopy(DRIFT) techniques have been used to study kaolinite and its intercalation compound with formamide. In the hydroxyl stretching vibration region of Raman spectrum, the formamide intercalation resulted in the decrease of the intensities of kaolinite inner surface hydroxyl bands at 3 699, 3 682, 3 665 and 3 642 cm^-1, and the appearance of additional bands at 3 610, 3 628 cm^-1. The two additional bands are attributed to the inner surface hydroxyls which formed hydrogen bond with the formamide C=O group. In the low frequency region of Raman spectrum, the ν_{1(A1g) mode of kaolinite Al(O,OH)6 octahedra consists of two bands at 180 and 193 cm^-1, which shift to a high frequency and become a single band centred at 201 cm^-1 after intercalation. It shows that the intercalation process decreases structural difference among the inner surface hydroxyls and makes them have a same orentation. The fact that the Raman active bands at 3 628 and 3 610 cm^-1 were not observed in the DRIFT spectrum shows that the C=O group is linearly linked with the inner surface hydroxyls and that the vibration group is highly symmetric. In the NH stretching region of DRIFT spectrum, there were two bands at 3 336 and 3 466 cm^-1 corresponding to the two types of the hydrogen bonds between formamide NH group and kaolinite. In the carboxyl stretching region, an additional band at 1 667 cm^-1 is assigned to C=O group that bonded to the inner surface hydroxyl of kaolinite. The formamide intercalation induces that the inner hydroxyl Al-OH vibration band 930 cm^-1 shift to high frequency 933 cm^-1, which is due to that the formamide NH group was keyed into the ditrigonal hole of kaolinite. The formamide intercalation not only resulted in the breaking of the hydrogen bonds between the Al(O,OH)6 octahedral hydroxyl groups and the SiO4 tetrahedral oxygens, but also the formation of new different type hydrogen bonds between formamide molecule and kaolinite inner surface hydroxyl and the SiO4 tetrahedral oxygen.}