Further Consideration of the ²⁹Si Nuclear Magnetic Resonance Spectrum of Kaolinite

Abstract

Abstract--The introduction of artificial +b/3 stacking faults into well-crystallized kaolinite by intercalating and removing hydrazine had no observable effect on the solid-state 29Si nuclear magnetic resonance spectrum of kaolinite. Also, the introduction of such stacking faults did not alter the hydroxyl-stretching region of the infrared spectrum, implying no change in the hydrogen bonding between the displaced layers. Calculations of Si...H distances and Si-O...H angles from reported structures for kaolinite indicated that the resolution of the two Si chemical environments was due to differences in hydrogenbonding at the surface of the silicate sheet.

Reactivity of ionic liquids with kaolinite: Melt intersalation of ethyl pyridinium chloride in an urea-kaolinite pre-intercalate

“…It displays two well resolved signals at −91.5 and −90.9 ppm attributed to the existence of two different but equally populated silicon sites. The observation of two different 29 Si NMR signals for kaolinite was reported previously [37][38][39][40][41]45]. It was proposed that interlayer hydrogen bonding resulting in two different silicon environments is the main reason for the 29 Si NMR signal splitting in kaolinite [40].…”

29Si and 27Al magic-angle-spinning NMR studies of the thermal transformation of kaolinite

“…The spectra of parent kaolinites consist of a single resonance at -91.5 ppm with FWHM of 2.5 ppm, characteristic of layered silicates and assigned to a Q3 Si environment (Si linked, via oxygens, to three other Si atoms). We have not observed the splitting of this signal as was sometimes reported (Barron et al 1983 ;Thompson and Barron 1987) under cross-polarization. The spectra of poorly and highly crystalline samples fired at 480 and 500 ~ C, respectively, are similar and exhibit three resolved signals (Figs.…”

New organophilic kaolin clays based on single-point grafted 3-aminopropyl dimethylethoxysilane

“…6b), due to a single grafting point. 47 Consequently, the APMS intercalation process was more efficient and generated long-distance ordered structures (higher crystallinity degrees) of intercalates thereof as reflected by the constant interlayer distances (no staking).…”