27Al Multiple-Quantum MAS NMR of Mechanically-Treated Bayerite (alpha-Al(OH)3) and Silica Mixtures

Two-dimensional Al-27 multiple-quantum magic angle spinning (MQMAS) NMR experiments are used to study mixtures of bayerite (alpha-Al(OH)(3)) with either silicic acid (SiO2.nH(2)O) or silica gel (SiO2) that have been ground together for varying lengths of time. This mechanical treatment produces changes in the Al-27 MAS and MQMAS NMR spectra that correspond to the formation of new Al species. Mean values of the quadrupolar interaction (P-Q) and isotropic chemical shift (delta(CS)) are extracted from the two-dimensional Al-27 NMR spectra for each of these species. The presence of significant distributions of both Al-27 quadrupolar and chemical shift parameters is demonstrated and the effect of grinding duration on the magnitudes of these distributions is discussed. (C) 2001 by Academic Press.