27Al multiple-quantum MAS NMR of mechanically treated bayerite (α-Al(OH)3) and silica mixtures

Two-dimensional (27)Al multiple-quantum magic angle spinning (MQMAS) NMR experiments are used to study mixtures of bayerite (alpha-Al(OH)(3)) with either silicic acid (SiO(2).nH(2)O) or silica gel (SiO(2)) that have been ground together for varying lengths of time. This mechanical treatment produces changes in the (27)Al 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 (27)Al NMR spectra for each of these species. The presence of significant distributions of both (27)Al 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.