✍ Scribed by Christian Jäger; João Rocha; Jacek Klinowski
No coin nor oath required. For personal study only.
High-speed MAS gives a three-fold gain in resolution of the m++m -I ( m = 3/Z and -I /2) satellite transitions of I= 5/2 nuclei in polycrystalline samples compared with the conventional "central transition" spectroscopy. This is demonstrated using a standard high-field NMR spectrometer and samples of tieilite and mullite. Signals from four-and six-coordinated Al are separated completely, and mtational sidebands do not overlap. Different six-and four-coordinated Al species can be distinguished.
📜 SIMILAR VOLUMES
41 MAS NMR spectroscopy with 'H cross-polarization is shown to be an efficient technique for distinguishing non-framework from framework Al in USY zeolites and has revealed the presence of non-framework tetrahedral Al. Field-dependent measurements and simulations show that the non-framework 30 ppm 2
spectra of aluminium acetylacetonate show distinct lineshapes depending on the experimental conditions as the different orientations within the powder cross-polarize with differmg efficiencies. Selective polarization transfer to the l/2++-l/2 transition occurs at rfpower levels corresponding to 3w,
Al 3Q MAS NMR spectroscopy has been applied to study small amount of pentacoordinated Al emerges. The majority of the signal, however, arises from distorted tetrahedral Al. the coordination state of the species giving the 30 ppm Al NMR signal in the 27 Al MAS NMR spectrum of activated A two-step cal