An experimental study of cross polarization from1H to27Al in crystalline and amorphous materials |
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Authors: | M G Mortuza R Dupree S C Kohn |
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Institution: | 1. Department of Physics, University of Warwick, CV4 7AL, Coventry, U.K.
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Abstract: | The conditions for successful1H?27Al cross polarization experiments have been investigated. It was found that boehmite was a good material for setting up the Hartmann-Hahn match condition, and both tetrahedral and octahedral aluminium was observed in a variety of environments. The contact time dependence of the CP signal was studied for several samples and simulations showed thatT IS could be estimated and hence information on mean1H?27Al distances in glasses deduced. CP signals could be obtained even ifT 1? Al is much less thanT IS, contrary to some previous suggestions. MAS reduces both the size of the CP signal and the optimum contact time and to maintain signal strength spinning should be as slow as possible. |
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