01846nas a2200229   4500008004100000022001400041245006000055210005900115260009500174300001200269490000600281520108900287653001501376653000901391653001201400653002501412100002101437700002001458700001701478700002701495856009401522       2008                        eng d  a1533-488000aSn-119 magic angle spinning NMR of nanocrystalline SnO20 aSn119 magic angle spinning NMR of nanocrystalline SnO2  a25650 NORTH LEWIS WAY, STEVENSON RANCH, CA 91381-1439 USAbAMER SCIENTIFIC PUBLISHERScJAN  a321-3280 v83 a<p>Nanocrystalline SnO2 samples of different grain sizes, prepared by inert gas condensation technique (IGCT) and chemical precipitation method and conforming to the tetragonal phase, have been studied by variable speed (3-10 kHz) Sn-119 MAS NMR at 11.74 Tesla field. Sn-119 solid-state NMR results show that the IGCT prepared samples have good crystallinity and phase purity compared to the samples prepared by the chemical method. The determination of Sn-119 chemical shielding parameters (delta(iso), Delta delta and eta) from slow MAS spectra shows that the Sn-119 isotropic chemical shift (delta(iso)) is strongly influenced at smaller grain sizes, attributable to the change in the O2- local symmetry for the surface Sn-119 ions at smaller grain sizes. The observed line widths in MAS spectra are significantly larger than the life-time broadening due to spin-lattice (T-1) and spin-spin (T,) relaxation. The Sn-119 MAS NMR spectra are thus inhomogeneously broadened by a distribution of isotropic chemical shifts, the line broadening increasing with decrease in grain size.</p>10aHydrolysis10aIGCT10aMAS NMR10ananocrystalline SnO21 aSabarinathan, V.1 aChandran, Vinod1 aRamasamy, S.1 aGanapathy, Subramanian  uhttps://library.ncl.res.in/content/sn-119-magic-angle-spinning-nmr-nanocrystalline-sno2-002013nas a2200169   4500008004100000022001400041245012600055210006900181260007100250300001400321490000800335520130800343100002101651700001701672700002701689856012701716       2010                        eng d  a1520-610600aPerturbations to Al-27 electric field gradients in nanocrystalline alpha-Al2O3 studied by high-resolution solid-state NMR0 aPerturbations to Al27 electric field gradients in nanocrystallin  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB  a1775-17810 v1143 a<p>Al-27 solid-state NMR has been employed to study the perturbations to Al-27 electric field gradients for the aluminum environments in nanocrystalline alpha-alumina. Triple quantum magic angle spinning experiments show that the octahedral aluminum coordination remains unchanged down to 12 nm, although severe perturbations to Al-27 electric field gradients are noticed at 28 nm and below. 3Q-MAS and SATRAS experimental data of nano alpha-alumina have been analyzed through extensive spectral simulations to probe Al-27 electric field gradients of aluminum in the grains and grain boundaries. While the aluminum in the grains has a unique field gradient tensor, the same octahedrally coordinated aluminum environments in the grain boundaries suffer a distribution of electric field gradients. This is evidenced by data analysis of both 3Q-MAS and SATRAS spectra. By invoking the Gaussian isotropic model, in which the (C-Q, eta(Q)) parameter space is discretely sampled by the Czjzek distribution, we have been able to analyze the Al-27 SATRAS spectra of nanocrystalline alpha-alumina samples having grain sizes of 52, 28, 20, and 12 nm. Good agreement between experimental and simulated spectra has led to the quantitative determination of grain and grain boundary components in these materials.</p>1 aSabarinathan, V.1 aRamasamy, S.1 aGanapathy, Subramanian  uhttps://library.ncl.res.in/content/perturbations-al-27-electric-field-gradients-nanocrystalline-alpha-al2o3-studied-high-0