Solid‐state 29Si NMR techniques were used to characterize laser‐synthesized silicon nitride powder prepared from the reaction of silane with ammonia. When the powder is exposed to water vapor, a hydrated layer rapidly forms at the surface. A comparison of 29Si cross polarization (CP) and Bloch decay (BD)‐MAS‐NMR spectra revealed differences between surface and bulk compositions. CP‐NMR identified Si‐NHx (x = 1, 2) species with a chemical shift of −45 ppm in the as‐synthesized (unexposed) powder. In BD‐NMR spectra, the nitride resonance is observed at −48 ppm. For the hydrated powder, CP‐NMR identified additional =Si‐OH (Q3), =Si‐(OH)2 (Q2), and SiO2 (Q4) species present at the surface. The CP‐NMR spectra were corrected for TlpH relaxation effects and deconvoluted into individual components in order to extract quantitative measurements of the various species present.
Bei Reaktion einer CH2Cl2‐Lösung von (I) mit wäßriger Salpetersäure erhält man nach Fällung mit Et2O den monomeren Komplex (II), während durch Pentan das Dimere (III) gefällt wurde.
The title complexes such as (I) are prepared from salicylaldehyde, the appropriate triamine and Fe(III) nitrate in EtOH in the presence of NEt3 and triethylorthoformate and characterized by Moessbauer spectra, magnetic moments and conductivity measurements.
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