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I Farnan

Publications and source records attributed to I Farnan.

4 recordsLinked to original sources
PubMed1995

71Ga and 69Ga nuclear magnetic resonance study of beta-Ga2O3: resolution of four- and six-fold coordinated Ga sites in static conditions.

71Ga and 69Ga nuclear magnetic resonance (NMR) spectra have been obtained for beta-Ga2O3 at magnetic fields of 11.7 and 7.0 T with a combination of static and spinning samples and using echo techniques. Isotropic chemical shifts and well constrained electric field gradient (EFG) tensors were measured for the GaIV and GaVI sites in beta-Ga2O3 and are reported for the first time. Due to its high quadrupolar coupling constant the GaIV site in beta-Ga2O3 is only resolved in static conditions. Analysis of spectral discontinuities obtained for different isotopes and magnetic field strengths and a method of readily obtaining very broad spectra without point by point acquisition demonstrate an approach that should be very useful in constraining the chemical shifts and quadrupole parameters involved in solid-state gallium NMR spectra.

Gallium↗
PubMed1995

A time resolved 27Al NMR study of the cooling process of liquid alumina from 2450 degrees C to crystallisation.

Nuclear magnetic resonance is able to give insight into the structure and dynamics of liquids at very high temperature (T > 2000 degrees C). 27Al NMR spectra have been recorded every 25 ms during the cooling of an aerodynamically levitated liquid alumina droplet from 2450 degrees C to crystallisation in less than 3 s. The temperature is measured jointly by pyrometry and NMR, and this time resolved experiment provides a unique way of exploring the temperature dependence of both the structure (shift) and the dynamics (relaxation time of 27Al of the liquid and the supercooled liquid alumina until the crystallisation of alpha-Al2O3. The apparent Arrhenian activation energy of 130 kJ mol-1, derived from T1 measurement, is understood as the signature of the macroscopic viscosity in this high temperature liquid.

Aluminum Oxide↗
PubMed1992

Quantification of the disorder in network-modified silicate glasses.

Local order in silicate glasses has been observed by many experimental techniques to be similar to that in crystalline materials. Details of the intermediate-range order are more elusive, but essential for understanding the lack of long-range symmetry in glasses and the effect of composition on glass structure. Two-dimensional 17O dynamic-angle-spinning nuclear magnetic resonance experiments reveal intermediate-range order in the distribution of inter-tetrahedral (Si-O-Si) bond angles and a high degree of order in the disposition of oxygen atoms around the network-modifying cations.

Glass↗