Calcium and strontium hexaluminates: NMR evidence that "pentacoordinate" cation sites are four-coordinated

Article Abstract:

High-resolution solid-state (super 27)Al NMR data for two members of the magnetoplumbite group of structures, strontium hexaluminate (SrAl12O19, 'SA6') and calcium hexaluminate (CaAl12O19, 'CA6,' synthetic hibonite), acquired at 14.1 and 18.8T fields are reported. The findings is consistent with the 'split-atom' refinements of the crystal structures, in which the most of probable position of the Al atom is displayed away from the average trigonal pyramidal site center, along the crystallographic 3-fold axis.

All Other Basic Inorganic Chemical Manufacturing, Calcium & Compounds, Nuclear magnetic resonance, Calcium compounds, Strontium

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Influence of the catalyst type on the growth of carbon nanotubes via methane chemical vapor deposition

Article Abstract:

The influence of three different procedures of catalyst preparation on the type and diameter of carbon nanotubes (CNTs) formed under identical growth conditions through methane chemical vapor deposition (CVD) is described. The results show the essential role of alumina particles in the formation of SWNTs, and the newly developed method opens up a way to the synthesis of diameter-controlled SWNTs through catalyzed CVD.

Chemical vapor deposition, Chemical properties, Nanotubes, Chemical vapour deposition

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Structural and morphological investigation of ceria-promoted Al(sub 2)O(sub 3) under severe reducing/oxidizing conditions

Article Abstract:

The characterization of ceria deposited on alumina is for the first time carried out under severe oxidizing and reducing condition. It is found that most of the structural modifications operated by ceria under oxidated conditions is observed at around 1373 K, and this is temperature is therefore critical in the study of the system.

Oxidation-reduction reaction, Oxidation-reduction reactions, Thermal properties

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