0000000000281708
AUTHOR
Sérgio R. Teixeira
Synthesis and characterization of catalytic iridium nanoparticles in imidazolium ionic liquids
Abstract The reduction of [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) dissolved in 1-n-butyl-3-methyl tetrafluoroborate, hexafluorophosphate and trifluoromethane sulphonate ionic liquids in the presence of 1-decene by molecular hydrogen produces Ir(0) nanoparticles. The formation of these nanoparticles follows the two-step [A → B, A + B → 2B ( k 1 , k 2 )] autocatalytic mechanism. The same mean diameter values of around 2–3 nm were estimated from in situ TEM and SAXS analyses of the Ir(0) nanoparticles dispersed in the ionic liquids and by XRD of the isolated material. XPS and EXAFS analyses clearly show the interactions of the ionic liquid with the metal surface demonstrating the formation of …
Structural properties of the quaternary Heusler compound Co2 Cr1−x Fex Al
Abstract The structural and chemical properties of the quaternary Heusler compound Co2 Cr1−x Fex Al were investigated comparing powder and bulk samples. The long range order was determined by means of X-ray diffraction, while the site specific (short range) order was proved by the extended X-ray absorption fine structure method (EXAFS). The chemical composition was analysed by means of X-ray photo emission spectroscopy (XPS) combined with Auger electron spectroscopy (AES) depth profiling. The results from these methods are compared to get a detailed idea about the differences between surface and bulk properties and appearance of disorder in such alloys.
Structural properties of the quaternary Heusler alloy Co2Cr1−xFexAl
The quarternary substitutional series Co2Cr1?xFexAl was investigated by means of surface and bulk sensitive techniques in order to exploit its structural and compositional properties. Both bulk and powder samples of the alloy series were investigated to obtain specific information about this material.The long range order was determined by means of x-ray diffraction and neutron diffraction, while the site specific (short range) order was proved by extended x-ray absorption fine structure spectroscopy. The magnetic structure was investigated by M?ssbauer spectroscopy in transmission and scattering modes in order to compare and separate powder and bulk properties. The chemical composition was …