Jean Pierre Costes

Determination of magnetic anisotropy in the LnTRENSAL complexes (Ln = Tb, Dy, Er) by torque magnetometry.

We report here a study about the magnetic anisotropy of the LnTRENSAL complexes (Ln = Tb, Dy, Er) performed by using cantilever torque magnetometry and electron paramagnetic resonance. For all of the compounds, we extracted a set of crystal-field parameters to obtain the energy-level splitting of the ground-state multiplet.

Tetranuclear [Co-Gd]2 complexes: aiming at a better understanding of the 3d-Gd magnetic interaction.

Tetranuclear [Co-Gd](2) complexes were prepared by using trianionic ligands possessing amide, imine, and phenol functions. The structural determinations show that the starting cobalt complexes present square planar or square pyramid environments that are preserved in the final tetranuclear [Co-Gd](2) complexes. These geometrical modifications of the cobalt coordination spheres induce changes in the cobalt spin ground states, going from S = 1/2 in the square planar to S = 3/2 for the square pyramid environments. Depending on the ligand, the complexes display antiferromagnetic or ferromagnetic Co(II)-Gd(III) interactions. The temperature dependence of the magnetic susceptibility-temperature products indicate that the Co-Gd interaction is ferromagnetic when high spin Co ions are concerned and antiferromagnetic in the case of low spin Co ions. This different magnetic behavior can be explained if we observe that the singly occupied σ d(x(2)-y(2)) orbital is populated (S = 3/2 Co ions) or unoccupied (S = 1/2 Co ions). Such an observation furnishes invaluable information for the understanding of the more general 3d-4f magnetic interactions.

Comparison of aerodynamics and mixing mechanisms of three mixers: Oxynator™ gas–gas mixer, KMA and SMI static mixers

Abstract In this paper, a new gas–gas mixer, Oxynator, is characterized. The performance of this mixer is compared with two static mixers: Sulzer SMI and Chemineer KMA. In order to study these three gas–gas mixers, first the pressure drop is measured. Secondly, the mixing efficiency is characterized by laser sheet visualizations at the outlet of the mixer. The hydrodynamics and turbulence induced by the mixers are then measured by laser Doppler anemometry (LDA). The purpose of this work is to understand the aerodynamics and the mixing mechanisms of the Oxynator mixer and to compare it with two static mixers. The mixing mechanisms of the Oxynator are very particular. The Oxynator creates eight swirls and a center zone, each zone increasing in space when they go away the injector. The homogeneity is reached when the zones meet and form a single zone. The intensity of turbulence created by this mixer is greater than the turbulence created by the other mixers and the pressure drop is minimum (lower than KMA and equal to SMI). The particularity of this mixer is that there is no impact between the secondary flow and the tube. The influence of flow rate on flow pattern is determined.