Advanced design of a x-ray absorption spectroscopy setup for measuring transition metals speciation in molten carbonates, hydroxides and hydrogenosulfates.

Battery recycling is currently becoming a crucial issue. One possible treatment path involves the use of molten salts. A mechanistic understanding of the underlying processes requires being able to analyze in situ speciation in molten salts at various temperatures. This can be advantageously achieved using x-ray absorption spectroscopy, the use of Quick-EXAFS facilities being particularly appropriate. Consequently, this paper presents the design and development of a new setup allowing carrying out Quick-EXAFS experiments in oxidizing molten salts at high temperatures. We describe the different components of a cell and the performance of the heating device. We illustrate the capabilities of the setup by analyzing the temperature evolution of Co speciation upon dissolution of LiCoO2, a typical battery electrode material, in molten carbonates, hydroxides, and hydrogenosulphates.

Microstructure of colloidal dispersions in the ionic liquid ethylammonium nitrate: influence of the nature of the nanoparticles' counterion.

In order to better identify the key parameters governing colloidal stability in ionic liquids we probe the influence of the nature of the initial counterion of citrate-coated maghemite nanoparticles (NP), with Na(+), Li(+) and ethylammonium (EA(+)) on their dispersions in ethylammonium nitrate (EAN). Chemical analysis shows that sodium and lithium counterions remain at the nanoparticle surface after their transfer from water to EAN, despite their low concentration compared with EA(+). Macroscopically, all suspensions are stable over the range of volume fractions ΦNP tested (∼ 1% to 8%). A microstructural study coupling small angle scattering and magneto-optic birefringence measurements shows that nanoparticles are perfectly dispersed with sodium counterions and interact through weak repulsions. Conversely, small clusters of a few nanoparticles are formed with lithium counterions, with the aggregation number increasing with ΦNP. However, such clusters are fragile; evidence that the attractions responsible for aggregation are of weak amplitude. Suspensions with EA(+) counterions show an intermediate behaviour. Our results demonstrate the determining role of initial counterions of the nanoparticles on the microstructure of colloidal dispersions in ionic liquids and therefore, the essential role of the interfacial zone between the solid and the liquid.

Diffusion of E and Z urocanic amphiphiles through skin and their insertion in a membrane model.

The incorporation of synthetic urocanic amphiphiles into a membrane model is described. A monomolecular film of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol was formed at the air-water interface and used as a model. In parallel, diffusion of these derivatives through the skin was studied using rat skin on flow-through diffusion cells. The flux and the cumulative amount were determined. Although the structure and the composition of the DPPC/cholesterol monolayer differed greatly from multilayers of epidermal lipids, the results obtained in the incorporation and diffusion studies were similar. The structure of the urocanic amphiphiles was very close, but the membranes led to the following flux or insertion classification: Ester E > Ester Z >> Amide E. From the results obtained and for simplicity, the technique of Langmuir monolayers seems to be highly suited to the primary screening of amphiphilic compounds.