The aggregation behaviour of reverse micelles, formed during the extraction of neodymium nitrate and nitric acid, in an organic phase composed of tetra‐bis(2‐ethylhexyl) diglycolamide (TEHDGA) in n‐dodecane (n‐DD) was studied, at various temperatures. The organic phase, 0.2 M TEHDGA/n‐DD was equilibrated with aqueous solutions of nitric acid in the presence and absence of neodymium nitrate. At certain nitric acid and Nd(III) concentration in aqueous phase, the organic phase underwent splitting into two phases, with top phase known as “diluent rich phase”, the other one known as “third phase” or “metal ion rich phase”. Dynamic light scattering, attenuated total reflectance (ATR) ‐Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopic methods were employed for probing the size and distribution of aggregates present in the organic phase before and after splitting. The investigations revealed that the aggregates, formed in organic phase, interact efficiently with the extracted metal ions and these interactions increased with increase in the concentration of nitric acid and neodymium nitrate in organic phase. In addition, the interaction among the reverse micelles in third phase appear to be very strong as compared to that observed in the organic phase before third phase formation, and such strong interactions resulted in a merger and narrow distribution of reverse micelles in third phase.
A fuel cell based amperometric room temperature hydrogen sensor with Nafion as proton conducting electrolyte, Pd as sensing electrode, Pt as both counter and reference electrodes has been developed. Sensing electrode was prepared by electrodeposition of Pd on carbon gas diffusion electrode using room temperature ionic liquid electrolyte. Pt spray coated on gas diffusion electrode forms the counter electrode in the sensor. Pd electrodeposition was carried out at an applied potential of −1.0 V vs Pd wire and resulted in the formation of Pd clusters. The microstructure of electrodeposited Pd was investigated using field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The crystal structure of the Pd nanoparticles was indexed to face centered cubic by X-ray diffraction (XRD) and selected area electron diffraction (SAED). X-ray photoelectron spectroscopy (XPS) confirmed metallic form of the deposited Pd nanoparticles. The scratch test endorsed the fact that Pd nanoparticles adhered firmly to the surface of the gas diffusion electrode and it is found to be stable up to the load of 2 N. Range of response of the sensor to H 2 was in the concentration range 1% to 5% and found to be linear.
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