Neutron Reflectometry: A Tool to Investigate Diffusion Processes in Solids on the Nanometer Scale

The investigation of self‐diffusion for the characterization of kinetic process in solids is one of the most fundamental tasks in materials science. We present the method of neutron reflectometry (NR), which allows the detection of extremely short diffusion lengths in the order of 1 nm and below at corresponding low self‐diffusivities between 10^?25 and 10^?20 m² s^?1. Such a combination of values cannot be achieved by conventional methods of diffusivity determination, like the radiotracer method, secondary ion mass spectrometry, quasielastic neutron scattering, or nuclear magnetic resonance. Using our method, the extensive characterization of materials which are in a non‐equilibrium state, like amorphous or nanocrystalline solids becomes possible. Due to the small experimentally accessible diffusion length microstructural changes (grain growth and crystallization) taking place simultaneously during the actual diffusion experiment can be avoided. For diffusion experiments with NR isotope multilayers are necessary, which are chemical homogeneous but isotope modulated films. We illustrate the basic aspects and potential of this technique using model systems of different classes of materials: single crystalline germanium, amorphous silicon nitride, and nanocrystalline iron.     

A Study on Thermal Conductivity and Stability of Nanofluids Containing Chemically Synthesized Nanoparticles for Advanced Thermal Applications

This study presents easy methods of synthesizing silver (Ag) and copper (Cu) nanoparticles through chemical route in an aqueous medium under atmospheric condition at ambient temperature. The synthesized nanoparticles have been characterized with different techniques, such as x-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, high-resolution transmission electron microscopy, UV–visible spectroscopy and dynamic light scattering measurements. Experimental observations have revealed the absence of any metal oxide layer around the nanoparticles which are found to remain stable under ambient conditions. The featured properties, such as narrow size distribution, stability, make these nanoparticles potential candidates for the synthesis of effective nanofluids. The nanofluids have been prepared by dispersing the nanoparticles synthesized through chemical route in a suitable base fluid. The thermal conductivity of nanofluids with different nanoparticles loading has been measured by transient hot-wire method, and the results have shown that the increasing trend of enhancement in thermal conductivity with respect to nanoparticles concentration is attainable only when the nanoparticles concentration is below some limiting value depending on the type of nanofluid. Beyond this limiting value of loading, the thermal conductivity of the nanofluid decreases due to pronounced agglomeration effect. The measurements of thermal conductivity of nanofluids over varying temperatures for a given volume fraction loading of nanoparticles have shown that the thermal conductivity increases markedly with the increase in temperature. Hence, nanofluids are likely to be much more promising at high-temperature applications.     

Quaternary ammonium-based task-specific ionic liquid: An efficient and ‘green’ separation for ‘f block’ elements

Functionalized ionic liquid based on quaternary ammonium salt was investigated for the specific task of the efficient extraction of f block elements in different oxidation states. It deals with the investigation of extraction efficiency, mechanism, speciation and associated kinetics and thermodynamics. The extracted species of Pu⁴⁺, PuO₂²⁺, Am³⁺, Eu³⁺ were found to be Pu(Hptha)(H₂O)₆³⁺, PuO₂(Hptha)(H₂O)₂⁺, Am(Hptha)(H₂O)₇²⁺, Eu(Hptha)(H₂O)₇²⁺, respectively where (Hptha)^? is the anionic part of the ionic liquid. Effect of radiation exposure on the performance of the ionic liquid was also investigated. The suitable back extraction procedure from the ionic liquid phase was developed using aqueous soluble complexing agents.     

Ionic liquid-assisted synthesis of tri-functional ruthenium oxide nanoplatelets for electrochemical energy applications

Journal of Materials Science - Nanostructured crystalline metal oxides are in great demand in industrial processes due to their unique physicochemical properties and ionic liquids (ILs) are...