arXiv subjects

Netram Kaurav

Publications and source records attributed to Netram Kaurav.

4 recordsLinked to original sources

arXiv2016

Quantum Size Effect Exponential Heat Capacity in 4 nm Natural Nickel Nanolattice

Quantum size effect-induced heat capacity of metal nanoparticles at low temperatures was predicted 79 years ago to be exponential. This, however, has not been reported until date. In defiance, we demonstrate here observation of exponentially decaying heat capacity, below 45.2 K, associated with quantum jumps, exceptionally in 4 nm naturally assembled hexagonal closed packed (hcp) lattice of nickel nanoparticles; high magnetic fields have negligible effect on these features. Magnetic susceptibilities in contrast reveal evolution of quantum size effects with decrease in particle size. They exhibit sharp rise below about 30 K and vestiges of saturations below 5 K. The former is explained by Curie-like characteristics of odd electrons while the latter tend towards the orthogonal even-like case. These characteristics, ascribed to the ensembles of Ni nanoparticles, will give a new direction in understanding this crucial thermodynamic phenome-non.

cond-mat.mes-hall↗

arXiv2016

Size-induced structural phase transition at ~6.0 nm from mixed fcc-hcp to purely fcc structure in monodispersed nickel nanoparticles

We have investigated the core issue of atomic lattices in monodispersed Ni nanoparticles (NPs) of sizes 3.8 nm to 10.1 nm using detailed analysis of X-ray diffraction, synchrotron radiation X-ray absorption spectroscopy (XAS) and magnetization data. This has revealed the very remarkable coexistence of atomic face-centered cubic (fcc) and hexagonal closed-packed (hcp) lattices in samples with particle size less than or equal to 6.0 nm with the prevalence of only fcc phase beyond this. They are also associated with reduced coordination number, modified electronic structure, and surface atom coordination with ligands. Magnetization data furthermore reveal coexistence of ferromagnetism and superparamagnetism at 300 K. Considered to be due to dominant roles of ligands, they are likely to open up far-reaching implications to their future applications.

cond-mat.mes-hall↗

arXiv2014

Influence of surfactants on the electrical resistivity and thermopower of Ni nanoparticles

Compacted pellets of nanocrystalline nickel (NC-Ni) of average particle size ranging from 18 to 33 nm were prepared using a variety of surfactants. They were characterized well and were studied on the influence of the surfactants on the electrical resistivity and thermopower in the temperature range 5 to 300 K. It was found that the type of the surfactant used dominates over the average particle size in their electrical transport and the detail transport behaviors have been discussed. Moreover, the observed thermopower and resistivity features were contrasting compared to what are normally seen in the well-known materials. They are interpreted as indicative of attractive features these surfactants for the design of nanostructured thermoelectric materials with enhanced thermoelectric figure of merits.

cond-mat.mes-hall↗

arXiv2014

Naturally self-assembled nickel nanolattice

This is the first report on the critical nature of nanolattice formability of different particle size (~4-10nm) of monodispersed nickel nanoparticles. They exhibit strikingly hexagonal close-packed (hcp) nanolattices without extra forces, whenever trioctylphosphine is (one of) the surfactant(s). This clearly establishes the unique role of nanolattice formability of trioctylphosphine. The c/a ratios are interestingly identical to those of atomic lattices. An attempt has also been made to explain them based on the balanced attractive and repulsive forces of the surfactant-generated cation-anion pairs on the surface of the nanoparticles. The present findings therefore will provide a far-reaching vista to fabrication of varieties of natural nanolattices and their understanding on applications in a new paradigm.

cond-mat.mes-hall↗