Mahesh Kumar Singh

In the present work, the growth kinetics of nickel nanorods inside commercially available Whatman nanoporous membrane is explored to achieve uniform deposition over a large area of the membrane. Uniform electrodeposition inside nanopores requires continuous presence of solute ions near the deposition site and reduction of ions. To control ion diffusion and reduction near the deposition site, the effect of DC potential and pulsed potential with various duty cycles and solution temperatures is analyzed. Time-dependent variation in deposition current is recorded for all experiments. For different experimental conditions, high-resolution scanning electron microscopy (SEM) image is acquired. SEM along with the current density profile helped to understand the deposition mechanism for various growth conditions. Experiments confirmed that pulse deposition with a small duty cycle is promising to achieve uniform deposition. Also, by changing the pulse duty cycle, a sectioned nanostructure can be obtained. Based on the electron microscopic observation for various deposition conditions used in this work, it is concluded that initially nickel ions adhere to the pore surfaces due to high surface energy. When a potential is applied, ions reduce and a hollow nanotube structure forms. With time, concentric growth continues by forming a solid nanorod structure.

A facile carbothermal route was adopted to obtain niobium carbide nanoparticles (NPs) embedded in carbon network from Nb₂O₅ to study photocatalytic behavior. Optimization of synthesis parameters to obtain single phase NbC NPs has been successfully done. The phase identification, morphology and nature of carbon were determined with the help of X-ray diffraction, transmission electron microscopy (TEM) and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) suggested the presence of multiple oxidation states of Nb associated to NbC and NbC_xO_y centers on the surface of NPs. Due to the presence of NbC_xO_y on the surface of NPs, absorption under visible region of EM spectrum has been observed by UV-visible spectroscopy. Different organic dyes (RhB, MB and MO) were used to study the effect of holding time on the photocatalytic performance of as-synthesized samples. RhB dye was found to be the most sensitive organic molecule among all the considered dyes and degraded 78% in 120 min.

We report here for the first time the development of ‘age-hardened/toughened’ ceramic alloy based on MgO in the bulk polycrystalline form. This route allows for the facile development of a ‘near-ideal’ microstructure characterized by the presence of nanosized and uniformly dispersed second-phase particles (MgFe₂O₄) within the matrix grains, as well as along the matrix grain boundaries, in a controlled manner. Furthermore, the intragranular second-phase particles are rendered coherent with the matrix (MgO). Development of such microstructural features for two-phase bulk polycrystalline ceramics is extremely challenging following the powder metallurgical route usually adopted for the development of bulk ceramic nanocomposites. Furthermore, unlike for the case of ceramic nanocomposites, the route adopted here does not necessitate the usage of nano-powder, pressure/electric field-assisted sintering techniques and inert/reducing atmosphere. The as-developed bulk polycrystalline MgO–MgFe₂O₄ alloys possess considerably improved hardness (by ~52%) and indentation toughness (by ~35%), as compared to phase pure MgO.