In the present study, economically viable NiO nanoparticles were produced by biogenic preparation using stevia leaf broth and their in-vitro antioxidant and antimicrobial activities were evaluated. The properties of the prepared NiO nanoparticles were confirmed by analytical techniques such as Ultraviolet-Visible (UV-Vis), X-ray diffraction (XRD), FE-SEM, and Fourier transform infrared spectroscopy (FTIR) analyses. Morphological studies using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the size of synthesized nanoparticles ranged from 20 to 50 nm, most of which were spherical and few of which were agglomerated. The role of the biological moieties, which reduce and cap the nanoparticles, was studied using FTIR analysis. The prepared nanoparticles strongly inhibited gram-negative bacteria, which is a camper with gram-positive bacteria and fungi. Furthermore, it performs an effective in-vitro activity through α,α-diphenyl-β-picrylhydrazyl (DPPH) reduction. Thus, it can be concluded that the effective and easy green synthesis process used for NiO nanoparticles provides potential antimicrobial agents against multidrug-resistant microbes.

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Nanoparticles of Eu3+ doped (1-9 mol%) CaTiO3 were prepared using low temperature (500°C) solution combustion technique using metal nitrates as precursors and urea as fuel. The powder X-ray diffraction patterns of the as-formed products show single orthorhombic phase. The crystallite size was estimated using Scherrer's method and found to be in the range 40-45 nm. The effect of Eu3+ ions on luminescence characteristics of CaTiO3 was studied and the results were discussed in detail. The phosphors exhibit bright red emission upon 398 nm excitation. The characteristic emission peaks recorded at ∼540, 593, 615, 653, 696 and 706 nm (5D0→7Fj=0,1,2,3,4,5) were attributed to Eu3+ ions. The electronic transition corresponding to 5D0→7F2 (615 nm) was stronger than the magnetic dipole transition 5D0→7F1 of Eu3+ ions (596 nm). The CIE chromaticity co-ordinates were calculated from emission spectra, the values (x,y) very close to NTSC standard value of red emission. Therefore, the present phosphors were highly useful for display applications.

Pyrochemical reprocessing involves the use of molten LiCl-KCl (lithium chloride-potassium chloride) eutectic salt at 773 K for the recovery of uranium and plutonium from spent metallic fuel of fast breeder reactors. The materials selected for such corrosive environments should withstand high temperatures and at the same time offer good corrosion resistance. The present work discusses the corrosion behavior of candidate materials like 2.25Cr-1Mo steel (UNS K21590), 9Cr-1 Mo steel (UNS K90941), Ni-based alloy 600 (UNS N06600), Ni-based alloy 625 (UNS N06625), and Ni-based alloy 690 (UNS N06690) in molten LiCl-KCl eutectic salt at 873 K for various durations under ultrahigh-purity argon atmosphere. Corrosion behavior of partially stabilized zirconia (PSZ) coating on candidate materials also was evaluated. Weight-loss results indicated that the corrosion resistance of the materials increased in the following order: 2.25Cr-1Mo > 9Cr-1 Mo > Ni-based alloys > PSZ coating. PSZ-coated specimens showed better corrosion resistance in molten LiCl-KCl salt when compared with uncoated specimens; however, accidental ingression of oxygen and moisture could result in premature spallation of the coating. Scanning electron microscopy (SEM) examination and grazing incidence x-ray diffraction (GIXRD) analysis of exposed Cr-Mo steels and Ni-based alloys exhibited dealloyed surfaces and corrosion product regions rich in Cr, indicating preferential leaching of Cr. The paper highlights the results of the present investigation.