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Your search keyword '"Kumar, Ashavani"' showing total 462 results
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462 results on '"Kumar, Ashavani"'

181. Fabrication of robust Fe2O3@NiCo2O4core-shell composite with spikey surface for high-performance asymmetric solid-state supercapacitor

Author

Agrawal, Anant, Kumar, Ashavani, and Gaur, Anurag

Abstract

The need for a cost-effective and efficient energy storage system instigates researchers to develop emerging electrode materials for energy storage devices. The α-Fe2O3-based electrode material for supercapacitor application has received interest due to its good electrochemical performance, high mechanical strength, corrosion resistance, low cost, and abundant availability. This work develops a cost-effective, robust Fe2O3@NiCo2O4core-shell composite with spikey surface via a facile hydrothermal strategy for high-performance electrode material for supercapacitors. The spikes of Fe2O3are developed on NiCo2O4to collaborate in a more accessible surface area, with robust morphological stability throughout electrochemical performances. The Fe2O3@NiCo2O4core-shell composite exhibits a high specific capacity of 364 C g−1at the scan rate of 5 mV s−1and 81% cycling stability up to 10,000 successive charge-discharge cycles at the current density of 15 A g−1. Moreover, an asymmetric solid-state supercapacitor (ASSC) device was fabricated using Fe2O3@NiCo2O4composite as a positive electrode and commercially purchased activated carbon as a negative electrode assembled via PVA/KOH gel electrolyte. The fabricated device offers a significant energy density of 31.7 W h Kg−1at a power density of 700 W Kg−1. The ASSC exhibits excellent capacitance retention of 90% with ultra-high coulombic efficiency of 99.7% up to 10,000 GCD cycles. The ASSC can illuminate the red and yellow LED light. This work indicates that a robust Fe2O3@NiCo2O4core-shell composite can be an economic strategy for fabricating high-performance practical supercapacitor applications.

Published
2022
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194. Enhanced Photocatalytic Performance of Chromium Doped Zinc Oxide Nanoparticles

Author

Ray, Rajeev, Kumar, Ashavani, Paul, A., and Tyagi, Sachin

Abstract

Pure and chromium doped ZnO nanoparticles were successfully synthesized by eco-friendly and cost effective sol–gel technique. Structural, morphological and optical properties of pure and Cr doped ZnO nanoparticles were analyzed by X-ray diffraction, transmission electron microscope, and UV–vis spectroscopic techniques, respectively. The crystallite size of pure ZnO nanoparticles were observed to decrease from 29 to 24 nm as dopant concentration was increased to 3 %. Band gap of pure ZnO nanoparticles were also observed to decrease from 3.5 to 3.37 eV with increase in dopant concentration. The photo-catalytic degradation of methyl blue dye under UV irradiation was examined for synthesized samples. The chromium doped zinc oxide nanoparticles were found to give enhanced photo degradation efficiency (75.5 %) than the pure zinc oxide nanoparticles (51.2 %).

Published
2016
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199. Nickel-induced structural, optical, magnetic, and electrical behavior of α-Fe2O3.

Author

Kocher, Jaspreet, Kumar, Ashok, Kumar, Ashavani, Priya, Shashank, and Kumar, Jitendra

Subjects
MAGNETIC properties of nanostructured materials, NANOPARTICLES, OPTICAL properties, OXALATES, PHOTOLUMINESCENCE, NICKEL, NITRATES, CHEMICAL precursors, THERMAL analysis
Abstract

We report a simple, eco-friendly facile wet chemical nitrate precursor route for the synthesis of pristine and nickel-containing nanocrystalline (∼44 nm) α-Fe2O3. Thermal analysis of the dried (∼70 °C) presumed oxalate powder, Fe2(C2O4)3 · 4H2O (also confirmed by X-ray diffraction), revealed two-step formation of the oxide; slower reaction as Fe2(C2O4)3 · 4H2O↓ → 4H2O↑ + 2CO2↑ + 2FeC2O4↓ and faster as 2FeC2O4 → Fe2O3↓ + CO2↑ + 3CO↑. The incorporation of nickel resulted in progressive increase of cell parameters and exhibited decrease in estimated direct and indirect band gap values. The direct band gap values were in close correlation with emission transitions. The direct nature and narrowing of band gap with nickel addition ensures the higher absorbance values and wider spectrum of absorbance; indicating the enhanced semiconducting properties for applications such as solar cells, photocatalytic activity, etc. Regarding magnetic properties, the saturation magnetization increased progressively with nickel content while coercivity reduced up to 2 wt% of Ni content and increased afterward. The resistivity values with nickel incorporation decreased, when substituted at Fe3+ sites. [ABSTRACT FROM AUTHOR]

Published
2014
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200. Comparative study of depth dose-distributions and partial fragmentation cross sections of 56Fe ions on polyethylene using GEANT4.

Author

Jalota, Summit and Kumar, Ashavani

Subjects
*PARTICLE physics, *IRON ions, *POLYETHYLENE, *MOLECULAR dynamics, *CROSS-sectional method, *COMPARATIVE studies
Abstract

Highlights: [•] Depth-dose distributions of 56Fe nuclei in polyethylene are obtained using GEANT4. [•] Fragmentation cross sections of 56Fe ion on polyethylene are calculated. [•] Validation of Geant4 models for calculating fragmentation cross sections and depth-dose distributions are performed. [•] Quantum Molecular Dynamics (QMD) model is good for calculating the fragmentation cross sections on polyethylene. [•] The study demonstrates the necessity to improve models for better description of fragmentation in heavy ion interaction. [ABSTRACT FROM AUTHOR]

Published
2014
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