Entity

Time filter

Source Type


Shrivastava R.,ICFAI University, Tripura | Kaur J.,Government Vyt Pg Autonomous College
Ferroelectrics | Year: 2016

Ca2MgSi2O7 doped with Eu/Dy, with varying concentration of Dy3+ (0.5, 1.0, 1.5, 2.0 mol%), keeping the concentration of Eu2+ constant have been prepared using conventional high temperature solid state reaction technique. Sample prepared with specific concentration of Dy3+ (1.5 mol%) was characterized by X-ray diffraction (XRD) technique, Scanning Electron Microscopy (SEM), and TG/DTG (Thermal Gravimetry/Differential Thermogravimetry). XRD pattern of the sample confirmed the proper preparation of the sample. Scanning Electron Microscope image of the sample was taken to investigate the morphology of the sample. For judging the stability of the sample, TG/DTG (Thermal Gravimetry/Differential Thermogravimetry) studies were performed. Sample was given excitation energy from a ultra-violet source of wavelength 365 nm for 10 minutes, after which its afterglow intensity was recorded with respect to time. Phosophorence decay curves exhibited, single exponential decay with fairly good decay rates. The major cause for the persistent afterglow is the number of electrons captured in the traps created either by Dy3+ ions or oxygen vacancies and its depths from the bottom of the conduction band of host material. © 2016 Taylor & Francis Group, LLC. Source


Shrivastava R.,ICFAI University, Tripura | Kaur J.,Government Vyt Pg Autonomous College | Dash M.,ICFAI University, Tripura
Superlattices and Microstructures | Year: 2015

Abstract Present paper reports the preparation of Sr2MgSi2O7 doped with Dy3+ ions by modified high temperature solid state reaction technique. Samples were prepared for different concentration of Dy3+ (0.5, 1.0, 1.5, 2.0 and 2.5 mol%). Sample with optimum photoluminescence intensity was characterized by X-ray diffraction (XRD) technique. Observed XRD spectrum matched with crystallographic open database card specifically appeared for Sr2MgSi2O7 phosphor. This is a confirmation of proper preparation of the sample. Photoluminescence studies of these samples were done. Emission spectra exhibited 5 prominent peaks at 480, 490, 575, 590 and 660 nm respectively. In this case Dy3+ acts as an activator. Peaks centered at 480 and 490 nm are due to the transition 4F9/2 → 6H15/2 (blue color) of Dy3+ ions occupied at different sites. Similarly 575 and 590 nm peaks are originated due to transition 4F9/2 → 6H13/2 (yellow-orange color) of Dy3+ ions occupied at different sites. Emission at 660 nm is due to transition 4F9/2 → 6H11/2 (red color). CIE coordinates have been calculated for each sample and its value exhibited that, overall emission is near white light. In order to investigate the suitability of the samples as white color light sources for industrial uses, correlated color temperature (CCT) and color rendering index (CRI) were calculated. Values of CCT and CRI were found, well within the defined acceptable range. © 2015 Elsevier Ltd. All rights reserved. Source


Kaur J.,Government Vyt Pg Autonomous College | Shrivastava R.,ICFAI University, Tripura | Dubey V.,Bhilai Institute of Technology | Parganiha Y.,Government Vyt Pg Autonomous College
Journal of Display Technology | Year: 2016

Di-barium magnesium silicate doped with Eu2+ and Tm phosphors were prepared for different concentrations of Tm2+ ions keeping the concentration of Eu2+ as 0.5 mol%. Photoluminescence (PL) studies of prepared samples were carried out. Emission spectra exhibited optimum green color emission at 509 nm when Tm2+ was 1.5 mol%. Emission is expected to arise due to the transition of Eu2+ ions from any of the sublevels of 4d6 5f1 to its ground state (8S7/2. This sample with 1.5 mol% of Tm is taken for X-ray diffraction analysis. XRD pattern confirmed that the sample follows monoclinic structure with C 1 2/c 1 (15) space group. Scanning Electron Microscope image of the sample exhibited the uniform morphology with average particle size of 222.54 μm. Thermoluminescence (TL) glow curves of the sample for different UV irradiation were also recorded which presented single broaden peak centered at about 91°C. Phosphorescence decay curve was indicative of presence of dual exponential decaying section with a fast decay followed by a long decaying part. © 2005-2012 IEEE. Source


Sharma N.,Government Vyt Pg Autonomous College | Tiwari A.,Government Vyt Pg Autonomous College
Desalination and Water Treatment | Year: 2016

The present research focuses on the adsorptive efficiency of nanomagnetite-loaded poly (acrylamide-co-itaconic acid) hydrogel for manganese removal from aqueous and contaminated solution by batch as well as column adsorption technique. The influence of pH, contact time, adsorbent dose, temperature, metal ion concentration, bed depth, feed flow rate and inlet metal ion concentration on the sensitivity of the removal process was inspected. The copolymer was synthesized and magnetized in situ. The sorption data was analyzed and fitted to linearized adsorption isotherm of the Langmuir and Freundlich equations, respectively. Equilibrium data fitted very well to the Freundlich model. The kinetics of sorption was analyzed using pseudo-first-order and pseudo-second-order kinetic models. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients for each kinetic model were calculated. Different thermodynamic parameters i.e. ΔG0, ΔH0, and ΔS0 were also evaluated which proved the sorption to be feasible, spontaneous, and exothermic in nature. This hydrogel has been found to be an efficient adsorbent for manganese removal from water (>99% removal) and could be regenerated efficiently for further experiments. © 2015 Balaban Desalination Publications. All rights reserved. Source


Sharma N.,Government Vyt Pg Autonomous College | Tiwari A.,Government Vyt Pg Autonomous College
Desalination and Water Treatment | Year: 2016

The present research focuses on the adsorptive efficiency of nano-ZnO-loaded poly (acrylamide-co-itaconic acid) hydrogel for iron removal from synthetic as well as contaminated water by batch and column adsorption techniques. The influence of pH, contact time, adsorbent dose, temperature, and metal ion concentration on the sensitivity of the removal process was inspected. The copolymer was synthesized and nano-ZnO particles were incorporated within the polymeric matrix by in situ technique. The size, structure, and coating of nano-ZnO particles were characterized by TEM, SEM, Fourier transform infrared spectroscopy, and AFM analysis, respectively. The sorption data were analyzed and fitted to linearized adsorption isotherm of the Langmuir, Freundlich, and Temkin equations, respectively. Equilibrium data fitted very well to the Freundlich model. The kinetics of sorption was analyzed using pseudo-first-order and pseudo-second-order kinetic models. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients for each kinetic model were calculated. Different thermodynamic parameters, i.e. ΔG°, ΔH° and ΔS° were also evaluated which proved the sorption to be feasible, spontaneous, and exothermic in nature. This hydrogel has been found to be an efficient adsorbent for iron removal from water (>99% removal) and could be regenerated efficiently for further experiments. © 2015 Balaban Desalination Publications. All rights reserved. Source

Discover hidden collaborations