Pragya Ojha

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Papers by Pragya Ojha

Study of the effect of urea concentration on optical properties of Boron Carbon Oxynitride (BCNO) nanophosphor

Optik, 2021

Abstract Effect of urea concentration on optical properties of BCNO phosphor materials has been s... more Abstract Effect of urea concentration on optical properties of BCNO phosphor materials has been systematically investigated. Greenish-yellow luminescent BCNO phosphor materials were successfully synthesized by low-temperature, eco-friendly and non-toxic, green synthesis method. In this process, Boric acid (H3BO3 - 2 mol), Urea (NH2CONH2 - 0.25 mol–2 mol) and Lemon Aqueous extract (LAE - 20v/v%) were used as precursors. PXRD ascertains the crystallinity of prepared BCNO phosphor materials which reduces with increasing concentration of urea. The SEM and AFM images show the flakes type structure of prepared BCNO phosphor materials. Quantum yield increased up to 61 % for 0.5 mol% of urea and further decreased for higher concentration of urea. The Photoluminescence emission peak undergoes redshift on increasing the urea concentration up to 1.5 mol% and then saturates at higher concentration. PL emission in Greenish-Yellow region of as-prepared BCNO nanophosphor offers its potential application in WLED.

Structural and optical studies of TiO2:Ag2O nanocomposite by sol-gel method

Materials Science-Poland, 2020

As TiO2 is suitable for electronic and electrical applications, in the present work the authors h... more As TiO2 is suitable for electronic and electrical applications, in the present work the authors have successfully modified TiO2 by adding silver (Ag) to form titanium oxide-silver oxide (TiO2:Ag2O) nanocomposite samples by using sol-gel technique. Characterizations of these composites have been performed using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV-Vis spectroscopy. XRD study revealed that the crystal structure of the samples consisted of tetragonal and cubic phases. This study further showed an increment in the average crystallite size from 8 nm to 38 nm with an increase in Ag concentration. The increase in crystallite size has been confirmed additionally by SEM and AFM. The increment in the average particle size of the samples may be attributed to an increase in silver molarity in the TiO2 matrix. Significant red shift in the absorption edge has been observed, causing reduction in the energy bandgap of the composites from ...

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Magneto Electret Behaviour of Porous Polytetrafluoroethlyene under Uniform and Nonuniform Magnetic Field

Charge decay characteristic of magnetoelectrets prepared using 50% porous Polytetrafluoroethlyene... more Charge decay characteristic of magnetoelectrets prepared using 50% porous Polytetrafluoroethlyene is investigated. The influence of temperature, on its surface charge density is also studied. The electrets were heated and prepared under the influence of fixed magnetic field. The decay of surface charge was observed continuously for 40 days and corresponding time constant were calculated accordingly. Negative iso charge is obtained in all the samples which are of the order of 10 C. The porous material is used for the first time in 9 magnetoelectrets. From the calculated values of time constant it is found that the stability of porous material is very high. The comparative studies of surface charge characteristics were done by preparing Porous magnetoelectrets using uniform and nonuniform magnetic fields. The properties of as prepared magnetoelectrets may have an application in various type of sensors especially in high efficiency Piezo electric sensors.

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XRD studies on magnetoelectrets using type-E orientation pattern

IEEE Transactions on Dielectrics and Electrical Insulation, 2012

Structural Studies of 50% porous PP (Polypropylene) magnetoelectrets under different temperatures... more Structural Studies of 50% porous PP (Polypropylene) magnetoelectrets under different temperatures and magnetic field conditions have been performed using X-ray diffraction (XRD) technique. Polarized samples showing orientation texture have been found at distinct angles. The preferred orientations detected in all samples were more in the direction perpendicular to the applied magnetic field. A general model is developed to explain the orientation.

The conductive heterojunctuon device of graphene and MoS2

This paper reports the estimation of graphene thickness, done by the intensity ratio of the 2D ba... more This paper reports the estimation of graphene thickness, done by the intensity ratio of the 2D band to the G band and the ration is found to be 1.91 which suggests, it is monolayer and bilayer MoS2. The RAMAN spectra shows presence of crystalline defects, considering high D/G ratio. The heterostructure device synthesized shows linear conductivity, making it a conductive device. These devices exhibit a promising device for a new generation of transparent, high performance, high response gas sensors and optoelectronic devices. The heterostructure device of graphene and MoS2 show promise for enhanced performance in photo detectors and phototransistors; with electrostatic coupling and high current capacity. This synthesis approach is used to fabricate a MoS2/Graphene on copper foil by growing large scale uniform MoS2 on graphene.

SIGNAL STRENGTH IN OPTICAL FIBER NETWORKS& ITS OPTIMIZATION

by Dr. Ved nath Jha and Pragya Ojha

Journal of Critical Reviews, 2020

The optical fiber network behaves as the backbone of 5 th generation communication but there are ... more The optical fiber network behaves as the backbone of 5 th generation communication but there are several limitations like attenuation, dispersion, fragility of fiber, splicing and connecting loss and nonlinearities. So, in order to make successful communication it is important to think how signal is transmitted; what amount of signal is transmitted and how long it is transmitted through the fiber. Finally, it is to be investigated the strength of the signal under the effect of Extinction Ratio for the given Fiber length with XPM treatment by OptiSystem 0.17.

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Magnetoelectrets prepared by using temperature gradient method

AIP Advances, 2015

A novel Temperature Gradient method for preparation of magnetoelectret is proposed. Non uniform m... more A novel Temperature Gradient method for preparation of magnetoelectret is proposed. Non uniform magnetic field and temperature gradient are expected to be the main cause for the formation of magnetoelectrets (MEs). Being bad conductors of heat, during their formation, there is a possibility for the existence of a temperature gradient along the dielectric electrode interface. In this condition, the motion of, molecules and charge carriers are dependent on Temperature Gradient in a preferred direction. To increase this temperature gradient on both sides of the sample novel method for the preparation of MEs is developed for the first time. For this method the special sample holders are designed in our laboratory. MEs are prepared in such a way that one surface is cooled and the other is heated, during the process. With the help of XRD analysis using Type-E orientation pattern and surface charge studies on magnetoelectrets, the two main causes Non uniform magnetic field and temperature gradient for the format...

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