Browsing by Author "Kamal Kumar Pandey"

Now showing 1 - 4 of 4

Dielectric Study of Multiwall Carbon Nanotube Dispersed Nematic Liquid Crystal Mixture
(Elsevier Ltd, 2018) Pankaj Kumar Tripathi; Anil Kumar; Kamal Kumar Pandey
In the present work, multiwall carbon nanotube dispersed/doped nematic liquid crystal mixture have been synthesized by ultrasonication technique and studied using dielectric spectroscopy tools in the frequency range of 10 kHz-40 MHz. We have observed that the dielectric permittivity, loss and relaxation frequency of a nematic liquid crystal (MBBA) are influenced by the presence of multiwall carbon nanotube as a function of frequency and temperature. The value of dielectric permittivity increases with the dispersion of multiwall carbon nanotube due to π-π interaction of MWCNT and LC molecules. However, an increase in relaxation frequency is also found in dispersed samples. The MWCNT with almost identical size within themselves are dispersed at 0.5% concentration into nematic LC. The MWCNT-nematic LC composites are not only of fundamental importance, but also useful materials for device applications such as liquid crystal displays. © 2018 Elsevier Ltd.
Effect of UV light irradiation on the dielectric behaviour of liquid crystal/nano composite
(Taylor and Francis Inc., 2017) Kamal Kumar Pandey; Alok Chandra Dixit; M. Saleem khan; Pankaj Kumar Tripathi; Abhishek Kumar Misra; Rajiv Manohar
In this work, we investigate the effect of UV light irradiation on the dielectric parameters of the nematic liquid crystal (5CB) containing dispersed ZnO nanoparticles. With addition of nanoparticles, nematic LC's are promising new materials for a variety of applications in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however one must optimize the properties of liquid crystal and understand how UV light irradiation interacts with the nanoparticles and LC molecules in dispersed/doped LC. The dielectric permittivity and loss factor are discussed for the pure nematic LC and dispersed/doped system after, during and before UV light exposure. Dielectric relaxation spectroscopy was carried out in the frequency range 100 Hz-10 MHz in the nematic mesophase. © 2017 Taylor & Francis Group, LLC.
Electro-optic switching and memory effect in suspension of ferroelectric liquid crystal and iron oxide nanoparticles
(Institute of Physics Publishing, 2019) Abhishek Kumar Misra; Pankaj Kumar Tripathi; Kamal Kumar Pandey; Fanindra Pati Pandey; Shri Singh; Abhilasha Singh
In this work, impact of dispersion of iron oxide nanoparticles (Fe2O3 NPs) into ferroelectric liquid crystal (FLC) SCE-13 mixture on the electro-optical and dielectric properties has been studied. It has been found that the dispersion of Fe2O3 NPs in host FLC matrix exhibits pronounced influence on response time, spontaneous polarization, rotational viscosity and voltage required for switching the FLC molecules. Also dispersed system shows memory effect as confirmed by the optical texture and dielectric permittivity studies. Effort has been made to explain the experimental results as for as possible. © 2019 IOP Publishing Ltd.
Ferroelectric liquid crystal matrix dispersed with Cu doped ZnO nanoparticles
(2013) Dharmendra Pratap Singh; Swadesh Kumar Gupta; Kamal Kumar Pandey; Satya Prakash Yadav; M.C. Varia; Rajiv Manohar
Abstract 10% Cu doped ZnO nanoparticles (NPs) prepared by hydrothermal and solvothermal method have been dispersed to the pure FLC 17/100 in 1% concentration of guest entity. Electro-optical, elastic and dielectric analysis has been made for the FLC-NPs composite system with the variation of temperature. The nature of the composite system clearly shows the alteration in FLC parameters with the dispersion of NPs. The interaction between crystalline NPs and non-crystalline ferroelectric liquid crystal matrix modifies the properties of the pure FLC system. The synthesis method of NPs is also responsible for the changes taking place in physical properties of the pure FLC. The size and surface defects of the NPs amend the FLC parameters like dielectric permittivity, relaxation frequency, relaxation strength, tilt angle, spontaneous polarization and rotational viscosity etc. The coupling of spontaneous polarization and tilting of the FLC molecules are factors responsible for the resultant electro-optical (E-O) parameters of the composite system. © 2012 Elsevier B.V.