Browsing by Author "Srivastava, A.K."

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    Effect of nickel oxide nanoparticles on dielectric and optical properties of nematic liquid crystal
    (American Institute of Physics Inc., 2015) Jamwal, G.; Prakash, J.; Chandran, A.; Gangwar, J.; Srivastava, A.K.; Biradar, A.M.
    In the present paper, we have studied the improvement in dielectric and optical properties of nematic liquid crystal (NLC) by doping of nickel oxide (NiO) nanoparticles. We have observed the dielectric and optical properties of pure and doped cells in order to understand the influence of NiO nanoparticles in the pure NLC. The experimental results have been analyzed through dielectric spectroscopic and optical texural methods.Detailed studies of dielectric parameters such as dielectric permittivity, dielectric loss and dielectric loss factor as a function of frequency with temperature were carried out. It has been observed that on doping the nanoparticles in NLC, the value of dielectric parameters (dielectric permittivity, dielectric loss and dielectric loss factor) decreases. The impedance and resistance of both pure and nanoparticles doped NLC cells were studied and found that for doped NLC, these parameter have low value. In addition to this, optical textures of the pure and doped samples have also been observed with a polarizing optical microscope at room temperature. All the results i.e. related to the investigation of dielectric and electro-optic properties have been explained by using existing theory of NLC. ? 2015 AIP Publishing LLC.
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    Preparation and characterization of MgO nanoparticles/ferroelectric liquid crystal composites for faster display devices with improved contrast
    (2014) Chandran, Achu; Prakash, Jai; Naik, Kush Kumar; Srivastava, Avanish; Dabrowski, Roma; Czerwinki, Michat; Biradar, A. M.; Chandran, A.; Prakash, J.; Naik, K.K.; Srivastava, A.K.; Da?browski, R.; Czerwi?ski, M.; Biradar, A.M.
    In this article, we present the formulation and characterization of a ferroelectric liquid crystal (FLC) mixture W301 composed of pyrimidine compounds. We observed that upon doping magnesium oxide nanoparticles (MgO NPs) into the host FLC, the MgO NPs/FLC composite showed significantly faster response and improved optical tilt angle. The decreased response time in the MgO NPs/FLC composite has been attributed to the decrease in rotational viscosity and increase in surface anchoring energy. The decrease in rotational viscosity of the composite is due to the torque experienced by both MgO NPs and FLC in the presence of an electric field and perturbations of order parameters of FLC. Due to the enhanced surface interaction of MgO NPs having surface defects with mesogens, strong surface anchoring is experienced on the FLC molecules that not only increased the speed of the response but also improved the optical tilt angle of the MgO NPs/FLC composites, which ultimately resulted in improved contrast. A systematic approach has been followed to elucidate the idea of designing faster display devices with improved contrast based on MgO NPs/FLC composites. ? 2014 The Royal Society of Chemistry.