• Praveen Malik

      Articles written in Bulletin of Materials Science

    • Morphological control and polarization switching in polymer dispersed liquid crystal materials and devices

      K K Raina Pankaj Kumar Praveen Malik

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      Liquid crystals dispersed in polymer systems constitute novel class of optical materials. The precise control of the liquid crystal droplet morphology in the polymer matrix is essentially required to meet the prerequisites of display device. Experiments have been carried out to investigate and identify the material properties and processing conditions required for the precise control of the droplet morphology of the dispersed liquid crystal systems. Polarization switching has been studied. Aligned liquid crystal dispersed systems showed higher polarization over unaligned ones.

    • Improvement in electro-optical and dielectric characteristics of ZnO nanoparticles dispersed in a nematic liquid crystal mixture

      AMIT SHARMA PRAVEEN MALIK RAVINDRA DHAR PANKAJ KUMAR

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      Reported herein is the effect of dispersion of a fixed amount of 0.5% (wt/wt) ZnO nanoparticles (NPs) in a nematic (E7) liquid crystal (LC) mixture. Dispersion of ZnO NPs results in a significant improvement in electro-optical and dielectric parameters of the nematic mixture. Comparative analysis of undoped and NP-dispersed samples shows a reduced threshold voltage with better transmittance without compromising dielectric permittivity characteristics. In addition, an increase in the contrast ratio, birefringence, alternating-current conductivity and band gap was observed after dispersion of ZnO NPs in LCs. A polarized optical microscopic study of the NP-dispersed sample substantiates a slight increase in nematic–isotropic phase transition temperature of LCs.

    • Interdependency among electro-optic characteristics and absorption coefficient of homeotropically aligned liquid crystal considering Beer’s law theory

      CHINKY PANKAJ KUMAR ANKIT RAI DOGRA PRAVEEN MALIK

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      In the present study, interdependency among electro-optic (E-O) characteristics and absorption coefficient of homeotropically aligned liquid crystal (HALC) considering Beer’s law theory has been studied. Specifically, HALC cellswere prepared using uniform dispersion of ZnO nanoparticles into the nematic liquid crystal without applying any surface treatment to the substrates. Then azo dichroic dye (orange) was added in a fixed concentration to the prepared nanoparticles dispersed LC mixture. The morphological and absorption characteristics of prepared HALC cells were found to be improved with the addition of azo dichroic dye. The optical textures observed at macroscopic and microscopic levels are in correspondence with each other and showed excellent OFF/ON switching with magnificently dark and bright views. Moreover, HALC cells doped with azo dichroic dye exhibited a higher value of absorption coefficient with an improved contrast ratio. Thus, a good consistency was observed among experimentally observed E-O characteristics and theoretically measured absorption coefficient.

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    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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