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Information × Registration Number 0212U006503, 0110U004525 , R & D reports Title Experimental physical characteristics study and application of stable inorganic nanoparticles dispersions in liquid crystals for optical information processing. popup.stage_title Head Reznikov Yuriy Olexandrovich, Registration Date 19-04-2012 Organization Institute of physics NASU popup.description2 This project is devoted to development and study of new materials based on liquid crystals doped with ferromagnetic and ferroelectric particles. Main goal of the project is (a) to expand functional properties of nematic and smectic LCs by adding nano-sized ferromagnetic and ferroelectric particles; (b) to provide stability of the dispersions and their solubility in LC matrix by improving surfactant properties: structure, adherence to inorganic surface of the NP, etc.; (c) to create comprehensive theory of LC nano-colloids and their behavior in electric and magnetic fields, and (d) to employ developed colloids in optical devices and for visualization of weak magnetic fields. Major tasks of the project are: to refine preparation method of stable nano- and micro-suspensions with magnetic particles of different nature based on nematic liquid crystals (thermotropic, lyotropic); to study basic physical (elastic, magnetic and magneto-optic) properties of the new type systems and their dependence on origin, size and structure of the particles; to develop a theory capable of forecasting system parameters, and prognosis new characteristics of the systems after doping liquid crystal with particles of different nature and shape. Main objects of research - liquid crystals with dispersed nano- and micro-particles, their macroscopic properties and response to external fields. During the project the following results have been obtained: 1.Liquid crystal hypersensitivity to magnetic field when doped with -filled carbon nanotubes is observed. Liquid crystal suspensions based on multilayered carbon nanotubes are reoriented by the magnetic field < 5 mT. It is shown that in liquid crystal cell magnetic dipole and van der Waals interactions between ferromagnetic nanotubes cause significant aggregation of the carbon nanotubes in nematic LC matrix, while anisotropy of the matrix favors elongated aggregates and orients them parallel to LC director. 2.It is found that adding spherical mono-dispersed hematite nanoparticles in low concentrations (1.4, 0.47, 0.23 and 0.12 vol.%) to nematic mineral lyotropic liquid crystal based on vanadium pentoxide causes giant increase of liquid crystal sensitivity to magnetic field, as well as decrease of magneto-induced Frederiks transition threshold. Strong magneto-induced birefringence is observed in the isotropic phase. It is shown that this effect is caused by strong orientational interaction between magneto-sensitive and insensitive components of the suspension. 3.Suspensions based on new surfactants, which provide increased stability of the particles in pentyl-cyanobiphenyl (5CB) nematic liquid crystal are studied. Side chains of the synthesized surfactants are similar to liquid crystal molecules and phosphate group provide strong interaction between surfactant and surface of the particles. It is shown that adding to nematic liquid crystal nano-particles with surfactant-modified surface decreases aggregation of the particles. While LC suspension shows reproducible and very strong response to the magnetic field. 4.The software is developed for numerical modeling of processes in ferronematic cells with twisted initial configuration of the nematic. It is shown that adding a small amount of (concentration ~ 5?10-9-5?10-11 cm-3) elongated (L/d?3) submicron (?300 nm) ferromagnetic particles to liquid crystal matrix essentially increases (by several orders of magnitude) system sensitivity to magnetic field. Process of particles' redistribution (segregation) in the system when changing applied magnetic field is studied. All the results are obtained for the first time and can be used to develop new composite materials and innovative devices for information processing, recording and display based on liquid crystalline systems. Suspensions with magneto-sensitive particles can be used to visualize weak magnetic forces. Product Description popup.authors Булуй Олександр Григорович Резніков Юрій Олександрович Слюсаренко Костянтин Юрійович popup.nrat_date 2020-04-02 Close