High concentration ferronematics in low magnetic fields

We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field $B_{bias}$, and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that $B_{bias}$ is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role.Comment: 13 pages, 6 figure

Saturation effect for dependence of the electrical conductivity of planar oriented nematic liquid crystal 6CB on the concentration of Cu7PS6 nanoparticles

The influence of Cu7PS6 nanoparticles with the average size 117 nm on the dielectric properties of planar oriented nematic liquid crystal 6CB has been investigated within the frequency range 10(1) ...10(6) Hz and at the temperature 293 K. It has been shown that when changing the concentration of nanoparticles within the range 0 to 1 wt.%, the conductivity of the liquid crystal changes stronger than its dielectric permittivity. It has been shown that the electrical conductivity increases monotonously with increasing the concentration of nanoparticles. However, for this dependence a saturation effect is observed. The mechanism of this effect was proposed.info:eu-repo/semantics/publishedVersio

Infrared study of biocompatible magnetic nanoparticles

Abstract. Magnetic fluids mainly consist of nano sized iron oxide particles (F

Characterization of Carbon Nanotubes

The aim of the presented work was to characterize single-walled carbon nanotubes as well as multi-walled carbon nanotubes by transmission electron microscopy, the Raman spectroscopy and magnetization measurements to obtain information about their size, structure, and magnetic properties. We show that having different carbon nanotubes one can easily distinguish the single-wall or multi-wall carbon nanotubes and determine their quality. The obtained results show that carbon nanotubes can be diamagnetic or ferromagnetic depending on their structural parameters

Dielectric properties of nematic liquid crystals with Fe₃O₄ nanoparticles in direct magnetic field

Researched within the frequency range 10⁻¹–10⁶ Hz were dielectric properties of pure 6CHBT liquid crystals and 6CHBT ones with the impurity of Fe₃O₄ nanoparticles that have the mean diameter 5 nm and weight concentration 10⁻⁴ %. The study was performed without and under the influence of direct magnetic field with the induction 0.45 and 0.60 T. It has been shown that the magnetic field influences on the parameters of the near-electrode area of liquid crystal. In the case of liquid crystal with magnetic nanoparticles, the parameter changes caused by the magnetic field depend on the induction value

Dielectric and electrical properties of nematic liquid crystals 6CB doped with iron oxide nanoparticles. The combined effect of nanodopant concentration and cell thickness

Dispersing nanomaterials in liquid crystals has emerged as a very promising non-synthetic way to produce advanced multifunctional and tunable materials. As a rule, dielectric and electrical characterization of such materials is performed using cells of single thickness. As a result, the published reports vary even for similar systems. Confusion still exists as to the effects of nanodopants and cell thickness on the dielectric and electrical properties of liquid crystals. This factor hinders a widespread use of liquid crystals – nanoparticles systems in modern tech products. In this paper, we report systematic experimental studies of the combined effect of the cell thickness and iron oxide nanoparticle concentration on the electrical and dielectric properties of nematic liquid crystals 6CB. The measured dielectric spectra can be divided into three distinct regions corresponding to a low frequency (<10 Hz) dispersion, dispersion free range (102 - 104 Hz (electrical conductivity) and 102 - 105 (dielectric permittivity)), and high frequency dispersion (104 - 106 Hz (electrical conductivity) and 105 - 106 Hz (dielectric permittivity)). The real part of the dielectric permittivity is not affected by the cell thickness and its value can be tuned by changing the concentration of nanoparticles. At the same time, the electrical conductivity depends on both cell thickness and nanoparticle concentration. At intermediate frequencies (102 - 104 Hz) the electrical conductivity obeys the Jonscher power law and is dependent on the cell thickness because of ion-releasing and ioncapturing effects caused by nanoparticles and substrates of the cell. In addition, its value is affected by the electronic conductivity due to iron oxide nanoparticles and their nanoclusters. At higher frequencies (104 - 106 Hz) the electrical conductivity follows a super linear power law and is nearly independent of the cell thickness and nanoparticle concentration

Peculiarities of nonadditive changes in conductivity of nano-PDLC under influence of magnetite and single-wall carbon nanotubes

Studied in this work has been the effect of nanoparticles – magnetite and single-wall carbon nanotubes – separately and together on the conductivity of nematic liquid crystal 6CHBT dispersed in polyvinyl alcohol. Morphology of these films was analyzed using an electron microscope. When using selected technologyof homogenizing the mixture components, there takes place formation of liquid crystals dispersed in the polymer matrix with the average sizes of liquid-crystal droplets close to 500 nm (nanoPDLC). It has been found that simultaneous introduction of magnetite and nanotubes results in lowering the conductivity of nano-PDLC as compared to the total conductivity of nano-PDLC with each kind of nanoparticles separately. It has been suggested that the main mechanism of this effect lies in formation of deep centers for electron capture by complexes with different types of nanoparticles, which leads to a decrease in electronic conductivity through the polymer matrix