Effective permittivity of liquid crystal nanodispersions and composites with different pore structure

A tunable substrate-integrated waveguide phase shifter using low-temperature co-fired ceramic (LTCC)-technology is presented in this paper. By changing the effective permittivity in the liquid crystal (LC)-filled waveguide, the differential phase can be tuned continuously. This is achieved by means of an analog signal applied to the electrodes, surrounding the LC. The design allows for precise tuning of the differential phase, which is proven with a Monte Carlo measurement resulting in phase errors of less than 3° at 28 GHz. Besides that, the ambient temperature dependency of the module is shown. The phase shifter has a high integration level and can be included into a complete and lightweight single-phased array antenna module. The phase shifter is realized with a high level of integration which is available through the multilayer process of the LTCC. It has a length of 50 and provides a differential phase shift of more than 360° at 28 GHz. The figure of merit for tunable phase shifters is >40°/dB.

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Study of electrical behavior of liquid crystal devices doped with titanium dioxide nanoparticles

Photonics Letters of Poland ◽

10.4302/plp.v9i1.712 ◽

2017 ◽

Vol 9 (1) ◽

pp. 20

Author(s):

Vicente Marzal ◽

Juan Carlos Torres ◽

Braulio García ◽

Isabel Pérez ◽

José Manuel Sánchez ◽

...

Keyword(s):

Titanium Dioxide ◽

Liquid Crystal ◽

Liquid Crystals ◽

Titanium Dioxide Nanoparticles ◽

Liquid Crystal Display ◽

Electrical Response ◽

Nematic Liquid Crystals ◽

Effective Permittivity ◽

Temperature Phase ◽

Ferroelectric Liquid Crystal

In the last years, nanostructures are widely used as dopants in liquid crystals to manipulate either their electrical or optical properties. In this work, we have analyzed the electrical response of a planar cell filled with a mixture of E7 liquid crystal doped with TiO2 nanoparticles. The effect of these dopants on the effective permittivity and conductivity of the cell has been studied in a wide frequency range at different temperatures. Full Text: PDF ReferencesP.J. Pinzón, I. Pérez, C. Vázquez and J.M.S. Pena, "Reconfigurable ????×????1×2 wavelength selective switch using high birefringence nematic liquid crystals", App.Opt. 51, pp.5960-5965 (2012) CrossRef C. Carrasco-Vela, X. Quintana, E.Otón, M.A. Geday, J.M. Otón, "Security devices based on liquid crystals doped with a colour dye", Opto?Electron. 19, pp.496-500 (2011). CrossRef J. Torrecilla, E. Ávila-Navarro, C. Marcos, V. Urruchi, J.M.S. Pena, J. Arias, M.M Sánchez-López, "Microwave Tunable Notch Filter Based on Liquid Crystal Using Spiral Spurline Technology", Microw. Opt. Technol. Lett. 55, 2420-2423 (2013). CrossRef G.B. Hadjichristov, Y. G. Marinov, A. G. Petrov, E. Bruno, L.Marino, N. Scaramuzzab, "Electro-Optics of Nematic/Gold Nanoparticles Composites: The Effect from Dopants", Mol. Cryst. Liq. Cryst. 610, 135?148 (2015). CrossRef T. Miyama, J. Thisayukta, H. Shiraki, Y. Sakai, Y. Shiraishi, N. Toshima, S. Kobayashi, "Fast Switching of Frequency Modulation Twisted Nematic Liquid Crystal Display Fabricated by Doping Nanoparticles and Its Mechanism", Jpn. J. Appl. Phys. 43, 2580 -2584 (2004). CrossRef W. T. Chen, P. S. Chen, C. Y. Chao, "Effect of Doped Insulating Nanoparticles on the Electro-Optical Characteristics of Nematic Liquid Crystals", Jpn. J. Appl. Phys. 48, 015006 (2009) CrossRef A. Siarkowska, M. Chychłowski, T.R. Woliński and A.Dybko. "Titanium nanoparticles doping of 5CB infiltrated microstructured optical fibers", Phot. Lett. Poland 8, 29-31 (2016). CrossRef O. Buchnev, A. Dyadyusha,M. Kaczmarek, V.Reshetnyak, Y. Reznikov, "Enhanced two-beam coupling in colloids of ferroelectric nanoparticles in liquid crystals", J. Opt. Soc. Am. 24, 1512-1516 (2004). CrossRef A. García-García, R. Vergaz, J.A. Algorri, X. Quintana, J.M. Otón, Beilstein J. "Electrical response of liquid crystal cells doped with multi-walled carbon nanotubes", Nanotechnol. 6, 396?403 (2015). CrossRef R. Pratibha, K. Park, I.I. Smalyukh and W. Park, "Tunable optical metamaterial based on liquid crystal-gold nanosphere composite", Opt. Express 17,19459-19469 (2009). CrossRef J.C. Torres, B. Garcia-Camara, I. Perez, V. Urruchi, J.M. Sanchez-Pena, "Temperature-Phase Converter Based on a LC Cell as a Variable Capacitance", Sensors 15, 5594 ? 5608 (2015). CrossRef P. Kumar, A. Kishore and A, Sinha, "Effect of different concentrations of dopant titanium dioxide nanoparticles on electro-optic and dielectric properties of ferroelectric liquid crystal mixture ", Adv. Mater. Lett. 7, 104-110 (2016). CrossRef R.K. Shukla, C.M. Liebig, D.R. Evans, and W. Haase, "Electro-optical behaviour and dielectric dynamics of harvested ferroelectric LiNbO3 nanoparticle-doped ferroelectric liquid crystal nanocolloids", RSC Adv. 4, 18529-18536 (2014). CrossRef

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Effective Permittivity of a Multi-Phase System: Nanoparticle-Doped Polymer-Dispersed Liquid Crystal Films

Molecules ◽

10.3390/molecules26051441 ◽

2021 ◽

Vol 26 (5) ◽

pp. 1441

Author(s):

Doina Manaila-Maximean

Keyword(s):

Liquid Crystal ◽

Effective Permittivity ◽

General Character ◽

Phase System ◽

Liquid Crystal Films ◽

Polymer Dispersed Liquid Crystal ◽

Crystal Films ◽

Polymer Dispersed ◽

Type Particle ◽

Multi Phase

This paper studies the effective dielectric properties of heterogeneous materials of the type particle inclusions in a host medium, using the Maxwell Garnet and the Bruggeman theory. The results of the theories are applied at polymer-dispersed liquid crystal (PDLC) films, nanoparticles (NP)-doped LCs, and developed for NP-doped PDLC films. The effective permittivity of the composite was simulated at sufficiently high frequency, where the permittivity is constant, obtaining results on its dependency on the constituents’ permittivity and concentrations. The two models are compared and discussed. The method used for simulating the doped PDLC retains its general character and can be applied for other similar multiphase composites. The methods can be used to calculate the effective permittivity of a LC composite, or, in the case of a composite in which one of the phases has an unknown permittivity, to extract it from the measured composite permittivity. The obtained data are necessary in the design of the electrical circuits.

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Freeze-fracture TEM of the helical smectic A* phase

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012179x ◽

1992 ◽

Vol 50 (1) ◽

pp. 278-279

Author(s):

K.J. Ihn ◽

R. Pindak ◽

J. A. N. Zasadzinski

Keyword(s):

Liquid Crystal ◽

Grain Boundary ◽

Grain Boundaries ◽

Freeze Fracture ◽

Smectic Phase ◽

Layer Spacing ◽

Screw Dislocations ◽

Smectic A ◽

Smectic Phases ◽

Discrete Amount

A new liquid crystal (called the smectic-A* phase) that combines cholesteric twist and smectic layering was a surprise as smectic phases preclude twist distortions. However, the twist grain boundary (TGB) model of Renn and Lubensky predicted a defect-mediated smectic phase that incorporates cholesteric twist by a lattice of screw dislocations. The TGB model for the liquid crystal analog of the Abrikosov phase of superconductors consists of regularly spaced grain boundaries of screw dislocations, parallel to each other within the grain boundary, but rotated by a fixed angle with respect to adjacent grain boundaries. The dislocations divide the layers into blocks which rotate by a discrete amount, Δθ, given by the ratio of the layer spacing, d, to the distance between grain boundaries, lb; Δθ ≈ d/lb (Fig. 1).

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Attractive mode force microscopy of chiral liquid crystal surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121740 ◽

1992 ◽

Vol 50 (1) ◽

pp. 268-269

Author(s):

B.D. Terris ◽

R. J. Twieg ◽

C. Nguyen ◽

G. Sigaud ◽

H. T. Nguyen

Keyword(s):

Liquid Crystal ◽

Crystal Surfaces ◽

Free Surfaces ◽

Control Range ◽

Force Microscopy ◽

Liquid Crystal Films ◽

Chiral Liquid Crystal ◽

Crystal Films ◽

Electrostatic Charging ◽

And Shifts

We have used a force microscope in the attractive, or noncontact, mode to image a variety of surfaces. In this mode, the microscope tip is oscillated near its resonant frequency and shifts in this frequency due to changes in the surface-tip force gradient are detected. We have used this technique in a variety of applications to polymers, including electrostatic charging, phase separation of ionomer surfaces, and crazing of glassy films.Most recently, we have applied the force microscope to imaging the free surfaces of chiral liquid crystal films. The compounds used (Table 1) have been chosen for their polymorphic variety of fluid mesophases, all of which exist within the temperature control range of our force microscope.

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Correlation of Pore Structure and Permeability by SEM-Image Analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100180896 ◽

1990 ◽

Vol 48 (1) ◽

pp. 428-429

Author(s):

C. A. Callender ◽

Wm. C. Dawson ◽

J. J. Funk

Keyword(s):

Image Analysis ◽

Pore Structure ◽

Imaging System ◽

Pore Space ◽

Simulation Models ◽

Image Analyzer ◽

Imaging Data ◽

Sem Images ◽

Thin Sections ◽

Rock Types

The geometric structure of pore space in some carbonate rocks can be correlated with petrophysical measurements by quantitatively analyzing binaries generated from SEM images. Reservoirs with similar porosities can have markedly different permeabilities. Image analysis identifies which characteristics of a rock are responsible for the permeability differences. Imaging data can explain unusual fluid flow patterns which, in turn, can improve production simulation models.Analytical SchemeOur sample suite consists of 30 Middle East carbonates having porosities ranging from 21 to 28% and permeabilities from 92 to 2153 md. Engineering tests reveal the lack of a consistent (predictable) relationship between porosity and permeability (Fig. 1). Finely polished thin sections were studied petrographically to determine rock texture. The studied thin sections represent four petrographically distinct carbonate rock types ranging from compacted, poorly-sorted, dolomitized, intraclastic grainstones to well-sorted, foraminiferal,ooid, peloidal grainstones. The samples were analyzed for pore structure by a Tracor Northern 5500 IPP 5B/80 image analyzer and a 80386 microprocessor-based imaging system. Between 30 and 50 SEM-generated backscattered electron images (frames) were collected per thin section. Binaries were created from the gray level that represents the pore space. Calculated values were averaged and the data analyzed to determine which geological pore structure characteristics actually affect permeability.

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