scholarly journals Tribological capabilities of chiral nematic liquid crystal additives in mineral motor oil

2020 ◽  
Vol 12 (7) ◽  
pp. 168781402094547
Author(s):  
Vadim Mokshin
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Coefficient Of Friction ◽  
Friction Pair ◽  
Contact Temperature ◽  
Test Machine ◽  
Regression Equations ◽  
Motor Oil ◽  
Oil Additives ◽  
Chiral Nematic

This article presents the results of experimental investigation of tribological properties of commercial mineral motor oil with chiral nematic (also known as twisted nematic or cholesteric) liquid crystal additives. Cholesteryl stearate and valerate (fatty acid cholesterol esters) liquid crystals were used as oil additives in investigation. Tribological experiments were performed using a block-on-disc-type tribo-test machine at constant experiment time and sliding velocity conditions. The load (contact pressure), concentration of liquid crystalline additive in oil and Rz roughness of steel–steel friction surfaces were taken as variable parameters. The mean coefficient of friction of steel–steel friction pair lubricated by oil with and without liquid crystal additives and near-contact temperature were taken as dependent variables. Regression equations were then derived for each lubricant and tribological efficiency of liquid crystals as oil additives was evaluated. It was established that coefficient of friction of steel–steel friction pair and near-contact temperature are reduced to about a half in the presence of liquid crystal additives. Results of tribological experiments show that tribological efficiency of liquid crystals as oil additives increases with increase in their molecular mass.

Effect of Photo-Isomerization of Azo Dyes on the Photonic Bandgap in Chiral Nematics

2011 ◽  
Vol 181-182 ◽  
pp. 257-260
Author(s):  
David Statman ◽  
Andrew Jockers ◽  
Daniel Brennan
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Azo Dyes ◽  
Azo Dye ◽  
Photonic Bandgap ◽  
Methyl Red ◽  
Central Wavelength ◽  
Chiral Nematic ◽  
Anchoring Energy ◽  
Pitch Length

Chiral nematic liquid crystals prepared with Grandjean texture demonstrate a photonic bandgap whose central wavelength is proportional to the pitch length, P, of the liquid crystal and whose width is given by (ne – no)P. We show that methyl red doped chiral nematics undergo a shift in the photonic bandgap upon photo-isomerization. This shift is a result of (1) photo-induced change in anchoring energy on the nematic surface, and (2) change in the natural pitch length from the photo-isomerization of the azo dye.

scholarly journals Beam splitting in chiral nematic liquid crystals

2018 ◽  
Vol 10 (4) ◽  
pp. 109
Author(s):  
Filip Sala
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Soft Matter ◽  
Nematic Liquid Crystals ◽  
Beam Propagation Method ◽  
Beam Propagation ◽  
Optical Solitons ◽  
Molecular Reorientation ◽  
Chiral Nematic

By lunching the beam into the chiral nematic liquid crystals it is possible to achieve a non-diffractive beam similar to a soliton. This effect is caused by the molecular reorientation i.e. nonlinear response of the material forming the areas of higher refractive index. Diffraction is suppressed by the focusing effect. For appropriate launching conditions it is also possible to achieve a beam which splits into two or more separate beams. Such phenomenon is discussed in this article and analyzed theoretical. To model this effect Fully Vectorial Beam Propagation Method coupled with the Frank-Oseen elastic theory is used. Simulations are performed for various input beam powers, widths, polarization angles and launching positions. Full Text: PDF ReferencesG. Assanto and M. A. Karpierz, "Nematicons: self-localised beams in nematic liquid crystals", Liq. Cryst. 36, 1161–1172 (2009) CrossRef G. Assanto, Nematicons: Spatial Optical Solitons in Nematic Liquid Crystals, John Wiley & Sons Inc. Hoboken, New Jersey (2013) DirectLink A. Piccardi, A. Alberucci, U. Bortolozzo, S. Residori, and G. Assanto, "Soliton gating and switching in liquid crystal light valve", Appl. Phys. Lett. 96, 071104 (2010). CrossRef D. Melo, I. Fernandes, F. Moraes, S. Fumeron, and E. Pereira, "Thermal diode made by nematic liquid crystal", Phys. Lett. A 380, 3121 – 3127 (2016). CrossRef U. Laudyn, M. Kwaśny, F. A. Sala, M. A. Karpierz, N. F. Smyth, G. Assanto, "Curved optical solitons subject to transverse acceleration in reorientational soft matter", Sci. Rep. 7, 12385 (2017) CrossRef M. Kwaśny, U. A. Laudyn, F. A. Sala, A. Alberucci, M. A. Karpierz, G. Assanto, "Self-guided beams in low-birefringence nematic liquid crystals", Phys. Rev. A 86, 013824 (2012) CrossRef F. A. Sala, M. M. Sala-Tefelska, "Optical steering of mutual capacitance in a nematic liquid crystal cell", J. Opt. Soc. Am. B. 35, 133-139 (2018) CrossRef U. A. Laudyn, A. Piccardi, M. Kwasny, M. A. Karpierz, G. Assanto, "Thermo-optic soliton routing in nematic liquid crystals", Opt. Lett. 43, 2296-2299 (2018) CrossRef F. A. Sala, M. M. Sala-Tefelska, M. J. Bujok, J. "Influence of temperature diffusion on molecular reorientation in nematic liquid crystals", Nonlinear Opt. Phys. Mater. 27, 1850011 (2018) CrossRef I-C Khoo Liquid crystals John Wiley & Sons, Inc (2007) DirectLink P. G. de Gennes, J. Prost, The Physics of Liquid Crystals, Clarendon Press (1995) DirectLink U. A. Laudyn, P. S. Jung, M. A. Karpierz, G. Assanto, "Quasi two-dimensional astigmatic solitons in soft chiral metastructures", Sci. Rep. 6, 22923 (2016) CrossRef J. Beeckman, A. Madani, P. J. M. Vanbrabant, P. Henneaux, S-P. Gorza, M. Haelterman, "Switching and intrinsic position bistability of soliton beams in chiral nematic liquid crystals", Phys. Rev. A 83, 033832 (2011) CrossRef A. Madani, J. Beeckman, K. Neyts, "An experimental observation of a spatial optical soliton beam and self splitting of beam into two soliton beams in chiral nematic liquid crystal", Opt. Commun. 298–299, 222-226, (2013) CrossRef G. D. Ziogos, E. E. Kriezis, "Modeling light propagation in liquid crystal devices with a 3-D full-vector finite-element beam propagation method", Opt. Quant. Electron 40, 10 (2008) CrossRef F. A. Sala, M. A. Karpierz, "Chiral and nonchiral nematic liquid-crystal reorientation induced by inhomogeneous electric fields", J. Opt. Soc. Am. B 29, 1465-1472 (2012) CrossRef F. A. Sala, M. A. Karpierz, "Modeling of molecular reorientation and beam propagation in chiral and non-chiral nematic liquid crystals", Opt. Express 20, 13923-13938 (2012) CrossRef F. A. Sala, "Design of false color palettes for grayscale reproduction", Displays, 46, 9-15 (2017) CrossRef

scholarly journals Experimental Evaluation of Oxide Nanoparticles as Friction and Wear Improvement Additives in Motor Oil

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Nicholaos G. Demas ◽  
Robert A. Erck ◽  
Cinta Lorenzo-Martin ◽  
Oyelayo O. Ajayi ◽  
George R. Fenske
Keyword(s):  
Laboratory Test ◽  
Coefficient Of Friction ◽  
Friction And Wear ◽  
Oxide Nanoparticles ◽  
Test Machine ◽  
Motor Oil ◽  
Test Configuration ◽  
Test Conditions ◽  
Contact Configuration ◽  
The Coefficient Of Friction

The effect of two nanoparticle oxides on friction and wear was studied under laboratory test conditions using a reciprocating test machine and two test configurations. The addition of these nanoparticles in base stock oil under certain conditions reduced the coefficient of friction and improved wear, but that depended on the test configuration. Examination of the rubbed surfaces showed the pronounced formation of a tribofilm in some cases, while polishing on the surface was also observed in other cases. Contact configuration is important when oxide nanoparticles are being evaluated and the conclusions about their efficacy can be vastly different.

Research of Tribological Properties of Mineral Motor Oil with Cholesteryl Stearate Additive

2009 ◽  
Vol 147-149 ◽  
pp. 552-557
Author(s):  
Vadim Mokshin ◽  
Vladas Vekteris
Keyword(s):  
Liquid Crystal ◽  
Average Height ◽  
Regression Equations ◽  
Motor Oil ◽  
Friction Zone ◽  
Friction Process ◽  
Controllable Factors ◽  
Twisted Nematic ◽  
Twisted Nematic Liquid Crystal ◽  
Zone Temperature

Results of tribological research of mineral motor oil with and without twisted nematic liquid crystal additive (stearic acid cholesteryl ester) are presented in the article. Experimental research was performed by means of a “fixed segment – rotating roller” tribometer according to the central three-factor second-order rotatable factorial design. The following parameters were accepted as controllable factors: contact pressure (3.32–6.68 MPa), concentration of liquid crystal in lubricant (0.16–1.84 ) and the average height of surface roughness of contacting surfaces of roller and segment (2.5–37.5 μm). The friction coefficient and friction zone temperature were served as output parameters. Regression equations describing the friction process were obtained and tribological efficiency of liquid crystal additive was established.

scholarly journals Reorientation behavior in the helical motility of light-responsive spiral droplets

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Federico Lancia ◽  
Takaki Yamamoto ◽  
Alexander Ryabchun ◽  
Tadatsugu Yamaguchi ◽  
Masaki Sano ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Molecular Motors ◽  
Chemical Processes ◽  
Water Droplets ◽  
Left Handed ◽  
Chiral Nematic ◽  
Physico Chemical ◽  
Unicellular Organisms ◽  
Chiral Dopants

AbstractThe physico-chemical processes supporting life’s purposeful movement remain essentially unknown. Self-propelling chiral droplets offer a minimalistic model of swimming cells and, in surfactant-rich water, droplets of chiral nematic liquid crystals follow the threads of a screw. We demonstrate that the geometry of their trajectory is determined by both the number of turns in, and the handedness of, their spiral organization. Using molecular motors as photo-invertible chiral dopants allows converting between right-handed and left-handed trajectories dynamically, and droplets subjected to such an inversion reorient in a direction that is also encoded by the number of spiral turns. This motile behavior stems from dynamic transmission of chirality, from the artificial molecular motors to the liquid crystal in confinement and eventually to the helical trajectory, in analogy with the chirality-operated motion and reorientation of swimming cells and unicellular organisms.

Observation of blue phase in chiral nematic liquid crystal and its stabilization by silica nanoparticles

2016 ◽  
Vol 30 (05) ◽  
pp. 1650011 ◽  
Author(s):  
Arshdeep Singh ◽  
Praveen Malik ◽  
Divya Jayoti
Keyword(s):  
Thermal Stability ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Binary Mixture ◽  
Silica Nanoparticles ◽  
Formation Process ◽  
Temperature Range ◽  
Chiral Nematic ◽  
Blue Phase ◽  
Thermal Stability Of

In the present work, we report the blue phase (BP) in a binary mixture of cholesteryl nonanoate (CN) and N-(4-ethoxybenzylidene)-4-butylaniline (EBBA). The mixture exhibits BP over a temperature range of 2.3 K at optimum composition (50:50) of liquid crystals (LCs). The effect of silica nanoparticles (SNPs) doping on thermal stability of BPs has also been demonstrated and nearly 6 K wide BP temperature range was achieved at 0.5 wt.% of SNPs. A porous type texture was also observed during the BP formation process in the doped samples.

scholarly journals Dual electrically and thermally responsive broadband reflectors based on polymer network stabilized chiral nematic liquid crystals: the role of crosslink density

2016 ◽  
Vol 52 (66) ◽  
pp. 10109-10112 ◽  
Author(s):  
Hitesh Khandelwal ◽  
Gilles H. Timmermans ◽  
Michael G. Debije ◽  
Albertus P. H. J. Schenning
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Crosslink Density ◽  
Nematic Liquid Crystals ◽  
Polymer Network ◽  
Thermally Responsive ◽  
Chiral Nematic ◽  
Polymer Stabilized

An adjustable broadband reflector based on a polymer stabilized chiral nematic liquid crystal has been fabricated.

NEMATICONS PROPERTIES AND STABILITY IN CHIRAL NEMATIC LIQUID CRYSTAL

2012 ◽  
Vol 21 (03) ◽  
pp. 1250036 ◽  
Author(s):  
URSZULA A. LAUDYN ◽  
FILIP A. SALA ◽  
MIROSŁAW A. KARPIERZ
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Beam ◽  
Nematic Liquid Crystal ◽  
Nematic Liquid Crystals ◽  
Beam Propagation ◽  
Numerical Results ◽  
Spatial Solitons ◽  
High Birefringence ◽  
Chiral Nematic

We report on the experimental and numerical results of the nonlinear light beam propagation in planar samples of chiral nematic liquid crystals, for both high- and low-birefringence chiral nematic liquid crystals. We investigate the properties and stability of obtained nematicons. We found that reorientational spatial solitons require larger excitation powers in low-birefringence chiral nematics than in high-birefringence but remain more stable and self-focused.

Temperature dependence of the pitch in chiral lyotropic chromonic liquid crystals

Soft Matter ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 109-115 ◽  
Author(s):  
Timothy Ogolla ◽  
Robert S. Paley ◽  
Peter J. Collings
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Temperature Dependence ◽  
Optical Microscopy ◽  
Helical Axis ◽  
Coexistence Region ◽  
Polarized Optical Microscopy ◽  
Chiral Nematic ◽  
Microscopy Image ◽  
Optical Microscopy Image

Polarized optical microscopy image of a fingerprint texture for a lyotropic chromonic liquid crystal entering the chiral nematic–isotropic coexistence region. The helical axis is in the plane of the image and the perpendicular distance between the stripes is around 50 μm, half the chiral nematic pitch.

New structure induced by elastic anisotropy in cylindrical nematic liquid crystal

2017 ◽  
Vol 13 (2) ◽  
pp. 4705-4717
Author(s):  
Zhang Qian ◽  
Zhou Xuan ◽  
Zhang Zhidong
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Elastic Anisotropy ◽  
Nematic Liquid Crystals ◽  
Gennes Theory

Basing on Landau–de Gennes theory, this study investigated the chiral configurations of nematic liquid crystals confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls. When the elastic anisotropy (L2/L1) is large enough, a new structure results from the convergence of two opposite escape directions of the heterochiral twist and escape radial (TER) configurations. The new defect presents when L2/L1≥7 and disappears when L2/L1<7. The new structure possesses a heterochiral hyperbolic defect at the center and two homochiral radial defects on both sides. The two radial defects show different chiralities.

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