Interface interactions in benzophenone doped by multiwalled carbon nanotubes

Lebovka, Nikolaï; Goncharuk, A. I.; Melnyk, V. I.; Puchkovska, G.

doi:10.1016/j.physe.2009.04.038

Cited by 9 publications

(9 citation statements)

References 20 publications

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“…A theory predicts an inverse proportionality between c c and the aspect ratio r of the conductive filler particles, c c~1 /r (Balberg et al, 1984;Foygel et al, 2005). For CNTs with very high aspect ratio, typically, r500-1000, this theoretical estimation results in extremely low values of the percolation threshold, c c <0.1 wt %, which is in full correspondence with available experimental data (Lisunova et al, 2007;Mamunya et al, 2008;Lebovka et al, 2009). The percolation behavior of electrical conductivity in different LC-CNTs composites was recently reported (Lisetski et al, 2007;Lebovka et al, 2008;Koval'chuk et al, 2008;Lisetski et al, 2009;Goncharuk et al, 2009).…”

Section: Percolation Behaviorsupporting

confidence: 76%

“…It lowers degree of connectivity of the nanotubes. Besides, the initial network is also partially damaged by thermal expansion of the host EBBA matrix (Lebovka et al, 2008;Lebovka et al, 2009). At high concentration of CNTs the network formed in LC is rather strong because of high density of connectedness between the nanotubes.…”

Section: Hysteretic Behavior and Effect Of Positive Temperature Coeffmentioning

confidence: 99%

See 1 more Smart Citation

Liquid Crystal Dispersions of Carbon Nanotubes: Dielectric, Electro-Optical and Structural Peculiarities

Dolgov¹,

Koval’chuk²,

Lebovka³

et al. 2010

Carbon Nanotubes

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A present chapter is focused on remarkable dielectric, electro-optical and micro-structural peculiarities of LC-CNTs dispersions, their correlation and mutual influence. It is mainly based on authors' original results obtained within recent years. The structure of this chapter is the following. The introductory part (section 1) gives short introduction to LC-CNTs composites and elucidates benefit of combination of LC and CNTs. It also outlines a field of questions further considered. A section 2 gives details of our samples and experimental methods. The next three sections correspondingly consider dielectric, electro-optical and structural peculiarities of LC-CNTs composites. Each of these topical sections starts with a short review and lasts with the authors' original results. The final, conclusion part (Section 6), summarizes most interesting properties of LC-CNTs suspensions, their application perspectives and mention some exciting problems for further investigations. www.intechopen.com Liquid crystal dispersions of carbon nanotubes: dielectric, electro-optical and structural peculiarities 453 power of 150 W. The concentration of CNTs, c, was varied in the range 0-2 wt %. Doping of CNTs has not influenced essentially the phase transition temperatures of LC-CNTs composites. 2.4 Cells The cells for electro-optical and dielectric measurements were made from glass substrates containing patterned ITO electrodes and aligning layers of polyimide. The polyimides AL2021 (JSR, Japan) and SE5300 (Nissan Chemicals, Japan) were used for homeotropic alignment of LC EBBA, MLC6608 and MLC6609, while the polyimide SE150 (Nissan Chemicals, Japan) was utilized for planar alignment of LC 5CB. The polyimide layers were rubbed by a fleecy cloth in order to provide a uniform planar alignment of LC in either fieldon state (EBBA, MLC6608 and MLC6609) or a zero field (5CB). The cells were assembled so that the rubbing directions of the opposite aligning layers were antiparallel. A cell gap was maintained by the glass spacers of appropriate size (16 m, if not otherwise stated). Finally, these cells were filled capillary with neat or CNTs doped liquid crystals heated to isotropic state. In some dielectric measurements the cells without alignment layers were utilized. The structure of LC-CNTs composites was monitored by observation of the filled cells placed between crossed polarizers, both by naked eye and in an optical polarizing microscope. 2.5 Electro-optical measurements The electro-optical measurements were carried out using the experimental setup described in (Koval'chuk et al., 2001a). The cell was set between two crossed polarizers so that the angle between the polarizer axes and the rubbing direction was 45°. The sinusoidal voltage 0-60 V (at frequency f=2 kHz) was applied to the cell. The voltage was stepwise increased from 0 to 60 V and then decreased back to 0; the total measuring time, i.e., time of voltage application, was about 1 min. The transmittance of the samples was calculated as =(I out /I in)*100%, where I in and ...

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Section: Percolation Behaviorsupporting

confidence: 76%

Section: Hysteretic Behavior and Effect Of Positive Temperature Coeffmentioning

confidence: 99%

Liquid Crystal Dispersions of Carbon Nanotubes: Dielectric, Electro-Optical and Structural Peculiarities

Dolgov¹,

Koval’chuk²,

Lebovka³

et al. 2010

Carbon Nanotubes

View full text Add to dashboard Cite

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“…4. The heating-cooling hysteretic behaviour during the heating-cooling cycle is typical for fluid systems filled with MWCNTs, and it was previously explained by enhanced aggregation of MWCNTs during the incubation of composites [26,36,46]. The nematic-isotropic transition influenced the temperature dependences of electrical conductivity, Fig.…”

Section: Aggregation Of Mwcnts and Percolation Thresholdmentioning

confidence: 63%

Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Lisetski

Minenko

Ponevchinsky

et al. 2011

Materialwissenschaft Werkst

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This work reports a study on microstructure, electrical conductivity and phase transitions of 5CB(4-pentyl-49-cyanobiphenyl) + multi-walled carbon nanotubes (MWCNTs) composite materials. The concentration of MWCNTs was varied within 0.025 and 1 wt.%. The unmodified (o) and modified (m) MWCNTs were used. The mild milling was applied for shortening length of MWCNTs. Direct microscopic observation of composites at different concentrations C of MWCNTs evidenced the presence of aggregation and percolation processes. Formation of percolation networks was observed at C p L 0.025 -0.05% wt and C=C p L 0.1 -0.25% wt for o-MWCNTs and m-MWCNTs composites, respectively. Increase of the percolation threshold for m-MWCNTs, possibly, reflected their smaller aspect ratio r. The conductivity exponents were approximately the same (t L 3.3 l 0.1) for both o-MWCNTs and m-MWCNTs. The microstructure of MWCNT aggregates was not stable in time. The initially formed loose aggregates (L-aggregates) transformed into the more compact C-aggregates during the incubation time of one week. The incubation resulted in decrease of anisotropy, change in phase behaviour near the nematic-isotropic transition, and influenced external electric field response of the studied composite material. Inkubation führt zu einer Abnahme der Anisotropie, einem Wechsel der Phase in der Nähe der nematischen-isotropen Umwandlung und beeinflusst die Antwort auf ein externes elektrisches Feld der studierten Kompositmaterialien.

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“…The obtaining of functional hybrid materials with high electrical conductivity is made possible, which preserves attractive properties of dispersion medium. [15] In this work, two different nematic LCs were separately doped with two different azo structured dyes and their mixture. Second, a small amount of single-walled carbon nanotubes (SWCNTs) and fullerene C60 were added to these solutions.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of azo dye and carbon nanoparticle-doped guest–host liquid crystalline matrix

Akkurt

2014

Liquid Crystals

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During the recent years, liquid crystals (LCs) have much attention owing to their wide range of possible application and structural properties in electronics and optics. In this study, two different azo structured dyes (Disperse Yellow 3 and 7) and their mixture were separately doped to each of two different nematic LCs (E8 and E63). Their solubilities (except dye mixture), order parameters, textures and phase transition temperatures were determined. Single-walled nanotubes and fullerene C60 in a small amount were separately added to each of these solutions, and the experiments were repeated at the final stage analogously except solubilities. The solubilities of dyes in the LC E63 were lower than those of E8. The highest order parameter value was attained with Yellow 7 dye in E63 nematic host.

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Interface interactions in benzophenone doped by multiwalled carbon nanotubes

Cited by 9 publications

References 20 publications

Liquid Crystal Dispersions of Carbon Nanotubes: Dielectric, Electro-Optical and Structural Peculiarities

Liquid Crystal Dispersions of Carbon Nanotubes: Dielectric, Electro-Optical and Structural Peculiarities

Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Characterisation of azo dye and carbon nanoparticle-doped guest–host liquid crystalline matrix

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