Thermal conductivity and thermal diffusivity of the cyanobiphenyl<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>(</mml:mo><mml:mi>n</mml:mi><mml:mi mathvariant="normal">CB</mml:mi><mml:mo>)</mml:mo></mml:math>homologous series

Marinelli, M.; Mercuri, F.; Zammit, U.; Scudieri, F.

doi:10.1103/physreve.58.5860

Cited by 81 publications

(56 citation statements)

References 24 publications

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“…It has been reported that the larger order parameter induces greater magnitude of the thermal conductivity. 6,8 The order parameter of the prepared homogeneous aligned films decreases from 0.87 to 0.79 with the increase of the compound 2 content. However, there is no remarkable relation between the thermal conductivity and the order parameter of the prepared films in the high order parameter.…”

Section: Thermal Conductivitymentioning

confidence: 97%

“…It is reported that the thermal transmission along the aligned molecular long axis direction is higher than that in the across direction, for example, 0.2 W/m Á K (long axis) and 0.1 W/m Á K (short axis). [1][2][3][4][5][6] The thermal conductive anisotropy of polymers have been investigated, for example, in the fibers and the films with the injection molding of the thermotropic liquid crystals, 7,8 the liquid crystal polymers cured under the magnetic field, 9 and the thin film on the silicon wafer, 10 and the free-standing films prepared with polymerizable liquid crystals (PLCs) by the rubbing method. 11 Up to now, the thermal conductivity of the main chain type polymers prepared from only bi-functional liquid crystals has been investigated.…”

Section: Introductionmentioning

confidence: 99%

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Relation between thermal conductivity and network formation with polymerizable liquid crystals

Kato

Nakamura

Agari

et al. 2006

J of Applied Polymer Sci

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The molecules with the mono-and bi-function at the sides in the acrylic PLC mixtures were aligned by the rubbing method. The alignment was immobilized by the photo polymerization to result the homogeneous acrylic films, which have good alignment with the higher order parameters. The thermal conductivity along the molecular long axis direction showed the larger magnitude of 0.62 W/m Á K, which is independent on ratio of the main chain and the side chain fractions.

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Section: Thermal Conductivitymentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Relation between thermal conductivity and network formation with polymerizable liquid crystals

Kato

Nakamura

Agari

et al. 2006

J of Applied Polymer Sci

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“…The thermal conductivity of SrTiO 3 increases by an applied electric field only below 50 K 7 , because the transverse optical (TO) phonon mode degenerated with the longitudinal acoustic (LA) phonon mode is shifted upward by the electric field, weakening the TO-LA interaction, thus increasing the thermal conductivity. The orientation of a uniaxially aligned nematic liquid crystal (cyanobiphenyl, 5CB) changes due to an AC electric field 8 and because its thermal conductivity (albeit small) depends on its molecular orientation 9 , it can act at TCS.…”

Section: Thermal Conductivity Switches (Tcs)mentioning

confidence: 99%

“…Size Effect Anisotropy (nCB [9]) Solid/Solid Transition (s/s) Solid/Liquid Transition (s/l) Superconductor (NbC 0.97 [22]) Active Thermal Conductivity Switch (TCS) Rectification (C 9 H 16 Pt coated CNT and BNNT [24], Asymmetric nano VO2 beam [25], Thermal diode [26]) Electric/ Magnetic/Stress (Bees-wax [6], SrTiO 3 [7], 5CB [8], Cu wire [10], InSb [11], Ferroric-twinned thin film [12]) MEMS (Thermal switch radiator [16], Solid-Liquid thermal interface [17,18]) Thermomechanical (Gas gap heat switch [19]) Thermal (Automatic heat switch [20], Thermal actuator [21]) Wetting (B nanoribbon [13,14], Film/transition boiling transition [15] [44], Te [32,45], InSb / GaSb [46], CdSb [47,48], AlSb [49][50][51], Zn 3 Sb 2 [52]) Semiconductor /Semiconductor (S/S) (LiNO 3 [35], InSe [41]) Metal /Metal (M/M) (Hg [32], K / Zn / Sb / Al / Cu [32,53], Sn [33,53], Ga [32,53,54], In [53,55,56], Cd …”

Section: Bulkmentioning

confidence: 99%

“…2. Liquid crystals have directional thermal conductivities and cyanobiphenyl (nCB) has s/s transition temperature (nematic below and isotropic above about 300 K) as the molecular arrangement changes 9 . It was found that the thermal conductivities of samples with a homeotropic orientation decrease at transition during heating, whereas those with a planar orientation increase, for n = 5 -9 (|Z TCS | < 0.5).…”

Section: Bulkmentioning

confidence: 99%

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Thermal conductivity switch: Optimal semiconductor/metal melting transition

Kim

Kaviany

2016

Phys. Rev. B

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Scrutinizing distinct solid/liquid (s/l) and solid/solid (s/s) phase transitions (passive transitions) for large change in bulk (and homogenous) thermal conductivity, we find the s/l semiconductor/metal (S/M) transition produces largest dimensionless thermal conductivity switch (TCS) figure of merit Z TCS (change in thermal conductivity divided by smaller conductivity). At melting temperature, the solid phonon and liquid molecular thermal conductivities are comparable and generally small, so the TCS requires localized electron solid and delocalized electron liquid states.For cyclic phase reversibility, the congruent phase transition (no change in composition) is as important as the thermal transport. We identify XSb and XAs (X = Al, Cd, Ga, In, Zn) and describe atomic-structural metrics for large Z TCS , then show the superiority of S/M phonon-to electrondominated transport melting transition. We use existing experimental results and theoretical and ab initio calculations of the related properties for both phases (including the Kubo-Greenwood and Bridgman formulations of liquid conductivities). The 5p orbital of Sb contributes to the semiconductor behavior in the solid-phase bandgap and upon disorder and bond-length changes in the liquid phase this changes to metallic, creating the large contrast in thermal conductivity.The charge density distribution, electronic localization function, and electron density of states are used to mark this S/M transition. For optimal TCS, we examine the elemental selection from the transition-, basic-and semimetals and semiconductor groups. For CdSb, addition of residual Ag suppresses the bipolar conductivity and its Z TCS is over 7, and for Zn 3 Sb 2 it is expected to be over 14, based on the structure and transport properties of the better known β-Zn 4 Sb 3 . This is the highest Z TCS identified. In addition to the metallic melting, the high Z TCS is due to the electron-poor nature of II-V semiconductors leading to the significantly low phonon conductivity.

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Discontinuous Thermal Diffusivity Change due to the Anchoring Transition of a Liquid Crystal on a Perfluoropolymer Surface

et al. 2014

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Thermal diffusivity of a liquid crystal, 4'-butyl-4-heptyl-bicyclohexyl-4-carbonitrile, was measured using a temperature wave method. The liquid crystal was sandwiched by two glass substrates, which were treated with three different surface agents for providing distinct molecular orientations. Here, we demonstrate that: 1) a large thermal diffusivity anisotropy arising from different orientations, that is, planar and homeotropic states, was found in the nematic and smectic A phases; 2) when substrates were coated with a perfluoropolymer, abrupt changes of the thermal diffusivity were observed in the nematic phase both on cooling and heating due to the discontinuous anchoring transition between planar and homeotropic states. The temperature dependence of the thermal diffusivity anisotropy was well described by a power law, with an exponent of 0.27 according to the mean-field theory.

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Thermal conductivity and thermal diffusivity of the cyanobiphenyl(nCB)homologous series

Cited by 81 publications

References 24 publications

Relation between thermal conductivity and network formation with polymerizable liquid crystals

Relation between thermal conductivity and network formation with polymerizable liquid crystals

Thermal conductivity switch: Optimal semiconductor/metal melting transition

Discontinuous Thermal Diffusivity Change due to the Anchoring Transition of a Liquid Crystal on a Perfluoropolymer Surface

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