Dielectric study on mixtures of ionic liquids

Thoms, Erik; Sippel, Pit; Reuter, D.; Weiß, Matthias; Loidl, A.; Krohns, S.

doi:10.1038/s41598-017-07982-3

Cited by 43 publications

(26 citation statements)

References 70 publications

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“…2 are normalized with respect to the characteristic frequency at which the real part of conductivity begins to increase with frequency 39 or corresponds to the frequency of the peak in the imaginary part of modulus (modulus M * (ω,T) = 1/ε * (ω,T) , not shown here e.g. 40 ), and, furthermore, the conductivity spectra in Fig. 2 are normalized with respect to plateaus in σ' .…”

Section: Resultsmentioning

confidence: 99%

The effect of thermal treatment on ac/dc conductivity and current fluctuations of PVDF/NMP/[EMIM][TFSI] solid polymer electrolyte

Sedlák

Gajdoš

Macků

et al. 2020

Sci Rep

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The experimental study deals with the investigation of the effect of diverse crystallinity of imidazolium ionic-liquid-based SPE on conductivity and current fluctuations. The experimental study was carried out on samples consisting of [EMIM][TFSI] as ionic liquid, PVDF as a polymer matrix and NMP as a solvent. After the deposition, the particular sample was kept at an appropriate temperature for a specific time in order to achieve different crystalline forms of the polymer in the solvent, since the solvent evaporation rate controls crystallization. The ac/dc conductivities of SPEs were investigated across a range of temperatures using broadband dielectric spectroscopy in terms of electrical conductivity. In SPE samples of the higher solvent evaporation rate, the real parts of conductivity spectra exhibit a sharper transition during sample cooling and an increase of overall conductivity, which is implied by a growing fraction of the amorphous phase in the polymer matrix in which the ionic liquid is immobilized. The conductivity master curves illustrate that the changing of SPEs morphology is reflected in the low frequency regions governed by the electrode polarization effect. The dc conductivity of SPEs exhibits Vogel–Fulcher–Tammann temperature dependence and increases with the intensity of thermal treatment. Spectral densities of current fluctuations showed that flicker noise, thermal noise and shot noise seems to be major noise sources in all samples. The increase of electrolyte conductivity causes a decrease in bulk resistance and partially a decrease in charge transfer resistance, while also resulting in an increase in shot noise. However, the change of electrode material results in a more significant change of spectral density of current fluctuations than the modification of the preparation condition of the solid polymer electrolyte. Thus, the contact noise is considered to contribute to overall current fluctuations across the samples.

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Section: Resultsmentioning

confidence: 99%

The effect of thermal treatment on ac/dc conductivity and current fluctuations of PVDF/NMP/[EMIM][TFSI] solid polymer electrolyte

Sedlák

Gajdoš

Macků

et al. 2020

Sci Rep

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“…That is, a dielectric (or dielectric composite) is an electrical insulator that can be polarized as a result of an applied electric field. When a dielectric is placed in an electric field, there is no flow of electric charges through the material as they do in an electrical conductor but slightly shift from their regular equilibrium points causing dielectric polarization [29]. As a result of dielectric polarization, positive charges are displaced in the direction of the field and negative charges shift in the opposite direction.…”

Section: Resultsmentioning

confidence: 99%

The Effects of SLS on Structural and Complex Permittivity of SLS-HDPE Composites

Meli

Abbas

Zaid

et al. 2019

Advances in Polymer Technology

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RS-4050 is a rigid epoxy based magnetic castable microwave absorbing material; it has been used in many areas of waveguide application as a microwave waveguide terminations and dummy loads. In recent years, there is a demand for composites material with lower dielectric constant higher loss factor for microwave application. This research, the effect of soda lime silica (SLS) on structural and complex permittivity of soda lime silica-high density polyethylene (SLS-HDPE) composites was conducted in order to explore the possibility of substituting RS-4050 with SLS-HDPE composites as a microwave waveguide terminations and dummy loads. Elemental weight composition of the SLS glass powder and HDPE was identified through scaling of different percentage of SLS and HDPE. X-ray diffraction (XRD) was used to investigate the crystallinity behavior of SLS-HDPE composites. The proposed SLS-HDPE composites material was studied at frequencies 8 to 12 GHz. The study was conducted using waveguide Agilent N5230A PNA technique. The effect of microwave frequency on complex permittivity properties for SLS-HDPE composites of different percentages of SLS and HDPE (10% SLS-90% HDPE, 20% SLS-80% HDPE, 30% SLS-70% HDPE, 40% SLS-60% HDPE, and 50% SLS-50% HDPE) were investigated. Results showed the diffraction patterns reveal good amorphous quality with a genuinely properties structure. The microwave frequency and composites percentages significantly influenced the complex permittivity (real and imaginary) properties of the composites. Moreover, the complex permittivity increased as the percentage of SLS filler increased in the host matrix HDPE as a result of increased in composite density due to less volume being occupied by the filler as the percentage increased. The complex permittivity of the smallest and largest percentages of SLS (10% and 50%) was (2.67-j0.05) and (3.45-j0.35), respectively. The study revealed that the best sample for waveguide application as microwave terminator is 50% SLS as it has the highest dielectric constant, highest loss factor, and highest loss tangent as compared to 10% SLS to 40% SLS. Also 50% SLS has the highest absorption properties as compare to 10% SLS, 20% SLS, 30% SLS, or 40% SLS. The XRD physical structure of the SLS-HDPE composites revealed the absorption characteristics of different percentages of the materials. The SLS-HDPE composites can be applied in the area of waveguide as a microwave waveguide terminations and dummy loads.

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“…[10,22,24,26]). Notably, in nearly all ILs a close inspection of the ' spectra reveals a steplike increase with decreasing frequency before the strong increase due to electrode polarization sets in at lower frequencies [10,11,19,21,22,23,24,27,31,39]…”

Section: A Dielectric Spectramentioning

confidence: 99%

Importance of reorientational dynamics for the charge transport in ionic liquids

et al. 2018

Self Cite

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Most ionic liquids contain at least one rather complex ion species exhibiting a dipolar moment. In the present work, we provide a thorough evaluation of broadband dielectric spectra of 12 ionic liquids taking into account the often neglected reorientational dynamics of these ions. We confirm that this dynamics leads to a clear relaxational signature in the spectra, a fact that so far only was considered in few previous works. The obtained reorientational relaxation times are well consistent with earlier inelastic light-scattering and high-frequency dielectric investigations. Evaluating our dielectric spectra in terms of reorientational motions reveals a close coupling of the ion-rotation dynamics to the ionic charge transport in a broad temperature range from the low-viscosity liquid above room temperature deep into the high-viscosity supercooled state close to T g . This coupling does not seem to be mediated by the viscosity but probably is of more direct nature, pointing to a revolving-door mechanism as also considered for plastic-crystalline ionic conductors. Our results show that the reorientational motion of the dipolar ions plays a significant and so far widely overlooked role for the ionic charge transport in ionic liquids.

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Dielectric study on mixtures of ionic liquids

Cited by 43 publications

References 70 publications

The effect of thermal treatment on ac/dc conductivity and current fluctuations of PVDF/NMP/[EMIM][TFSI] solid polymer electrolyte

The effect of thermal treatment on ac/dc conductivity and current fluctuations of PVDF/NMP/[EMIM][TFSI] solid polymer electrolyte

The Effects of SLS on Structural and Complex Permittivity of SLS-HDPE Composites

Importance of reorientational dynamics for the charge transport in ionic liquids

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