Dielectric relaxation and thermally activated a.c. conduction in (PVDF)/(rGO) nano-composites: role of rGO over different fillers

Mohammed, M.I.; Fouad, S.S.; Mehta, N.

doi:10.1007/s10854-018-9941-z

Cited by 30 publications

(20 citation statements)

References 67 publications

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“…The ac electrical conductivity σ ac (ω) values of PVA/ CMC blend and their nanocomposites films can be calculated using the equation [51] ac = 2 f 0 �� . The real part of the AC conductivity, (w ), is obtained by the formula:…”

Section: Ac Conductivity and Conduction Mechanism Evaluationmentioning

confidence: 99%

Enhancement of physico-chemical, optical, dielectric and antimicrobial properties of polyvinyl alcohol/carboxymethyl cellulose blend films by addition of silver doped hydroxyapatite nanoparticles

Nasrallah

Ibrahim

2022

J Polym Res

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Hydroxyapatite nanoparticles doped with silver AgHA-NPs were synthesized successfully then added with various mass fractions to a mixed solution of polyvinyl alcohol (PVA)/ carboxymethyl cellulose (CMC) using the casting technique. Experimentally, the influence of silver doped hydroxyapatite nanoparticles on the structural, optical, dielectric and antimicrobial properties of nanocomposite films was investigated. X-ray diffraction and Fourier transformation infrared spectroscopy were used to explore the structural features of these films. The XRD analysis revealed the amorphous nature of PVA/CMC blend and the intensity of the characteristic peak of the virgin polymers in the nanocomposite spectrum being much reduced as the doping level was increased. The FT-IR spectra indicated that the blend components were miscible by revealing the functional groups of two polymers that interacted through the formation of a hydrogen bond while, the FT-IR spectra of nanocomposite confirmed the good interaction between the blend chains and AgHA-NPs. The morphological graphs of the prepared blend were formed as hexagonal grains with size distribution around 18.36–24.11 μm. The addition of AgHA-NPs changed the surface morphology of the blend significantly. The optical properties of PVA/ CMC blend and nanocomposites films were measured in the 200–800 nm wavelength range. Optical measurements showed that the optical transmittance for pure blend was nearly 90% while it decreased to 50% with increasing AgHA-NPs contents up to 40 wt.%. The energy gap values calculated by Tauc's model and those determined by ASF model are consistent, where their values reduced by AgHA-NPs incorporation. The dielectric constant of all samples were studied in range of temperatures (303–405 K) and from100 kHz to 1.0 MHz, range of frequencies. The Correlated Barrier Hopping (CBH) is the most appropriate conduction mechanism based on the frequency dependence of the ac conductivity. Silver ion release was examined showed that he film loaded with 10 wt.% AgHA-NPs has a small release of silver ion, while the amount of the Ag+ released from the samples increased slowly with increasing the content of AgHA-NPs. PVA/CMC/AgHA films were tested for antibacterial activity against both (Bacillus subtilis) and (Escherichia coli) as well as the anti-fungal activity against (Candida albicans),their results showing an increase in the activity index as the filling level of AgHA-NPs increases. The study confirmed that doping of AgHA-NPs into PVA/CMC improves both electrical conductivity and antimicrobial efficiency and these nanocomposites might be recommended for further work in biomedical applications such as wound dressing and infection control.

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Section: Ac Conductivity and Conduction Mechanism Evaluationmentioning

confidence: 99%

Enhancement of physico-chemical, optical, dielectric and antimicrobial properties of polyvinyl alcohol/carboxymethyl cellulose blend films by addition of silver doped hydroxyapatite nanoparticles

Nasrallah

Ibrahim

2022

J Polym Res

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“…The dependence of both ε ′( ω ) and ε ″( ω ) on temperature for pure PVDF and PVDF/LTO PNC at fixed frequencies of 1 kHz and 1 MHz, as representative examples, are depicted in Figure 9. For all studied samples, ε ′( ω ) increases with rising temperature due to the thermal agitation, which enhances the orientational freedom of the polar sites in the polymer chain according to the alternating field 56 . Besides, with increasing temperature, the dipoles are relatively free to respond to the electric field, causing the gradual increase of ε ″( ω ) with temperature up to 363 K. At higher temperatures (≥363 K), the abrupt growth of ε ″( ω ) values can be attributed to a considerable increase in the LTO NPs doped PVDF matrix's interfacial polarization.…”

Section: Resultsmentioning

confidence: 97%

“…The ac electrical conductivity σ ac ( ω ) can be calculated using the equation 56 :

σ_{ac} ((), ω) = ω ε_{o} ε^{'} ((), ω) \tan δ

…”

Section: Resultsmentioning

confidence: 99%

Structural, thermal, and dielectric properties of porous PVDF/Li₄Ti₅O₁₂ nanocomposite membranes for high‐power lithium‐polymer batteries

Nasrallah

El-Metwally

Ismail

2020

Polymers for Advanced Techs

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Polymer nanocomposites consisting of materials such as ionic polymers and nano‐ceramic fillers are widely used in high‐power lithium‐polymer batteries because of their high ionic conductivity, good mechanical strength, electrothermal stability, and better compatibility with electrodes. Nanocomposite films of polyvinylidene fluoride (PVDF)/lithium titanium oxide Li4Ti5O12 (LTO) with different volume fractions of LTO nanoparticles (NPs) are prepared via casting method. The DSC thermograms revealed a slight decrease in the melting temperature Tm and a noticeable reduction in the degree of crystallinity with increasing the volume fraction of LTO. This decrease is confirmed by the increment in the relative fraction of β‐phase in the PVDF matrix calculated from both XRD and FTIR. SEM images indicated the growth of porous globular structures in the presence of LTO NPs. Besides, the hydrophilicity of PVDF is improved by incorporating LTO NPs. The dielectric constant ε′(ω), loss ε″(ω), ac conductivity σac(ω), complex impedance Z*(ω), and Nyquist plots of PVDF/LTO nanocomposites are investigated in the temperature range from 303 to 413 K and frequency range from 100 Hz to 1 MHz. The σac(ω) and frequency exponent s are found to obey the correlated barrier hopping model. Values of the frequency exponent s and the charge carriers binding energy Wm for the studied nanocomposite films decrease with rising temperature and LTO addition. Furthermore, dielectric constant ε′(ω), loss ε″(ω), and ac electrical conductivity σac(ω) of films are found to be strongly frequency and temperature dependent. The localized states density N(EF) at the Fermi level increase with increasing temperature and LTO NPs volume fraction, resulting in the Wm decrease and the enhancement of the ac electrical conductivity σac(ω). The impedance spectrum and Nyquist plots provide an insight into the influence of LTO vol% in the resistive and capacitive characteristics of PVDF/LTO films. These results recommend the choice of LTO NPs as dopants to enhance the electrical properties of the PVDF matrix to be used in high‐power lithium‐ion batteries and electronic devices.

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“…The real ε1 and imaginary ε2 parts of the dielectric constants can be derived using the following relations [52,53]:…”

Section: Dielectric Properties Of Zno Filmsmentioning

confidence: 99%

Investigation of dispersion parameters, dielectric properties and opto–electrical parameters of ZnO thin film grown by ALD

Zaka

Parditka

Erdélyi

et al. 2020

Optik

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Highly transparent zinc oxide thin films with varied layer thicknesses have been prepared on microscopic glass substrates at 200 °C. Films thickness was measured by stylus profilometer. The films have been investigated for their structure using X-Ray diffraction; the patterns showed their amorphous nature. The dispersion parameters i.e. refractive index (n) and extinction coefficient (k) are computed in the wavelength range (350 -2500 nm). The Tauc model was used to determine the optical band gap and Urbach tail with direct allowed transitions. The real and imaginary parts of the high frequency dielectric constant were discussed. Other parameters such as penetration depth, cut-off wavelength, dissipation factor, volume and surface energy loss functions, reflection loss factor, optical, electrical and thermal conductivities have also been determined. A systematic study of a wide range of optical parameters of ALD prepared ZnO films can serve as a valuable data source and can enrich the knowledge of the studied material.

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Dielectric relaxation and thermally activated a.c. conduction in (PVDF)/(rGO) nano-composites: role of rGO over different fillers

Cited by 30 publications

References 67 publications

Enhancement of physico-chemical, optical, dielectric and antimicrobial properties of polyvinyl alcohol/carboxymethyl cellulose blend films by addition of silver doped hydroxyapatite nanoparticles

Enhancement of physico-chemical, optical, dielectric and antimicrobial properties of polyvinyl alcohol/carboxymethyl cellulose blend films by addition of silver doped hydroxyapatite nanoparticles

Structural, thermal, and dielectric properties of porous PVDF/Li₄Ti₅O₁₂ nanocomposite membranes for high‐power lithium‐polymer batteries

Investigation of dispersion parameters, dielectric properties and opto–electrical parameters of ZnO thin film grown by ALD

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Dielectric relaxation and thermally activated a.c. conduction in (PVDF)/(rGO) nano-composites: role of rGO over different fillers

Cited by 30 publications

References 67 publications

Enhancement of physico-chemical, optical, dielectric and antimicrobial properties of polyvinyl alcohol/carboxymethyl cellulose blend films by addition of silver doped hydroxyapatite nanoparticles

Enhancement of physico-chemical, optical, dielectric and antimicrobial properties of polyvinyl alcohol/carboxymethyl cellulose blend films by addition of silver doped hydroxyapatite nanoparticles

Structural, thermal, and dielectric properties of porous PVDF/Li4Ti5O12 nanocomposite membranes for high‐power lithium‐polymer batteries

Investigation of dispersion parameters, dielectric properties and opto–electrical parameters of ZnO thin film grown by ALD

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Structural, thermal, and dielectric properties of porous PVDF/Li₄Ti₅O₁₂ nanocomposite membranes for high‐power lithium‐polymer batteries