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The present study aims to improve the mechanical, thermal and dielectric properties of polyetherimide (PEI) nanocomposite via simplified method, involving the creation of a nanocomposite using PEI incorporated with exfoliated‐chemical functionalization induced hexagonal boron nitride nanosheets (BNNS). XRD, FTIR and Raman elucidated the chemical structure of functionalized BNNS and indicated the success preparation of functionalized BNNS. Functionalization effectively improved the compatibility of nanocomposites and contributed to the property improvements. Morphological analysis unveiled a compact and dense microstructure within the nanocomposites in correlation with functionalized BNNS. Broad band dielectric spectroscopy revealed excellent dielectric properties of produced PEI nanocomposite. DMA testing verified a noteworthy enhancement in both Tg and storage modulus upon incorporating of BNNS. In summary, this comprehensive investigation highlights the impact of functionalized BNNS on mechanical, thermal and dielectric properties of developed PEI dielectric nanocomposite and is expected to expand the application of PEI in the field of high‐temperature energy storage. Highlights: Polyetherimide (PEI) was used as polymer matrix and boron nitride derivatives as dielectric fillers to prepare PEI dielectric nanocomposite.Due to the influences of dielectric properties by interface polarization effect and the local distribution of electric field of the fillers in PEI matrix, the dielectric constant, breakdown strength and energy storage density of PEI nanocomposites were obviously improved compared with pure PEI.The effects of interfacial interactions between PBNNS and PEI contributes to the uniform dispersion and comprehensive property improvements of PEI dielectric nanocomposites.This work presents a systematic investigation into the fabrication of PEI/BNNS nanocomposite using a one‐step solution blending method, inspiring the research and development of PEI in the energy storage applications areas in the future. [ABSTRACT FROM AUTHOR]

The conductive properties of CNT/polymer composites have been extensively studied. However, the impact of CNT distribution in the matrix on the composite polarization remains underexplored and poorly understood. Since it is difficult to achieve a uniform distribution of CNTs in polymers, most researchers have focused only on indiscriminately aggregated states. In this article, a new blending method was suggested to prepare a series of epoxy resin-based composite samples with varying levels of CNT uniformity/aggregation and the same filling fractions. Notably, the permittivity values turned out to be inversely related to the composite uniformity: the lowest permittivity values were obtained in the most uniform formulation, and vice versa. With 0.1% CNT, the real part values of the most uniform and aggregated samples were 6.6 and 16.2 at 107 Hz and 11.6 and 370.5 at 101 Hz, respectively. For the filler content of 0.1–0.5%, the conductive properties were largely determined by the distribution of CNTs and not their content. Within the entire frequency range, the uniform sample with 0.2% CNT exhibited significantly lower permittivity than the aggregated sample with 0.1% CNT. These findings emphasize the importance of the aggregation factor and underscore the non-universality and limitations of the percolation theory and power laws. The observed phenomenon is best explained by the micro-capacitor model, or the Maxwell–Wagner polarization, and suggests that a significant portion of the literature in the field needs to be reconsidered.

Polymer-derived SiAlCN ceramics as sensing materials are promising materials for wireless temperature sensors to achieve application in high-temperature harsh environments. However, limited understanding for the electric and dielectric properties of SiAlCN ceramics restricts the development of wireless sensors. Herein, the electrical and dielectric properties of polymer-derived SiAlCN ceramics pyrolyzed at different temperatures are investigated systemically. The results reveal that the electric resistance of the free-carbon phase and amorphous SiAlCN ceramic phase are comparable, however, the dielectric constant of the ceramic phase is much higher than that of the free-carbon phase. The maximum dielectric constant can reach up to 2.4E+5. Furthermore, the detailed mechanism analysis reveals that the SiAlCN ceramics with different pyrolysis temperatures all obey the same relaxation process, which is interfacial polarization and non-Debye relaxation. The deep understanding of the dielectric property of polymer-derived SiAlCN ceramics is very practical to design wireless sensors for potential applications in high-temperature and harsh environments. [ABSTRACT FROM AUTHOR]

This study reports copolymer composition tailored wrapping of carbon nanotubes, leading to a gigantic dielectric permittivity and peculiar nonlinear rheological response in a nonfluoro copolymer/carbon nanotube (CNT) hybrid system. Specifically, we observed a strong interfacial polarization effect in ethylene vinyl acetate (EVAc) copolymer/CNT nanocomposites, resulting in a dielectric permittivity of approximately 4000 at 10 Hz and 450 (dielectric loss <1) at 1 kHz, with only 1% volume fraction of CNTs and 40% vinyl acetate (VAc) content. No such effect was observed in EVAc with 12% VAc. Extensive amplitude oscillatory rheology studies prompted us to propose a novel hook‐wrap‐type mechanism, wherein polar interactions act as hooks and nonpolar segments allow wrapping, depending on the optimal interactions between the CNT and copolymer. Raman spectroscopy, small‐angle x‐ray scattering, and relaxation studies also revealed a significant change in segmental dynamics and mass fractal compactness with a change in the VAc content. This work provides a melt processing‐based scalable route to develop polymer dielectrics while advancing the fundamental understanding of polymer‐CNT interactions and the underlying mechanisms of dielectric behavior in nanocomposites. [ABSTRACT FROM AUTHOR]

This work investigates the enhancement of dielectric properties of La 2 NiO 4 -CuO terpolymer nanocomposites using surface modified SiC nanoparticles as fillers. SiC nanoparticles were subjected to acid treatment and annealing at 1000 °C to tailor the surface chemistry. Acid treatment involved immersing the SiC powder in a mixture of H 2 SO 4 and HNO 3 acids and sonicating for 30 min, followed by stirring at 60 °C for 6 h. Annealing was carried out at 1000 °C for 2 h in an inert argon atmosphere. La 2 NiO 4 and CuO nanoparticles were synthesized by sol-gel and precipitation techniques respectively, with average particle sizes of 20–40 nm and 10–15 nm confirmed by XRD and FESEM. Nanocomposites were fabricated by dispersing 2–10 wt% of untreated, acid treated and annealed SiC nanoparticles in a La 2 NiO 4 -CuO mixture solution, using PVDF as the polymer matrix. Impedance spectroscopy revealed that addition of 5 wt% acid treated SiC resulted in the highest dielectric constant of 42 at 1 kHz, in comparison to 25 for the unfilled polymer. This was attributed to increased interfacial polarization arising from uniform dispersion of nanoparticles and abundant charge trapping sites introduced by the SiC filler. [ABSTRACT FROM AUTHOR]

[Display omitted] • The N -doped-rGO/g-C 3 N 4 was prepared for the first time, its density is only 0.035 g/cm3. • The impedance matching of the N -doped-rGO/g-C 3 N 4 composite was well adjusted by g-C 3 N 4. • g-C 3 N 4 distributing among N -doped-rGO sheets can produce more polarization effect and relaxation effect by increasing the lamellar spacing. • N atoms are doped into rGO successfully, C-N dipoles can produce dipole polarization and further attenuating incident waves. • The RL min of N -doped-rGO/g-C 3 N 4 could reach −49.59 dB, the EAB could reach 4.56 GHz with the filling loading of 5 wt% when the thickness was 1.6 mm. "Thin thickness", "lightweight", "wide absorption bandwidth" and "strong absorption" are the new standards of contemporary science and technology for microwave absorption(MA) material. In this study, N -doped-rGO/g-C 3 N 4 MA material was prepared for the first time by simple heat treatment, which the N atoms were doped into rGO and g-C 3 N 4 was dispersed on the surface of N -doped-rGO, and its density is only 0.035 g/cm3. The impedance matching of the N -doped-rGO/g-C 3 N 4 composite was well adjusted by decreasing the dielectric constant and attenuation constant due to the g-C 3 N 4 semiconductor property and the graphite-like structure. Moreover, the distribution of g-C 3 N 4 among N -doped-rGO sheets can produce more polarization effect and relaxation effect by increasing the lamellar spacing. Furthermore, the polarization loss of N -doped-rGO/g-C 3 N 4 could be increased successfully by doping N atoms and g-C 3 N 4. Ultimately, the MA property of N -doped-rGO/g-C 3 N 4 composite was optimized significantly, with a loading of 5 wt%, the N -doped-rGO/g-C 3 N 4 composite exhibited the RL min of −49.59 dB and the effective absorption bandwidth could reach 4.56 GHz when the thickness was only 1.6 mm. The "thin thickness", "lightweight", "wide absorption bandwidth" and "strong absorption" of MA material are actually achieved by the N -doped-rGO/g-C 3 N 4. [ABSTRACT FROM AUTHOR]

Polymeric epoxy-based nanocomposites have rapidly developed in high energy density and power industry components. The composite insulation undergoes harsh extreme temperature conditions and a high electric field with varying frequencies. This paper dissects the components of complex permittivity in epoxy/ZnO nano and micro composites that were synthesized using different methods, utilizing dielectric spectroscopy as per ASTM D150. The performance of the composites was studied by analyzing the spectra over a frequency range spanning from 1 mHz to 1 kHz. We presume interfacial polarization arises in the composites due to particle clustering. Furthermore, we evaluated the effect of varying filler concentration at 25, 50, 70, and 90 °C. The real permittivity positions the α-steps at 70 and 90 °C. The real and imaginary permittivities remain largely unpretentious by the synthesis method over the entire frequency range. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel C@HTO@AO core-double shell structure was successfully prepared. • The multi-level hierarchical interface achieved a gradient reduction of carriers. • The transition layer with heterojunction exhibited large interfacial polarization. • C@HTO@AO/PVDF exhibited excellent integrated dielectric properties. In this work, to prohibit the undesirable large dielectric loss and electric-field distortion of the conductive fillers/polymer with a high dielectric constant, TiO 2 (TO) and Al 2 O 3 (AO) shells were successively coated on the surface of amorphous carbon (C) to prepare the C@TO@AO core-double shell nanoparticles. This novel design of gradually varying the multilayer hierarchical interface achieved the gradient reduction of carrier concentration from the C core to the TO and AO layers. And the introduction of the multilayer hierarchical interface was advantageous to the enhancement of interface polarization. Moreover, the excellent integrated dielectric properties could be effectively achieved by adjusting the layer thickness and crystal structure of the TO layer. It was worth noting that the TO transition layer with anatase and rutile heterojunctions (HTO) had a significant enhancement in the dielectric constant of the composites induced by the strength of interfacial polarization and built-in electric field inside the HTO layer. Furthermore, the simulated electric field distribution inside the composites was further investigated to reveal the mechanism of enhanced dielectric properties. This work exerts important guiding significance for the reasonable structure design and the elaborate regulation of the shell micro-structures to improve the dielectric properties of composites. [ABSTRACT FROM AUTHOR]

The reduction process for graphene oxide (GO) is important for this kind of graphene to be used as a conducting nanomaterial. After encapsulating barium titanate (BTO) powder particles in GO platelets, the GO-encapsulated BTO was chemically reduced with hydrazine (H 2 NN(CH 3) 2) by varying the reduction time (6, 12, 18, and 24 h). Reduced-graphene-oxide--encapsulated BTO (RGO@BTO) fillers were mixed with a polymer matrix, to boost the performance of the dielectric composites with the help of interfacial polarization. All the composite samples with RGO@BTO fillers exhibited substantially higher dielectric constants (52–72%) due to encapsulation, while suppressing dielectric losses. The best dielectric performance was obtained from 18 h (the second longest time) not from 24 h. It can be interpreted that 18 h is a balancing point between the main process of removing oxygen-functional groups and the collateral process of attaching nitrogen-functional groups from a reduction agent of hydrazine. Detailed analyses of XRD, XPS, Raman scattering, and impedance analysis, support the specialty at 18 h. Additionally, AC-driven inorganic electroluminescence devices with RGO@BTO fillers yielded to the best performance at 18 h. Therefore, during the chemical reduction of RGO, optimizing the reduction time is imperative for high dielectric performance. [Display omitted] [ABSTRACT FROM AUTHOR]

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In the realm of advanced electrical equipment and systems, polymer nanocomposites possess significant application value due to their excellent dielectric properties. Metal@ceramic fillers with a core-shell structure can enhance the dielectric constant (ε ′) of polymer nanocomposites; however, their application is limited by the high dielectric loss (tan δ). A magnetic field tailoring strategy is introduced in this article to significantly improve the dielectric properties of poly(vinylidene fluoride) (PVDF) composites. Magnetic CaCu 3 Ti 4 O 12 –Ni (CN) composite fibers are formed by embedding Ni nanoparticles within CaCu 3 Ti 4 O 12 (CCTO) fibers. Furthermore, the CN fibers are horizontally orientated in the PVDF matrix by tailoring the optimal magnetic field to 1.0 T–150 ℃. This results in a significant increase in the ε ′ of 25, which is 92 % and 194 % higher than that of a CN fiber without magnetic field treatment and pure PVDF, respectively, while maintaining a low tan δ of 0.08. Experimental and simulation results indicate that the magnetic orientation tailoring enhances the multi-interface polarization, especially the inner interfacial polarization (△ P in) at the CCTO/Ni interfaces, dominantly improving dielectric performance, as evidenced by the high interfacial polarization strength, △ ε 2 ∼ 141.51, the low activation energy, E a ∼ 0.81 eV, and the large △ P in ∼ 1.06×104 μC/m2. This magnetic orientation tailoring strategy offers a new paradigm and significant guidance for the development of polymer dielectrics with exceptional dielectric properties. [Display omitted] • Ni nanoparticles are embedded within CaCu 3 Ti 4 O 12 fibers. • CN fibers are horizontally orientated in PVDF matrix by tailoring magnetic field. • Magnetic orientation tailoring enhances multi–interface polarization and ε′ of 25. • P/CN–(1.0 T–150 ℃) film shows a low E a of 0.81 eV and a large △P in of 1.06×104 μC/m2. [ABSTRACT FROM AUTHOR]

To synergistically bolster breakdown strength (E b) and restrain dielectric loss in the copper (Cu)/poly(vinylidene fluoride, PVDF) presenting a giant dielectric constant (ε), we explore the PVDF nanocomposites with a serial of core@double-shell Cu@CuO (copper oxide)@MgO (magnesium oxide) nanofillers with various MgO shell thicknesses. The double-shell CuO@MgO not only improves the interface compatibility between filler and matrix but also increases the energy barrier height for charge migration across the nanocomposites and facilitates the formation of charge traps, thus impeding long-distance carrier transport and resulting in restrained dielectric loss. Further, the MgO shell with appropriate ε and wide bandgap effectively alleviates the strong dielectric mismatch between neat Cu and PVDF, which significantly lessens the local electric field distortion thereby resulting in elevated E b. Moreover, the overall dielectric performances of the Cu@CuO@MgO/PVDF can be modulated via altering the MgO shell thickness. This core@double-shell strategy offers a new paradigm for the design and preparation of percolating nanocomposites with desirable integrated dielectric performances. [Display omitted] • The Cu@@CuO@MgO/PVDF exhibits superior dielectric properties than Cu/PVDF. • The CuO@MgO mitigates dielectric mismatch elevating elevated breakdown strength. • The wide band gap MgO reduces dielectric loss by preventing electron migration. • The excellent dielectric performance of composites by altering MgO shell thickness. [ABSTRACT FROM AUTHOR]

Colossal permittivity (CP) materials are critical in ceramic capacitor applications and have been extensively studied. However, investigations into their dielectric properties under various environmental conditions remain sparse. This study aims to explore the CP characteristics of (Tb 1/2 Ta 1/2) x Ti 1- x O 2 (TbTTO– x , with x = 1%, 5%, and 10%) as functions of frequency, temperature, and relative humidity (%RH). Notably, the TbTTO–10% composition exhibits outstanding dielectric properties, with a permittivity (ε′) of ∼6 × 104 and a low-loss tangent (tanδ∼0.009) at 1 kHz. The temperature dependence of ε′ varies between −2.95% and 10.3% over a range of −60°C–200°C, while maintaining a low tanδ, even at 200°C (tanδ∼0.075). Dielectric relaxations were analyzed across an extensive temperature range from −258°C to 210°C. Using an integrated analysis of phase structure, microstructure, and X-ray photoelectron spectroscopy, the remarkable CP properties are attributed to both intrinsic and extrinsic factors. In addition to the impressive giant dielectric properties of the TbTTO–10%, the 3-D surface contour plot for the RH–temperature dependence of capacitance (C p) reveals minimal changes (<5%) in C p dependence on humidity, spanning 30%–90%RH, across temperatures ranging from 25°C to 85°C. This research provides insights into the complex influences on the dielectric properties of TbTTO, highlighting their potential for advanced ceramic capacitor applications, particularly in varying environmental conditions. • (Tb 1/2 Ta 1/2) x Ti 1- x O 2 (x = 10%) exhibited ε′∼6×104 and tanδ∼0.009. • Low Δε′ (-2.95 – 10.3%) was obtained, ranging from −60–200°C. • At 200 °C, tanδ was as low as 0.075. • 3–D plots for RH–temperature dependence of C p -were studied. • ΔC p (RH–T)<5% can be optimized (30–90%RH, 25–85°C). [ABSTRACT FROM AUTHOR]

In this work, nanocomposites consisting of TiO2-nanorods (TiO2-NRs) with less than 100 nm in size and poly(vinylidene fluoride) (PVDF) were prepared using a liquid-phase assisted dispersion and hot-pressing methods. At 1 kHz and 25 °C, the high dielectric permittivity of ∼66 and loss tangent of ∼0.03 can be obtained in the nanocomposite with a filler volume fraction of 0.5, which was higher than that of a neat PVDF matrix by a factor of 6. Dielectric permittivity of TiO2-NRs/PVDF nanocomposites not only highly increased with TiO2-NRs, but also almost independent of the frequency range of 102–106 Hz. The significant enhancement in dielectric permittivity is mainly attributed to the interfacial polarization at the interfaces of TiO2-NRs and PVDF, and semiconducting properties of TiO2-NRs. Among the various models used for rationalizing the dielectric behavior, the experimental dielectric data is in close agreement with EMT (n = 0.11) and Yamada models (n = 8). [ABSTRACT FROM AUTHOR]

Tribopositive, scalable, and biocompatible materials are highly desired for high‐performance triboelectric nanogenerators (TENGs). In this study, polyethylenimine (PEI) functionalized N‐doped carbon dots (NCDs‐PEI) are synthesized and a novel approach to develop high‐output TENGs by incorporating high permittivity NCDs‐PEI into polyvinyl alcohol (PVA) as the tribopositive composite (CPP composite) is proposed for the first time. By systematically manipulating the mass ratio of NCDs/PVA and PEI‐functionalized concentration, the optimized CPP composite‐based TENGs (CPP‐TENGs) reveal a remarkable enhancement in power density by 28.5 times as compared with pure PVA‐based TENGs. The considerable electric outputs of CPP‐TENGs can be attributed to the synergistic effect of interfacial polarization enhanced permittivity of CPP composite and boosted surface charge density induced by dual charge transfer pathways. Moreover, CPP‐TENGs present superior high‐output stability, durability, and humidity‐resistance, and can also effectively drive electronics at different humidity and monitor human body movements. This work renders a simple, feasible, and scalable pathway to boost the electrical performance of TENGs for biomotion energy harvesting as well as providing insights for exploiting novel tribomaterials in the development of high‐output TENGs. [ABSTRACT FROM AUTHOR]

Chitosan–iron (Cs–Fe) complexes are prepared electrochemically in an aqueous acidic medium in one-compartment cell at different times. XRD pattern of Cs–Fe complex samples has been investigated in the range from 5° to 50° and revealed that chitosan is characterized by certain crystalline peaks at 8.73°, 11.92° and 18.96°. In addition, the crystallinity of Cs–Fe complex samples is increased with increasing the content of Fe3+. Ultraviolet–visible (UV–Vis) and Fourier transform-infrared (FTIR) spectroscopies have been used to investigate the optical properties of Cs–Fe complex samples. UV analysis showed that pure chitosan is characterized by absorption band at 214 nm resulted from the amide linkages and at 311 nm, as a shoulder which is attributed to intraligand n → π and π → π* transitions of the chromophoric C=O group. On the other hand, two new bands are observed in Cs–Fe complex samples at nearly 350 and 389 nm with increasing Fe3+ content. The optical parameters of all the samples, such as optical band gap energy (Eg), Urbach energy (EU), dispersion energy (Ed) and oscillator energy (Eo) have been estimated. It is found that these parameters are significantly affected due to the Fe3+ content. FTIR spectra revealed that many of the characteristic bands of pure chitosan have been affected either in its position or its intensity due to the presence of Fe3+, confirming that the formation of complex between chitosan and Fe3+ is occurred. Dielectric relaxation spectroscopy technique has been used to investigate the dielectric properties of pure chitosan and Cs–Fe complex samples in a wide range frequency and a temperature range extended from RT to 433 K. The investigation showed that the existence of Fe3+ resulted in a modification in the dielectric constant (ε′) and dielectric loss (ε′′) behaviour. Dielectric loss tangent (tan δ) showed that pure chitosan is characterized by two different types of relaxations, whereas Cs–Fe complex samples are characterized by only one relaxation process. [ABSTRACT FROM AUTHOR]

Magnetoelectric Zn0.5Co0.5Fe2O4 – PbZr0.58Ti0.42O3 nanocomposites are synthesized considering chemical reaction process at low temperature and solid-state reaction technique. Structural characterization is performed by X-ray diffraction analysis, which shows two types of nanometric grains coexisting simultaneously. The materials surface morphology displays that the fabrication method is quite effective for preparation of nanocomposites. Crystallite size of different constituent phases is observed to in manometer range. The dependency of temperature on electrical response and dielectric constant of nanocomposites are analyzed with a variation of frequency. The dielectric constant with temperature decreases attributing the thermal excitation of electrons. Moreover, we have evaluated the magnetoelectric coefficient in two configurations (longitudinal and transverse) with increasing applied magnetic field. The coupling coefficient is observed to ∼0.8 mV/cm-Oe in transverse configuration, whereas in longitudinal configuration it is increasing in behavior with measured magnetic field. At room temperature, the observing magnetoelectric coupling may be as a cause of magnetic field dependent strain transfer to the piezoelectric phase to the piezomagnetic phase of the nanocomposites. [ABSTRACT FROM AUTHOR]

Dielectric composites based on polybasic components with hierarchical structures have promising potentials for electromagnetic absorber. However, strategy to strengthen coupling of transition metal oxides still demands to be optimized to enhance electromagnetic loss. Herein, inspired by the hierarchical structure of balsam pear, ultrafine ZnO is uniformly distributed and tightly capped in MnO2 by self‐assembly hydrothermal method. The unique hierarchical structure provides abundant polarization centers with large specific surface area. The compositions promote attenuation performance of electromagnetic waves, enhance relative permittivity and satisfy impedance matching as compared with that of pure ZnO or MnO2. The effective bandwidth (RL< −10 dB) reaches 5.93 GHz obtained with thin thickness of 1.8 mm. The effective bandwidth reaches 15 GHz via regulating their thickness. The fabricated MnO2/ZnO composites can achieve great adaptability in microwave. MnO2/ZnO composites keep stability even heated 700 °C in air. The phase and weight remain unchanged. The proposed interfacial modulation strategy can provide new opportunities for the design of efficient electromagnetic absorber with thermal stability. [ABSTRACT FROM AUTHOR]

A film of cobalt sulfate (CoSO4)-doped polyvinylpyrrolidone (PVP) blend was spin-coated on n-Si. Electrical measurements were conducted on the Au/n-Si structure with the CoSO4-PVP film sandwiched between them. The frequency dispersion of the main electrical and dielectric parameters and the corresponding mechanisms were evaluated. The extra capacitance originating from the contribution of interface states (Nss) resulted in a fairly large frequency dispersion in C–V plots. These states also influence the carrier transport and conduction mechanism, thus the determination of real Nss values is crucial to evaluate the nonideal behavior of such plots. The values of Nss were calculated using the Hill–Coleman method. The dielectric constant (ε′) and dielectric loss (ε″) exhibited higher values in the low-frequency region as a result of interface and dipole polarization, while the alternating-current (AC) electrical conductivity (σac) generally decreased. The variation of the loss tangent with increasing frequency of the applied field confirmed the effect of some internal field within the CoSO4-PVP film accompanied by the external AC field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boron nitride nanosheet with N-doped carbon modification as novel dielectric filler. • Enhanced compatibility and interfacial polarization between filler and PVDF matrix. • Simultaneously increased dielectric constant and breakdown strength. • Outstanding energy density and efficiency achieved in sandwich-structured film. It is a challenge to simultaneously enhance dielectric constant and breakdown strength of dielectrics and achieve a greatly elevated energy density. Herein, polyaniline was first coated onto the surface of boron nitride nanosheets (BN), and then nitrogen-doped carbon (NC) was formed through a carburization process, resulting in BN@NC composite, which was subsequently added to poly(vinylidene fluoride) (PVDF) to prepare a composite film with high dielectric performance. The characterization showed that BN@NC effectively preserved the nanosheet structure of BN and formed strong hydrogen bonding interactions with the PVDF matrix, promoting the β-PVDF formation. This not only improved the compatibility but also enhanced the interfacial polarization between conductive NC and the polymer, leading to a high dielectric constant. Moreover, the electrically insulating BN prevented the formation of leakage current, resulting in a high breakdown strength. Finally, a sandwich-structured film was constructed, and exhibited a dielectric constant of 10.2 (at 1 kHz), a breakdown strength of 380 MV m−1, and an energy density of 6.1 J cm−3, which were 20%, 36%, and 74% higher, respectively, than those of pure PVDF film (8.5, 280 MV m−1, and 3.5 J cm−3). This work highlights significant potential for applications in low-cost and high-energy density dielectric composites. [ABSTRACT FROM AUTHOR]

Spinel-structured nickel ferrite has been prepared using co-precipitation method. The ferrite particles prepared were characterized using XRD, FTIR, and TEM and were confirmed to be in the nano-regime. Natural rubber composites were prepared with different loadings of nickel ferrite like 5, 15, 25, 50, and 75 (in part per hundred rubber, phr). The mechanical, swelling, and magnetic properties were analyzed using the standard methods. Dielectric measurements show that permittivity decreases with increase in frequency and increases with increase in ferrite loading. Tan delta value also was found to increase with filler loading which may be attributed to the presence of interfacial polarization. [ABSTRACT FROM AUTHOR]

Structural, dielectric and magnetic properties of dense Dy-substituted strontium titanate ceramics are investigated. In the Sr 1-1.5 x Dy x TiO 3 system, incorporation of Dy onto the Sr site is confirmed by a linear decrease of the lattice parameter up to x = 0.05. Dielectric spectroscopy analysis of Sr 1-1.5 x Dy x TiO 3 ceramics reveals four relaxations. Two relaxations observed below 55 K are attributed to dipoles formed by off-centre displacement of Dy 3+ ions on the Sr sites. Other two dielectric relaxations found at higher temperatures are attributed to the oxygen vacancy related mechanisms. As result, very high dielectric permittivity of ∼33500 at 28 K and of ∼9600 around room temperature at moderate dissipation factor of ∼0.02 are obtained for Sr 0.985 Dy 0.01 TiO 3 ceramics, making it a promising material for capacitor electronic applications. Paramagnetic behaviour observed for Sr 1-1.5 x Dy x TiO 3 as well as for Sr 1- x Dy 2 x Ti 1- x O 3 ceramics indicates impossibility to induce a magnetic order and hence magnetoelectric coupling in strontium titanate by Dy substitution. [ABSTRACT FROM AUTHOR]

Dopamine@(In 0.05 Nb 0.05 )Ti 0.9 O 2 /poly(vinylidene-fluoride) (DA@INTO/PVDF) composites are fabricated via a physical mixing method followed by heat treatment. TEM results show that DA is uniformly coated on the surface of INTO particles with a thickness of 10 nm. SEM results show that the DA@INTO particles are homogeneously dispersed in PVDF. Compared with INTO/PVDF composites, DA@INTO/PVDF composites exhibit excellent dielectric constant and energy discharge efficiency, which is due to the improved interfacial polarization and reduced leakage current. DA plays an important role in the enhanced dielectric properties of DA@INTO/PVDF composites. [ABSTRACT FROM AUTHOR]

Five types of nanofillers, namely, silica, surface-silylated silica, alumina, surface-silylated alumina, and boron nitride, were tested in this study. Nanocomposites composed of an epoxy/amine resin and one of the five types of nanoparticles were tested as dielectrics with a focus on (i) the surface functionalization of the nanoparticles and (ii) the water absorption by the materials. The dispersability of the nanoparticles in the resin correlated with the composition (OH content) of their surfaces. The interfacial polarization of the thoroughly dried samples was found to increase at lowered frequencies and increased temperatures. The β relaxation, unlike the interfacial polarization, was not significantly increased at elevated temperatures (below the glass-transition temperature). Upon the absorption of water under ambient conditions, the interfacial polarization increased significantly, and the insulating properties decreased or even deteriorated. This effect was most pronounced in the nanocomposite containing silica, and occurred as well in the nanocomposites containing silylated silica or non-functionalized alumina. The alternating current (AC) breakdown strength of all specimens was in the range of 30 to 35 kV·mm−1. In direct current (DC) breakdown tests, the epoxy resin exhibited the lowest strength of 110 kV·mm−1; the nanocomposite containing surface-silylated alumina had a strength of 170 kV·mm−1. In summary, water absorption had the most relevant impact on the dielectric properties of nanocomposites containing nanoparticles, the surfaces of which interacted with the water molecules. Nanocomposites containing silylated alumina particles or boron nitride showed the best dielectric properties in this study. [ABSTRACT FROM AUTHOR]

Flexible polymer composites with high dielectric constant and breakdown strength thus high energy storage density are highly desired in electrical and electronic technologies. In this study, hybrids of nano Ag particles discretely grown on the surface of BaTiO3 nanofibers (BTnfs) were synthesized and used to fabricate PVDF based nanocomposites. The results demonstrated that the dielectric constant and energy storage density of the composites were largely enhanced. An energy density of 10.25 J/cm3 was obtained for the composite containing only 2.5 vol% hybrids, increased by more than 2 times in comparison with pure PVDF. [ABSTRACT FROM PUBLISHER]

In this paper, the effects of carbon nanotubes (CNT) implantation and sisal fibre size on the electrical properties of sisal fibre-reinforced epoxy composites are reported. For this purpose, the epoxy composites reinforced with CNT-implanted sisal fibre of 5 mm and 10 mm lengths were prepared by hand moulding and samples characterized for their electrical properties, such as dielectric constant (ε′), dielectric dissipation factor (tanδ) and AC conductivity (σac) at different temperatures and frequencies. It was observed that the dielectric constant increases with increase in temperature and decreases with increase in frequency from 500 Hz to 5 KHz. Interestingly, the sample having CNT-implanted sisal fibre of 5 mm length exhibited the highest value of dielectric constant than the one with length 10 mm. This is attributed to the increased surface area of sisal fibre and enhancement of the interfacial polarization. At a constant volume and a length of 5 mm of the fibres, the number of interfaces per unit volume element is high and results in a higher interfacial polarization. The interfaces decrease as the fibre length increases, and therefore, the value ofε′ decreases at 10 mm fibre length. The peak value of the dielectric constant decreases with increasing frequency. A continuous decrease in dissipation factor (tanδ) with increasing frequency for all samples was observed, while at lower temperatures, the values of tanδremains approximately same. The AC conductivity for 5 mm length sisal epoxy composite and 10 mm length sisal fibre–epoxy composites is higher than that of pure epoxy at all the frequencies. [ABSTRACT FROM PUBLISHER]

Polymer nanocomposites with high dielectric constant and low-loss tangent materials have been extensively used in devices. Polyvinylidene fluoride (PVDF)-carbon dot (C-dot) nanocomposites have been synthesized to investigate the effect of C-dot on AC conductivity and dielectric properties. The FTIR spectra of synthesized samples confirm the formation of composites. The broadening of the peak in XRD patterns with an increase in the C-dot concentration has been observed, indicating the interaction of PVDF with C-dot. Morphological studies were carried out using Scanning electron microscopy (SEM). Frequency-dependent conductivity and dielectric properties were studied in the frequency range of 10 Hz to 8 MHz. AC conductivity graphs were found to obey Jonscher's power law and show no contact loss behavior. Prepared samples show improved dielectric constant with an increase in C-dot filler concentrations. Moreover, all samples show tangent loss of less than 0.015 at 1 kHz frequency. These results demonstrate that composite possesses broad application prospects in device electronics. • PVDF -carbon dots composites have been synthesized to improve dielectric performance of the composite samples. • The improved dielectric constant with a small increase in C-dot concentration has been observed. • The MWS type of interfacial polarization phenomenon has been observed. • Lower value of loss tangent, indicating the potential application of the samples for the device applications. [ABSTRACT FROM AUTHOR]

This brief reports on the analysis of a circuit model for human whole blood in a microfluidic dielectric sensor. The sensor employs a novel, 3-D, parallel-plate, capacitive sensing structure with a floating electrode integrated onto a microfluidic channel with 9 \mu \textL of sample volume. A circuit model is developed that accurately captures the characteristics of the capacitive double-layer formed due to the ionic content of blood, as well as the characteristics of the dispersion region attributed to interfacial polarization of the red blood cells. The sensor-measured permittivity of human whole blood and blood samples with hematocrit levels of 0.2, 0.4, and 0.6 show an excellent agreement to simulated data from the circuit model, with rms errors less than 2.14% and 1.17% for the real and imaginary parts of permittivity, respectively, for all samples and over the full measurement frequency range of 10 kHz–100 MHz. [ABSTRACT FROM PUBLISHER]

[Display omitted] • The porous heterogeneous SiC/SiO 2 microspheres were constructed. • Achieving structure evolution and component control by varying temperature. • Synergistic polarization loss of multiphase enhanced electromagnetic attenuation. • The EAB of 8.49 GHz and the RL min of −54.68 dB were achieved, while the filling rate is just 10 wt%. It is confirmed that the composites with multiple components and plentiful heterogeneous interfaces have been considered as preferred efficient electromagnetic (EM) wave absorbers. The special structure for hollow, porous, and core-shell has good adjustable dielectric properties. Herein, porous heterogeneous SiC/SiO 2 microspheres are prepared based on the self-assembly technology and carbothermal reduction strategy. The structural evolution and composition control of porous heterogeneous SiC/SiO 2 microspheres can be achieved by adjusting the carbothermal reduction temperature. The results indicate that structure and composition have a significant effect on the absorption performance. Especially, when the temperature is 1400 °C, the porous heterogeneous SiC/SiO 2 microspheres exhibit the most excellent EM wave absorption properties; the minimal reflection loss (RL min) value is −54.68 dB at 8.99 GHz. The maximum effective bandwidth (EAB max) for RL min < −10 dB reaches 8.49 GHz, exhibiting absorption capacity in almost all bands (S, C, X, and Ku bands). It can well satisfy the comprehensive requirements of efficient EM wave absorption absorbers for lightweight and broad EAB characteristics. The excellent performance is due to the strong interfacial polarization caused by plentiful heterogeneous interfaces between different phases. Meanwhile, a highly porous structure and SiO 2 phase can regulate complex dielectric constant, leading to better impedance matching. This work provides useful thinking for the design of efficient EM wave absorption absorbers. [ABSTRACT FROM AUTHOR]

The microwave absorption characteristics of a Korean anthracite were explored by determining its dielectric properties (relative dielectric constant and loss factor) using the cavity perturbation technique up to approximately 1000 °C at 915 MHz and 2450 MHz in ultra-high purity argon. The dielectric parameters increase gradually below 800 °C, showing an interestingly linearly increasing tendency with temperature essentially associated with breaking of chemical bonds and removal of volatiles during pyrolysis. With a further increase in temperature, both parameters increase considerably mainly because of enhanced electronic conduction caused by more free charges induced and potential interfacial polarization as a result of build-up of charges at contact areas or interfaces. The continuously decreasing microwave penetration depth within the temperature range further reveals the increased microwave absorption in the coal during pyrolysis. According to the reflection loss patterns of the coal, the maximum microwave absorption is achievable at an appropriate sample thickness. This corresponds to the minimum reflection losses of − 44.18 dB and − 13.03 dB for sample thicknesses of 0.02 m and 0.04 m at respectively 915 MHz and 2450 MHz. The sample thickness substantially influences the microwave absorption in coal during pyrolysis, especially in the initial stage. [ABSTRACT FROM AUTHOR]

The present paper aims to investigate the sensitivity of dielectric spectroscopy to changes in concentrations of pollutants (heavy metals and metal oxides) uptake by the water hyacinth plant collected from agriculture wastewater drainage. The measurements were carried out on the dried root and shoot plant parts before and after subjecting to different microwave heating powers for different times. Dielectric properties of the untreated root were investigated at temperature range (30–90 °C). X-ray fluorescence spectroscopy (XRF) results showed that the concentration of metals and metals oxides are higher in plant root than in plant shoot. Accordingly, the obtained dielectric properties were found to depend on the applied electric field frequency, magnitude of heating power as well as concentrations of pollutants. Analysis of experimental data represented by the imaginary part of the dielectric modulus M″ (ω) revealed to the presence of three different relaxation processes. The lower frequency relaxation process was associated to charge carriers conduction whereas those appeared at higher frequencies were associated to different types of interfacial polarization. The plant ability for removing heavy metals and metal oxides from the aquatic environments would be enhanced upon subjecting to microwave heating power with 400 W for 30 min. [ABSTRACT FROM AUTHOR]

Poly(2-nonyl-2-oxazoline)80-stat-poly(2-dec-9'-enyl-2-oxazoline)20 and poly(2-dec-9'-enyl- 2-oxazoline)100 can be synthesized from the cationic ring-opening polymerization of monomers that can be derived from fatty acids from renewable resources. These (co)poly(2-oxazoline)s can be crosslinked with di- and trifunctional mercapto compounds using the UV-induced thiol-ene reaction. The complex permittivity of the corresponding networks increases with the temperature and decreases with the network density. In a frequency range from 10-2 to 106 Hz and at temperatures ranging from -20 to 40 °C, the changes of the real part of the complex permittivity as well as the loss factor can be explained by interfacial polarization within the material. At a temperature of 20 °C and a frequency of 50 Hz, the permittivity of the crosslinked (co)poly(2-oxazoline)s covers a range from 4.29 to 4.97, and the loss factors are in the range from 0.030 to 0.093. The electrical conductivities of these polymer networks span a range from 5 x 10-12 to 8 x 10-9 S/m, classifying these materials as medium insulators. Notably, the values for the permittivity, loss factor and conductivity of these copoly(2-oxazoline)s are in the same range as for polyamides, and, hence, these copoly(2-oxazoline)-based networks may be referred to as "green" alternatives for polyamides as insulators in electronic applications. [ABSTRACT FROM AUTHOR]

Five types of nanofillers, namely, silica, surface-silylated silica, alumina, surface-silylated alumina, and boron nitride, were tested in this study. Nanocomposites composed of an epoxy/amine resin and one of the five types of nanoparticles were tested as dielectrics with a focus on (i) the surface functionalization of the nanoparticles and (ii) the water absorption by the materials. The dispersability of the nanoparticles in the resin correlated with the composition (OH content) of their surfaces. The interfacial polarization of the thoroughly dried samples was found to increase at lowered frequencies and increased temperatures. The β relaxation, unlike the interfacial polarization, was not significantly increased at elevated temperatures (below the glass-transition temperature). Upon the absorption of water under ambient conditions, the interfacial polarization increased significantly, and the insulating properties decreased or even deteriorated. This effect was most pronounced in the nanocomposite containing silica, and occurred as well in the nanocomposites containing silylated silica or non-functionalized alumina. The alternating current (AC) breakdown strength of all specimens was in the range of 30 to 35 kV·mm−1. In direct current (DC) breakdown tests, the epoxy resin exhibited the lowest strength of 110 kV·mm−1; the nanocomposite containing surface-silylated alumina had a strength of 170 kV·mm−1. In summary, water absorption had the most relevant impact on the dielectric properties of nanocomposites containing nanoparticles, the surfaces of which interacted with the water molecules. Nanocomposites containing silylated alumina particles or boron nitride showed the best dielectric properties in this study.

• SnTTO ceramic exhibited a high ε′ value of 44,112 and a low tanδ value of 0.011. • Δε′(%) was less than 15% in the temperature range of −60 – 170 °C. • Dielectric behavior can be well described by the IBLC model. • Roles of Ta5+ and Sn4+ were to create free charges and increase R gb , respectively. The excellent dielectric performance of an Sn4+–isovalent/Ta5+–pentavalent doped TiO 2 (SnTTO) ceramic was investigated. Substitution of Sn4+ into TiO 2 caused slight changes in the dielectric permittivity (ε′) and loss tangent (tanδ). Although doping TiO 2 with Ta5+ can cause a substantial increase in ε′, tanδ was very large. Notably, the SnTTO ceramic exhibited a high ε′ value of 44,112 and a low tanδ value of 0.011 at 1 kHz and 25 °C. Furthermore, the temperature coefficient of ε′ (Δε′(%)) was less than 15% in the temperature range of −60–170 °C. The microstructure of the codoped SnTTO consisted of semiconducting grains and grain boundaries (GBs) with very large GB resistance (R gb) value, thereby leading to effective retention of a low tanδ value and a small Δε′(%) value. Evidently, the primary roles of the Ta5+ and Sn4+ doping ions were to increase the interfacial polarization via increased free charges and increased R gb by reducing the oxygen vacancies at the GBs. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work we report on the permittivity of suspensions of elongated goethite particles in silicone oils of different viscosities. In spite of the low conductivity of the systems, the electrode polarization is significant. To correct this phenomenon, the procedure chosen is the one called logarithmic derivative of the real part of the permittivity, and it proves to efficiently reduce the effect of electrodes to the extent that the spectra of pure liquids are flat in the accessible frequency range (20 Hz–1 MHz). In our suspensions, we observe the presence of a dielectric relaxation for frequencies in the range 4–40 kHz. In principle, such relaxations might be ascribed to the Maxwell–Wagner (MW) polarization. However, it is found that both the characteristic frequency and the relaxation amplitude of the suspensions increase with volume fraction, something unexpected for an MW relaxation. Such discrepancy can be explained by considering the Frenkel–Trukhan model, which reproduces the Maxwell–Wagner results in conditions of thin electrical double layers (which it is not our case). An excellent agreement is found between our data and the model predictions, using only the particle surface charge as a parameter. [ABSTRACT FROM AUTHOR]

• Zn Fe 2 O 4 were prepared by the solid-state reaction. • Large value of the dielectric permittivity. • The dielectric process obeys to three relaxation phenomena. • Our samples have a giant permittivity which can be used in energy storage technology. With good stability in temperature and frequency this material proves to be an interesting candidate to replace the materials traditional dielectrics. Spinel ferrites especially zinc ferrites are of enormous importance in technological applications such as chemical sensors, electrical appliances, microwave industries. Their properties are subject to different studies to investigate the involved mechanisms. The present research work undertakes the study of the conductivity and dielectric permittivity of ZnFe 2 O 4 spinel ferrite as a function of frequency and temperature. Thus, we prepared zinc ferrite spinel by the solid-state reaction route. The structural analysis by X-ray diffraction and scanning electronic microscopy shows that the obtained sample is pure, single-phase composed of prismatic grain of crystallites with a size of 72 nm. The impedance, dielectric permittivity and conductivity of zinc ferrite sample were studied in the frequency range 40 Hz–10 MHz and in the temperature range 300–700 K. Dc conductivity is found thermally activated with an activation energy of 236 meV, indicating an electronic conduction process. The variation of the conductivity with frequency follows power low at low frequency and Drude low at high frequency. Such mechanism change is explained by the increase of free carrier density. Three-relaxation process are identified from impedance spectroscopy analysis. Their associated relaxation times are thermally active and the activation energy of the one associated with grain is close to the one obtained from conductivity, indicating the intra grain conduction dominates transport mechanism. Finally, the compound shows a high dielectric constant in a wide range of frequency, making it suitable for super capacitor application [ABSTRACT FROM AUTHOR]

Abstract: Due to the interest in protein dynamics, there are numerous dielectric relaxation studies of proteins in water and in glass-forming aqueous solvents such as glycerol–water mixtures. In the regime of low frequencies, the inevitable dc-conductivity of such systems limits the resolution of dynamics that are slow compared with the solvent relaxation. Solutions of myoglobin in glycerol/water mixtures of various compositions are measured by dielectric spectroscopy in the frequency range from 10mHz to 10MHz. The resolution of low frequency modes is improved by two approaches: electrical ‘cleaning’ and the analysis of the derivative of the real component of permittivity, which shows no direct signature of dc-conductivity. Effects of internal interfacial polarization are also addressed by measuring the same solvents in confinement as well as mixed with glass beads. We find two processes, the structural relaxation of the solvent and the slower rotational mode of the protein, with no indication at even lower frequencies of a dielectric signature of fluctuations associated with protein dynamics. [Copyright &y& Elsevier]

Abstract: In this study, we report layer thickness effect on the electrical insulation property of polysulfone (PSF)/poly(vinylidene fluoride) (PVDF) multilayer films having a fixed composition of PSF/PVDF = 30/70 (vol./vol.). Breakdown strength, dielectric lifetime, and electrical conductivity were studied for 32- and 256-layer films having various total film thicknesses. Among these films, those having thinner PVDF and PSF layers exhibited lower breakdown strength, shorter lifetime, and higher electrical conductivity than those having thicker layers. These experimental results were explained by Maxwell–Wagner–Sillars interfacial polarization due to contrasts in dielectric constant and electronic conductivity for PVDF and PSF, respectively. When both PVDF and PSF layers were thick (ca. > 100–200 nm), more space charges were available in PVDF and no electronic conduction was allowed for PSF. These accumulated interfacial charges could serve as effective traps for injected electrons from metal electrodes under high electric fields. As a result, reduced electrical conductivity and enhanced breakdown strength/dielectric lifetime properties were obtained. When both layers were thin (ca. < 100 nm), fewer space charges were available in PVDF and significant electronic conduction through PSF resulted in low interfacial polarization. Consequently, higher electrical conductivity, lower breakdown strength, and shorter lifetime were observed. These results provide us insights into potential physics to enhance electrical insulation property of polymer films using a multilayered structure having large dielectric constant contrast. [Copyright &y& Elsevier]

In this paper, the effect of silver coating and size of fibre on electrical properties of sisal fibre-reinforced epoxy composites has been reported. For this purpose, epoxy composites reinforced with silver-coated sisal (of 5 and 10 mm length) prepared by hand moulding and samples were characterized for their electrical properties, such as dielectric constant ( ε′), dielectric dissipation factor (tan δ) and AC conductivity ( σ), at different temperatures and frequencies. It was observed that dielectric constant increases with increase in temperature and decreases with increase in frequency from 500 Hz to 5 kHz. The peak height at the transition temperature decreases with increasing frequency. Interestingly, sample having silver-coated fibre of 5 mm length exhibited higher value of dielectric constant as compared to the sample having 10 mm of fibre length, which is attributed to the increased surface area of coated fibre. This behaviour of the material can be explained in terms of interfacial polarization. At a constant volume of fibres and at a length of 5 mm, the number of interfaces per unit volume element is high and this results in high interfacial polarization. The number of interfaces decreases as the fibre length increases and therefore the value of ε′ decreases at 10 mm fibre length. To study the changes in structure of samples, Fourier transform infrared spectrometry and scanning electron microscopy of the samples were carried out. [ABSTRACT FROM AUTHOR]

Poly(2-nonyl-2-oxazoline)80-stat-poly(2-dec-9′-enyl-2-oxazoline)20 and poly(2-dec-9′-enyl-2-oxazoline)100 can be synthesized from the cationic ring-opening polymerization of monomers that can be derived from fatty acids from renewable resources. These (co)poly(2-oxazoline)s can be crosslinked with di- and trifunctional mercapto compounds using the UV-induced thiol-ene reaction. The complex permittivity of the corresponding networks increases with the temperature and decreases with the network density. In a frequency range from 10−2 to 106 Hz and at temperatures ranging from −20 to 40 °C, the changes of the real part of the complex permittivity as well as the loss factor can be explained by interfacial polarization within the material. At a temperature of 20 °C and a frequency of 50 Hz, the permittivity of the crosslinked (co)poly(2-oxazoline)s covers a range from 4.29 to 4.97, and the loss factors are in the range from 0.030 to 0.093. The electrical conductivities of these polymer networks span a range from 5 × 10−12 to 8 × 10−9 S/m, classifying these materials as medium insulators. Notably, the values for the permittivity, loss factor and conductivity of these copoly(2-oxazoline)s are in the same range as for polyamides, and, hence, these copoly(2-oxazoline)-based networks may be referred to as “green” alternatives for polyamides as insulators in electronic applications.

Highlights: [•] Dielectric constant decreases sharply with frequency and shows a DFT. [•] The system shows a dielectric loss including two regions with DC conductivity part. [•] Real and imaginary impedance parts represent an equivalent RC circuit design. [•] AC conductivity is CBH type and activation energies for DC conductivity: 0.55 and 0.33eV. [•] Densities of localized states are in range of (7.7–3.2)×1023 eV−3 cm−3. [ABSTRACT FROM AUTHOR]

Abstract: Most of biological cells have microvilli on their surfaces, which significantly influence their dielectric properties. The complex permittivity of a cubical system containing a spherical cell model with cylindrical projections was calculated over a frequency range of 10kHz to 100MHz using the three-dimensional finite-element method. The spectra of the complex permittivity consisted of low- and high-frequency relaxation processes which were respectively attributed to the polarization of the membranes covering the projections and the spherical body. Conventional analysis based on the spherical shell model was applied to the simulated spectra to discuss the effects of cell surface morphology on the electric parameters estimated for the plasma membrane and the cytoplasm. [Copyright &y& Elsevier]

Abstract: Dielectric dispersion analysis of cellular suspension is generally based on the analogy to equivalent periodic material made up of identical inclusions. However, under true physiological conditions, when coupling and aggregation events usually occur, this analogy can introduce severe errors when attempting to probe the dielectric characteristics of the suspended fraction. In the framework of this study, a theoretical examination of the effect of aggregation on the dielectric characteristics of spherical cellular suspension is presented. Here, small clusters of coupled and fused (gap connected) shelled spheres were used to imitate the presence of aggregates when suspended in a homogenous suspension of spherical cells. The permittivity spectra of the aggregate-cell mixtures were numerically calculated by applying computational solution of complex potential problem using 3D Boundary Element Method. The dispersion characteristics of the mixtures have been determined as function of both aggregates shape and concentration. Those reveal significant deviations in comparison to the characteristics of homogenous cellular suspension. Quantitative analyses of the induced fields and transmembrane potential gradients of the interacted cells suggest that those deviations are mainly induced due to changes occur on the polarization state of the membranes. [Copyright &y& Elsevier]

Abstract: Nanocomposites based on natural rubber and nano-sized nickel were synthesized by incorporating nickel nanoparticles in a natural rubber matrix for various loadings of the filler. Structural, morphological, magnetic and mechanical properties of the composites were evaluated along with a detailed study of dielectric properties. It was found that nickel particles were uniformly distributed in the matrix without agglomeration resulting in a magnetic nanocomposite. The elastic properties showed an improvement with increase in filler content but breaking stress and breaking strain were found to decrease. Dielectric permittivity was found to decrease with increase in frequency, and found to increase with increase in nickel loading. The decrease in permittivity with temperature is attributed to the high volume expansivity of rubber at elevated temperatures. Dielectric loss of blank rubber as well as the composites was found to increase with temperature. [Copyright &y& Elsevier]

Dielectric measurements were carried out for dense sediments of quaternary ammonium type anion-exchange resin beads dispersed in deionized water over a frequency range of 30 Hz to 130 MHz. According to a method proposed in previous studies the relative permittivities and electrical conductivities of ion-exchange beads were evaluated from the relaxation data observed in a megahertz region on the basis of a theory of interfacial polarization. The permittivities of the ion-exchange beads were found to be unchanged irrespectively of the salt form and somewhat lower than that of a continuous medium, while the conductivities of the ion-exchange beads were characteristic of the salt form. The equivalent ionic conductances of different counter anions in the beads were estimated from the conductivities of the ion-exchange beads. These results indicate an ion-binding effect in the resin beads. [ABSTRACT FROM AUTHOR]