Dielectric Properties Of Composites Research Articles

Electrical properties of conventional and microwave sintered lead free magnetoelectric composites

Here we report comparison of dielectric properties of composition synthesized by microwave and conventional sintering. Microwave sintering requires less time and temperature to achieve the same quality of materials as sintered by conventional route. The material sample was prepared by conventional solid state method and sintered in conventional & microwave furnace. Sintered samples were then subjected to XRD analysis. X-ray diffraction revealed the formation of single phase material. The dielectric and ferroelectric properties were recorded for both the samples and properties were found to improve in microwave sintered samples. There is also a significant improvement in density by microwave processing.

Dielectric Properties of Composites with Bentonite Fillers

The paper describes the results of a study of composites with bentonite fillers and their dielectric properties as a function of the percentage of the dispersant and the alternating electric field frequency. It has been found that the pronounced dispersion of the dielectric parameters of the composites is caused by charge migration and localization at intrinsic point defects and at the interfaces with the sublattice of the dispersant.

Synthesis and characterization of borosilicate glass/β-spodumene/Al2O3 composites with low CTE value for LTCC applications

Glass + ceramic composites based on low-softening-point borosilicate (BS) glass, β-spodumene and Al2O3 were produced in this work. The influence of ceramic filler composition on the microstructure, sintering quality, mechanical properties, thermal properties and dielectric properties of composites were studied. XRD and DSC indicated that both kinds of ceramic filler as well as the BS glass maintained their characteristics after sintering. The addition of β-spodumene would decrease the coefficient of thermal expansion (CTE) value of composites to match with silicon well. The better wetting behavior between β-spodumene and BS glass would lead to better sintering quality, microstructure and dielectric properties for composites containing more β-spodumene. With appropriate Al2O3 content, the flexural strength of composites could be enhanced. Composite with 45 wt% BS glass, 30 wt% β-spodumene and 25 wt% Al2O3 sintered at 875 °C showed good properties which meet the requirements of low temperature co-fired ceramic applications: dense microstructure with high relative density of 96.27%, proper CTE value of 3.57 ppm/°C, high flexural strength of 156 MPa, low dielectric constant of 6.20 and low dielectric loss of 1.9 × 10−3.

Comparative analysis on dielectric properties of polymer composites reinforced with synthetic and natural fibers

This article presents the study of dielectric properties of synthetic and natural fiber reinforced epoxy composites. Bamboo and glass fibers were both chopped and woven. These fibers were then used for reinforcing epoxy, with different fiber loadings. The dielectric properties of these composites were studied with reference to their fiber loadings, frequencies, and chemical treatment of the natural fibers at room temperature. It was found that dielectric properties increased with the increase in the concentration of fibers filled in the epoxy matrix, for the entire frequency range. This was due to the increase in the orientation and interfacial polarization. The treated fiber composites had lower dielectric properties due to decreased hydrophilicity of the natural fiber. The chopped glass fibers reinforced epoxy composites have the highest dielectric constant, among all tested composites. J. VINYL ADDIT. TECHNOL., 24:E201–E216, 2018. © 2018 Society of Plastics Engineers

Retraction Note to: Effect of Temperature on the Dielectric Properties of Carbon Black-Filled Polyethylene Matrix Composites Below the Percolation Threshold

The temperature dependence of dielectric properties of carbon black-filled polyethylene matrix composites below the percolation threshold was studied based on the effect medium approximation theory (EMA theory). Although the literature on calculation based on the EMA theory by changing the parameters is vast, an overall discussion taking into account the EMA theory is required to explain the dielectric properties of the composites and their temperature dependence. Changes of the dielectric properties of carbon black-filled PMC and their temperature dependence below the percolation threshold for the volume fraction of carbon black have been discussed based on the EMA theory. The composites satisfy the universal law of conductivity above the percolation threshold, whereas it gives the critical exponent of s = 1 for dielectric constant below percolation threshold. The rates of the decrement of both % changes of dielectric constant and dielectric loss factor for temperature become larger with an increase in the volume fraction below percolation threshold. By incorporating the effect of thermal expansion into the EMA theory, the temperature dependence of dielectric properties is successfully explained.

Dielectric properties of nanocomposites based on potassium iodate with porous nanocrystalline cellulose

ABSTRACTLinear and non-linear dielectric properties of composites based on KIO3 and nanocrystalline cellulose Acetobacter Xylinum were investigated. An increase in temperatures of the structural transitions IV→III and III→II by 20 and 24 К respectively for potassium iodate embedded into the pores of nanocellulose as compared to phase transitions of the bulk of KIO3 was found.

Enhancement of mechanical strength associated with interfacial tension between barium titanate and acrylonitrile–butadiene rubber with different acrylonitrile contents by surface modification

ABSTRACTAcrylonitrile–butadiene rubber (NBR) with different acrylonitrile (ACN) contents was filled with barium titanate (BT) to prepare the polymer dielectrics. The neat NBR, NBR/untreated BT, and NBR/bis‐(γ‐triethoxysilylpropyl)‐tetrasulfide (silane coupling agent KH845‐4) modified BT (MBT) composites were prepared. At low ACN content (ACN content 20 wt %), the tensile strength of the NBR/MBT composites increased by 173.6% from 2.69 to 7.36 MPa compared to the neat NBR. The pleasing results were not found in those composites with high ACN content. Both surface modifications of BT and NBR with low ACN content would result in lower interfacial tension between BT and NBR. A strong interfacial adhesion was observed between MBT and NBR with 20 wt % ACN content. The interfacial adhesion had great contribution to the mechanical strength of composites. Moreover, the dielectric properties of composites were also investigated in detail. The addition of BT enhanced the dielectric constant of composites markedly. This study can be applied in manufacturing electronic devices, which are subjected to oily environments for a long time. At the same time, the study can provide some help for researchers to select the polymer matrix and the appropriate surface modification agent of functional filler. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45936.

Enhanced dielectric properties of all-organic acrylic resin elastomer-based composite with doped polyaniline

Polyaniline (PANI) doped with p-toluene sulfonic acid (PTSA) was synthesized by chemical oxidation method under the condition of conventional magnetic stirring (PTSA–PANI) and ultrasonic vibration (uPTSA–PANI) separately. Acrylic resin elastomer (ArE) was synthesized via radical polymerization. Novel all-organic dielectric elastomer composites (refer to the resultant composites herein as ArE/PTSA–PANI and ArE/uPTSA–PANI) were obtained by solution casting method. Chemical and microstructure characterization of the two kinds of resultant composites suggested that uPTSA–PANI possessed larger crystalline domain than that of PTSA–PANI and a unique branched structure. The dielectric properties of composites were measured in a wide frequency range, and the results demonstrated that both ArE/2.0% PTSA–PANI and ArE/2.0% uPTSA–PANI owned a high dielectric constant of more than 30 at 100 Hz, representing ten times increase with respect to neat ArE matrix (≈ 3). Moreover, it was found that ArE/2.0%uPTSA–PANI held better comprehensive dielectric properties at high frequency than that of ArE/2.0% PTSA–PANI composite; that was to say, ArE/2.0% uPTSA–PANI composite possessed not only high dielectric constant but also low dielectric loss. In addition, the thermogravimetric analysis indicated that the composite possessed better thermal stability than that of neat ArE. In addition, the elastic modulus of ArE/2.0% uPTSA–PANI composite was lower than 5 MPa.

Influences of Thermal Treatment on the Dielectric Performances of Polystyrene Composites Reinforced by Graphene Nanoplatelets.

Dielectric properties of composites near percolation threshold (fc) are often sensitive to thermal treatments, and the annealing temperature is usually associated with a polymer’s rheological properties. In this study, the influences of the thermal treatment on dielectric properties are investigated for the polystyrene (PS) matrix composite reinforced by graphene nanoplatelets (GNP) fillers near fc. It can be found that the thermal treatment can not only increase the dielectric constant, but also decrease the dielectric loss for the PS/GNP composite. This interesting phenomenon possibly happens in the interfacial region of PS/GNP with the thickness about 4–6 nm according to the electron energy-loss spectroscopy (EELS) results. The free volumes around the interface can be easily altered by the movement of polymeric segments after annealing at the glass transition temperature.

Fabrication and Dielectric, Mechanical, and Thermal Properties of Low-Density Polyethylene (LDPE) Composites Containing Surface-Passivated Silicon (Si/SiO2 Core/Shell Nanoparticles)

ABSTRACTComposites of low-density polyethylene containing between 1 and 5 wt% of Si/SiO2 core/shell nanoparticles were prepared by ball milling method. The thermal, mechanical, and dielectric properties of composites were investigated in terms of composition, frequency, and temperature. The results showed that the dielectric permittivity increased smoothly with a rise of Si/SiO2 particle. The dielectric permittivity and loss decreases and increases with temperature, respectively. The resistance of composites to erosion due to partial discharge was significantly improved by adding nanoparticles. The results have demonstrated that ball milling was an effective method for producing relatively homogeneous nanocomposite up to 4 wt% Si/SiO2.

Enhanced Thermal Conductivity and Dielectric Properties of Iron Oxide/Polyethylene Nanocomposites Induced by a Magnetic Field

Iron Oxide (Fe3O4) nanoparticles were deposited on the surface of low density polyethylene (LDPE) particles by solvothermal method. A magnetic field was introduced to the preparation of Fe3O4/LDPE composites, and the influences of the magnetic field on thermal conductivity and dielectric properties of composites were investigated systematically. The Fe3O4/LDPE composites treated by a vertical direction magnetic field exhibited a high thermal conductivity and a large dielectric constant at low filler loading. The enhancement of thermal conductivity and dielectric constant is attributed to the formation of the conductive chains of Fe3O4 in LDPE matrix under the action of the magnetic field, which can effectively enhance the heat flux and interfacial polarization of the Fe3O4/LDPE composites. Moreover, the relatively low dielectric loss and low conductivity achieved are attributed to the low volume fraction of fillers and excellent compatibility between Fe3O4 and LDPE. Of particular note is the dielectric properties of Fe3O4/LDPE composites induced by the magnetic field also retain good stability across a wide temperature range, and this contributes to the stability and lifespan of polymer capacitors. All the above-mentioned properties along with the simplicity and scalability of the preparation for the polymer nanocomposites make them promising for the electronics industry.

Study of Electrical Charge Storage in Polymer‐Carbon Quantum Dot Composite

AbstractNovel carbon quantum dots (CQDs) with unexplored potential, are interesting nanomaterials for electronic investigations. Formation of surface defect sites in these Q‐dots is a consequence of combinations of various carbon hybridizations. In this work nanocomposites of CQDs with an electronically inert polymer, poly vinyl alcohol (PVA), have been electrically characterized. The electronic properties were observed to be tunable by compositions of component materials. A detail conduction mechanism of charge storage within composites’ layer has been worked out. The dielectric properties of composites are observed to be dependent on morphologies developed from segregation of CQDs within composites. The composites possess improved dielectric properties compared to individual component materials. Simulation of the dielectric properties reveals that the nanocomposites actually derive qualities of its’ component materials.

Dielectric properties and thermal conductivity of graphene nanoplatelet filled poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend

Poly(methyl methacrylate) (PMMA) and graphene nanoplatelet (GNP) was introduced into poly(vinylidene fluoride) (PVDF) via a solution blending process, and a series of PVDF/PMMA/GNP composites were obtained. Scanning electron microscope (SEM) micrographs of the composite with 4 wt% GNP loading showed that GNP randomly dispersed and partly arranged parallel to each other in the matrix. Fourier transform infrared (FT-IR) spectroscopy results and X-ray diffraction (XRD) analysis revealed the increasing percentage of β- and γ-phase PVDF crystals in the composites with increasing the GNP contents. The frequency dependent electrical conductivity and dielectric properties of composites have been performed in the range of 102 − 107 Hz which obeyed the percolation theory. Dielectric constant and dielectric loss of composites increased with increasing GNP contents in the all frequency region. A dielectric constant of ~148 and dielectric loss of ~0.3 was observed at 102 Hz with 4 wt% of GNP loading, which is near the percolation threshold. Meanwhile, the thermal conductivity reached up to 0.84 W/m K for PVDF/PMMA/GNP composites with 4 wt% of GNP loading. An approch was provided to develop a variety of highly thermally conductive dielectric materials.

Microstructure and Dielectric Properties of PTFE-Based Composites Filled by Micron/Submicron-Blended CCTO

This paper investigated a polymer-based composite by homogeneously embedding calcium copper titanate (CaCu3Ti4O12; CCTO) fillers into a polytetrafluoroethylene matrix. We observed the composite filled by CCTO powder at different sizes. The particle size effects of the CCTO filling, including single-size particle filling and co-blending filling, on the microstructure and dielectric properties of the composite were discussed. The dielectric performance of the composite was investigated within the frequency range of 100 Hz to 1 MHz. Results showed that the composite filled by micron/submicron-blended CCTO particles had the highest dielectric constant (εr = 25.6 at 100 Hz) and almost the same dielectric loss (tanδ = 0.1 at 100 Hz) as the composite filled by submicron CCTO particles at the same volume percentage content. We researched the theoretical reason of the high permittivity and low dielectric loss. We proved that it was effective in improving the dielectric property of the polymer-based composite by co-blending filling in this experiment.

Elastic and Dielectric Properties of Active Ag/BaTiO3 Composites

This study examines the elastic and dielectric properties of active composites consisting of barium titanate (BaTiO3) and silver (Ag) constituents using experimental and numerical approaches. The elastic constants including Young’s modulus, shear modulus and Poisson’s ratio were measured by resonant ultrasound spectroscopy (RUS), a nondestructive dynamic technique, while a dielectric (impedance) spectroscopy was used to measure the relative permittivity and dielectric loss at different frequencies. The dielectric tests were also conducted at temperature ranges from −50 to 200 °C where the two phase transformations of barium titanate at around 0 °C and 120 °C were examined. The experimental results in this study were compared to data available in the literature. In addition to the experimental work, a numerical method is also considered in order to study the effects of blending silver into barium titanate on the effective elastic and dielectric properties of the composite and the local field fluctuations. For this purpose, two micromechanics models describing the detailed composite microstructures were constructed. The first model is based on two dimensional (2D) images of realistic microstructures obtained by the scanning electronic microscopy (SEM), while the second model is based on randomly generated three-dimensional (3D) microstructures with spherical particles. The effects of loading direction, porosity, particle shape and dispersion were examined using the micromechanics models. Numerical predictions of the effective elastic and dielectric constants were compared to the experiment results.

Fabrication and dielectric properties of Ba0.6Sr0.4TiO3 / acrylonitrile–butadiene–styrene resin composites

Ba0.6Sr0.4TiO3 (BST)/acrylonitrile–butadiene–styrene (ABS) composites were prepared via solution casting method. Effects of volume fraction of BST on microstructure and dielectric properties of composites were studied. Dielectric constants were simulated by Lichtenecker, Maxwell, Landzu–Lifishitz, and Yamada models. It was found that the permittivity of BST/ABS resin composites increases from 4.5 to 18 while loss tangent from 0.021 to 0.082 at 1 kHz with BST fillers increasing from 10 to 40 vol%. The permittivity value calculated by Yamada’s model matched well with the experimental results and the deviation was less than 2% with a shape factor (n) of 3.2. The dielectric tunability of the composites improved with increasing the amount of BST fillers. Dielectric properties of ABS resins were enhanced by increasing BST fillers due to the interface polarization mechanism. The development of BST/ABS dielectric functional composites broadens the range of candidate materials for 3D printed electronic devices.

Synthesis of CCTO and Doped CCTO Nanopowders and its Applications in the Field of Electronics

Demand for miniaturization of electrical and electronic devices has raised a challenge for development of capacitors with large dielectric constant and low dielectric loss. Calcium Copper Titanate, CaCu3Ti4O12 (CCTO) possess high dielectric constant, which has attracted much attention for the development of capacitors materials for electronic industries. CaCu3Ti4O12 (CCTO) and MgTiO3 Nano powders was synthesized in this work by applying Co-precipitation method followed by sintering of CCTO at 800°C and MgTiO3 at 600°C for 1h, sintering processes were employed in order to improve phase structures, morphology and dielectric properties. The microstructure, structural morphology of CCTO and MgTiO3 has been studied by XRD and SEM. Then CCTO/ MgTiO3 composites was prepared using CCTO and MgTiO3 Nano powders, then the dielectric properties of composites was studied using impedance spectroscopy.

Enhanced dielectric properties of poly(vinylidene fluoride) composites filled with nano iron oxide-deposited barium titanate hybrid particles.

We report enhancement of the dielectric permittivity of poly(vinylidene fluoride) (PVDF) generated by depositing magnetic iron oxide (Fe3O4) nanoparticles on the surface of barium titanate (BT) to fabricate BT–Fe3O4/PVDF composites. This process introduced an external magnetic field and the influences of external magnetic field on dielectric properties of composites were investigated systematically. The composites subjected to magnetic field treatment for 30 min at 60 °C exhibited the largest dielectric permittivity (385 at 100 Hz) when the BT–Fe3O4 concentration is approximately 33 vol.%. The BT–Fe3O4 suppressed the formation of a conducting path in the composite and induced low dielectric loss (0.3) and low conductivity (4.12 × 10−9 S/cm) in the composite. Series-parallel model suggested that the enhanced dielectric permittivity of BT–Fe3O4/PVDF composites should arise from the ultrahigh permittivity of BT–Fe3O4 hybrid particles. However, the experimental results of the BT–Fe3O4/PVDF composites treated by magnetic field agree with percolation theory, which indicates that the enhanced dielectric properties of the BT–Fe3O4/PVDF composites originate from the interfacial polarization induced by the external magnetic field. This work provides a simple and effective way for preparing nanocomposites with enhanced dielectric properties for use in the electronics industry.

Dielectric properties of composites containing melt-extracted co-based microwires

Abstract We have investigated the microwave properties of epoxy-based composites containing melt-extracted Co 69.25 Fe 4.25 B 13.5− x Si 13 Nb x ( x =0, 1, 3) microwires of various length annealed using a so-called combined current-modulation annealing (CCMA) technique. The observation of a double-peak feature in the permittivity spectra is believed due to the coexistence of the amorphous phase and a small amount of nanocrystallites on the wires with a high Nb content. CCMA was found to be favorable for a better-defined circular anisotropy of microwires and had suppressed the high-frequency peak due to residual stress relief for the composite with 25 mm long wires. Neither the shift of resonance peak nor the characteristic double peak feature was detected for composites containing as-cast 15 or 35 mm long microwires.

Ag-NBCTO-PVDF composites with enhanced dielectric properties

Three-phase composites with enhanced dielectric permittivity and low dielectric loss were prepared by incorporating the giant dielectric permittivity material Na0.5Bi0.5Cu3Ti4O12 (NBCTO) and conductive Ag nanoparticles in Poly(vinylidene fluoride) (PVDF) polymer matrix by melt mixing and hot pressing process, in which the filler content (volume fraction) of Ag nanoparticles and NBCTO powders was set at 50vol% and PVDF was set at 50vol%. The structure and thermal stability of the composites were characterized using X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). Studies on the dielectric properties of composites in the frequency range from 10 to 106Hz showed that the Ag-NBCTO-PVDF composite exhibited high dielectric permittivity of 222.4 and low loss tangent of 0.32 at 1kHz when the content of Ag was 5vol%. A percolation threshold of fAg=5.9vol% was calculated through the percolation theory.