Dielectric Constant Of Nanocomposites Research Articles

The effect of Ag2O/NbO2 nanostructures on the dielectric characteristics of PVA/PVP bled used in electronics

Nanocomposites may be employed in a wide range of applications, including as biosensors, diodes, antibacterial, transistors, and so on. In the current study, a new type of nanocomposites (PVA-PVP-Ag2O-NbO2) were prepared by solution casting method. The polymeric mixture (polyvinyl alcohol-polyvinylpyrrolidone) was produced with various polyvinyl alcohol concentration (50 wt. %), polyvinylpyrrolidone (50% wt.%), as well as niobium oxides and silver nanoparticles oxides were added to the polymeric mixture with different percentages, which are (0.0025, 0.005, 0.0075 and 0.01 wt. percent). The effect of each of the niobium oxide nanoparticles and silver oxide nanoparticles on A.C was studied. The alternating electrical properties were studied at room temperature in the frequency range (100Hz-5MHz). Results of the experiment showed an increase of both the dielectric constant and the alternating conductivity of electricity and the loss of dielectric of polymeric mixture (PVA-PVP) an increase in increasing concentrations of niobium oxide nanoparticles and silver oxide nanoparticles, and the dielectric loss and dielectric constant of nanocomposites (PVA-PVP-Ag2O-NbO2) a rise in increasing in the applied electric field’s frequency, and alternating With increasing frequency, electrical conductivity increases.

Enhancement investigations on dielectric and electrical properties of niobium pentoxide (Nb2O5) reinforced poly(vinylidene fluoride) (PVDF)- graphene oxide (GO) nanocomposite films

ABSTRACT An ultra high dielectric constant nanocomposites comprising of poly(vinylidene fluoride) (PVDF) as a polymer matrix and niobium pentoxide (Nb2O5)-reinforced graphene oxide (GO) have been successfully developed using solution casting technique. Scanning electron microscopy (SEM) demonstrates that the homogeneous dispersion of Nb2O5 and GO within the PVDF matrix was realized. The dielectric and electrical properties of the resulting PVDF-GO-Nb2O5 nanocomposite films as a function of frequency were studied. The dielectric constant of the nanocomposites system reached a value of about ≈140 at 100 Hz, with a relatively low dielectric loss factor (≈ 1.4). The enhanced dielectric performance of the PVDF-GO-Nb2O5 nanocomposites was ascribed to the presence of Nb2O5 onto the GO, which exhibits strong interaction between GO and PVDF matrix through hydrogen bonding. Moreover, the experimental results fit well with percolation theory and near the percolation threshold (fc < 2 wt %) with high dielectric constant was achieved for PVDF-GO-Nb2O5 nanocomposites. Furthermore, the AC electrical conductivity was also noticeably enhanced. Our strategy provides a facile method to prepare high dielectric constant and relatively low dielectric loss PVDF-GO-Nb2O5 nanocomposite films that might be suitable for energy storage applications.

Electrical response with temperature and magnetoelectric coupling of multiferroic nanocomposites

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.

Study on the Structure and Dielectric Properties of Zeolite/LDPE Nanocomposite under Thermal Aging.

Nanodoping is an effective way to improve the dielectric properties and the aging resistance of polyethylene. Nano-zeolite has a nano-level porous structure and larger specific surface area than ordinary nano-inorganic oxide, which can be used to improve dielectric properties of low-density polyethylene (LDPE) nanocomposite. The zeolite/LDPE nanocomposites were prepared and subjected to thermal aging treatment to obtain samples with different aging time. Using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and the differential scanning calorimetry (DSC) test to study the microscopic and structure characteristics, it was found that nano-zeolite doping can effectively reduce the thermal aging damage to the internal structure of the nanocomposite; carbonyl and hydroxyl decreased significantly during the thermal aging time, and the crystallinity effectively improved. Nano-zeolite doping significantly improved the morphology and strengthened the aging resistance of the nanocomposite. In the dielectric strength test, it was found that nanodoping can effectively improve the direct current (DC) and alternating current (AC) breakdown field strength and the stability after the thermal aging. The dielectric constant of nanocomposite can be reduced, and the dielectric loss had no obvious change during the aging process. Moreover, the zeolite/LDPE nanocomposite with the doping concentration of 1 wt % had the best performance, for the nano-zeolite was better dispersed.

Size Effect in Nanocomposites Based on Molecular Ferroelectric Diisopropylammonium Bromide

We present the results of studies of the dielectric properties of nanocomposites based on Al2O3 oxide films with a pore size of 330 and 60 nm with particles of an organic ferroelectric diisopropylammonium bromide (C6H16BrN, DIPAB) introduced into the pores, aimed at determining the size dependences of phase transition parameters. A shift in the phase transition to low temperatures and diffusion of the transition are found, which become more significant for smaller pores. A broadening of the temperature hysteresis of the dielectric constant of nanocomposites during the phase transition was also observed. The decrease in the phase transition temperature in nanocomposites with DIPAB nanoparticles is consistent with theoretical models of the size effects on the structural phase transition.

Fabrication of enhanced dielectric PVDF nanocomposite based on the conjugated synergistic effect of ionic liquid and graphene

In recent years, due to its excellent dielectric property in polymers, polyvinylidene fluoride (PVDF) has been widely used to prepare polymer based electrical device and manufacture flexible sensors, transducers and energy harvesters. However, compared with some inorganic materials, the finite dielectric property of PVDF still limited its application as piezoelectric material in high-sensitivity pressure sensors for detecting dynamic signals. In this report, we prepared a high dielectric flexible material based on PVDF compositing with graphene and ionic liquid (IL, 1-butyl-3-methylimidazolium hexafluorophosphate). The introduction of IL improves the dispersion of graphene in nanocomposite matrix, and the conjugated synergistic effect of IL and graphene enhance the dielectric property of PVDF nanocomposite. IL can help to improve the interfacial polarization effect between graphene and PVDF matrix, and increase the content of β phase due to the ion-dipolar interaction between the -CF2 of the polymer backbone and imidazolium cation. Meanwhile, the uniform dispersion of graphene in PVDF can promote the formation of tiny graphene microcapacitor structure in matrix, which is significant in improvement of dielectric and electrical properties of PVDF nanocomposite. The nanocomposite with the concentration of 2.0 wt% graphene and 2.0 wt% ionic liquid has the best dielectric property in our work, the dielectric constant of nanocomposite is nearly 6 times higher than that of pure PVDF. In addition, the dielectric loss is less than 0.2 when the frequency between 104-106Hz, which is acceptable in applications.

Preparation and characterization of zinc ferrite—Polyaniline nanocomposite for removal of rhodamine B dye from aqueous solution

Zinc Ferrite (ZnFe2O4), a magnetic ferrite of nanodimension was synthesized and characterized by XRD and SEM techniques. In situ technique was used to prepare Zinc Ferrite-Polyaniline nanocomposite. Electrical conductivity and dielectric constant of nanocomposite were determined at different frequency and temperature. Rhodamine B dye (RHB) from aqueous solution was removed by adsorbent Zinc Ferrite-Polyaniline nanocomposite. Effect of contact time, concentration of nanocomposite and dye, pH of the dye solution and temperature on the removal of dye were studied. Different isotherm and kinetic models were tested. Thermodynamic parameters were calculated. Role of NaCl on the removal of dye was investigated. Nanocomposite was desorbed again and again and used for adsorption.

Improved dielectric behaviour of graphene oxide-multiwalled carbon nanotube nanocomposite

We have prepared graphene oxide (GO)-multiwalled carbon nanotube (MWCNT) composite film through vacuum filtration method. In this work, we carried out the dielectric behaviour of GO-MWCNT composite film in the frequency range of 100 Hz to 1 MHz and temperature range of 30–200 °C. The GO-MWCNT composite film showed significantly higher dielectric constant as 6021 than the GO (5031) which was even very high compared to conventional dielectric materials. The enhancement of dielectric constant is attributed to the strong interaction between sp2 MWCNT fillers and sp3 GO matrix as well as the formation of microcapacitors by highly conductive MWCNT segregated by GO sheets. Furthermore, we found interesting transition between semiconductor to conductor was attained at 165 °C. It is suggested that the temperature dependent transition of electrical properties of GO-MWCNT composite film is closely related with the ion mobility, removal of water molecules and reduction of GO in the composite. The effect of interfacial polarization and relaxation process were studied. The redox peak current has increased significantly for the GO-MWCNT composite electrode than the GO and MWCNT where the highly conducting MWCNT provide the necessary conduction pathways on the electrode surface. These flexible, high dielectric constant nanocomposites are potential flexible dielectric materials for use in high frequency capacitors and in electronic devices.

An approach to developing high dielectric constant nanocomposites based on polyrotaxane derivative

Polyrotaxane as a kind of supramolecular material has attracted more and more attention from researchers. Owing to the special topological interlocked structure, many properties and potential applications have been discovered. In this paper, a new polyrotaxane derivative has been synthesized based on the polyrotaxane end capped by 2,4-dinitrofluorobenzene (DNFB). And through cross-linking the polyrotaxane derivative meanwhile grafting copper phthalocyanine oligomer (CuPc) onto the side chains, high dielectric constant elastomeric nanocomposite was fabricated. TEM image showed the size of most CuPc particles is in the range of 10–20nm and the particles were dispersed uniformly in the matrix. According to the results of thermal analysis, compared to the pure cross-linking matrix the thermal stability of composites was obviously improved with the existence of CuPc fillers. At 100Hz, the dielectric constant of composite with 8wt% CuPc reaches to 135 and the dielectric loss is just 0.34 at room temperature.

Enhancement of the dielectric response in polymer nanocomposites with low dielectric constant fillers.

In order to increase the dielectric constants of polymer-based dielectrics, composite approaches, in which inorganic fillers with much higher dielectric constants are added to the polar polymer matrix, have been investigated. However, high dielectric constant fillers cause high local electric fields in the polymer, resulting in a large reduction of the electric breakdown strength. We show that a significant increase in the dielectric constant can be achieved in polyetherimide nanocomposites with nanofillers whose dielectric constant can be similar to that of the matrix. The presence of nanofillers reduces the constraints on the dipole response to the applied electric field, thus enhancing the dielectric constant. Our results demonstrate that through nanostructure engineering, the dielectric constant of nanocomposites can be enhanced markedly without using high dielectric constant nanofillers.

Fluorine ligand exchange effect in poly (vinylidenefluoride-co-hexafluoropropylene) with embedded fluorinated barium titanate nanoparticles

Poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) nanocomposites were prepared with fluorinated barium titanate (BaTiO3) nanoparticles. BaTiO3 nanoparticles was treated with 2,2,2-trifluoroacetic acid in Novec-7500 and the modified surface characteristics of the nanoparticles showed good solubility in the fluorous solvent and fluorous polymer. The optimized fluorinated BaTiO3 condition had explored by controlling temperature and ligand ratio. The prepared nanocomposite through fluorinated nanoparticles were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, impedance spectroscopy and atomic force microscopy in order to investigate their structural and electrical properties. Root mean square roughness of nanocomposites was increased only 0.48nm after adding 20vol.% of fluorinated BaTiO3 nanoparticles. Also, dielectric constant of nanocomposite was predicted and agreed well with experimental data through the modified Kerner model. Dielectric constant of PVdF-HFP nanocomposite was increased about 15 thorough an addition of 20vol.% of fluorinated BaTiO3 nanoparticles. The application of near edge X-ray absorption fine structure spectroscopy of PVdF-HFP/fluorinated BaTiO3 nanocomposites was presented.

All‐organic nanocomposites of functionalized polyurethane with enhanced dielectric and electroactive strain behavior

For a dielectric elastomer, increasing its dielectric constant substantially could lead to a high electric field induced strain under a low operation field. In this work, high dielectric constant nanocomposites were developed by chemically bonding copper phthalocyanine oligomer (CuPc), a high dielectric constant organic semiconductor, to polyurethane (PU). Transmission electron microscope‐observed morphologies revealed that the sizes of CuPc particles in a nanocomposite of PU attached with 8.78 vol.% of CuPc were in the range of 10–20 nm, much smaller than the sizes (250–600 nm) in physical blend of PU with the same volume fraction of CuPc. At 100 Hz, the nanocomposite film exhibited a dielectric constant of 391, representing a more than 60 times increase with respect to the neat PU. The enhanced dielectric response in the nanocomposite makes it possible to induce a high electromechanical response. A strain of 17.7% and an elastic energy density of 0.927 J/cm3 were achieved under an electric field of 10 V/µm. Copyright © 2014 John Wiley &amp; Sons, Ltd.

A polyurethane-based elastomeric nanocomposite with a high dielectric constant

To increase the electric energy density of dielectric elastomer substantially, high dielectric constant nanocomposites were developed using polyurethane (PU) as matrix and copper phthalocyanine oligomer (CuPc)—a high dielectric constant organic semiconductor—as filler. Transmission electron microscope (TEM)-observed morphologies revealed that the sizes of CuPc particles in nanocomposite of PU chemically attached with 8.78 vol% of CuPc were in the range of 10–20 nm, much smaller than the sizes (250–600 nm) in the physical blend of PU with the same volume fraction of CuPc. At 100 Hz, the nanocomposite film exhibited a dielectric constant of 391, representing more than 60-fold increase with respect to the pure PU. The enhanced dielectric response of the nanocomposite makes it possible to induce a high electromechanical response under a much reduced electric field (a strain of 17.7 % was achieved under a field of 10 V/μm).

“Grafting to” route to PVDF-HFP-GMA/BaTiO3 nanocomposites with high dielectric constant and high thermal conductivity for energy storage and thermal management applications

The introduction of high dielectric constant ceramic nanoparticles into an insulating polymer is an important approach to prepare high dielectric constant nanocomposites for electric energy storage applications. A key to obtaining desirable properties is the homogeneous dispersion of the nanoparticles in the corresponding polymer. Conventional methods used to improve the nanoparticle dispersion enhance the physical interaction between the nanoparticle and the polymer matrix via nanoparticle surface modification. In this work, the covalent bonding between the nanoparticle and the polymer matrix was utilized to simultaneously enhance the nanoparticle dispersion and nanoparticle/polymer interaction by functionalizing both the polymer and the nanoparticles. The poly(vinylidene fluoride-co-hexafluoropropylene) [PVDF-HFP] was functionalized with glycidyl methacrylate (GMA) via atom transfer radical polymerization. The barium titanate (BaTiO3) nanoparticles were modified by amino-terminated silane molecules. Then the nanocomposites were prepared by a “grafting to” method. Namely, grafting GMA functionalized PVDF-HFP to the surfaces of the BaTiO3 nanoparticles. The introduction of GMA into the PVDF-HFP not only increases the dielectric constant, but also changes the dielectric response of PVDF-HFP. More importantly, this “grafting to” approach results in core–shell structured BaTiO3@PVDF-HFP-GMA and thus a homogeneous dispersion of BaTiO3 nanoparticles in the nanocomposites. The dielectric constant, electric energy density and thermal conductivity of the nanocomposites are significantly enhanced with the increase of BaTiO3, while the dielectric loss shows a slight decrease as the nanoparticle loading increases.

A new low dielectric constant barium titanate - poly (methyl methacrylate) nanocomposite films

In the present investigation, nanocomposite films with poly(methyl methacrylate) (PMMA) as a polymer matrix and barium titanate as a filler were prepared by solution casting method. Barium titanate nano particles were prepared using Ti(IV) triethanolaminato isopropoxide and hydrated barium hydroxide as precursors and tetra methyl ammonium hydroxide (TMAH) as a base. The nanocomposite films were characterized using XRD, FTIR, SEM and dielectric spectroscopy techniques. Dielectric measurements were performed in the frequency range 100 Hz-10 MHz. Dielectric constant of nanocomposites were found to depend on the frequency, the temperature and the filler fraction. Dissipation factors were also influenced by the frequency and the temperature but not much influenced by the filler fractions. The 10 wt% of BT-PMMA nanocomposite had the lowest dielectric constant of 3.58 and dielectric loss tangent of 0.024 at 1MHz and <TEX>$25^{\circ}C$</TEX>. The dielectric mixing model of Modified Lichtenecker showed the close fit to the experimental data.

Investigation of solution processable albumen–BaTiO3 nanocomposite and its application in high-k films

Abstract Albumen and BaTiO3 nanoparticles are employed to make solution processable nanocomposite for high permittivity films. The nanoparticles are modified with poly(acrylic acid) molecules to achieve homogeneous dispersion in albumen aqueous solution and made into films by drop casting. The dielectric constant and loss tangent of albumen–BaTiO3 nanocomposites are investigated as the function of volume fraction of BaTiO3. The nanocomposites exhibit maximum relative permittivity of 52 and good dielectric stability over a wide range of frequency, while the loss tangent is below 0.05 even at high BaTiO3 loading of 80 vol%. The dielectric constants of nanocomposites with lower volume fractions (

Enhanced Dielectric Response in Polyurethane Based All-Organic Nanocomposite

A high dielectric constant nano-composite was fabricated using polyurethane (PU) as matrix and poly (p-chloromethyl styrene) (PCMS) grafted with copper phthalocyanine oligomer (CuPc, a planar multiring semiconductor with dielectric constant&gt;105) (name the grafting product as PCMS-g-CuPc) as filler. According to the TEM-observed morphologies, PCMS-g-CuPc balls (~80 nm) distribute uniformly in PU matrix, while in PCMS-g-CuPc balls the PCMS acts as “matrix” which contains dispersed CuPc particles with a average size of ca. 25nm [1/20 of that of CuPc in simple blend of PU and CuPc (PU/CuPc)]. At 100Hz, the dielectric constant of the nanocomposite reaches 345, almost 7 times higher than that of PU/CuPc. The enhanced dielectric response in the nano-composite can be explained by the remarkably strengthened interface exchange coupling effect as well as the Maxwell-Wagner-Sillars polarization mechanism due to the significantly reduced CuPc particle size in the nano-composite.

New approach to nanocomposites of polyimides containing polyhedral oligomeric silsesquioxane for dielectric applications

Low dielectric constant nanocomposites of polyimides with grafted methacrylate side chains containing polyhedral oligomeric silsesquioxane (POSS) were successfully synthesized by thermally initiated free-radical graft copolymerization of methacrylcyclopentyl-POSS (MA-POSS) with the ozone-preactivated poly(amic acid), followed by thermal imidization. The dielectric constant of the film can be tuned by varying the molar ratio of the grafted MA-POSS side chains in the copolymer.