Comparation two types of nanowires on the dielectric properties of epoxy resin with SiO2 nanoparticles (original) (raw)
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Effect of nanofillers on the dielectric properties of epoxy nanocomposites
Advances in materials Research, 2012
Epoxy resin is widely used in high voltage apparatus as insulation. Fillers are often added to epoxy resin to enhance its mechanical, thermal and chemical properties. The addition of fillers can deteriorate electrical performance. With the new development in nanotechnology, it has been widely anticipated that the combination of nanoparticles with traditional resin systems may create nanocomposite materials with enhanced electrical, thermal and mechanical properties. In the present paper we have carried out a comparative study on dielectric properties, space charge and dielectric breakdown behavior of epoxy resin/nanocomposites with nano-fillers of SiO 2 and Al 2 O 3. The epoxy resin (LY556), commonly used in power apparatus was used to investigate the dielectric behavior of epoxy resin/nanocomposites with different filler concentrations. The epoxy resin/nanocomposite thin film samples were prepared and tests were carried out to measure their dielectric permittivity and tan delta value in a frequency range of 1 Hz-1 MHz. The space charge behaviors were also observed by using the pulse electroacoustic (PEA) technique. In addition, traditional epoxy resin/microcomposites were also prepared and tested and the test results were compared with those obtained from epoxy resin/nanocomposites.
Study of dielectric relaxations in zinc oxide-epoxy resin nanocomposites
Journal of Alloys and Compounds, 2009
Thermally stimulated depolarization current (TSDC) and dielectric relaxation spectroscopy (DRS) techniques were employed to study the relaxations and the conductivity phenomena in epoxy-based polymer. In addition to the primary ␣ relaxation process associated with the glass-rubber transition, significant interfacial relaxation and ionic conduction process have been revealed. The ac conductivity is temperature and frequency dependent and shows a dc plateau at low frequencies. Above the glass transition temperature, dc conductivity is described by a Vogel-Tamman-Fulcher-Hesse (VFTH) equation while it shows Arrhenius behaviour at higher temperatures.
Dielectric relaxations investigation of a synthesized epoxy resin polymer
A diglycidylether of bisphenol A (DGEBA) epoxy resin was synthesized, and cured with 3, 3′- diaminodiphenyl sulfone (DDS) at a curing temperature of 120 ◦C. The relaxation properties of the realized polymers were studied by two complementary techniques: dielectric relaxation spectroscopy (DRS), in the temperature range 173–393K and in the frequency interval 10−1–106 Hz, and thermally stimulated depolarization current (TSDC) with a windowing polarization process. Current-voltage (I-V) measurements were also carried out to study interfacial relaxations. Dielectric data were analyzed in terms of permittivity and electric modulus variations. Three relaxation processes (, and ) have been identified. They were found to be frequency and temperature dependent and were interpreted in terms of the Havriliak-Negami approach. Relaxation parameters were determined by fitting the experimental data. The temperature dependence of the relaxation time was well fitted by the Arrhenius law for secondary relaxations, while the Vogel-Fulcher-Tamann model was found to better fit the (T) variations for relaxation. We found 0 = 4.9 10−12 s, 9.6 10−13 s and 1.98 10−7 s for , and relaxations, respectively. The obtained results were found to be consistent with those reported in the literature. Due to the calculation of the low-frequency data of dielectric loss by the Hamon approximation, the Maxwell-Wagner-Sillars (MWS) relaxation was highlighted.
Energies
The paper presents the effects of gradual temperature curing on the dielectric properties of epoxy nanocomposite samples. Samples were prepared based on Class H epoxy resin filled with nano-alumina (Al2O3) for different wt% loadings (0.5 wt% to 5.0 wt%) and two different filler sizes (13 nm and <50 nm), i.e., two different specific surface area values. During the research, specimen sets were cured gradually at increasingly higher temperatures (from 60 °C to 180 °C). Broadband dielectric spectroscopy (BDS) was used to determine the characteristics of the dielectric constant and the dielectric loss factor in the frequency range from 10−3 Hz to 105 Hz. As a result, it was possible to analyze the impact of the progressing polymer structure thermosetting processes on the observed dielectric parameters of the samples. The nano-Al2O3 addition with 0.5 wt%, 1.0 wt%, and 3.0 wt% resulted in a decrease in dielectric constant values compared to neat epoxy resin samples. The most significant...
The influence of ZnO nanoparticles on the dielectric properties of epoxy resin
APPLIED PHYSICS OF CONDENSED MATTER (APCOM 2019)
Interesting electrical properties represent the epoxy nanocomposites, because the addition of nanofillers to a pure epoxy resin demonstrate several advantages opposite to pure epoxy resin without nanofillers. In the last 20 years, the dielectric properties (the complex permittivity and dissipation factor) of epoxy nanocomposites had been evaluated and the results clearly show that they are lower than that of base epoxy and microcomposites when insulating oxides were used as the fillers. Nowadays the epoxy and epoxy based composites are preferred insulating materials for many electrical applications. The influence of the various concentrations of ZnO nanoparticles in epoxy resin Vukol 022 on the changes of the complex permittivity and dissipation factor has been measured at the temperature range from 20 °C to 120 °C by a capacitance method in the frequency ranges from 1 mHz to 1 MHz. In this contribution, we present a study of the influence of 1,0 wt.% and 5,0 wt. % concentrations of ZnO nanofillers on the dielectric properties of the epoxy resin. From the frequency dependence of dissipation factor, α-relaxation process and its shift to lower frequencies with ZnO fillers were observed.
Polymer Composites, 2014
Composites reinforced with microparticles using a polymer matrix reinforced by nanoparticles represent a new emerging class of materials. Epoxy composites have been prepared using quartz as microfillers and organically modified Montmorillonite as nanofillers in order to study the dielectric properties of such new materials. The structure of the composites as determined by transmission electron microscopy, is neither exfoliated nor intercalated, although the thickness of C30B stacks is in the nanometric range. The influence of nano-and microparticles on epoxy matrix amorphous structure has been highlighted through Differential Scanning Calorimetry experiments. C30B has not effect on glass transition temperature but a drastic from 357 K to 325 K decrease is observed with the addition of microparticles. Heat capacity step remains unchanged, except for the microcomposite. And finally, Broadband Dielectric Spectroscopy has been used to characterize the dielectric properties at different temperatures. The spectra have been fitted with Havriliak-Negami equation to extract the relaxation times and the dielectric strengths associated with local b and c relaxations and the main a relaxation.
2007
The dielectric properties of epoxy resin were studied as a function of hydration by dielectric spectroscopy. The dielectric spectroscopy measurements show different conduction and quasi-DC behaviors at very low frequencies (<10-2 Hz) with activation energies dependent on the hydration. These observations lead to the development of a model in which a "water shell" is formed around the nanoparticles. The multiple shell model, originally proposed by Lewis and developed by Tanaka, has been further developed to explain low frequency dielectric spectroscopy results in which percolation of charge carriers through overlapping water shells was shown to occur. At 100% relative humidity, water is believed to surround the nanoparticles to a depth of approximately 10 monolayers as the first layer. A second layer of water is proposed that is dispersed by sufficiently concentrated to be conductive. If all the water had existed in a single layer surrounding a nanoparticle, this layer would have been approximately 5 nm thick at 100% RH. Filler particles that have surfaces that are functionalized to be hydrophobic considerably reduce the amount of water absorbed in nanocomposites under the same conditions of humidity. PEA results show that the wetted epoxy specimens have a higher threshold field of space charge accumulation than such dry specimens since water enhances charge decay.
Broadband Dielectric Relaxation Spectroscopy in Polymer Nanocomposites
Macromolecular Symposia, 2008
Dielectric spectroscopy in the frequency domain and thermally stimulated depolarization currents techniques, covering together a broad frequency range (10 À4 -10 9 Hz), were employed to investigate molecular dynamics in relation to structure and morphology in polymeric nanocomposites. Several systems were investigated, three of them with the same epoxy resin matrix and different inclusions (modified smectite clay, conducting carbon nanoparticles and diamond nanoparticles) and two with silica nanofiller (styrene-butadiene rubber/silica and polyimide/ silica nanocomposites). Special attention was paid to the investigation of segmental dynamics associated with the glass transition of the polymer matrix, in combination also with differential scanning calorimetry measurements. Effects of nanoparticles on local (secondary) relaxations and on the overall dielectric behavior were, however, also investigated. Several interesting results were obtained and discussed for each of the particular systems. Two opposite effects seem to be common to the nanocomposites studied and dominate their behavior: (1) immobilization/reduction of mobility of a fraction of the chains at the interface to the inorganic nanoparticles, due to chemical or physical bonds with the particles, and (2) loosened molecular packing of the chains, due to tethering and geometrical confinement, resulting in an increase of free volume and of molecular mobility.
Polymers
The influence of various types of nanoparticle fillers with the same diameter of 20 nm were separately incorporated into a single component impregnating resin based on a polyesterimide (PEI) matrix and its subsequent changes in complex relative permittivity were studied. In this paper, nanoparticles of Al2O3 and ZnO were dispersed into PEI (with 0.5 and 1 wt.%) to prepare nanocomposite polymer. Dielectric frequency spectroscopy was used to measure the dependence of the real and imaginary parts of complex relative permittivity within the frequency range of 1 mHz to 1 MHz at a temperature range from +20 °C to +120 °C. The presence of weight concentration of nanoparticles in the PEI resin has an impact on the segmental dynamics of the polymer chain and changed the charge distribution in the given system. The changes detected in the 1H NMR spectra confirm that dispersed nanoparticles in PEI lead to the formation of loose structures, which results in higher polymer chain mobility. A shif...
Dynamics and dielectric properties of polymer/nanoparticle nanocomposites by dielectric spectroscopy
Dynamics and dielec. properties of nanocomposites based on polymer matrixes and different types of nanoparticles, as studied by several authors, have been reviewed. Studies on nanocomposites based both on thermoplastic (conductive, non conductive and liq. crystals) and thermosetting matrixes are presented, with several types of nanoparticles (ceramic, metallic, metal oxide and others) as fillers. Their effect on dielec. properties and mol. dynamics has been analyzed, underlaying the strong effect of the interfaces on them. Theor. models such as those corresponding to the percolation theory proposed by several authors to quantify those effects are presented and compared, discussing the values and evolution of the fitting parameters.