Towards an understanding of nanometric dielectrics (original) (raw)
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Role of the interface in determining the dielectric properties of nanocomposites
The 17th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2004. LEOS 2004.
It has been demonstrated that the electrical breakdown properties of polymer composites can be substantially enhanced when the filler particles are of nanometric dimensions. These benefits are likely related to the mitigation and redistribution of internal charge. Using the example of an epoxy-TiO 2 nanodielectric (and a comparable conventional composite), this contribution seeks to examine this issue from the physical and chemical viewpoint. It is shown that a reduction in free volume cannot be used to explain the dielectric enhancements. The free volume of nanomaterials is actually higher than that of conventional samples. This conclusion is consistent with recent application of electron paramagnetic resonance methods, which have confirmed earlier speculation that the environment associated with the interface is radically changed when the in-filled particulates are reduced to nanometric dimensions and the associated interfacial area is greatly increased. Through examinations of infrared absorption & EPR, the paper provides some speculation on the part played by an interaction zone surrounding the particulate inclusions. The presence of a highly mobile interlayer is thought to be the key to the electrical property changes seen.
Dielectric response and energy storage efficiency of low content TiO2-polymer matrix nanocomposites
Composites Part A: Applied Science and Manufacturing, 2015
TiO 2 /epoxy nanocomposites were prepared at different filler concentrations varying from 3 to 12 phr (parts per hundred resin per weight). The dispersion of TiO 2 was examined by Scanning Electron Microscopy and proved to be adequate. Differential Scanning Calorimetry was implemented to determine the glass to rubber transition temperature of the polymer matrix. The dielectric analysis was performed via Broadband Dielectric Spectroscopy in a wide frequency and temperature range. Five different mechanisms were observed in the spectra of the examined composites which are identified, in terms of increasing temperature at constant frequency, as c, b, Intermediate Dipolar Effect (IDE), a and Interfacial Polarization (IP) relaxation modes. The activation energies of all relaxation modes were calculated. Finally, the dielectric response of the TiO 2 nanocomposites compared to that of the TiO 2 microcomposites reveals that the former exhibit significantly higher energy storage efficiency even at lower TiO 2 concentration than the corresponding of the microcomposites.
Internal charge behaviour of nanocomposites
Nanotechnology, 2004
The incorporation of 23 nm titanium dioxide nanoparticles into an epoxy matrix to form a nanocomposite structure is described. It is shown that the use of nanometric particles results in a substantial change in the behaviour of the composite, which can be traced to the mitigation of internal charge when a comparison is made with conventional TiO 2 fillers. A variety of diagnostic techniques (including dielectric spectroscopy, electroluminescence, thermally stimulated current, photoluminescence) have been used to augment pulsed electro-acoustic space charge measurement to provide a basis for understanding the underlying physics of the phenomenon. It would appear that, when the size of the inclusions becomes small enough, they act co-operatively with the host structure and cease to exhibit interfacial properties leading to Maxwell-Wagner polarization. It is postulated that the particles are surrounded by high charge concentrations in the Gouy-Chapman-Stern layer. Since nanoparticles have very high specific areas, these regions allow limited charge percolation through nano-filled dielectrics.
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.
2022 International Conference on Diagnostics in Electrical Engineering (Diagnostika)
In this study, the effect of 0.75 weight percent filler silica (SiO2) with PI or PA nanowires for dielectric properties of epoxy resin EPOXYLITE 3750 LV (ER) was studied. For this purpose, direct unidirectional conductivity measurements and broadband dielectric spectroscopy measurements were used to describe changes in the dielectric responses of ER / SiO2 nanocomposites with nanowires in the frequency and temperature range. The presence of nanowires and nanoparticles in the epoxy resin affected the segmental dynamics of the polymer chain and altered the charge distribution in the system. These changes caused a change in permittivity values and a shift in local relaxation peaks in the imaginary permittivity and dissipation factor spectra of nanocomposites. Experiments have shown that temperaturedependent transitions of electrical properties in nanocomposites are associated with to relaxation processes.
Candidate Mechanisms Responsible for Property Changes in Dielectric Nanocomposites
2006
This contribution seeks to provide some insight for the documented changes in the electrical properties of filled polymers when the filler size is reduced to nanometric dimensions. After examining the possible underlying mechanisms, experiments are described in which composites based on a benign biphenol epoxy resin formulation are subjected to photo- and electro-luminescence studies in which the spectrum of the
The influence of nanoparticles in the epoxy resin on dielectric parameters and partial discharges
2018 ELEKTRO
In order to study the influence mechanism of nanoparticles on the dielectric properties of epoxy resin materials for composite insulators under different nanoparticle filling amounts, the free volume, dielectric relaxation, breakdown strength and trap distribution of the samples were tested by positron annihilation lifetime spectroscopy, breakdown strength, broadband dielectric spectroscopy (BDS) and thermally stimulated current (TSC). The results show that the limiting effect of nanoparticles rapidly reduced the number of traps in the amorphous zone of materials at a low filling amount. As a result, the free path of carriers was increased and the concentration of free volume was decreased, which can limit the injection and transportation of carriers, resulting in the increase of material breakdown strength. At a high filling amount, a large number of interfacial deep traps were introduced into the nanoparticles, and the carrier free volume concentration and size were reduced. The traps inside the material were mainly interfacial deep traps. Under the action of an external electric field, a hetero polar charge was formed on the other end to cause electric field distortion, thus the breakdown field strength of the material was weakened.
2009
This paper looks at the dierences in dielectric response between epoxy resin com- posites with conventional and nanoscale alumina filler. Host material, namely bisphenol-A epoxy resin, is the same for all samples. Preparation of the samples is described in detail. Both filler types are treated in similar fashion to ensure comparability of the results. An even distribution of the alumina in case of the nanoscale filler was validated by means of transmis- sion electron microscopy. It is shown by means of dielectric spectroscopy how the particle size and preparation influence the material properties. Measurements were performed in a broad frequency range between 0.01 and 10 MHz, for temperatures between -20C and the glass transition temperature of the host material close to 120C. Possible explanations for the witnessed behavior are presented and the contributing factors discussed.
Dielectric characterisation of epoxy nanocomposite with barium titanate fillers
IET Nanodielectrics, 2020
High permittivity materials are currently in use for mitigation of electrical stress in high-voltage apparatus and energy storage systems. In this work, epoxy-based high permittivity nanocomposites with Barium titanate (BaTiO 3) nanofillers are considered, for the purpose of stress mitigation. Uniform dispersion of the fillers in the polymer up to 10% by volume is achieved. Apart from the use of as-received fillers, the effect of using surface-functionalised nanoparticles (with 3glycidoxypropyltrimethoxy-silane) before use is also investigated. The nanocomposite is characterised in terms of its complex permittivity, DC conductivity, short-term AC breakdown strength and space charge accumulation, to gauge its suitability for use in high-voltage insulation. Complex permittivity is measured using broadband dielectric spectroscopy over a broad frequency range of 1 mHz to 1 MHz. DC conductivity is studied from polarisation-depolarisation current measurements. Short-term AC breakdown strength tests are performed at power frequency (50 Hz). Space charge density along the sample thickness is obtained using pulsed electro-acoustic technique. A computational case-study is presented to show the feasibility of using the high permittivity nanocomposite for electric stress control in high-voltage equipment (viz., at mounting flanges of 69 kV bushings).