Role of the interface in determining the dielectric properties of nanocomposites (original) (raw)
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Polymer Nanocomposite Dielectrics – The Role of the
Dielectrics and …, 2005
The incorporation of silica nanoparticles into polyethylene increased the breakdown strength and voltage endurance significantly compared to the incorporation of micron scale fillers. In addition, dielectric spectroscopy showed a decrease in dielectric permittivity for the nanocomposite over the base polymer, and changes in the space charge distribution and dynamics have been documented. The most significant difference between micron scale and nanoscale fillers is the tremendous increase in interfacial area in nanocomposites. Because the interfacial region (interaction zone) is likely to be pivotal in controlling properties, the bonding between the silica and polyethylene was characterized using Fourier Transformed Infra-red (FTIR) spectroscopy, Electron Paramagnetic Resonance (EPR), and X-ray Photoelectron Spectroscopy (XPS) The picture which is emerging suggests that the enhanced interfacial zone, in addition to particle-polymer bonding, plays a very important role in determining the dielectric behavior of nanocomposites.
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
Journal of Applied Physics
This work presents a comprehensive investigation into the effects of nanoparticles and organic additives on the dielectric properties of insulating polymers using reinforced silicone rubber as a model system. TiO 2 and ZrO 2 nanoparticles (d ¼ 5 nm) were well dispersed into the polymer via a bimodal surface modification approach. Organic molecules with the potential of voltage stabilization were further grafted to the nanoparticle to ensure their dispersion. These extrinsic species were found to provide deep traps for charge carriers and exhibited effective charge trapping properties at a rather small concentration ($10 17 cm À3). The charge trapping is found to have the most significant effect on breakdown strength when the electrical stressing time is long enough that most charges are trapped in the deep states. To establish a quantitative correlation between the trap depth and the molecular properties, the electron affinity and ionization energy of each species were calculated by an ab initio method and were compared with the experimentally measured values. The correlation however remains elusive and is possibly complicated by the field effect and the electronic interactions between different species that are not considered in this computation. At high field, a super-linear increase of current density was observed for TiO 2 filled composites and is likely caused by impact excitation due to the low excitation energy of TiO 2 compared to ZrO 2. It is reasoned that the hot charge carriers with energies greater than the excitation energy of TiO 2 may excite an electron-hole pair upon collision with the NP, which later will be dissociated and contribute to free charge carriers. This mechanism can enhance the energy dissipation and may account for the retarded electrical degradation and breakdown of TiO 2 composites. Published by AIP Publishing.
The Promise of Dielectric Nanocomposites
Conference Record of the 2006 IEEE International Symposium on Electrical Insulation, 2006
Several research groups worldwide have now been able to document some significant improvements that can be made in the electrical, and other, properties of polymer composites through the incorporation of nanoparticulates. Although it is now becoming clear that the mechanisms responsible for these changes are by no means universal, some of the benefits are substantial and rely on the large interface areas which are inherent in the introduction of materials of nanometric dimensions. By examining a variety of nanomaterials, this contribution seeks to review the property changes that can be brought about and examines the possibilities for commercial applications. This involves not only the electrical properties, but the implications for the attendant mechanical characteristics and the polymer processing necessary for utilization of this emerging breed of dielectric material. In this context, the functionalization of the particulate surfaces to provide preferential coupling to the host polymer will be explored since, by this means, a degree of preferred assembly can be accommodated. Through experimental examples, the use of this technique to tailor the properties of nanodielectrics is illustrated.
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.
Interfacial charge behavior in nanodielectrics
2009 IEEE Conference on Electrical Insulation and Dielectric Phenomena, 2009
In recent years, the availability and low cost of nanometric-sized filler particles have generated great interest in polymer nanocomposites for a host of applications, including electrical insulation with enhanced breakdown and voltage endurance properties. This work combines the results of several experiments to add insight to the processes taking place in the crucial polymer transition region near the particle surfaces. The relative tendency to accumulate space charge under a high DC field is investigated through pulsed electroacoustic (PEA) apparatus. DC transient (absorption) currents reveal a quasi-DC conductivity that is surprisingly high in the nanocomposite, a result that is reinforced by dielectric spectroscopy, which also indicates a reduction in the nanocomposite's real permittivity. Thermally-stimulated currents reveal the presence of shallow traps that accompany the nanoparticle inclusions. Taken together, the results of the study indicate that the transition region is responsible for the desirable nanocomposite bulk properties which are today of interest, and help explain the difference in performance between these new materials and both unfilled resin and conventional composites composed of micronsized fillers.
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.
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.
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.