Internal charge behaviour of nanocomposites

Nelson, J. K.; Fothergill, J.C.

doi:10.1088/0957-4484/15/5/032

Cited by 475 publications

(326 citation statements)

References 22 publications

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“…Figure 1 compares breakdown results obtained from Material C and Material E and shows the effect of MMT dispersion. Where the MMT has been poorly dispersed, in Material C, the ramp breakdown strength is greatly reduced compared with the master batch system, Material E. This general behaviour is in line with that previously reported in systems based upon titania and an epoxy resin (14) , a copper phthalocyanine oligomer and a fluorinated copolymer (1) and silica and polyethylene (3) . Conversely, Hong et al (2) report that in their zinc oxide/polyethylene systems, micro-and nanocomposites behave similarly.…”

Section: Electrical Testingsupporting

confidence: 85%

“…Fleming et al (9) suggested that the thickness of an interface layer should be taken as "the distance over which a given physical property changes from being characteristic of the particle to being characteristic of the host"; a typical value of 10 nm is suggested. Nelson and Fothergill (14) have considered nanodielectrics in terms of local layers of immobilized polymer and, more generally, in terms of an interaction zone, where the presence of the nanofiller serves to modify the polymer's behaviour. In polyethylene, there is good reason to imagine that interaction zones could be extensive, since the dimensional scales involved in a well-dispersed MMT system are comparable to those exhibited by polyethylene lamellae, which are typically 10-20 nm in thickness and some microns in lateral extent (15) .…”

Section: Introductionmentioning

confidence: 99%

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Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown

2006

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Polymeric composites containing nanometric fillers have attracted considerable interest because of the attractive properties that such materials can display. In the area of nanodielectrics, many workers have stressed the significance of the interfaces that exist between such fillers and the host polymer as being critical in influencing properties. Indeed, Tanaka (1) proposed a concentric shell model in which interactions can be thought of as occurring at a range of dimensional levels; Nelson and Fothergill (2) considered nanodielectrics in terms of an interaction zone. In this work, we set out to prepare a range of nanocomposites based on polyethylene (PE) and montmorillonite nanoclay (MMT), to examine the effect of MMT dispersion on properties and structure formation and, thereby, to explore both short-range molecular effects and the extent of the polymer/nanoclay interaction zone. Figure 1 compares AC ramp breakdown results obtained from 3 materials at a ramp rate of 50 V s -1 . Where dispersion of the MMT is poor (C Quenched), the breakdown strength is greatly reduced compared with a comparable system containing well-dispersed nanoclay (E Quenched). This is in line with behaviour reported for nano-and microcomposites (2) , suggesting that it is attributable to aggregation of the MMT in C. However, attempts to improve the breakdown strength of E by controlled crystallization were unsuccessful; systems prepared by rapid quenching from the melt or by prolonged isothermal crystallization both behaved in an equivalent manner. This is in contrast to the same polymer, but without MMT (B 117 o C), where controlled crystallization can lead to improved properties, as reported elsewhere (3) . Thus, when quenched, equivalent polyethylene materials with and without MMT exhibit similar breakdown behaviour, provided the MMT is well dispersed. However, in the absence of MMT, isothermal crystallization can result in improved performance whereas, when MMT is present, this appears not to occur.To explore the origin of the above effects, the influence of MMT on structural evolution in PE was examined. In the scanning electron microscope (SEM), all the materials where MMT was absent or poorly dispersed were found to exhibit spherulitic morphologies. In contrast, Fig.2 shows a sample of Material E, which contains 5% by weight MMT, following crystallization at 117 o C. An MMT aggregate ~1 µm in size can be seen near the centre of this image but, elsewhere, it is not possible to distinguish MMT platelets from polymer lamellae. Although the material is highly nucleated, the lamellar texture also appears highly disrupted. Thus, in the absence of MMT or when the MMT is poorly dispersed, crystallization of the polymer leads to conventional morphologies, whereas well-dispersed MMT appears to promote nucleation but, subsequently, to disrupt the processes by which ordered structures form. This interpretation of fig.2 is supported by quantitative studies of crystallization kinetics and the thermodynamics of crystallization. MMT increases...

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Section: Electrical Testingsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown

2006

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“…Indeed, thanks to the presence of the nanofiller/polymer interfaces [5][6][7][8][9], such material systems have been envisioned as an answer to many high voltage insulation problems [10]. For example, the partial discharge resistance, electrical treeing growth, space charge formation and dielectric breakdown performance of nanodielectrics have been compared with the respective unfilled and microfilled counterparts and worthwhile improvements in such properties have been reported [11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Polyethylene/silica nanocomposites: absorption current and the interpretation of SCLC

Lau

Vaughan

Chen

et al. 2016

J. Phys. D: Appl. Phys.

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The topic of nanodielectrics continues to receive significant attention from today's dielectrics community, due to the property enhancements that can stem from the unique interfacial features within such material systems. Nevertheless, understanding of the interfacial phenomena that occur in nanodielectrics and which determine their electrical behaviour is challenging. In this paper, we report on an investigation into the absorption current behaviour of two nanocomposite systems, one containing an untreated nanosilica and the other containing the same nanofiller chemically modified using trimethoxy(propyl)silane.The results indicate that the absorption current behaviour of all the nanocomposites is very different from that of the reference, unfilled polymer; while the current flowing through the unfilled polyethylene decreased monotonically with time in a conventional manner, all nanocomposites revealed an initial decrease followed by a period in which the current increased with increasing time of electric field application. Possible mechanisms leading to the observed absorption current behaviour in the nanocomposites are discussed with the aid of space charge measurements. The presence of space charge limited conduction (SCLC) and its trap-filled limit is proposed.Keywords: nanocomposites, nanosilica, interface, absorption current, space charge limited conduction. 2 IntroductionThe addition of a nanofiller to a polymer matrix has been shown to be a flexible means of tailoring the dielectric properties of materials [1][2][3] and Chen et al. [19], for example, have emphasized the unsatisfactory nature of our understanding of charge transport mechanisms. In conventional polymeric insulation, charge transport mechanisms are extremely complicated, when compared with many conducting and semiconducting materials [20,21]. In semicrystalline polyethylene, for example, chainfolded lamellar crystals are surrounded by amorphous conformations and there is likely to be a high concentration of traps relating to each of these structural motifs. On the addition of a nanofiller, charge transport mechanisms will become yet more complicated, since the inclusion of nanoparticles will introduce extensive interfacial surfaces between the nanofiller and the polymer. The presence of such interfaces may directly introduce additional nanofiller/polymer trapping sites and/or modify the surrounding polymer morphology, thereby affecting the local density of states within the system.The current flow caused by the action of an applied electric field on charge carriers within a dielectric material can broadly be categorized into three types [22]: the initial current that flows through the material is the capacitive charging current, which causes a dramatic rise at the very beginning of the voltage application. This is followed by a gradual decrease of current, known as the absorption current or the anomalous current. Conventionally, the absorption current decreases slowly until it reaches a quasi-steady state, providing a conduction c...

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“…The increase of frequency of electric field expectedly leads to the permittivity decrease for the samples fabricated in all the considered conditions. At the same time, for the samples with core/shell filler there is much more intense increase of k in the low frequency region due to increased interface (particle/shell, shell/polymer) and associated with Maxwell-Wagner effect (interfacial polarization) [10]. Dissipation factor in low frequency range also increases significantly while above 10 kHz it is comparable to samples with non-modified filler.…”

Section: -3 Jjap Conf Proc (2016) 011101mentioning

confidence: 88%

Ferroelectric core/magnetic shell approach to control electric properties of composites

Sychov

Olga

Polina

et al. 2016

Proc. 14th Int. Conf. On Global Research and Education, Inter-Academia 2015

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Electrical properties of polymer-inorganic nanocomposites depend strongly on their structure, i.e. distribution of filler phase in a polymer matrix. This factor is especially important in the case of composites consisting of two phases with significantly different properties. To improve electric properties of such composites in this study ferroelectric core/magnetic shell approach is suggested. BaTiO3 core was coated with a SiO2-CoFe2O4 magnetic shell followed by incorporation of thus obtained core/shell particles into a polymer in the presence of external magnetic field to obtain composites featuring with a significantly increased dielectric permittivity. The developed composites may find various applications including embedded capacitors and other electronics devices, as well as sensors, electromagnetic radiation shields etc.

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Internal charge behaviour of nanocomposites

Cited by 475 publications

References 22 publications

Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown

Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown

Polyethylene/silica nanocomposites: absorption current and the interpretation of SCLC

Ferroelectric core/magnetic shell approach to control electric properties of composites

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