Nanodielectrics

Flur, S.-FL Yoon, M.-H. Gaur, A. Shim, M. Facchetti, A. Marks, T. J. Rogers, J. A. 2005. Organic nanodielectrics for low voltage carbon nanotube thin-film transistors and complementary logic gates. J. Am. Chem. Soc. 127 13808-13809. 

Sanghyun, J. Lee, K. Janes, D. B. Yoon, M-H. Facchetti, A. Marks, T. J. 2005. Low operating voltage ZnO nanowire field-effect transistors enabled by self-assembled organic gate nanodielectrics. Nano Lett. 5 2281-2286. 

K.Y. Lau, A.S. Vaughan, G. Chen, I.L. Hosier, Polyethylene nanodielectrics the effect of nanosilica and its surface treahnent on electrical breakdown strength, in Annual Report -Conference on Electrical Insulation and Dielectric Phenomena, CEIDP, 6378712, 2012, pp. 21-24. 

Nanodielectrics The Role of Structure in Determining Electrical Properties... 

Fig. 9.1 Schematic representation of the range of structuring that may influence the behaviour of a nanodielectric (a) aggregation (b) nanoparticle parameters (c) interfacial factors...

As far as dielectrics are concerned, electrical behaviour can be grossly divided into surface properties and bulk properties and these two areas will be briefly discussed in the following sections. While nanodielectrics have exhibited clear promise in both of these domains, our understanding of the fundamental physics and chemistry that underlie the effects that have been reported is, however, often poor. 

The complete topic of the bulk electrical performance of nanodielectrics includes a very wide range of phenomena and properties and, consequently, a comprehensive discussion of this is not possible here. Rather, just two areas are considered below, since these well illustrate the major issues associated with the bulk characteristics of nanocomposites in dielectric applications. 

In the case of a multi-component system such as a nanodielectric, an effective medium approach can be used to define the real permittivity of the whole based upon the composition and the properties of the individual components Myroshnychenko and Brosseau (2005) provide a good overview of the topic, as applied to binary systems. The Lichtenecker-Rother equation is an example of such a relationship ... 

Kochetov et al. (2012) described the dielectric response of a range of nanodielectrics based upon particulate nanofillers dispersed within an epoxy matrix. In all cases, with the exception of nano-silica, the inclusion of a low volume fraction (<5 %) of nanofiller resulted in a reduction in the measured real permittivity, below that of the host matrix, despite S In another epoxy-based... 

Fig. 9.4 Imaginary permittivity data obtained from nanodielectrics based upon nano-silica in an epoxy resin (a) frequency dependent data obtained at the indicated temperatures from a system containing 2 % of unfunctionalised nano-silica (NCO) (b) data obtained from systems where the nano-silica had been functionalised with increasing amounts (NCl- NC16)of 3-glycidyloxypropyl) trimethoxysilane...

Applying such concepts to the real permittivity data described above, it is evident that this inequahty does not hold. This suggests that the situation in nanodielectrics is more complex, which implies that the presence of the nanoparticles is affecting the overall performance of the system in a much more subtle and complex way. 

It can be argued that the lamellar nature of semi-crystalline polymers means that all such systems contain at least two phases in which at least one characteristic dimension falls into the nanometric range. This section will therefore take a less conventional approach to the topic of nanodielectrics where, here, the concept is broadened to include blend systems that have been intentionally manufactured to exhibit internal stmcture that are <100 nm in size and which, consequently, exhibit novel properties. 

Green CD, Vaughan AS, Mitchell GR, Liu T (2008) Structure property relationships in polyeth-ylene/montmorillonite nanodielectrics. IEEE Trans Diel Electr Insul 15 134—143... 

Roy M, Nelson JK, MacCrone RK, Schadler LS, Reed CW, Keefe R, Zenger W (2005) Polymer nanocomposite dielectrics—the role of the interface. IEEE Trans Diel Electr Insul 12 629-643 Roy M, Nelson JK, MacCrone RK, Schadler LS (2007) Candidate mechanisms ctmtrolling the electrical characteristics of silica/XLPE nanodielectrics. J Mater Sci 42 3789-3799 Saccani A, Motori A, Patuelli F, Montanari GC (2007) Thermal endurance evaluation of isotactic poly(propylene) based nanocomposites by short-term analytical methods. TREE Trans Diel Electr Insul 14 689-695... 

Takala M, Ranta H, Nevalainen P, Pakonen P, Pelto J, Karttunen M, Virtanen S, Koivu V, Pettersson M, Sonerud B, Kannus K (2010) Dielectric properties and partial discharge endurance of polypropylene-silica nanocomposite. IEEE Trans Diel Electr Insul 17 1259-1267 Tanaka T, Kozako M, Fuse N, Ohki Y (2005) Proposal of a multi-core model for polymer nanocomposite dielectrics. IEEE Trans Diel Electr Insul 12 669-681 Vaughan AS, Swingler SG, Zhang Y (2006) Polyethylene nanodielectrics the influence of nanoclays on structure formation and dielectric breakdown. Trans lEE Jpn 126 1057-1063 Venkatesulu B, Thomas MJ (2010) Erosion resistance of alumina-filled silicone rubber nanocomposites. IEEE Trans Diel Electr fiisul 17 615-624 Weibull W (1951) A statistical distribution function of wide applicability. J Appl Mech Trans ASME 18 293-297... 

Zanetti M, Camino G, Reichert P, MuUiaupt R (2001) Thermal behaviour of poly(propylene) layered silicate nanocomposites. Macromol Rapid Commun 22 176-180 Zhang C, Stevens GC (2008) The dielectric response of polar and non-polar nanodielectrics. IEEE Trans Diel Electr Insul 15 606-617... 

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