|عنوان فارسی مقاله:||خصوصیات الکتریکی نانوکامپوزیت های پلیمر گرافن|
|عنوان انگلیسی مقاله:||Electrical Properties of Graphene Polymer Nanocomposites|
|رشته های مرتبط:||مهندسی مواد و مهندسی پلیمر، مهندسی مواد مرکب، کامپوزیت، نانوفناوری و نانو مواد|
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|نشریه||اسپرینگر – Springer|
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Graphene, a monolayer of sp2 hybridized carbon atoms arranged in a two dimensional lattice has attracted electronic industrial interest due to its exceptional electrical properties. One of the most promising applications of this material is in polymer nanocomposites in which the interface of graphene based materials and polymer chains merge to develop the most technologically promising devices. This chapter presents the electrical properties of such graphene based polymer nanocomposites and also discusses the effect of various factors on their electrical conductivity. Graphene enables the insulator to conductor transition at significantly lower loading by providing percolated pathways for electron transfer and making the polymers composite electrically conductive. The effect of processing conditions, dispersion, aggregation, modification and aspect ratio of graphene on the electrical conductivity of the graphene/polymer nanocomposites is conferred.
Keywords Conductivity · Percolation · Filler modification · Volume fraction · Fabrication
Graphene, a two-dimensional, single-atom-thick structure of sp2 bonded carbon atoms, has attracted tremendous research interest due to their excellent reinforcement, electrical properties, unique physical characteristics and high mechanical properties. Therefore, recent research has focused on developing high performance polymer nanocomposites, with the benefit of graphene nanotechnology, to achieve novel composite materials for a wide range of industrial fields. Graphene dramatically improves the properties of polymer based composites at a very low loading and its most fascinating property is the very high surface conductivity leading to the formation of numerous electrically conductive polymer composites. Such conducting graphene nanocomposites have been widely applied in anti-static materials, electromagnetic interference (EMI) shielding, chemical sensor, bipolar plates for fuel cells etc. Other possible applications include radio-frequency interference shielding for electronic devices and electrostatic dissipation [1–3]. By using conventional processing methods, graphene composites can be easily fabricated into intricately shaped components with excellent preservation of the structure and properties. This is very important to make full use of the outstanding properties of graphene. Compared with carbon nanotubes (CNTs), graphene has a higher surface-to-volume ratio because of the inaccessibility of the CNT’s inner tube surface to polymer molecules. This makes graphene potentially more favorable for improving the properties of polymer matrices, such as electrical properties. Therefore, graphene-based polymer composites have attracted both academic and industrial interest . The present chapter gives an overview of the electrical properties of graphene based polymer nanocomposites. A brief description about the synthesis and characterization of graphene is also included in this chapter. Since the present book deals with the applications of graphene nanocomposites in various fields of flexible and wearable electronics, we think this chapter is of much significance as electrical conductivity is the basis for graphene’s such applications. After giving an outline about the electrical properties of graphene polymer composites, the various factors affecting the conductivity such as filler aspect ratio, dispersion, modification of graphene surfaces etc. are also discussed here. The phenomenon of percolation threshold is also well pictured and finally this chapter ends with a few applications.
2 Synthesis and Characterization
2.1 Synthesis of Graphene
Graphite is available in large quantities as in the form of both natural and synthetic sources and is rather inexpensive . The main graphite derivatives include EG, graphite oxide, graphene nanoplatelets (GNP), graphene oxide (GO), reduced graphene oxide (RGO), and graphene. Because the electronic, photonic, mechanical, and thermal properties of graphene depend on the number of layers  [although the monolayer (ML), bi-layer (BL), and tri-layer (TL) graphenes have practical significance] and its crystalline structure, the controlled synthesis of graphene with defined layers is rather significant. The mechanical peeling method by which graphene is first produced  is not used for an industrial scale of production. The GO and RGO derivatives are usually synthesized via solution-based oxidation and reduction by thermal and chemical methods, whereas graphene layers with superior electron transport characteristics are always synthesized using dry methods such as chemical vapor deposition (CVD) and surface segregation [6–13]. Although more than 95 % of graphene has been grown on Cu foil , this growth was not epitaxial, and thus complete growth over the entire substrate remains a major challenge. The surface of Ni(III) proved to be the best substrate for the epitaxial growth of structurally homogeneous graphene due to the small lattice mismatch of this surface with that of graphene and highly oriented pyrolytic graphite . However, this method suffers from the disadvantage of carbon solubility in nickel, and thus achieving uniform thickness throughout the substrate is difficult. The simple method of surface segregation [15–17] was recently introduced to solve this problem and to epitaxially grow graphene over Ni film (~100 nm thick) . Raman spectroscopy and scanning tunneling microscopy (STM) verified the homogeneity of the graphene layer over the entire Ni film [19–21].