Preparation and characterization of graphene filled epoxy thin film nanocomposite for electronic applications
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Date
2016-08-01
Authors
Zaid Aws Ali Ghaleb
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Abstract
Graphene has attracted great attention in electronic applications because of the unique mechanical, electrical and thermal properties arising from its two dimensional structure. Graphene nanopowder (GNP) filled epoxy thin film nanocomposites were fabricated using ultrasonication and the spin coating techniques. The effect of GNP loading and sonication time, chloroform as dispersion solution for GNP (ch-GNP), amine as coupling agent for GNP (m-GNP) and hybrid system using GNP and multi-walled carbon nanotubes (MWCNT) (GNP-MWCNT) on the tensile, electrical and thermal properties of epoxy composites were investigated in this study. Generally, the addition of GNP decreased the tensile strength and modulus for all epoxy composites. However, the GNP/epoxy composites produced using 20 minutes of sonication time had a slightly higher tensile strength and modulus, with a lower electrical percolation threshold volume fraction (0.1 vol%). Morphological study via scanning electron microscopy (SEM) showed that improvement in GNP dispersion was achieved with increased sonication time. However, GNP deformation was observed after a long sonication time. Both ch-GNP/epoxy and m-GNP/epoxy composites produced using 20 minutes of sonication time had slightly higher tensile properties than GNP/epoxy composites, especially at low filler loading. However, the m-GNP/epoxy composites exhibit percolation threshold value at higher filler loading (0.6 vol%) compared to 0.05 and 0.1 vol% for ch-GNP/epoxy and GNP/epoxy composite, respectively. Morphological analysis via SEM showed a higher degree of dispersion and exfoliation of ch-GNP and m-GNP in the epoxy composites. However, morphological study via transmission electron microscopy (TEM) showed that both ch-GNP and m-GNP size was far smaller than the as received GNP. From the thermal properties, it was found that ch-GNP/epoxy and m-GNP/epoxy composites showed a higher glass transition temperature than GNP/epoxy composites. The GNP-MWCNT/epoxy hybrid composites showed improvement in the tensile properties with increasing concentration of MWCNT compared to GNP. GNP-MWCNT/epoxy hybrid composite with 0.1:0.4 ratio of GNP:MWCNT with total nanofiller volume fraction of 0.5 vol% showed the optimum properties among all composites even higher tensile properties than the unfilled epoxy with highest electrical conductivity of 1.82 × 10-2 S/cm, which is an order of magnitude higher than that of the epoxy composite with 0.5 vol% GNP. Finally, this study involves the use of two different types of epoxy resin using GNP-MWCNT hybrid system on the properties of epoxy hybrid composite. As compared to epoxy-DER (0.1:0.4) hybrid composites, epoxy-Epolam (0.1:0.4) hybrid composites showed lower tensile and thermal properties while the electrical conductivity of the hybrid composite remains very close to that of the pure insulating epoxy-Epolam matrix.