The work carried out during the fellowship has consisted of developing 3D-printable graphene-based nanocomposites with advances properties. During the synthesis of the material, the efforts have been directed towards the integration step, where the polymer and filler (graphene-based structures) join into one unique material. We employed solution-blending method for integrating the filler into the polymer structure, which allows increasing the dispersability of the graphene-based structure in the solvent with the polymer matrix and therefore improving the electrical and thermal properties of the nanocomposites. In this sense, two different strategies at this point were evaluated: i) by reducing “in situ” graphene oxide (GO) as precursor of graphene during the integration step through hydrazine as reducing agent and ii) by mixing in solution the already reduced graphene oxide (RGO) with the polymer. In first place, in both cases we synthesized graphene oxide as starting material from graphite flakes. In parallel to this work a third graphene-based structure was also synthesized, chemically expanded graphite (CEG), to be integrated with the polymer, which showed similar properties to those composites based on reduced graphene oxide (RGO) or even better properties in some cases. Graphene oxide was synthesized by following the well know Hummer’s method. On the other hand, chemically expanded graphite (CEG) was synthesized according to the methods described in literature. To carry out the synthesis of the nanocomposites employing GO and CEG as fillers, we followed the schemes of the Figure 7. Therefore, characterization methods were carried out for graphenic structures and nanocomposites. In this sense, we employed different characterization tecniques, including: SEM/EDX, TEM, XPS, BET, XRD, Raman, TGA, DSC and synchrotron radiation (SAXS/WAXS at ALBA facilities and BESSY facilities), and electrical conductivity. With the analysis of all these techniques, we have have been able to confirm that the graphene nanocomposites are provided with improved properties like better electrical conductivity when compared to the original polymers. During the secondment at EURECAT (ASCAMM), it has been carried out the molding of the composites into three dimensional structures, by employing new ultrasonication technology developed by EURECAT.
The results obtained from the work carried out during the fellowship have been presented in several internationally recognized scientific conferences as well as in internal technical meetings. In the Tables 6 and 7, information related to the attended conferences within the project is given.
