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Design, manufacturing and control of INterfaces in THERMally conductive polymer nanocomposites

Periodic Reporting for period 3 - INTHERM (Design, manufacturing and control of INterfaces in THERMally conductive polymer nanocomposites)

Reporting period: 2018-03-01 to 2019-08-31

INTHERM project addresses the design, manufacturing and control of interfaces in thermally conductive polymer/graphene nanocomposites. In particular, the strong reduction of thermal resistance associated to the contacts between conductive particles in a percolating network throughout the polymer matrix is targeted, to overcome the present bottleneck for heat transfer in nanocomposites.
The project includes the investigation of novel chemical modifications of nanoparticles to behave as thermal bridges between adjacent particles, advanced characterization methods for particle/particle interfaces and controlled processing methods for the preparations of nanocomposites with superior thermal conductivity.
The results of this project will contribute to the fundamental understanding of heat transfer in complex solids, while success in mastering interfacial properties would open the way to a new generation of advanced materials coupling high thermal conductivity with low density, ease of processing, toughness and corrosion resistance.
In the first half of the project selection of nanoparticles was carried out and different strategies for their functionalization were developed, through both covalent and non-covalent modifications. Experimental activites in nanoparticles functionalization were carried out in parallel with computational modelling to calculate thermal conductances of model functional interfaces. Meanwhile, a new method for the measurement of heat transfer on supported individual nanoparticles was developed via Scanning Thermal Microscopy. This method allowed to demonstrate experimentally for the first time the strong dependance of heat transfer properties over the nanoflakes on the structural defectiveness in graphene related materials. A strong increase of thermal conductivity of nanoparticles was observed upon the high temperature annealing, leading to a reduction in structural defectiveness in the nanoflakes. Such an improved heat transfer performance was directly reflected in their polymer nanocomposites, with a two- to three-fold increase in thermal conductivity observed upon high temperature annealing of graphene related materials.
The manufacturing of molecular junctions was successfully obtained, leading tosignificant enhancements in both in-plane e and cross-plane thermal conductivity of the networks of nanoparticles, thus validating the fundamental concept of INTHERM
The effect of local crystallization of polymers on the surface of graphene related materials was also demonstrated to enhance remarkably the quality of thermal contacts, thus providing an additional route for the design and obtainment of efficient heat transfer in nanocomposites.
Recent research activities were focused on the controlled preparation of nanocomposites, the structural and thermal characterization of materials, based on the results from previous reporting periods on the design and manufacturing of molecular junctions. Screening of both covalent and non-covalent junction between conductive nanoflakes was completed in this reporting period. Self-organization of graphene-related materials into thermally conductive networks, referred to as nanopapers, was carried-out by filtering suspensions of graphite nanoplatelets, either functionalized or not. Nanopapers based on supramolecularly functionalized GnP, exploiting selected bispyrene derivatives were demonstrated to achieve better thermal diffusivity performance compared to pristine GnP nanopaper and, even more importantly, to perform better than copper foil in the application as heat spreaders. Preformed GnP nanopapers were also impregnated with solutions of various polymers, obtaining composite films with very high thermal conductivity, in the range between 15 and 90 W/mK.
Research carried out in INTHERM is expected to generate impact on the thermally conductive polymer composites research field, in term of new solutions for the manufacturing of high performance (nano)composites. Several application field may benefit of the results form INTHERM, including heat exchanger for low temperature heat recovery, heat dissipators in flexible electronic devices and heat exchanger for harsh corrosive environments.
INTHERM project concept