Thesis topic

Nanodielectrics … materials for the future ?

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Nanodielectrics is the subject of study related to the dielectric phenomena of nanoscopic materials having the morphology of particles, sheets, wires, and tubes. Although the topic of nanodielectrics was advanced by Lewis in a seminal paper in 1994, it was not, until the experimental works of Henk, and Nelson, that it became clear that this novel class of materials (i.e. dielectric polymer nanocomposites) may, indeed, be advantages to be gained in the field of electrical insulation. The experimentally observed anomalous behavior of dielectric nanocomposites has been attributed to the nanometric size of the fillers. Consequently, at this scale, since interphases start to monitor the final material properties, the local characterization of these nanometric regions becomes undoubtedly fundamental. The main underlying reason for the changes and improvements in properties that are being seen is mainly related to the plurality of interfaces introduced through the use of nanomaterials.
The major goal of our project is both to try to optimize the benefits and, perhaps more importantly, to provide a better understanding of the physics and the chemistry of the interfaces/interphases on which these materials are relying. We aim to establish the fundamental interrelationships between the nanoscale dielectric properties (i.e. electric susceptibility, complex dielectric permittivity, dielectric polarization, dielectric breakdown, …) of the nanocomposites and their corresponding macroscopic properties. The measurements will be performed in function of the frequency of the probing signal and by varying the temperature of the sample. To do so, we will use a series of well-adapted techniques based on Scanning Probe Microscopy (SPM) and, more particularly, the electrical modes to map, at the nanoscale, the complex dielectric properties of the studied model nanocomposite materials and compare them to the macroscopic ones obtained by dielectric spectroscopies and ellipsometry. This experimental approach seeks to try to highlight some of the potential benefits and starts to provide insights into the way in which these materials function to provide characteristics that are most of the time different from the (polymer) matrix and the fillers (nanoparticles). The confrontation of the obtained results to the different existing theoretical models will constitute an important part of our project

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Department of Nanomaterials Physics and Energy
Philippe LECLERE

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