Examining Surface Interactions at the Filler-Matrix Interface in Silicone-Matrix Nanocomposites Containing Barium Titanate Nanoparticles for Energy Devices

The surface interactions and filler-matrix interfaces in nanocomposites composed of barium titanate (BaTiO₃ or BTO) nanoparticles and polydimethylsiloxane (PDMS) will be explored in this presentation through computational simulation and experimentation. BTO is a ferroelectric perovskite that has a bulk dielectric constant of up to ~7,000. Elastomers containing BTO can be used in energy storage applications such as thin multilayer capacitors and flexible electronics, which have motivated our research into silicone-BTO nanocomposites. The chemistry on the surfaces of BTO nanoparticles and the formation of interfaces between BTO and PDMS impact the properties and performance of the nanocomposites, and examining them will give us a holistic understanding of their internal chemistry. However, more sophisticated modeling is needed to (1) better understand the nature and complexity of interfaces formed between BTO and PDMS and (2) investigate the relationships between interfacial properties, nanocomposite properties, and nanoparticle properties. This talk will focus on Density Functional Theory (DFT) computer simulations that have been developed to help comprehensively understand the interfacial phenomena in PDMS-BTO nanocomposites. The surface theory and simulation discussed in this presentation will elucidate the interactions between siloxane with BTO. The DFT simulations also support experiments investigating the effect of nanoparticle size on the permittivity of these nanocomposites. Additionally, studies into different rotations and placements of the siloxane molecule on a BTO surface will be demonstrated. These studies enable the binding energy for each interaction to be calculated, which provides insight into the most favorable configurations of siloxane on BTO. The results from the DFT modeling advance our understanding of surface interactions of BTO in polymers, which could lead to new methods of uniformly dispersing inorganic fillers in polymers and achieving higher volume loadings of BTO nanoparticles in polymer-matrix nanocomposites. Ultimately, the new knowledge obtained from simulating surface interactions in BTO-PDMS nanocomposites could enable the development of improved materials with enhanced permittivity for electronic devices and energy storage systems.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This work was in part supported by the Air Force Research Laboratory, Directed Energy Directorate, High Power Microwave Division (AFRL/RDH).