Dielectric properties of cyanate ester/silicon nanocomposites for multifunctional structural capacitors

Novel composites performing both dielectric and mechanical functions have a potential application in vehicle structures of both energy storage and load bearing capacity, leading to reduction in weight and associated energy costs. Multifunctional silicon nanoparticles/bisphenol E cyanate ester (Si/BECy) nanocomposites were synthesized and their dielectric properties were investigated. Si nanospheres, with average diameter 130 nm, were homogenized with BECy monomers for composite synthesis at 18 and 40 wt.%, corresponding to 10 and 26 vol.%, respectively. The effect of these Si nanofillers on dielectric behavior of BECy matrix was investigated using broadband dielectric spectroscopy from 10^-2 to 10^-6 Hz at temperatures from -100 to 260 °C. The dielectric spectra were modeled by a combination of Havriliak-Negami functions and a power-law conductivity dependence. The Arrhenius plot of characteristic frequencies reveals a β- and a γ-relaxation of Si/BECy composites and neat BECy. The temperature dependence of these relaxations obeys the Arrhenius law, showing significantly decreased activation energies with Si loading compared to those of neat BECy.