Silanized-silicon/epoxy nanocomposites for structural capacitors with enhanced electrical energy storage capability

The surface treatment of Si nanoparticles (nano-Si) by silane coupling agents is shown to contribute to improved dispersion of nano-Si in an epoxy matrix, leading to a 25% increase of dielectric breakdown strength, a 38% increase in dielectric constant, and no significant increase in loss tangent at 10 wt.% silanized-Si loading, compared to neat epoxy, over a wide temperature range. The extremely low loss tangent of these polymer-matrix nanocomposites is observed over a wider frequency range (10−2 to 106 Hz) than previously reported. The silanization of Si nanoparticles also doubles the maximum filler loading and simplifies the fabrication process of the nanocomposite. Additionally, silanized-Si imparts a higher dielectric breakdown strength (Ebr) than that of the pristine Si filled nanocomposite at the same nanofiller loading, contributing to an increased energy storage capability. Furthermore, the introduction of 10 wt.% silanized nano-Si increases the storage modulus of epoxy by 40% at 30 °C and the glass transition temperature shows preserved thermal stability. Silanized Si/epoxy nanocomposites can therefore be regarded as promising candidates for structural capacitors in engineering systems.