• Ebel, Thomas
• Greenbank, William

Abstract

Nanocomposite dielectrics are an increasingly important area of innovation in capacitor research as an avenue to<br/>improve capacitive energy density, electrical breakdown strength, and temperature stability of devices. In such<br/>devices, morphology control is critical in order to optimise electrical field distribution in the device and to<br/>prevent the clustering of nanoparticles lowering breakdown voltages. However, this is difficult to achieve with<br/>large-scale fabrication techniques, such as melt extrusion and stretching, as melt processing can induce clustering<br/>and offers few possibilities for fine structure control of length scales below 1 μm. Layer-by-layer fabrication offers<br/>a potential bottom-up alternative whereby dielectrics are printed by successive depositions of ultra-thin layers of<br/>a room-temperature-stable polymer ink. This would allow fine thickness and morphology control and could<br/>easily be adapted to industrial-scale printing techniques, like roll-to-roll slot-die coating. This study explores this<br/>technique by developing polypropylene-based inks in industry-friendly solvents that are then used to fabricate<br/>capacitor devices. A gel ink was able to be used to deposit ultrathin (sub-200 nm) layers of mostly amorphous<br/>polypropylene with high reproducibility. Capacitors based on these polypropylene layers perform commensurate<br/>with commercial devices, exhibiting excellent self-clearing and breakdown performance. Successive depositions<br/>of the ink were also demonstrated, allowing the fabrication of devices with finely tuned thicknesses and ca-<br/>pacitances, as well as nanocomposite capacitors. This demonstrates the viability of layer-by-layer dielectric<br/>printing at large scale and paves the way for commercial ultra-thin conformable polypropylene capacitors, multi-<br/>component sandwich nanocomposite capacitors, and multilayer polypropylene capacitors, as well as brand new<br/>possibilities in dielectrics research.

Topics

• nanoparticle
• Deposition
• nanocomposite
• density
• impedance spectroscopy
• polymer
• amorphous
• energy density
• melt
• strength
• clustering
• melt extrusion