Achieving High Energy Density, High Temperature and Low Loss Multilayer Polymer Films with Enhanced Breakdown Strength and Lifetime
Abstract
Abstract: Through past decade support by Office of Naval Research, multilayer dielectric film technology for Navy~s pulsed power capacitor applications have reach a stage that fundamental working mechanisms have been understood to a large extent. Both advantageous and disadvantageous dielectric properties have been identified. The advantageous properties include dipolar polarization of paraelectric/amorphous poly(vinylidene fluoride) (PVDF) dipoles andinterfacial polarization from various charge carriers such as thermally activated electrons and impurity ions. The disadvantageous properties include ferroelectric switching of crystalline PVDF dipoles, impurity ion conduction loss, and AC electronic conduction loss, especially at high temperatures and under high electric fields. In this proposal, we aim to decrease various dielectric losses, and the goal is to further enhance dielectric breakdown strength and lifetime for PVDFbased multilayer films at high temperatures. Eventually, we will be able to make our multilayer films ready for Navy~s needs for all-electric ships. First, we propose to achieve flat-on primary crystals for PVDF in nanolayers (<100 nm thick) utilizing nanoconfined crystallization at elevated temperatures. The hypothesis is that flat-on primary crystals are much more insulating to the conduction of space charges. Alternatively, we propose to incorporate organoclay nanoplatelets in PVDF layers. It is expected that inorganic nanoplatelets can also effectively block space charge conduction to increase breakdown strength and lifetime. Second, we propose to study dielectric breakdown mechanisms in electronic and thermal breakdowns. Electric treeing by the needleplane geometry will be used to understand electromechanical and electrochemical effects during electronic breakdown. Weibull analyses of AC and DC breakdown strengths will be used to understand the effect of AC electronic conduction on thermal breakdown. Once these mechanisms are understood, we can propose viable approaches to enhance breakdown strength and lifetime for multilayer films. Third, the effect of rigid amorphous fraction (RAF) on dielectric properties in uniaxially or biaxially stretched poly(ethylene naphthalate) (PEN)/PVDF multilayer films will be studied. It is expected that RAF will significantly reduce chain dynamics, and thus decrease space charge conduction to enhance breakdown strength. Various dielectric characterization methods, such as dielectric spectroscopy, D-E loop test, Weibull breakdown/lifetime analysis, leakage current, and thermally stimulated current studies will be used to achieve the above objectives.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 17, 2018
- Source ID
- N000141912032
Entities
People
- Lei Zhu
Organizations
- Case Western Reserve University
- Office of Naval Research
- United States Navy