Ming-Jen Pan

Bio: Ming-Jen Pan is an academic researcher from United States Naval Research Laboratory. The author has contributed to research in topics: Dielectric & Bilayer. The author has an hindex of 4, co-authored 7 publications receiving 761 citations.

High energy density nanocomposites based on surface-modified BaTiO(3) and a ferroelectric polymer.

Abstract: The dielectric permittivity and electric breakdown strength of nanocomposites comprising poly(vinylidene fluoride-co-hexafluoro propylene) and phosphonic acid surface-modified BaTiO3 nanoparticles have been investigated as a function of the volume fraction of nanoparticles. The mode of binding of pentafluorobenzylphosphonic acid on the BaTiO3 particles was investigated using infrared and 31P solid-state nuclear magnetic resonance spectroscopy, and the phosphonic acid was found to form well ordered, tightly bound monolayers. The effective permittivity of nanocomposites with low volume fractions (<50%) was in good agreement with standard theoretical models, with a maximum relative permittivity of 35. However, for nanoparticle volume fractions of greater than 50%, the effective permittivity was observed to decrease with increasing nanoparticle volume fraction, and this was correlated with an increase in porosity of the spin-coated nanocomposite films. The dielectric breakdown strength was also found to decre...

Enhancement of breakdown strength and energy density in BaTiO3/ferroelectric polymer nanocomposites via processing-induced matrix crystallinity and uniformity

Abstract: We have investigated the impact of the processing methodology on nanocomposite thin films formed via blade casting versus spin coating on the electric breakdown strength and energy storage properties of BaTiO3 nanoparticle/poly(vinylidene fluoride-co-hexafluoropropylene) nanocomposites. Nanocomposite films containing 50% volume loading of surface-modified BaTiO3 nanoparticles fabricated by the use of blade casting showed a denser and more uniform morphology, and larger polymer crystallite domains, relative to those obtained via spin coating. The improved morphology has resulted in an increase of up to 60% in the breakdown strength and in energy density by a factor of ∼2–3 and for blade-cast vs. spin coated nanocomposite films containing 50 or 120 nm BaTiO3 nanoparticles, yielding a maximum extractable energy density of 7 J cm−3. We attribute the increase in energy density and dielectric breakdown strength to the effects of the improved uniformity and the formation of polymer nanocrystalline domains in the matrix, as shown by cross-sectional SEM and topological AFM images, and X-ray diffraction results. These results stress the importance of controlling nanoscale morphology for optimizing energy storage capacity of solution-processed nanocomposite thin films for pulsed power, gate dielectrics, and other thin-film power applications.

High-Energy-Density Sol–Gel Thin Film Based on Neat 2-Cyanoethyltrimethoxysilane

Abstract: Hybrid organic–inorganic sol–gel dielectric thin films from a neat 2-cyanoethyltrimethoxysilane (CNETMS) precursor have been fabricated and their permittivity, dielectric strength, and energy density characterized. CNETMS sol–gel films possess compact, polar cyanoethyl groups and exhibit a relative permittivity of 20 at 1 kHz and breakdown strengths ranging from 650 V/μm to 250 V/μm for film thicknesses of 1.3 to 3.5 μm. Capacitors based on CNETMS films exhibit extractable energy densities of 7 J/cm3 at 300 V/μm, as determined by charge–discharge and polarization-electric field measurements, as well as an energy extraction efficiency of ∼91%. The large extractable energy resulting from the linear dielectric polarization behavior suggests that CNETMS films are promising sol–gel materials for pulsed power applications.

High-energy-density hybrid sol–gel dielectric film capacitors with a polymeric charge blocking layer

Abstract: We report dielectric and energy storage characteristics of a bilayer structure based on a hybrid dielectric sol–gel film with a polymeric charge blocking layer. Poly(p-phenylene oxide) (PPO) serves as an interfacial charge blocking layer that suppresses charge injection from a metal electrode into the sol–gel dielectric film based on 2-cyanoethyltrimethoxysilane (CNETMS). The charge blocking layer reduces leakage current in the PPO–CNETMS bilayer film capacitor by more than one order of magnitude, and consequently leads to a maximum discharged energy density of 31 J cm−3 at 670 V μm−1, determined by a charge–discharge measurement. Analysis of the field-dependent polarization reveals that the PPO–CNETMS bilayer films exhibit significantly reduced polarization hysteresis upon charge/discharge cycles, so that the energy extraction efficiency remains higher than that of a neat CNETMS sol–gel film throughout the entire electric field range. We attribute this enhancement to the heightened and widened potential energy barrier at the metal–dielectric interface by the low-loss PPO interlayer. Detailed investigation on the height and width of a potential energy barrier at the metal–dielectric interface, by varying the work function of an electrode (potential energy barrier at zero bias) and the thickness of the PPO layer, indicates the critical role of interface energetics in the energy storage performance of dielectric film capacitors for pulsed power applications.

Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

Abstract: Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers...

Flexible Nanodielectric Materials with High Permittivity for Power Energy Storage

Abstract: Study of flexible nanodielectric materials (FNDMs) with high permittivity is one of the most active academic research areas in advanced functional materials. FNDMs with excellent dielectric properties are demonstrated to show great promise as energy-storage dielectric layers in high-performance capacitors. These materials, in common, consist of nanoscale particles dispersed into a flexible polymer matrix so that both the physical/chemical characteristics of the nanoparticles and the interaction between the nanoparticles and the polymers have crucial effects on the microstructures and final properties. This review first outlines the crucial issues in the nanodielectric field and then focuses on recent remarkable research developments in the fabrication of FNDMs with special constitutents, molecular structures, and microstructures. Possible reasons for several persistent issues are analyzed and the general strategies to realize FNDMs with excellent integral properties are summarized. The review further highlights some exciting examples of these FNDMs for power-energy-storage applications.

Mutual Insight on Ferroelectrics and Hybrid Halide Perovskites: A Platform for Future Multifunctional Energy Conversion.

Abstract: An insight into the analogies, state-of-the-art technologies, concepts, and prospects under the umbrella of perovskite materials (both inorganic-organic hybrid halide perovskites and ferroelectric perovskites) for future multifunctional energy conversion and storage devices is provided. Often, these are considered entirely different branches of research; however, considering them simultaneously and holistically can provide several new opportunities. Recent advancements have highlighted the potential of hybrid perovskites for high-efficiency solar cells. The intrinsic polar properties of these materials, including the potential for ferroelectricity, provide additional possibilities for simultaneously exploiting several energy conversion mechanisms such as the piezoelectric, pyroelectric, and thermoelectric effect and electrical energy storage. The presence of these phenomena can support the performance of perovskite solar cells. The energy conversion using these effects (piezo-, pyro-, and thermoelectric effect) can also be enhanced by a change in the light intensity. Thus, there lies a range of possibilities for tuning the structural, electronic, optical, and magnetic properties of perovskites to simultaneously harvest energy using more than one mechanism to realize an improved efficiency. This requires a basic understanding of concepts, mechanisms, corresponding material properties, and the underlying physics involved with these effects.